‘Bailey’ (Reg. No. CV‐111, PI 659502) is a large‐seeded virginia‐type peanut (Arachis hypogaea L. subsp. hypogaea var. hypogaea) with partial resistance to five diseases that occur commonly in the Virginia‐Carolina production area: early leaf spot (caused by Cercospora arachidicola Hori), late leaf spot [caused by Cercosporidium personatum (Berk. & M.A. Curtis) Deighton], Cylindrocladium black rot [caused by Cylindrocladium parasiticum Crous, M.J. Wingf. & Alfenas], Sclerotinia blight (caused by Sclerotinia minor Jagger), and tomato spotted wilt (caused by Tomato spotted wilt tospovirus). It also has partial resistance to southern stem rot (caused by Sclerotium rolfsii Sacc.). Bailey was developed as part of a program of selection for multiple‐disease resistance funded by growers, seedsmen, shellers, and processors. Bailey was tested under the experimental designation N03081T and was released by the North Carolina Agricultural Research Service (NCARS) in 2008. Bailey was tested by the NCARS, the Virginia Agricultural Experimental Station, and five other state agricultural experiment stations and the USDA‐ARS units participating in the Uniform Peanut Performance Tests. Bailey has an alternate branching pattern, an intermediate runner growth habit, medium green foliage, and high contents of fancy pods and medium virginia‐type seeds. It has approximately 34% jumbo and 46% fancy pods, seeds with tan testas and an average weight of 823 mg seed−1, and an extra large kernel content of approximately 42%. Bailey is named in honor of the late Dr. Jack E. Bailey, formerly the peanut breeding project's collaborating plant pathologist.
Sclerotinia minor is a major pathogen of peanut in North Carolina, Virginia, Oklahoma, and Texas. Partial resistance to S. minor has been reported based on field screening, but field performance is not always correlated with laboratory or greenhouse evaluations of resistance. More efficient screening methods and better understanding of the mechanisms contributing to Sclerotinia blight resistance are needed, and a detached leaf assay was developed and evaluated. Detached leaflets of 12 greenhouse-grown peanut lines were inoculated on the adaxial surface with a 4-mm-diameter mycelial plug of a single isolate of S. minor. Leaflets were incubated in the dark at 20°C in Nalgene utility boxes containing moistened sand. Lesion length 3 days after inoculation ranged from 11 to 24 mm, with a mean of 19 mm. Lengths differed significantly among the entries, with GP-NC WS 12, an advanced breeding line derived from a cross of NC 6 × (NC 3033 × GP-NC WS 1), being the most resistant. Forty-eight isolates of S. minor obtained from peanut were inoculated on leaflets of the susceptible cultivar NC 7 and aggressiveness was assessed by measuring lesion-length expansion. Three days after inoculation, lesion length differed among the isolates and ranged from 2 to 24 mm, with a mean of 15 mm. Finally, the potential for specific interactions between peanut lines and S. minor isolates was evaluated. A subset of S. minor isolates was selected to represent the observed range of aggressiveness and a subset of peanut entries was selected to represent the range of resistance or susceptibility. Nine-week-old greenhouse- or field-grown plants were compared for five peanut entries. Main effects of isolates and entries were highly significant, but isolate-entry interactions were not significant. The most resistant peanut entry (GP-NC WS 12) performed consistently with all isolates regardless of plant source.
Pod rot diseases historically caused significant losses in peanut production in North Carolina. Advances in the understanding of pod rot diseases and changes in cultural practices minimized losses in the years since 1979. By the early 1990s, however, some peanut growers began to observe pod rot that apparently was not associated with infection by common soilborne pathogens. Incidence of pod rot also was high in research plots used to study conservation tillage methods. Selected farms were surveyed in the fall of 1994, 1995, and 1996 to identify the fungi associated with pod rot symptoms in North Carolina. Over the three years of the study, more than 6,000 symptomatic pods from 125 peanut fields were assayed for Rhizoctonia spp., Pythium spp., Cylindrocladium parasiticum, Sclerotium rolfsii, and Sclerotinia minor. All five pathogens were isolated during the field survey, with Pythium spp. and Rhizoctonia spp. isolated most frequently. Rhizoctonia spp. were the dominant pathogen in the majority of fields in 1994, whereas Pythium spp. predominated in 1995 and 1996. Combinations of pathogens were identified from 12 to 15% of pods; Rhizoctonia spp. + Pythium spp. and Pythium spp. + C. parasiti-cum were the most frequent combinations. The mean estimated incidence of pod rot was 6.6% in 1995 and 5.9% in 1996. The effects of cover crops and tillage on pod rot incidence were studied in microplots in 1995 and 1996. In 1995, winter cover crops (wheat, oat, rye, and fallow soil) did not affect pod rot incidence, but incidence was greater in no-till treatments compared to plots with conventional tillage. Pod rot incidence did not differ among infestation treatments and no interactions among pathogen, cover crop, or tillage treatments were significant. In contrast, significant (P = 0.04) interactions among winter cover crops and tillage occurred in 1996. Tillage did not affect pod rot incidence following wheat or oats, but incidence following rye was much greater in no-till than in tilled plots.
Cylindrocladium black rot (CBR) caused by Cylindrocladium parasiticum and Sclerotinia blight caused by Sclerotinia minor are two economically important diseases of peanut (Arachis hypogaea) in the Virginia-Carolina production area. Developing cultivars with resistance to both diseases requires screening of new peanut breeding lines for resistance. Because field evaluations of resistance to these diseases often fail to produce usable results, greenhouse protocols were used to screen breeding lines and cultivars for resistance. For CBR, two seeds of a genotype were planted in a ''cone-tainer'' filled with a planting medium artificially infested with 25 microsclerotia of C. parasiticum per g of medium. After approximately 8 wk, the roots were washed and rated for degree of decay on a 0-5 proportional scale (0 5 no decay to 5 5 completely decayed). For Sclerotinia blight, plants were inoculated at 6 wk after planting by pushing a plug of potato dextrose agar (PDA) colonized by S. minor and protected from desiccation in a BEEM embedding capsule onto a freshly cut petiole on the main stem of the plant. Inoculated plants were placed in a mist chamber to maintain the high humidity necessary for infection. Lesion lengths were measured 4, 5, 6, and 7 days after inoculation, and areas under the disease progress curves (AUDPC) were calculated. All tests were conducted as incomplete block designs with six replications for CBR tests and four replications for Sclerotinia blight tests. Adjusted entry means were computed from each year's tests and used in summary analyses. Of the 125 breeding lines and checks tested at least once from 2003 through 2006, 51 were tested in at least two years, 34 in at least three years, and 15 lines were tested in all four years. Of the 15 lines tested in all four years, registered germplasm line N96076L had the lowest AUDPC for Sclerotinia blight (58 mm days), but had the greatest CBR root decay score (4.1 decay rating units). Several closely related breeding lines descended from a cross of N96076L and NC 12C were not significantly different from the most resistant line for either disease with scores ranging from 2.2-3.0 decay rating units for CBR and 63-99 mm days for Sclerotinia blight. Correlations of multiple-year greenhouse assay means with field disease incidence means were 0.83 for CBR and 0.35 for Sclerotinia blight. The greenhouse assay for CBR was a reasonably good predictor of field performance, but the assay for Sclerotinia blight was less reliable as a predictor.
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