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- Author or Editor: R. Petzoldt x
Narrow sense heritabilities were 28%, 56%, 45%, and 74%, respectively, imbibition at 5°C and, at 16°, for seedling vigor, plant vigor, and days to bloom in a cross of NY 590 × BBL 92. Cold tolerance at these stages was inherited independently. Pod set at 16° behaved as a recessive, compared to only setting at warmer temperatures. Selections made under 16° generally did very well in an unusually cool season in New York. Double setting was absent in lines that showed set at 16°, and present in many cultivars.
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.
Heat at any growth stage can damage green beans (Phaseolus vulgaris L.), but plants are most susceptible at or near bloom. The effect of heat during the bloom period resulted in reduction of a yield in proportion to the duration of the heat period. The most critical growth stage was found to be 2 to 3 days before anthesis, rather than at anthesis itself. By subjecting F1 plants to heat during the bloom period, genetic selection for heat tolerance was moderately effective. The heritability for heat tolerance was quite low. Broad-sense heritability was 19% to 79% and narrow-sense heritability 0% to 14%. These values are probably conservative, since during the genetic study the heat period was initiated on the first day of bloom, which resulted in some escapes and excess variability.
Isogenic white-seeded (WS) lines of common bean (Phaseolus vulgaris L.) were developed from colored seeded (CS) lines by backcrossing and mutagenesis. Each CS line was selected for its specific resistance to Pythium, Fusarium, Rhizoctonia, seed corn maggot, mechanical damage, or cold tolerance. In all instances, the WS lines, with the p gene, were inferior to the CS lines with P.