Green seedcoat, a mutant discovered in a normally white-seeded breeding line, Ala. 963.8, of southernpea, Vigna unguiculata (L.) Walp. is controlled by a single recessive gene. The green seedcoat, which persists to dryness, results in a product uniform in color with improved consumer appeal in the frozen pack.
Screening for resistance to blackeye cowpea mosaic virus (BlCMV) and rootknot nematode on the same plant is possible if the two pathogens do not interact significantly. To determine if such interactions were present four cultivars were planted in 72-cell styrofoam flats, with a combination of BlCMV and nematode inoculations (--, -+, +-, and ++). `Freezegreen' is known to be susceptible to both pathogens, `Mississippi Silver' is resistant to both, `California Blackeye #5' is susceptible to BlCMV, and `Worthmore' is resistant to BlCMV. Nematode treated seeds were inoculated at planting with 2,000 eggs of (Meloidogyne incognita Race 3); BlCMV was inoculated on primary leaves a week later. Plants were visually rated for symptoms: either negative or positive for BlCMV and 1-5, no galls and heavily galled respectively, for rootknot. Analyses of variance using percentage of plants negative for virus symptoms or average nematode score as the dependent variable, resulted in non-significant virus × nematode interactions. Results by cultivar indicated simultaneous screening did not change their resistance/susceptible classifications.
Nine southernpeas, varying in their resistance to cowpea curculio, and the susceptible California Blackeye # 5 (CBE) were tested with six treatments: methyl parathion and endosulfan at recommended and one-quarter rate, a control with tractor traffic, and one without traffic. CBE had 42.7% curculio-damaged seeds over all treatment, while resistant entries ranged from 3.7% to 9.5%. Over all entries, methyl parathion at the recommended rate resulted in the lowest percentage of curculio-damaged seed (7.3%); endosulfan at the recommended rate was next with 9.1%. The percentage of damaged seed was not significantly different for the methyl parathion and endosulfan treatments using one-quarter recommended rates, the control with traffic, and the control without traffic—10.8%, 11.2%, 12.6%, and 11.7%, respectively. `Carolina Cream' (3.7% damaged seed over all treatments) and methyl parathion at the recommended rate resulted in the lowest percentage of curculio damaged seed: 1.3%.
An antibiotic type of resistance has been demonstrated in sweet corn inbred lines and hybrids by periodic growth measurements of corn earworm larvae feeding on resistant and susceptible types. Resistant types could be distinguished readily from the susceptible by a significant increase in larval mortality on the former. Resistant lines also retarded larval growth, decreased depth to which larvae penetrated the ear, and delayed pupation of the insect.
The force necessary to puncture pods of southernpea (Vigna unguiculata (L.) walp) was measured with a Model 1122 Instron fitted with a 1 mm diameter stainless steel probe. ‘California Blackeye No. 5’ and the breeding lines CR 22-2-21 and Ala 963.8 represented types with low, intermediate and high pod factor resistance, respectively, to the cowpea curculio, Chal-codermus aeneus (Boh.). Pods were selected at 7 stages of maturity for each type. There were no consistent differences in pod puncture force at the 3 immature stages, but at the 4 mature stages pod puncture forces for the resistant lines were significantly higher than for the susceptible cultivar.
The inheritance of resistance to cowpea chlorotic mottle virus (CCMV) in southern pea, Vigna sinensis (L.) Savi., Plant Introduction 255811, was determined in crosses with the susceptible cvs. Knuckle Purple Hull, Mississippi Silver, and Princess Anne. Segregation of F2 and backcross populations indicated that resistance to CCMV in P.I. 255811 is governed by 1 major recessive gene pair.
A high level of resistance to the cowpea strain of bean yellow mosaic virus (BYMV-CS) in southern pea, Vigna sinensis, was found in P.I. 297562. Its mode of inheritance was determined in crosses with 3 susceptible cvs.: Knuckle Purple Hull, Mississippi Silver, Princess Anne, and an Alabama breeding line, Ala. 562.3-1-2.
Results of virus inoculation tests of F1, F2 and backcross populations showed that resistance in P.I. 297562 was governed by a single recessive gene pair. The high level of resistance of P.I. 297562 should prove valuable for breeding and development of resistant cultivars.
Germplasm accessions and advanced lines were evaluated for seed transmission of the seed borne viruses, cucumber mosaic (CMV), cowpea severe mosaic (CSMV), and blackeye cowpea mosaic (B1CMV). Seed samples from 822 field plots (274 out of 300 accessions in 3 replications) which had been evaluated for insect resistance in 1992 were planted in the greenhouse. Mosaic virus symptoms had been apparent throughout the 1992 field planting. Evaluation for mosaic symptoms was done at the seedling stage in the greenhouse and 89 entries exhibited seed borne virus symptoms in one or more plants. Of these, 78 were shown by ELISA (enzyme linked immunosorbant assay, direct antigen coating method) to contain at least one of the seed borne viruses for which we were evaluating.
Four southernpea (cowpea) [Vigna unguiculata (L.) Walp.] cultivars representing various combinations of resistance and susceptibility to blackeye cowpea mosaic virus (BlCMV) and southern root-knot nematode [Meloidogyne incognita (Kofoid and White) Chitwood] were used to determine effectiveness of simultaneous screening of plants for resistance to both pathogens. Plants were inoculated with both pathogens simultaneously, each pathogen separately, or left uninoculated as controls. The resistance classification of the cultivars based on treatments with only one pathogen was not different from that based on the treatment with both pathogens. Virus × nematode interaction was not a significant source of variation in BlCMV symptoms and root-knot nematode galls. Simultaneous screening for both pathogens in southernpeas appears to be a feasible option.
Seed harvested from 41 entries in the 1994 southernpea variety trial was grown in a greenhouse for evaluation of seedborne mosaic viruses. When second trifoliate leaves were fully expanded, 100 plants per plot per block (4) were evaluated for blackeye cowpea mosaic virus (B1CMV), cucumber mosaic virus (CMV), cowpea severe mosaic virus (CSMV), and southern bean mosaic virus (SBMV). The average number of plants with virus symptoms ranged from 2% (Pinkeye Pinkpod) to 44% (Bettergreen). Plants with symptoms were assayed using enzyme-linked immunosorbent assay (ELISA). At least one virus was detected with ELISA in all entries, except for `Zipper Cream' in which none were evident. All viruses were detected in seven entries. B1CMV and CMV were present in 13. CMV was present in all but `Zipper Cream', `Mississippi Cream', and `Texas Pinkeye'. Symptomatology was poorly correlated to ELISA results: six entries having all four viruses had symptoms on less than 13% of their plants.