Three dry bean (Phaseolus vulgaris L.) genotypes differing in seedcoat color, mineral brown (P C D J G B v), yellow brown (P C D J G b v), and pale greenish yellow (P C D J g b v), were analyzed phytochemically. Kaempferol 3-O-β-d-glucoside (astragalin) was isolated and identified by nuclear magnetic resonance spectroscopy from all three genotypes, and was the main flavonoid monomer present. Flavonoid polymers (condensed tannins) were detected by thin layer chromatography, but anthocyanins were not detected in the three genotypes. High pressure liquid chromatography analyses indicated that astragalin was present at similar concentrations in pale greenish yellow and mineral brown genotypes, but was significantly lower in yellow brown. Presently, we do not know the functions of the G and B color genes, although the presence of astragalin in the three genotypes studied indicates these genes do not appear to act in a qualitative manner with regard to astragalin production, but may control the amount of astragalin present. Subtle differences in color between these genotypes may be due to the amount and type of tannins which have secondarily polymerized with phenolics and flavonoid monomers.
Selfed progenies were generated using 10 day-neutral genotypes from the University of California (UC) strawberry breeding program as parents and their offspring were classified for late-summer flowering response. The grandparents of each selfed progeny included one of four day-neutral genotypes and one of eight short-day genotypes. Under the null hypothesis of genetic control by a single locus with the allele for day-neutrality dominant to the allele for short-day flowering response, all of these day-neutral parent genotypes must be heterozygous and their selfed offspring were expected to fit a 3:1 ratio of day-neutral: short-day phenotypes. The percentage of day-neutral offspring observed over all progenies was 70.9%, and was significantly smaller than the expected value of 75% (χ2 1 = 5.08, P < 0.02). The percentage of day-neutral offspring for individual progenies ranged from 41.4% to 84.8%, and highly significant heterogeneity was detected among progenies (χ2 9 = 40.3, P < 0.01). Selfed progeny means for the cumulative late-summer flowering score calculated using the day-neutral fraction of offspring varied from 1.31 to 2.35 and progeny means for the number of inflorescences per plant ranged from 3.5 to 9.9; these differences among progenies were highly significant (P < 0.01). These observations can be used to conclusively reject the hypothesis that day-neutrality in this domestic strawberry population is controlled by a single locus.
Means and variance components were estimated for genotype, environment (year), and genotype-year interactions for 28 nut and kernel traits of almond (Prunus amygdalus Batsch). The analysis involved over 2,500 genotypes and 20 years of observations. Estimates of heritability were obtained for 19 traits. The latter analysis involved some 100 families. The genetic component of variance and heritabilities tended to be large for shell type, size, shape, double kernels, bitterness, and crease. Year and genotype-year effects were large for quality factors such as shell and kernel color, callus, shriveling, pubescence, grade, blanks, smoothness, gumminess, and broken and split kernels.
Disease of beans, particularly common bacterial blight (CBB) (DR, NE), rust (DR, NE), web blight (WB) (DR) and bean golden mosaic virus (BGMV) (DR) are major constraints to bean yields and seed quality. The objectives were to identify resistant (R) germplasm, to conduct genetic studies, to develop R cultivars (DR, NE), to improve research facilities and capabilities (DR), to train personnel and educate graduate students (DR, NE). The expected impact is (1) the improvement of breeding programs, yields and income to farmers and (2) returning specialists will permit improved research in the DR. The most significant advances in research were as follows: (i) BAC-6 dry bean breeding line was found to be R to CBB seed infection, (ii) The reaction to CBB was inherited quantitatively with low NSH estimates, (iii) Rust race nonspecific R was correlated with abaxial leaf pubescence; the latter trait was inherited qualitatively, (iv) R to BGMV and WB were identified and (v) Improved cultivars and breeding lines were developed (DR, NE).
Phaseolus coccineus was found to be cross-pollinated because of extrorse stigmas, hairs around the stigmas, and dehiscence of self-pollen on stylar hairs below the stigmas. Phaseolus coccineus was found to be self-fertile when self pollen was pushed through the stigmatic hairs onto the stigmatic surface. Application of White's nutrient solution to P. coccineus stigma surfaces prior to pollination with P. vulgaris pollen resulted in pollen germination and fertilization. Mature seed with viable hybrid embryos developed in pods with partially broken pedicels and in those removed from the plant and cultured in sealed ‘Ziploc’ bags. Use of these techniques open up new possibilities in bean breeding. Pollen viability was high in the F1 P. coccineus × P. vulgaris, but low in the reciprocal F1. Stigma shape of P. coccineus was dominant in the former F1 but not dominant in the reciprocal. Stigma shape, hairiness of stigma, and cotyledon position were inherited quantitatively in the cross P. vulgaris × P. coccineus, while discrete segregation for cotyledon position was observed in the reciprocal cross. Cotyledon position, stigma shape, hairiness and flower color were controlled by cytoplasmic as well as genic factors.
