Abstract
Resistance to watermelon mosaic virus 1 in derivatives of Cucumis melo L., Plant Introduction (PI) 180280, was found to be controlled by a single dominant gene. The gene symbol Wmv-1 is proposed.
Abstract
The tendency for axillary head (AH) development in Brassica oleracea (Capitata group) was shown to be a heritable characteristic. In 11 crosses between high and low AH lines carried at least through the F2 generation, AH was recessive and largely controlled by one or a few genes. In other crosses, in which only the F1 generation was studied, AH tendency usually resembled that of the parent having a low level of AH, but in certain crosses was intermediate or closer to the high scoring parent. Expression of AH was continuous and apparently influenced by modifying genes and the environment. Broadsense heritability estimates were high, but narrowsense heritability estimates were very low indicating dominance effects. No consistent or apparently important differences were found between reciprocals. The weight of AH was not related to yield of main heads in F2 plants.
Abstract
The inheritance of 8 monogenically controlled plant, fruit, and seed characters in Carica species is reported. The gene for red stem is dominant to that for green stem and the gene for red petiole is dominant to that for green stem and the gene for red petiole is dominant to that for green petiole. Genes for white and purple-blush flower colors are dominant to those for pale yellow; while the gene for red skin color of ripe fruit is dominant to that for yellow. However, the gene for red skin color is not dominant to that for orange skin color; the heterozygote has pink-skinned fruits. The gene for ridging on the fruit (carpel fusion lines) is dominant to that for wide groove, which in turn is dominant to that for narrow groove. Spiny vs. non-spiny seed coat produces an intermediate F1, indicating no dominance. The gene for succulent fruit pulp is dominant to that for dry pulp. The gene for bushy branching is dominant to that for sparse branching.
Iron Deficiency Chlorosis (FeDC) is a problem in cowpea because it affects the ability of the plant to produce chlorophyll. Earlier studies indicated that FeDC was conditioned by a single gene. Pinkeye Purple Hull (PEPH), a susceptible variety, and Texas Pinkeye Purple Hull (TXPE), a resistant variety, were crossed and allowed to self for one generation. The F1s were backcrossed to the parents. SPAD readings were taken on each population. SPAD measures the transmission of light through the leaves at a wavelength where chlorophyll absorbs and a wavelength where it does not. The SPAD reading is calculated based on a ratio of these two numbers. Thus, the SPAD value is unitless and is an indication of the relative amount of chlorophyll present in the leaf. Chlorophyll was extracted from leaves, and regressed on the SPAD readings from the same leaves. An R 2 of .9102 was obtained as well as a regression equation of y = 12.8x + 54.5. Thus, a SPAD value of 1 corresponds with a chlorophyll content of ≈67.3 μg chlorophyll/gfw. The data was analyzed using a bootstrap method, and indicated that FeDC is not controlled by a single gene. A P-value of .0004 showed a highly significant difference between the expected and observed segregation ratios in the F2 plants. Narrow sense heritibility (Mather) was estimated at 0.3.
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.
Progeny of 158 F5 × F5 crosses of Antirrhinum majus (snapdragon) selected within and among cut flower postharvest longevity (PHL) categories (long = 12.6-16.8 days, middle = 9.3-12.1 days, and short = 4.8-8.9 days) were evaluated for PHL and quality traits. Results were compared with previous studies involving F2 × F2 progeny, and F3, F4, and F5 inbred lines. Heritability of PHL in F5 × F5 progeny (0.77 ± 0.11) agrees with that of inbred lines (0.79 to 0.81) but is higher than in F2 × F2 progeny (0.41). Therefore, selection for increased PHL should progress more rapidly and predictably through application of inbred lines rather than F2 individuals. Significant differences between F5 × F5 progeny PHL categories confirm PHL is heritable with a significant additive component. Heritabilities of quality traits in A. majus are high, suggesting selection for quality traits should progress without difficulty. Phenotypic and genotypic correlations of PHL with quality traits are not consistently significant across PHL studies in A. majus. Discrepancies between studies suggest most traits may not be correlated to PHL or are subject to strong environmental influence.