|University Archives of Virginia Tech|
A History of Plant Pathology in Virginia: The Foy Era (1974-1980)
During the Foy Era, C. R. Drake served as fruit pathologist at Blacksburg. His appointment was split three ways, 10% instruction, 30% research, and 60% extension. In both research and instruction, he worked to improve production of apples and peaches in southern and southeastern Virginia. He also devoted time to strawberries, cane fruits, grapes, and nectarines. K. D. Hickey was the pathologist at the Winchester Fruit Laboratory until May 1, 1976, when he resigned to become Professor of Plant Pathology and Scientists-in-charge of the Fruit Research Laboratory of the Pennsylvania State University at Biglerville. He was replaced by Keith S. Yoder on November 11, 1976. Although there appears to be a period when the Winchester Station was without a pathologist, Hickey continued projects into the Foy Era that he had initiated at Winchester and cooperated with Virginia growers from his Biglerville location until Yoder arrived on the scene. The Winchester based projects had been outlined in a news item announcing Hickey's appointment at Biglerville: "His duties...have included the evaluation of potential fungicides for fruit disease control, evaluation of application methods, spray timing, and other factors necessary in the development and maintenance of up-to-date recommendations for disease control on fruit.------ In recent years he has been active in doing research on low volume and alternate row spraying in orchards and their effect on disease control and has related this information on spraying methods." (Phytopathology News 10 (8) : 6-7 1976). Most of Hickey's publications in the 1974-76 period were in Fungicide and Nematicide Test Results. Powdery mildew of apple received special attention because it was difficult to control. New materials were being examined but by the time Hickey resigned, satisfactory control had not yet been found, especially on 'Jonathan.' When new procedures and materials were approved, recommendations were promptly incorporated into the annual Virginia Spray Bulletin for Tree Fruits (Va. Coop. Ext. Ser. Publ. 219) and the annual Virginia Plant Disease Control Guide (Va. Coop. Ext. Ser. Control Series 2). Needless to say, when Yoder took the position, he continued these projects in both research and extension.
K. S. Yoder began studying Virginia fruit diseases in the late fall of 1976. He was appointed 75% research and 25% extension time. He came to Winchester after several years of experience in the development of fruit fungicides while working at the. DuPont Laboratories in Wilmington, Delaware. Fungus resistance to fungicides had been a primary topic of his research and he was well aquatinted with eastern orchard diseases. Although there is little evidence that he devoted much time to resistance of fungi to fungicides, he continued evaluating new fungicides and methods of applying them. Reports of progress were given regularly at meetings of the Cumberland-Shenandoah Fruit conference, The Virginia State Horticultural Society, and in the American Phytopathological Society annual publication Fungicide and Nematicide Test Results. When deemed feasible, spray recommendations were modified. Thus, his primary mission was "to provide the Virginia industry with economical disease management information, emphasizing orchard monitoring and timely use of management measures to reduce overall chemical inputs and to advise growers of changes in fruit pesticide regulations." (From a 1996 description of the "Alson H. Smith, Jr. Agricultural Research and Extension Center"). In the Foy Era, Hickey and Yoder executed these objectives exceptionally well.
Even though Hickey was in Pennsylvania for two-thirds of the Foy Era, Yoder and Hickey interacted through various grower groups which found political boundaries as something to be recognized but otherwise ignored. The Cumberland-Shenandoah Valley Fruit Conference was comprised of professional fruit workers in four states (Md., Penn., Va., W.Va.) and pesticide industry personnel. Information was generated, exchanged, pooled, and shared with growers in respective states. Furthermore, members of the Conferences participated in preparation of regional publications, executing regional experiments, and holding regional field days. Yoder and Hickey prepared an eloquent review on the status and control of apple powdery mildew. Although published in 1983, the article included much of the expertise and information the two had generated in the Foy Era. (Plant Disease 67: 245-248). Powdery mildew remained an undefeated adversary beyond the Foy Era.
Some specific accomplishments by Yoder included finding apple powdery mildew inoculum in 1977 at an earlier growth stage than before and a subsequent recommendation in the 1978 Spray Bulletin to spray earlier. He clarified the confusion by growers in recognizing the differences between Phytophthora collar rot and apple graft union necrosis, a virus disease. Growers had been wasting fungicides thinking their trees had collar rot when in fact they had the virus disease (Va. Fruit 68 (3): 51-53). In 1977, a Benlate-resistant strain of Penicillium expansum was discovered in local apple storage facilities. Managers were advised on how to decontaminate the storages. Yoder was invited to serve on the EBDC (ethylene bis dithiocarbamate) Fungicide Benefits Assessment Team. This was a very important assignment as the eastern U. S. fruit industry was heavily dependent upon EBDC fungicides to control several important foliage and fruit diseases. Re-registration of these products was vital to keep growers in the East in a competitive position. Yoder and C. R. Drake forwarded data collected under RPAR (rebuttable presumption against registration) to the Fungicide Benefits Assessment Teams representing these materials.