162 ORAL SESSION 46 (Abstr. 344–350) Genetics/Vegetable
Root knot caused by Meloidogyne spp. is an important disease of cucumber. Resistance to M. javanica in cucumber (Cucumis sativus L.) is conferred by the newly discovered mj gene. The objective of this research was to determine whether mj was linked to other genes controlling morphological or disease resistance traits in cucumber. Four inbred lines homozygous for mj (LJ 90430, `Manteo', NCG-198, and NCG-199) were crossed with inbreds (`Coolgreen', M 21, NCG-101, WI 2757, and `Wisconsin SMR 18') to form six families: NCG-101 × LJ 90430, WI 2757 × LJ 90430, NCG-199 × `Wis. SMR 18', NCG-198 × M 21, `Manteo' × M 21, and NCG-198 × `Coolgreen'. F2 progeny were evaluated in all families, and BC1 progeny were evaluated only in the NCG-199 × `Wis. SMR 18' family. Meloidogyne javanica resistance and the 17 other traits controlled by simple genes were evaluated in greenhouse or field tests. None of the 17 genes were linked with mj. Therefore, cucumber breeders interested in nematode resistance should be able to incorporate the trait into lines without having to break linkages with the 17 genes used in this study.
Leaf emergence was studied on main and first-order shoots of peach and nectarine [Prunus persica (L.) Batsch.] trees belonging to nine standard cultivars, during their first growing season. The number of emerged leaves was recorded on main shoots (originating from the grafted buds) and on first-order shoots (inserted directly on main shoots). Similarly shaped leaf emergence curves were observed on main and first-order shoots for all the cultivars. Leaf emergence rate decreased gradually as the number of leaves increased. The number of emerged leaves could be modeled as a monomolecular function of accumulated thermal units. Significant differences were found between cultivars in a multiple analysis of variance of the model parameters, for main and first-order shoots. The ranking of the cultivars was similar for both types of shoots. Leaf emergence rate was lower on first-order shoots than on main shoots. Differentiating between shoot types is necessary for a reliable comparison of genotypes.
The B-biotype sweetpotato whitefly, Bemisia tabaci (Gennadius), feeds on and damages numerous vegetable crops including watermelon (Citrullus sp.). Seven watermelon cultivars, a triploid line, and 16 U.S. Plant Introduction accessions (PIs) of C. lanatus var. lanatus; 10 PIs of C. lanatus var. citroides; and eight PIs of C. colocynthis, were evaluated for resistance to B. tabaci. Bioassays were based on nonpreference and performance of the whiteflies on the 42 Citrullus genotypes. Most of the watermelon cultivars and C. lanatus PIs tested were highly susceptible to whitefly infestation, while the C. colocynthis accessions exhibited whitefly resistance. Among the C. colocynthis accessions tested, PI 386015, PI 386018, and PI 386024 were most resistant to B. tabaci. This study identified useful sources of germplasm that can be used for the improvement of watermelon for resistance to whiteflies.
Selection for and incorporation of host plant resistance into cultivars is a fundamental strategy to control insects and diseases and may help reduce reliance on synthetic pesticides. The sweetpotato whitefly, Bemisia tabaci (Gennadius), is an important pest of watermelon [Citrullus lanatus (Thunberg) Matsum. and Nakai var. lanatus] and is among the most damaging pests in many agricultural systems worldwide. Citrullus colocynthis L., a perennial melon species indigenous to arid regions of northern Africa, the Mediterranean region, and southwestern Asia, is a valuable source of resistance to insect pests and diseases of watermelon. Laboratory and greenhouse experiments were conducted to evaluate selected C. colocynthis genotypes for sources of resistance to B. tabaci. Thirty genotypes of C. colocynthis, collected in different geographic regions, were evaluated against the heirloom cultivar Calhoun Gray using first a horizontal Y-tube olfactometer in the laboratory. A selected subset of the genotypes was evaluated in a second experiment in the laboratory using a vertical monitoring assay. In this assay, whiteflies could freely move upward to feed and oviposit on leaves placed in the upper portion of a Y-tube. In a third experiment, a choice assay was conducted on selected genotypes in cages in the greenhouse. Of the 30 C. colocynthis genotypes evaluated, PI 346082 (collected in Afghanistan) exhibited the highest level of resistance against B. tabaci based on all three experiments. PI 537277 (collected in Pakistan) exhibited a significantly high level of whitefly resistance based on low survival of adult whiteflies and a low ratio of nymphs to eggs. PI 346082 and PI 537277 should be a useful source for breeding projects aiming to improve whitefly resistance in watermelon cultivars.