Abstract
Bacterial pathogens cause destructive diseases on many important vegetable crops throughout the world. Satisfactory chemical control measures for bacterial pathogens have not been achieved. Recommended control measures are: use of disease-free seed and transplants; hot water treatment of seed if feasible; suitable rotations; deep plowing of plant debris; and use of resistant cultivars if available (13, 50, 51, 53, 73, 75, 76, 77).
Abstract
Most biologists agree that the genetic composition of the plant determines the potential response of the plant. Against this genetic background, the environment exerts its effect by enhancing or limiting the myriad of potential biochemical sequences that reside in the plant genotype.
Apical dominance, i.e., the inhibition of lateral bud growth due to growth substances released by the terminal bud, has been considered as a limiting factor for the perennial productivity of plantains (Musa spp., AAB group). Segregation ratios in F1 and F2 plantain-banana hybrids suggest that inheritance of apical dominance is controlled by a major recessive gene, ad. The dominant Ad allele improved the suckering of plantain-banana hybrids, as measured by the height of the tallest sucker at flowering and harvest. At harvest, the ratoon crop of the diploid and tetraploid hybrids had completed 70% to 100% of its vegetative development, whereas the ratoon of the plantain parents, due to high apical dominance, was only at 50% of total pseudostem growth. Sucker growth rates are generally the result of gibberellic acid (GA3) levels, and it is suggested that the Ad gene regulates GA3 production. However, the Ad gene has incomplete penetrance, genetic specificity, and variable expressivity. Increased frequency of the Ad gene and a commensurate improvement in the suckering behavior of the diploid populations may be achieved by phenotypic recurrent selection.
Avocado (Persea americana Mill.) progeny that originated from 11 crosses (both self-pollinations and crosses between cultivars) were evaluated for the length of their juvenile period. Time to first flowering, “flowering age,” and time to first fruit production, “fruiting age,” were recorded for each progeny. The mean values for both ages, the sd, and the progeny distribution were calculated. Significant statistical differences in flowering age and fruiting age between various progeny populations were detected. No differences were detected between self-pollinated plants and crosses. The time until first flowering was found to be the limiting factor in evaluation of seedlings.
Abstract
Nectary development in cytoplasmic male sterile (cms) Brassica campestris L. was partially restored through 3 cycles of selection for nectary size and number. No major anatomical differences between nectaries of normal and cms plants were apparent under light and scanning electron microscopes (SEM). Half-sib family analysis of nectary development showed negligible additive genetic variance but a prominent maternal effect. Differential response to selection observed in 3 pedigrees suggests the possibility of capitalizing on nuclear-cytoplasmic diversity for the improvement of nectary function.
Abstract
Red stem, found in PI 157083, is controlled by a single recessive gene, r. Red pigment appeared in vascular traces of hypocotyls about 2 weeks after planting. Seed coat color of red-stemmed plants was reddish or tan, in contrast to white or yellow seed coats of green-stemmed plants. Pale, a spontaneous mutant in a second backcross hybrid from ‘Campo’ × PI 180280, is controlled by a single partially dominant gene, Pa, which acts as a recessive lethal: Pa/Pa plants die; Pa/+ are pale; and +/+ are normal. Pale did not affect expression of red stem. Testcross segregations fit the expected ratio for independent assortment of the 2 loci.
Abstract
The inheritance of resistance to Fusarium solani f. phaseoli Kend. & Sny.) in Phaseolus vulgaris lines P. I. 203958 (N203), and 2114-12 which derives its resistance from P. coccineus, was studied under greenhouse and field conditions. It was concluded that: N203 and 2114-12 respectively possess 4 and 5-6 genes for resistance under the greenhouse-test conditions used; 4 of the 2114-12 genes for resistance are the same as the N203 genes; gene action is mostly additive but partial dominance of resistance appears in 9-13-week-old field-tested plants. Broad sense heritability was estimated as 62-64% under greenhouse conditions and as 22% and 79%, respectively, in 5 and 9-13-week-old field tested plants. The additive variance under greenhouse conditions was estimated as 72% and 40% respectively for resistance from 2114-12 and N203.
Abstract
Resistance to T. basicola was found in Phaseolus vulgaris lines P.I.203958 (N203) and 2114-12. To determine the inheritance of resistance, these 2 lines were crossed with each other and with the susceptible cv. Redkote. Greenhouse tests were conducted on parental, F1, F2, and backcross progenies of each of the 3 crosses, and on F3 progenies of crosses ‘Redkote’ × 2114-12 and ‘Redkote’ × N203. The data indicate that N203 and 2114-12 possess the same genes for resistance, that resistance is partially recessive, and that resistance is controlled by approximately 3 genes. Broad sense heritability was estimated as 59% and the additive variance as 39%.
Abstract
A crack resistant tomato strain,‘Oregon State University 251’ (OSU 251) with fleshy calyx, was crossed with non-fleshy calyx lines to produce F2 segregations of 1 fleshy : 2 intermediate : 1 non-fleshy and backcross ratios of 1 : 1. Short sepal length, wide lobe width, and thick calyx are pleiotropic effects of the fleshy calyx gene, fl. Comparative anatomy of calyx and pedicel is described. The fleshy pedicel of ‘OSU 251’ had the widest cortex, vascular bundle and pith areas, but the areas occupied by the vascular bundle and pith when expressed on a percentage basis were smaller than those of the other parental lines and F1’s. Fruits of segregates with fleshy calyx were significantly more crack resistant than those with non-fleshy calyx. Crack resistance in ‘OSU 251’ is thought not to be a pleiotropic effect of fl, but the fleshy calyx morphology is considered to be of value in selection of plants resistant to fruit cracking.