From the foregoing, one may conclude that all fruit work during the Foy Era was centered at Winchester. On the contrary, C. R. Drake at Blacksburg was contributing to the betterment of fruit and fruit growers statewide. Throughout the Foy Era, he tested numerous fungicides in a high density planting at Blacksburg and in commercial plantings in southwestern Virginia. Target diseases were on apple, leaf blotch, sooty blotch, fly speck, powdery mildew, and fruit rots, especially post-harvest rots. On peach, he emphasized brown rot, Rhizopus rot, scab and powdery mildew. Results of these tests were reported regularly at the Cumberland-Shenandoah Fruit Conference and in the American Phytopathology Society annual publication, Fungicide and Nematicide Test Results (FTN). Significant results and new recommendations were incorporated into various Extension publications. In 1975, Drake made use of an abandoned apple orchard at Woolwine, Patrick Co., where he must have reasoned that if he controlled diseases there, he could control them anywhere. Certainly, fungicides would be rigorously tested. However, fruit was severely damaged by hail and only reliable data on powdery mildew were obtained. Polyram and EL222 gave excellent results.
Drake cooperated with both Hickey and Yoder on various aspects of fruit disease control and they all collaborated in publishing many useful Extension bulletins and leaflets. The fruit industry was well-served during the Foy Era.
Most of the effort on soybeans in the Foy Era was toward detecting viruses, resistance to them, and making a genetic analysis of resistance to viruses. This was a cooperative project involving a field crop pathologist, C. W. Roane; a virologist, S. A. Tolin; a plant breeder, G. R. Buss; and a graduate student, E. R. Shipe. The work was supported by grants form the Virginia Soybean Commission.
Surveys for virus diseases were conducted throughout the Foy Era. Soybean mosaic (SMV) was found to be widespread and demonstrated to be seedborne. Peanut mottle (PMV) was found only south of the James River and generally distributed throughout peanut producing counties. It was most severe in soybeans following peanuts. 'York' was found to be resistant to both SMV and PMV; thus, for the Foy Era it was recommended for use in rotations with peanuts. Toward the end of the Foy Era, two cvs., 'Shore' and 'Ware', both carrying resistance to PMV, SMV, and peanut stunt virus (PSV) were released. The addition of PSV resistance was fortuitous because it was not known until these two cvs. were named and released that they were triply resistant. It was also recommended that soybeans should not follow peanuts in rotations, as volunteer peanut plants would furnish virus inoculum. In one such circumstance, over 80% of the soybean plants displayed virus symptoms.
Studies were made to determine the percentage of seed transmission of viruses in soybean. SMV was consistently transmitted from generation to generation through seeds; PMV was not. In surveys where bean pod mottle (BPMV) and peanut stunt (PSV) virus disease were also found, caused milder symptoms similar to those induced by tobacco ring spot virus (TRSV), known as bud blight. Soybeans grown next to clover fields frequently exhibited bud blight-like symptoms leading us to believe TRSV was common, but Tolin's work and inoculation experiments revealed that TRSV was rare in soybean except near tobacco fields. The culprits were BPMV and PSV.
In the breeding program, resistance to SMV and PMV received priority. Resistance to these viruses was believed by some to be conditioned by the same gene. The cv. York was resistant to both. We found its parents, 'Dorman' and 'Hood' each to be resistant to one of the viruses, Dorman to PMV and Hood to SMV. Furthermore, many lines in the breeding program were found to be resistant to one or the other virus and some were resistant to both. It was already pointed that SMV is seed-borne in soybean and PMV is not. In a genetic analysis of SMV and PMV resistance a cross of York X 'Lee 68' was studied. As the progenies were advanced to F3, Lee 68, susceptible to SMV and PMV, was found to be resistant to PSV. Thus, in one experiment, we had the opportunity to study simultaneously the genetics of reaction to three viruses. After partitioning populations of seed from each F2 plant into three aliquots, triplicate nurseries could be planted and seedlings therein could be inoculated with different viruses. The genotype for each F2 plant could be established. Genes conditioning reaction to all three viruses segregated monogenically; reaction to PSV was independent of reaction to PMV and SMV but reactions to the later two were linked by 3.7% recombination. Despite this study and reports that a line could be resistant to one virus, there were those who continued to say that resistance to PMV and SMV were conditioned by the same gene.
There was one final aggravating aspect of this work. Preliminary results of the study had been published (Phytopathology 70: 692; Soybean Genetics Newsletter. 7: 100-102) but when the detailed manuscript was submitted to the Journal of Heredity the editor required that the PSV genetics be deleted because the data was not "clean" enough. It clearly showed that PSV resistance was independent of PMV and SMV resistance (J. Heredity 14: 289-291). Genetics of reaction to viruses remained a viable topic for many years, even into the molecular genetics years.
