Few sources of physiological resistance to the fungal pathogen Sclerotinia sclerotiorum (Lib.) de Bary, causal organism of white mold disease in common bean (Phaseolus vulgris L.), have been found and exploited by breeders. Our objective was to screen a subsample of the core collection of P. vulgris accessions representing the active USDA National Plant Germplasm System collection of 1698 accessions from Central and South America for reaction to white mold using a greenhouse straw test. White mold reactions were rated for 89 accessions from 1 = no disease symptoms to 9 = total plant collapse. Eleven core accessions, Pis (plant introductions) 152311, 207136, 207154, 290990, 290995, 293353,313850, 415886, 415906, 415913, and 415936, with scores <5 were identified as having putative physiological resistance to white mold. An expanded screening among 35 accessions from the active collection which had similar passport data to the resistant core Pis 207136, 290990, and 313850 revealed 20 resistant accessions with disease scores <5. A similar expanded screening of 18 accessions with similar passport data to core Pis 310674, 313608, and 415954 that had scores >6, revealed only four accessions with scores <5. These results indicated that a subsample of the core collection was useful for identifying ranges of accessions within the active Phaseolus collection that possessed a high incidence of putative physiological resistance to white mold.

Five lines of dry beans (Phaseolus vulgaris L.) were selected for differences in protein content and were used as parents in crosses. The F1, F2, and F3 mean crude protein contents were generally between the parents, but slightly closer to the low‐protein parent. Reciprocal differences in protein of F1 seeds and its absence in F2 seeds showed that the maternal genotype controlled seed protein content.Broad‐sense heritability estimates ranged from 30.7% to 63.7%. The narrow‐sense heritability estimates were 20.1% for backcrosses and 5.0% and 12% based on F3/F2 regression. These low values indicate high environmental influence on crude protein content and relatively low additive genetic variance.Yield and crude protein percentage were generally negatively correlated in F2 and F3 plants from crosses between low and high percent crude protein bean lines. Seed yield and protein yield were highly correlated. The highest total seed protein was produced by plants average or below average in percent crude protein. In breeding for total protein production per unit area, progress appears more likely if efforts are directed toward increased seed yield while maintaining percent crude protein near average levels rather than by selecting for high protein in the seeds alone.Generally, high‐yielding segregates tended to be relatively low in protein percentage. Among F2 and F3 progenies, however, there were plants that were high in seed yield and had above‐average percent crude protein.

Resistance to black rot caused by the bacterium Xanthomonas campestris pv. campestris was studied in Brassica oleracea, B. campestris, and B. napus. Two accessions of B. napus, PI 199947 and PI 199949, exhibited the highest resistance so far found in cultivated Brassica spp. In B. napus, the high level of resistance was conferred by one dominant gene. In B. campestris, two Chinese cabbage accessions showed quantitative inheritance for moderate levels of resistance. Resistance was transferred to B. campestris from B. napus, but a unilateral incongruity was observed for black rot and morphology, but not for stem color or bolting. The bridge line 15 was used to transfer resistance to B. oleracea.

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Resistance to downy mildew [Peronospora parasitica (pers.) ex. Fr.] in broccoli (Brassica oleracea L. Italica Group) depends on plant age. Seedling resistance seems to be independent of mature-plant resistance, where a mature plant is defined as having eight or more leaves. Our results suggest that, by using mature-plant resistance, an almost continuous variation instable levels of mature-plant resistance can be developed. Similarities in the response of mature plants of various lines to isolates from California, Washington, New York, and South Carolina indicated that the predominant race was the same at all locations. Correlations between resistant and susceptible responses to isolates from California, Washington, New York, and South Carolina varied from r = 0.48 to 0.74 depending on isolate source. The results indicated that selecting for high levels of resistance in mature plants at one location should result in good resistance elsewhere in the United States. Selecting immature plants (three to six leaves) may provide less reliable results due to the transitional status of the plant; i.e., between seedling and mature plant.

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Bean lines (Phaseolus vulgaris L.) with good pod and plant type have been bred with the ability to germinate at 8 to 10 C. At temperatures of 10 C day and 8 C night these lines grew faster than the cultivars with which they were compared. Seed color and resistance to seed decay by soil organisms were strongly associated with good germination at low temperatures. However, a low percentage of white‐seeded lines also had good germination and decay resistance. Heritability for germination at low temperatures was about 35%. No specific segregation pattern was detectable.

Forty hybrid broccoli [Brassica oleracea L. (Italica Group)] accessions were screened for heat tolerance and holding ability over three planting dates in 1988 at the Long Island Horticultural Research Laboratory in Riverhead, N.Y. Holding periods were quantified using the number of consecutive days between the time individual heads reached 10 cm diameter and cutting, which occurred when the sepals had fully expanded and had just begun to separate. In 1989 and 1991, heat stress was applied at various weeks during maturation to determine the most sensitive stage or stages of plant development in terms of reduction in holding period and head weight. Field studies and heat stress experiments indicate that heat stress may be most critical during the time the immature inflorescence measures 5 to 10 mm in diameter. This stage corresponds to ≈ 3 weeks before harvest for summer plantings in the northeastern United States.