Randolph G. Gardner
Randolph G. Gardner
S.J. Scott, J. McFerran, and M.J. Goode
James R. Baggett and R.O. Hampton
The inheritance of tolerance to infection by bean leaf roll luteovirus (BLRV) in Pisum sativum L. was studied in the cross of cv. Parlay (sensitive to BLRV infection) × cv. Oregon Sugarpod II (BLRV tolerant). The parents, reciprocal F1, back-crosses, F2, and 234 random F3 families were screened in 1986 and 1987 in the field at Twin Falls, Idaho, under natural BLRV inoculation by aphids. Overall disease index scores for the F1, F2, and F3 were about intermediate between indices of the parents, with the F1 usually slightly higher than midparent values. Backcross disease indices were intermediate between the F1 and the respective parent involved. Distribution of individual F3 family indices was continuous and semi-normal. BLRV-sensitivity ranges within parents and selected cultivars, as well as segregating populations showed continuous variation and differed between the 2 years, suggesting that expression of a major gene was significantly influenced by natural variation in BLRV inoculation pressure and timing. An apparent “additive gene action” was probably an artifact of nonuniform timing and levels of infection within plant populations. Chi-square analyses of segregating populations indicated that a major recessive gene, called lrv, conferred BLR disease tolerance.
J.R. Baggett, D. Kean, and N.S. Mansour
Wayne L. Schrader and Keith S. Mayberry
Randolph G. Gardner
Linda R. Fredrick and Jack E. Staub
Combining ability estimates for characters relating to yield and fruit quality were undertaken to determine if lines derived from Cucumis sativus var. hardwickii (R.) Alef. (hardwickii) could be used in the development of higher-yielding commercial cucumbers. General and specific combining ability estimates were obtained in a North Carolina Design II experiment for nine near-homozygous processing cucumber (Cucumis sativus L.) lines, five of which were derived from hardwickii germplasm. Lines were evaluated under two planting densities (29,000 and 58,000 plants/ha) for three harvests, and environments sampled were two planting times (2 weeks apart within the same year). Traits evaluated included fruit number per plant, primary lateral branch number, percentage of pistillate flowers, days to anthesis, fruit length, and fruit length : diameter (L:D) ratio. General combining ability (GCA) mean squares were significant at both planting densities for all traits when combined over planting times, except for fruit L:D ratio at the higher density. Specific combining ability mean squares were significant for days to anthesis. Of the lines evaluated, WI 2963 and 4H261 produced the greatest GCA female and male effects, respectively, for three harvest yield and primary lateral branch number, but the lowest effects for fruit size. Our results suggest that further selection within these high-performance hardwickii derivatives for fruit shape will produce lines that perform well at a high planting density when crossed with sativus lines having good general combining ability.
A. K. Nandgaonkar and L. R. Baker
From progenies of crosses between 2 multi-pistillate (MP) and 2 single-pistillate (SP) gynoecious pickling cucumber (Cucumis sativus L.) cultivars, it was determined that MP is recessive to SP expression. Genetic analyses suggested that one major gene with several modifying factors affect this character. The gene symbol proposed for multipistillate expression is mp.
I. I. S. El-Shawaf and L. R. Baker
The top cross method was used to judge the performance of 17 hermaphroditic lines (pollen parents) for parthenocarpic yield and associated characters of cucumber (Cucumis sativus L.). Hybrid yields of 3 to 6 parthenocarpic fruits per plant were observed with 68 to 99.5% gynoecious expression. Four hermaphroditic lines were judged outstanding based on their hybrid performance for the necessary high percent of gynoecious expression combined with high yield. Significant correlations were detected between days-to-flower and nodal position of first-pistillate flower, and between the latter and yield. Heritabilities were 64%, 63%, and 73% for days-to-flower, nodal position of the first-pistillate flower, and gynoecious expression, respectively. The heritability for yield (number of fruit/plant) of parthenocarpic fruits was 20%. Accordingly, plant breeders might enhance selection gains for associated characters, but realize somewhat less success for yield (fruit number).