Several inoculation experiments were conducted to determine the effects of viruses on growth and yield of soybeans. In 1974, 0/3, 1/3, 2/3, and 3/3 of the plants in plots of 4 cvs. (Clark, Essex, Kent, Wye) were inoculated with 3 viruses (BPMV, PMV, SMV); BPMV was the most destructive, PMV the least. However, since PMV is the most frequently occurring virus, its impact on commercial production is greatest. It has long been known that SMV caused seeds to mottle (also called bleeding hilum, streak) especially in the dark hilum cultivators. From the various inoculation experiments, it was discovered that all viruses (BPMV, PMV, PSV, SMV, TRSV) caused seed mottling or bleeding hilium. On cvs. with light colored hila, mottling occurred but was inconspicuous and consequently, these types are not downgraded by the buyers.
During the surveys, soybean brown stem rot, caused by Cephalosporuim gregatum, was found to be widespread north of The James River. Roane thought that growing resistant cvs. might be the solution to controlling it but a uniformly infested plot of land would be needed for tests. It was easy to isolate the fungus but isolates were difficult to increase. By culturing the fungus on steamed grain, enough inoculum was generated to inoculate a half-acre plot. Test plants in the first year had no symptoms of brown stem rot. The process was repeated for two more years but no plants ever developed symptoms. Since no reliable field test was developed the urge to breed or select for brown stem rot resistance ebbed. Growers were encouraged to practice 3 year rotations to minimize losses. The work on viruses began to utilize both time and funds.
Soybeans were grown throughout the peanut producing counties; peanut and soybean are hosts to many of the same pathogens. The U.S.D.A. pathologist, K. H. Garren and D. M. Porter and beginning in 1978, the state pathologist, P. M. Phipps, all studying peanut diseases, sometimes reported on soybean diseases they encountered. In August 1978, Phipps and Porter reported finding Sclerotinia blight in several fields of York and Essex soybean. Both Sclerotinia minor and S. sclerotiorum were present. S. minor predominated. Sclerotinia sclerotiorum had been known on soybean in Virginia for many years but S. minor having been first discovered on peanut in the United States in eastern Virginia in 1971, was probably first recognized on soybean in 1978.
Powdery mildew is fairly common on soybean in Virginia in late summer. Martha K. and C. W. Roane examined some cleistothecia in collections and observed what appeared to be branched and unbranched appendages in different collections. Knowing that there had been some confusion in the early literature as the fungus had first been assigned to Erysiphe but later was reassigned to Microsphaera, they submitted a manuscript entitled, "What causes powdery mildew of soybean?" The editor proposed that it be re-titled, "Erysiphe and Microsphaera as dual causes of powdery mildew of soybeans." The authors did not agree (Plant Dis. Reptr. 60: 611-612. 1976). Later, it was pointed out that the "Erysiphe" cleistothecia were probably immature Microsphaera cleistothecia. The authors conceded and consoled themselves that they had caused others to take a better look.
Soybean and peanuts were common suscepts of several diseases. Among them, Cylindrocladium black rot, CBR, caused by Cylindrocladium crotolarie. The damage by this disease was less to soybean than to peanut but having two crops in a rotation that succumbed to the same pathogen made it difficult to control the pathogen. Although soybeans were a very profitable crop, in about six counties of southeastern Virginia, peanuts were king. Most studies on CBR centered around survival of its primary propagule, microsclerotia, in soil. That work will be covered in the sections on peanut and soil microbiology. As a soybean disease, CBR received little attention.
At the beginning of the Foy Era, two U. S. Department of Agriculture plant pathologists were stationed at The Tidewater Agricultural Research and Extension Center, Suffolk, Virginia. Kenneth H. Garren had been assigned there since 1955. He had worked to reduce losses caused by Sclerotium rolfsii, Pythium myriotylum and Aspergillus flavus. In 1966, D. Morris Porter joined with the assignment to find more effective control measures for peanut leafspot. Garren worked mostly on diseases of underground parts, Porter on diseases of aerial parts.
In 1978, Patrick M. Phipps was hired by the Virginia Agricultural Experiment Station and Cooperative Extension Service on a 40/60 basis. At first, he concentrated on developing a series of Extension demonstrations and generating useful Extension publications for peanut area growers. For his more basic studies, he concentrated on nematodes and Sclerotinia blight. With three pathologists devoting full time to peanut diseases, and pathologists in Blacksburg also concentrating part time to these problems, peanut growers were very well served.
Garren had found in the mid-sixties that Pythuim myriotylum for the most part and Rhizoctonia solani to a lesser extent caused peanut pod rot. After demonstrating that applying a heavier rate of landplaster would decrease losses due to pod rot, he devoted time to seeking resistant cultivars. Cooperating in this work were Porter and P. H. Van Shaik (Peanut Sci. 2: 15-18, 1975). They found that, in general, the most widely grown cultivars in Virginia were the most resistant. After publishing that report, Garren narrowed his research to Cylindrocladium black rot (CBR) and mycotoxigens, especially Aspergillus flavus. In the mid-seventies, much emphasis was on detection of CBR by remote sensing.
