Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] flesh color is controlled by several genes to produce red, orange, salmon yellow, canary yellow, or white. The objective of these experiments was to study the interaction of three independently reported gene loci, each having two or three alleles: C (canary yellow) versus c (red), y (salmon yellow) versus Y (red) versus y؇ (orange), and i (inhibitory to C) versus I (noninhibitory to C). The interaction of C, y, y؇, and i is of interest to those developing new cultivars of watermelon and has not been reported previously. Five crosses were used to study gene action: Yellow Baby ؋ Tendersweet Orange Flesh, Yellow Doll ؋ Tendersweet Orange Flesh, Yellow Baby ؋ Golden Honey, Yellow Doll ؋ Golden Honey, and Yellow Baby ؋ Sweet Princess. Based on performance of P A , P B , F 1 , F 2 , BC 1A , and BC 1B , the parents have the following genotypes: Yellow Baby ‫؍‬ CCYYII, Yellow Doll ‫؍‬ CCYYII, Tendersweet Orange Flesh ‫؍‬ ccy؇y؇II, Golden Honey ‫؍‬ ccyyII, and Sweet Princess ‫؍‬ ccYYii. Segregation of flesh color in the progeny of the five families supported the previous report of a multiple allelic series at the y locus, where Y (red) was dominant to y؇ (orange) and y (salmon yellow). In conclusion, epistasis is involved in the genes for major flesh colors in watermelon, with ii inhibitory to CC (canary yellow), resulting in red flesh, and CC (in the absence of ii) epistatic to YY, producing canary flesh.

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High temperatures encountered during the growing season reduce tuber dry matter content in commercial tetraploid potato (Solanum tuberosum L.). Variability in dry matter content as measured by specific gravity was observed in a diploid hybrid population of S. tuberosum Group Phureja and S. tuberosum Group Phureja and S. tuberosum Group Stenotomum grown under high temperatures. The objective of this research was to estimate heritability of specific gravity in this diploid hybrid population under high temperature growing conditions in North Carolina. Heritability was estimated by midparent offspring regression. Parents were grown at three high‐temperature locations and offspring at eight. Analyses of variance on specific gravity for each of the eight offspring locations revealed heterogeneity of error variances, therefore data were not combined over years and locations for further analyses. Twenty‐four estimates of heritability were obtained, 16 of which were unbiased (parents and offspring were grown in different years and different locations). The average unbiased estimate of heritability was 0.28 (range −0.07 to 0.77). Four estimates were biased because parents and offspring were grown at similar locations in different years. The average of these estimates was 0.57 (range 0.51‐0.63). Two estimates were biased because parents and offspring were grown in the same year in different locations, the average of which was 0.38 (range 0.29–0.46). Two estimates were biased because parents and offspring were grown in the same year at similar locations. These averaged 0.41 (range 0.40‐0.42). Considered together, the moderate estimates of heritability suggest that it should be possible to continue to improve this population for specific gravity under high‐temperature growing conditions. There was an apparent upward bias in the heritability estimates when the parents and offspring were not grown in different years and different locations.

No abstract

A laboratory procedure for assaying Lycopersicon spp. for resistance to the tobacco hornworm Manduca sexta (L.) is described. Results from this procedure, which employed excised foliage from greenhouse grown plants and first instar hornworm larvae from a colony maintained in the laboratory on artificial diet, were similar to those obtained with intact plants, with field collected hornworm larvae, and with field grown resistant plants. The Lycopersicon hirsutum f. glabratum accessions PI 134417 and LA 407 were highly resistant to M. sexta. Resistance was manifest as a significant reduction in larval survival and in weight gained by survivors over a 72 hour period. The interplant variation in larval weight gains within accessions was highly significant, suggesting that most of the accessions tested were segregating for resistance to M. sexta.