In 1970, Cylindrocladium crotolariae was found by K. H. Garren, D. M. Porter, and A. H. Allison, causing black root rot (CBR) of peanut in Nansemond County (now Suffolk) (Pl. Dis. Reptr. 55: 419-421). By 1972, CBR had been found in all peanut-producing counties of North Carolina and Virginia. Garren, G. J. Griffin, Porter, and with N. L. Powell, agronomist, as leader, cooperated with the National Aeronautics and Space Administration staff at Wellops Island, Virginia to study by remote infrared sensing the distribution, rate of spread, and losses caused by CBR (Peanut Sci. 3: 25-29, 1976; Pl. Dis. Reptr. 60: 1003-1007, 1976). They found that CBR could easily be detected in known areas of infestation and, as a consequence, previously unknown areas of infestation were detectable, and because plants were killed in detected areas, yield losses could be determined. Powell, Porter, Pettry, and Cobb employed this remote sensing technique for the detection of Sclerotinia blight and estimating damage and loss caused by it (Peanut Sci. 3: 21-24; 4: 75-77). The method was remarkably accurate but because of the costly equipment needed (multi-engined aircraft, remote airbases, photo equipment), the work was discontinued after a contract with NASA expired. Thereafter, the researchers engaged in conventional studies.
Garren, Porter, Griffin, and graduate students D. T. Krigsvold and J. D. Taylor examined soils to determine survival modes of the CBR fungus. Microsclerotia were the survival propagules. Under the leadership of Griffin, factors affecting the density and survivability were studied. They found that microsclerotia were clumped rather than randomly distributed and environmental factors more than crop sequence affected survival (Phytopathology 71: 1297-1302). Summer droughts and excessively cold winters destroyed microsclerotia and after such weather events Phipps and M. K. Beute of North Carolina reported that CBR was less severe (Phytopathology 67: 1104-1107). This field research was reinforced by controlled experiments of Griffin, Powell, and students D. A. Roth and P. J. Graham, who found that germinability of microsclerotia was depressed when infested soil was incubated at 5 degrees Celsius, -3 degrees Celsius, or -10 degrees Celsius for four weeks. Microsclerotia did not appear to survive the -10 degrees Celsius regime. Air drying to -2000 bars also resulted in apparent loss of germinability. However, restoring moisture and incubation at 26 degrees Celsius (not a critical temperature) for 2 to 4 weeks resulted in partial recovery of germinability (Phytopathology 68: 887-891; Canad. J. Microbiol. 25: 157-162, 1979). As Griffin explained it, membrane damage by freezing or heat was not fatal but repair of the membranes required several days; as a result, it appeared that one could "bring 'em back alive."
Concurrently, Garren and T. A. Coffelt (U. S. D. A. Plant Breeder at Suffolk), were examining peanut germplasm for CBR resistant cultivars and sources of resistance. Initially, they found poor tolerance among 11 Virginia types. The one Spanish type tested had excellent tolerance (Pl. Dis. Reprtr. 60: 175-178, 1976). Later after examining a broader spectrum of germplasm, they reported Spanish types to be the most resistant, Valencia types the least resistant, and Virginia types intermediate (Peanut Sci. 9: 1-8, 1982).
There were efforts to reduce the impact of CBR by treating soil with various chemicals. Porter and associates found PCNB, DCNA, benomyl, chlorothalonil, and CuSO4 to be only partially effective (Pl. Dis. Reptr. 59: 697-701, 1975). Research Associate S. B. Hanounik, statistician W. B. Pirie, and Extension Plant Pathologist Osborne collaborated in a greenhouse study of sodium azide (NaNO3) on CBR. They found that the chemical reduced CBR (Pl. Dis. Reptr. 61: 431-435, 1977). B. A Womble and Garren also sound that sodium azide offered some promise for CBR control (Proc. Amer. Peanut Res. Ed. Assoc 10: 53, 1978.). Graduate student C. I. Umechuruba working with Hale and Griffin found sodium azide effective in sandy soils but not in clumpy clay soils (Pl. Dis. Reptr. 62: 1-5, 1978.). By the end of the Foy Era, no feasible chemical control for CBR had been found.
Sclerotinia minor was found for the first time in the United States on a farm in eastern Virginia in 1971. Thereafter, it was observed throughout the U. S. peanut producing states and its severity greatly intensified. Fungicides applied for Cercospora leaf spot control resulted in greater losses from Sclerotinia blight. Captafol and chlorothalonil in particular while effective against peanut leaf spot seemed to favor Sclerotinia blight. Thus, other fungicides were suggested for leaf spot control where the blight was a known threat (Compenduim of Peanut Diseases. Amer. Phypothol. Soc., 1984). Growers had to wait a while for economic methods of control of CBR Sclerotinia blight. Intense research was underway.
J. C. Wells, Extension Plant Pathologist at North Carolina State University, and Phipps at the Suffolk station collaborated in 1980 to produce a beautifully illustrated publication entitled, "Peanut Disease Guide" (Va. Coop. Ext. Serv. Pub. 896; also issued by N. C. Ext. Ser.). Each photograph was accompanied by a brief description of the disease, its cycle, factors favoring it and the principles of its control. Since details of control could be provided in other releases, frequent revision would not be necessary. The guide should be an enduring publication. At the end of the Foy Era, graduate student Roberta Dow, under the guidance of Porter, Phipps, and Powell initiated studies leading to forecasting peanut leaf spot. This work would be continued after the Foy Era.
Thus, it seems that peanut diseases were being adequately studied during the Foy Era.
Prior to 1974, tobacco disease research was conducted at four locations., The flagship station was at Chatham where three pathologists were stationed. At Blacksburg, two tobacco research pathologists and one tobacco extension pathologist were stationed. Tobacco pathology was also conducted at Charlotte Court House and Glade Spring under the supervision of Blacksburg and Chatham pathologists. In 1974, a new station, primarily for centralized tobacco research was opened at Blackstone and the Charlotte C. H. and Chatham stations were closed. The new station was named the Southern Piedmont Research and Extension Center. None of the pathologists had to relocate. W. H. Wills had already transferred to Blacksburg; J. L. Troutman had resigned, and J. L. La Prade had retired. Only extension specialist W. W. Osborne and research pathologist L. D. Moore, both of Blacksburg, were devoting any time to tobacco pathology. Obviously, Virginia's leading cash and revenue generating crop deserved more intensive pathology research. The situation improved when on January 15, 1975, John J. Reilly was appointed Assistant Professor and Research Pathologist at Blackstone. In 1977, Wyatt Osborne took a disability retirement leaving tobacco growers without any Extension Specialist in pathology. In April 1979, Dean Komm was appointed Assistant Professor and Extension Specialist for tobacco pathology and he too was station at Blackstone. Thus, during the Foy Era, tobacco pathology was virtually completely shifted to Blackstone. Some tobacco virology, physiology and nematology was still conducted at Blacksburg by S. A. Tolin, L. D. Moore, and J. A. Fox, respectively.
John Reilly was appointed to a research position in the virtual center of the tobacco production area at a time when there was no tobacco Extension Specialist in plant pathology. At a field station, when problems arise and there are queries about plant disease and diagnoses to be made, one cannot say, " I am in research; it's not my responsibility." In order to maintain support from the commodity groups and growers, someone has to step forward. Thus, for four years until Komm became the Extension Specialist for tobacco Reilly had to serve tobacco as both research and extension specialist. As a result his research efforts may have been diluted by mandate. From a list of his publications beginning in 1976 until Komm was appointed in 1979, two-thirds were Extension (12 of 18). Four were titled "Flue-cured tobacco variety information for (the years 1976, -77, -78, -79)." Three agronomists and Reilly were the authors. No doubt, Reilly provided disease reactions and edited statements pertaining to plant pathology. Even after Komm arrived, Reilly was co-author of this annual publication well into the '80's'. Another publication that was revised and issued annually, "Virginia Pest Management Guide," had a subsection in the section on "Tobacco" titled "Disease Control." Reilly and other pathologists prepared this section, (S. A. Tolin, virus diseases; J. A. Fox, nematode diseases; J. D. Taylor, miscellaneous information.). It covered seed-bed preparation, seedling disease control, field fumigation, variety selection, harvesting, and curing. The entire publication was a manual for County Extension Agents; it covered most of Virginia's agricultural plant products.
From the beginning, Reilly studied the effects of three chemicals on control of tobacco mosaic virus primarily during transplanting. Milk had been touted for many years as a suitable product for controlling TMV by spraying it on plants before they were pulled and by having workers wash their hands in it before and during transplanting operations. Reilly compared the effectiveness of milk with Monosan (= sodium alginate) and a phosphate detergent. His conclusion was, "Both milk and Monosan were better than not washing, but neither was as effective as washing in a strong detergent solution" (Tobacco Sci. 23: 97-99, 1979). Reilly also investigated the effect of various chemicals with potential for controlling black shank caused by Phytophthora parasitica var. nicotianae. Propamocarb and metalaxyl surfaced as the most efficacious of the several tested. These materials are convenient in that they can be used in the transplant water, applied in rows as granular, or as spray treatments to young plants and no waiting period is required between application and transplanting. However, these materials gave best results in combination with the more resistant cultivars. Treatments economically feasible with susceptible cultivars were not found (Plant Dis. 64: 274-277, 1980.). R. G. Henderson retired from the Department in 1973, but in 1978 he contributed two papers on tobacco breeding. He worked with Agronomist J. L. Jones of Blackstone to evaluate the results of a two-year (1970, 1971) study on F1, hybrids of male sterile dark-fired tobacco. Hybrids yielded 97 to 114% of the higher yielding parent in crosses and averaged 109%. Black shank resistance and quality were intermediate to parents of hybrid. The results were not encouraging enough to continue the work (Tobacco Sci. 22: 109-111, 1978).
In a second paper, Henderson and J. F. Chaplin, U. S. D. A. Agronomist, Oxford, N. C., found perfect correlations between reactions to root knot nematodes (RKN) and potato virus Y (PVY) in tobacco. Plants homozygous and heterozygous resistant and homozygous susceptible to RKN were inoculated with PVY, veinal necrosis strain. Homozygous resistant plants developed an acute veinal and stem necrosis, heterozygous plants developed mottling and vein banding typical of PVY infection. Either the genes conditioning reactions to these two pathogens are tightly linked or there is a single pleiotrophic gene controlling the two characters. Whatever the genetic situation, this relationship had been used for several years in Virginia to select tobacco lines for RKN resistance by obtaining their reactions to PVY (Tobacco Sci. 22: 126-127,1978).
An interesting observation was made by J. A. Fox in 1976. Spores of Corynespora cassiicola were found in along with nematodes that had been separated from soils of tobacco fields. The fungus was isolated and a student, J. C. Adams III, used it as the subject for a M. S. thesis. He found that lesions developed on wounded inoculated stems of tobacco. Foliar inoculations yielded lesions on one of four tobacco cultivars tested. Results with other species except tomato were varied; 'Tiny Tim' tomato was susceptible. Fox, subsequent to the 1976 discovery, found spores of C. cassiicola in nematode extracts (sugar flotation method) of soils from widely scattered tobacco, soybean, and peanut fields in central and eastern Virginia. It was concluded that although the fungus has the potential for becoming pathogenic on tobacco, it apparently exists as a saprophyte [Tobacco Sci. 24: 122-125, 1980; Adams, J. C., III, 1978, Growth and pathogenicity of six isolates of Corynespora cassiicola (Berk. & Curt.) Wei. M. S. Thesis, Dept. Pl. Path. & Physiol., V.P.I. & SU. 50pp.].
There was an attempt by L. D. Moore, Associate Professor of Plant Pathology at Blacksburg, to relate total nonstructural carbohydrate (TNC) content of tobacco to reaction to Phytophthora parasitica var. nicotianae. He could find no differences in TNC for moderately resistant 'Vesta 5' and susceptible 'Virginia Gold.' Decline of TNC was correlated with increased disease severity (Tobacco Sci. 20: 10-13, 1976.). Graduate student L. E. Trevathan and Moore evaluated the effects of different levels of calcium on response to ozone in a single cultivar, NC88, of flue-cured tobacco. Although the authors did not say, they must have chosen NC88 because of its susceptibility to weather fleck caused by natural exposure to O3. A negative correlation was observed between Ca content of foliage and ozone damage. A positive correlation was observed between the amount of Ca supplied and its content in leaves. It was known that increased Ca content and increased sugar contents are positively correlated and sugar content and ozone damage are negatively correlated. These correlations may explain the relationship between Ca content and ozone damage (Tobacco Sci. 20: 67-68, 1976). Moore also cooperated with T. R. Terrill, Associate Professor of Agronomy, and Reilly of the Blackstone station to evaluate genotype effects on response to ozone. They found that cultivars with similar genetic background reacted similarly and concluded that cultivars and breeding materials should be rated annually, under different environmental conditions, if progress was to be made in breeding cultivars resistant to O3 damage (Tobacco Sci. 21: 29-30, 1977).
These same workers examined the effects of major fertilizer nutrients on weather fleck. They concluded that phosphorus was the most critical element affecting fleck, high levels producing the least fleck; nitrogen was secondary and potassium was irrelevant. They published a chart of optimum fertilization for two of the three cvs. used in the study, NC88 and Coker 347 (Moore, Reilly, Terrill, 1997).
Trevathan, Moore, and Orcutt (1979), investigated the effects of ozone on lipid concentration in two weather fleck-susceptible cvs. Ozone caused an increase in total lipid concentration; different ozone levels caused corresponding changes in lipid concentration but these changes were not correlated with symptom expression.
Small grains: During the Foy Era, 1974-1980, the project on breeding disease-resistant wheat and barley cultivars began to mature. T. M. Starling, the plant breeder; C. W. Roane, the plant pathologist; and H. M. Camper, Jr., agronomist and station superintendent at Warsaw, aided by a host of technicians but most notably research supervisors William Sisson at Warsaw and Allen Price at Blacksburg released several cultivars of barley. The cultivars, 'Henry', 'Surry', and 'Maury', all at the time of release in 1975, were resistant to powdery mildew, leaf rust, net blotch, and scald; some were highly tolerant of barley yellow dwarf virus. 'Maury', released a year later, was similar but susceptible to leaf rust and net blotch. All had stiff straw, excellent yielding ability and test weights. They fulfilled the aims to breed competitive, multiple disease resistant cultivars. These cultivars were registered in Crop Science in 1980 (Crop Sci. 20: 284-284, 1980).
Only one wheat cultivar, Potomac, was released during the Foy Era. This was a joint release with the Maryland Agricultural Experiment Station from a line bred in Virginia. It was characterized by resistance to leaf rust, powdery mildew and soil-borne viruses.
Some old diseases plagued our wheat and barley in the Foy Era. In 1972 and again in 1975, scab caused serious damage to wheat in Virginia. Distribution of wheat and variation in maturity assured that damage was spotty. The primary cultivars affected were 'Arthur' and 'Blueboy.' It was estimated that about 2% of the Virginia wheat crop was destroyed. However, because of the nature of the disease, it is very difficult to calculate the true loss. In addition to reduced grain yield, the fungus causing it, Gibberella roseum, produces a variety of toxins. When scab occurs, the threshed grain contains kernels covered with pink mycelium and spores. In the grain trade, these are called tombstones and when they are present above a certain percentage, the grain is graded scabby and is rejected by the buyer. The scab fungus kills several spikelets and the rachis at the site of infection, uninfected kernels distal to this site many ripen but are shriveled. This contributes to yield and test weight reduction. Rejected grain may be used by the grower as feed, but because it contains mycotoxins, such as T-2 toxin, zearalenone, emetic and refusal factors, it must be in a cost increasing process diluted with other scab-free grain to bring the toxins to such a low level that no symptoms occur in the recipient animals. Toxin levels can be determined and a safe dilution level may be prescribed, but the procedure is costly.
Stem rust struck eastern Virginian wheat fields unexpectedly in 1974 and 1975. Typically, in Virginia stem rust (Puccinia graminis) occurs only in southwestern Virginia where native or Alleghany barberry, Berberis canadensis, abounds. This plant is an alternate host of P. graminis and normally stem rust occurs only when wheat or oats are planted near it. Outbreaks in southwestern Virginia do not spread to eastern Virginia because crops in the Piedmont and Coastal Plain ripen before spores of the rust fungus can be produced in western Virginia and be blown eastward. For years, large wheat fields occurred in the barberry-infested areas and attempts were made to produce rust-resistant cultivars but wheat virtually disappeared from the region when by 1965, wheat production had shifted to the Coastal Plain. Breeding for stem rust resistance was deleted from the wheat breeding program.
In 1974, stem rust struck a number of cultivars in the Coastal Plain. Rust susceptible varieties, 'McNair 701' and 'Blueboy' had become widely planted in Southeastern U. S. and in the fall of 1973, Virginia fields were showered with spores. In early spring, pockets of rusted wheat in Georgia furnished additional inoculum that blew northeastward into North Carolina and Virginia where stems of McNair 701 were scored as high as 80% severity. The epidemic was repeated in 1975. Varieties growing in various nurseries in eastern Virginia reacted diversely. McNair 701, Blueboy, and their derivatives were severely rusted but 'Arthur' and 'Blueboy II' and many Virginia breeding lines remained rust-free. Before a breeding program to protect Virginia wheats was initiated, states to the south discontinued production of McNair 701 and Blueboy and the problem disappeared, in addition, no overwintering pockets were detected in the South. The episode reminded us that our crops remain vulnerable to freakish occurrences of plant diseases.
About 1972, labels for all mercurial seed treatment compounds were cancelled. There followed an increased incidence of barley stripe and covered smut. Mercurial compounds had been very effective against these diseases. In Virginia, the appearance of stripe in foundation, registered, and certified barley fields meant that some fields failed to qualify in their intended category. Roane and Starling collaborated to find the most efficacious products and favorable environmental regimes that would ensure the barley certified seed program would not be disrupted. In two years, (1979, 1980) of experimenting, carboxin at 6 and 8 oz/100 lbs seed, carboxin + thiram, and carboxin + mancozeb at 2 + 3 oz controlled stripe in early fall plantings (warm soil) but much higher rates were required in late fall plantings (cold soils). So we were caught between the proverbial "rock and a hard place." By planting early, stripe could be readily controlled but there would probably be a high incidence of barley yellow dwarf (BYD); by planting late, BYD would be of minor importance but stripe would be difficult to control (Barley Newsletter 25: 42-44, 1981). By using heavy doses of carboxin (Vitavax) plus thiram or mancozeb, Bruce Boehm, superintendent of the Virginia Crop Improvement Association farm at Mt. Holly, Westmoreland county, was able maintain the production of foundation barley seed without a loss.
Cephalosporium gramineum causes stripe of wheat, barley and rye in the Great Plains and Pacific Northwest. In 1975, it was detected in a small area of winter wheat nursery in Blacksburg. Its origin could not be determined (Pl. Dis. Reptr. 60: 345, 1976). In May 1977, symptomatic volunteer rye was observed near Blacksburg and in 1979, rye plants growing in a housing development where rye straw had been used for mulch to help establish a new lawn exhibited stripe symptoms. The straw was believed to be imported from Illinois. In Augusta county in June 1979, wheat and barley in yield trails on the Shenandoah Valley Research Station (the original Cyrus McCormick Farm) were symptomatic. The fungus was recovered from wheat but not from barley (Pl. Dis. 64: 325, 1980).
Corn: During the Couch Era, 1965-1974, maize virus diseases and gray leaf spot became very destructive in Virginia. In the Foy Era, there was a continued cooperative effort between agronomists and plant pathologists to improve resistance and decipher genetics of resistance to these diseases. Supplemental financial support was furnished by the Virginia Agricultural Foundation and Virginia Corn Commission.
Although tests for reaction to maize dwarf mosaic virus (MDMV) could be made at Blacksburg as a result of artificial inoculation, it was also necessary to obtain response to infection by maize chlorotic dwarf virus (MCDV). This could be done only in the presence of johnsongrass. Therefore, continued cooperation with a farmer, Cliff Wood, who lived at Wingina in Nelson County, where highway Va 56 crosses the James River, was considered necessary. Test plots had been planted on the Wood farm since the beginning of the couch Era. Cliff was an excellent cooperator who had learned to cope successfully with johnsongrass and as a result had reestablished a once failing corn crop as a profitable feed crop for his dairy herd. As a research cooperator, he always had the land ready at planting time. From 1974 to 1976, C. F. Genter was the cooperating breeder and C. W. Roane and Sue A. Tolin were the pathologists. Genter resigned and in 1977, H. S. Aycock replaced him. Fortunately, Aycock was interested in continuing to breed for and in studying genetics of MDMV resistance. The Wood farm remained the principal site for testing commercial hybrids for reaction to MDMV and MCDV. From data obtained there, varietal recommendations were made to farmers who had johnsongrass/virus problems. Experimental hybrids were also tested and from results with these, commercial seed corn producers selected appropriate inbred lines from which to make adapted, resistant hybrid varieties. Gradually, losses from the viruses were suppressed even though johnsongrass infestations persisted.
One study on the inheriatnce of reaction to MDMV had been completed by Roane, Tolin, and Genter. Only an abstract had been published (Proc. Amer. Phytopathol. Soc. 4: 140, 1977). Two resistant inbred lines, OhO7B and Pa91 and their progeny were scored in F1, F2, and F3 generations. OhO7B crosses segregated monogenically, resistance dominant. T8 crosses segregated in unexplainable inconsistent ratios. A significant fact of this work is in the manner of classification of individual plants. A new scale was devised in which seven types of responses were described. This was necessary because all previous classification scales had been devised for use in naturally infected populations where both MDMV and MCDV were present. The new scale is more useful where only MDMV is present. The scale was illustrated in the 1983 publication of this study (Phytopathology 73: 845-850, 1983). A further significant facet of this study was the pedigreed method of following progenies into the F3. Most previous genetic studies with MDMV reaction were based on estimating genes in diallel systems. This study was the first to use the methods Mendel had taught us and the outcome was entirely different from those previously published by others. It lay the groundwork for subsequent illuminating studies. Genetics of MDMV resistance was carried much beyond the Foy Era.
As mentioned earlier, gray leaf spot (GLS) was very damaging and because the no-till method of growing corn was becoming more popular, GLS was becoming even more damaging. At the second Interregional Corn Conference at Cincinnati, Ohio, February 9-12, 1976, Roane and Genter summarized the work they had done to find hybrid varieties and inbred lines resistant to GLS.
From observations on commercial hybrids through 1974, it was apparent that little resistance was available for immediate relief from GLS. Two hybrids, McNairX190 and Northrup-King PX79 gave the most resistant reactions but in nurseries where they were showered with spores from neighboring plots, it could not be predicted whether on a field basis they could offer adequate protection. This, incidentally, is one of the weaknesses of predicting field performance from small plot performance. In 1974, a test field in Augusta county with a record of sequential corn crops and severe GLS was used to test 193 commercial and experimental hybrids and 541 in bred lines. From this test 26 inbred lines were selected for intercrossing and 180 crosses were made and planted in 1976 at the Augusta county site. Eight inbred lines were identified as contributing the greatest resistance. The GLS tests in Augusta were continued in 1976 and 1977. No data was obtained in 1976 due to a severe drought but in 1977, two Northrup-King entries were superior among 18 commercial hybrids. Only one experimental V. P. I. hybrid exceeded them in resistance but it flunked the yield test. After 1977, no further work was done with GLS in the Foy Era.
Genter, the corn breeder resigned after the 1977 growing season; D. E. Brann, and R. L. Harrison, Extension Agronomists, managed the corn tests in 1978 and H. S. Aycock, corn breeder, resumed the corn breeding and testing program in 1979. Testing for GLS would be resumed in 1981.
Previous Table of Contents Next
VT History | Digital Library and Archives | Special Collections | University Archives
Send questions or comments to:
Tamara Kennelly, University Archivist
P.O. Box 90001
Blacksburg, VA, 24062-9001
Last Modified on: Thursday, 21-Oct-2004 13:15:24 EDT by Mark B. Gerus