Inheritance of a twisted pod characteristic, in which bean pods develop with a twist that sometimes exceeds 360°, was studied in crosses between round-podded green bean cultivars. In crosses between `Oregon 91G' (normal) or `Oregon 54' (normal) and OSU 5256-1 (twisted), the F1 was normal. Segregation in F2 populations, tested over a 4-year period and including 4,995 plants, clearly fit a 3 normal: 1 twisted ratio. All plants of backcrosses of the F, to the normal parent were normal and backcrosses of the F1 to the twisted parent segregated 1 normal: 1 twisted. The ratios observed indicated that twisted pods are conditioned by a single recessive gene for which the symbol tw is proposed.
‘Gallatin 50’, a bush cultivar not of ‘Blue Lake’ background, and ‘Oregon 1604’, a bush cultivar of ‘Blue Lake’ type, were crossed with distortion susceptible lines of ‘Blue Lake’ type. Environment affected distortion expression; the best expression was obtained in the greenhouse while expression was much reduced in the field. Ratios obtained suggested distortion is primarily controlled by a single dominant gene, designated Ld. ‘Oregon 1604’ carries the recessive allele for normal. ‘Gallatin 50’ carries a major dominant gene, designated Ds, that supresses the expression of the dominant gene Ld for leaf distortion tendency. Results also suggested that modifying factors are involved and are responsible for levels of susceptibility among parents and progenies. Additional crosses between susceptible lines showing severe to mild distortion indicated that these lines carried the same major genes for distortion, but differed in modifying factors.
The heritability of efficiency in phosphorus utilization under deficiency stress was investigated using 6 bean families derived from crosses between selected efficient, moderately inefficient, and inefficient lines. Total plant dry weight (DW) was used as an index of efficiency. Epistasis, notably additive by additive and dominance by dominance gene effects, made imyor contributions to the efficiency in P utilization. Additive and dominance gene effects also made significant contributions. Estimates of broad sense heritability for total plant DW showed that efficiency in P utilization was a highly heritable trait. Narrow sense heritability estimates for total plant DW were high in all families studied.
Commercial pea (Pisum sativum L.) cultivars, plant introduction (PI) lines, and Oregon State Univ. (OSU) breeding lines were tested for resistance to pathotype P2 (lentil strain) and pathotype P1 (type strain) of pea seedborne mosaic virus (PSbMV) and to bean yellow mosaic virus (BYMV) to assess the relative proportion of resistant and susceptible pea genotypes. Of the 161 commercial cultivars tested, 117 (73%) were resistant and 44 were susceptible to PSbMV-P2. Of these PSbMV-P2-resistant cultivars, 115 were tested for resistance to BYMV and all were resistant. Of the 44 PSbMV-P2-susceptible cultivars, 43 were tested for BYMV susceptibility and all were infected except two, `Quincy' and `Avon', both of which were susceptible to a BYMV isolate in another laboratory. Of 138 commercial cultivars inoculated with PSbMV-P1, all were susceptible. All PI lines and OSU breeding lines that were resistant to PSbMV-P1 were resistant also to PSbMV-P2. The high percentage of commercial cultivars resistant to PSbMV-P2 was probably attributable to the close linkage of genes sbm-2 and mo and the widespread use by breeders of BYMV-resistant `Perfection' and `Dark Skin Perfection' in developing new pea cultivars. Segregation ratios in progenies of three separate crosses between PSbMV-P2-resistant and PSbMV-P2-susceptible cultivars closely fit the expected 3 susceptible: 1 resistant ratio expected for resistance conferred by a single recessive gene.
The inheritance of resistance to neck rot, incited by Botrytis allii Munn, was studied in four crosses between resistant and susceptible bulb onion (Allium cepa L.) lines, one cross between two resistant lines, and one cross between two susceptible lines. Using tests of excised scale pieces inoculated with a spore suspension and incubated in plastic boxes at 20C for 6 days, parents, F1, F2, and backcrosses were assigned disease indices (DI) derived from infection severity scores of individual bulbs. Generation means and frequency distribution of DI indicated that inheritance was quantitative and mostly additive with a small amount of dominance for susceptibility. Estimates of gene effects using a three-parameter model also indicated that additive effects predominated, with some dominance and no epistasis. Broad-sense heritability estimates ranged from 42% to 63% in the resistant x susceptible crosses.
Analysis of parents and progeny generations of bulb onion (Allium cepa L.) crosses among parents with differing content of soluble solids (SS) and pyruvic acid (PA) showed that SS and PA are expressed and inherited in a quantitative manner. Distribution of SS and PA in both parents and progenies covered a range of values. Generation means, frequency distributions, deviation from midparent value, and estimates of gene effects all indicated that inheritance of SS and PA was additive, except for small deviations from the additive hypothesis in several individual backcrosses. Estimates of broad-sense heritability ranged from 48% to 53% for PA and 8 % to 56 % for SS. Phenotypic correlations between PA and SS estimated from the F2 generations of two crosses, were moderate and positive (r = 0.50 and 0.42).
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.
Broccoli (Brassica oleracea L. Italica Group) lines with heads borne above the foliage (exserted) favorably for mechanical harvest were crossed with inbred lines with nonexserted heads. Length of the heads, defined as the portion of the plant above the highest major leaf, was ≈50% of the total plant height in short and tall parents and all plants of the F1, F2, and backcross generations. The principal characteristic identified with good head exsertion was long internodes. Internode length was inherited mostly in an additive manner, with some effect of hybrid vigor apparent in the F1, F2, and backcross to the tall parent. Plant height was also inherited in an additive manner. Head weight in the high-exsertion parent was much lower than in the low-exsertion parent. Within each parent and the F1, head weight was greater in plants with longer internodes and greater plant height. In the segregating generations (F2 and backcross), head weight increased with decreasing internode length, indicating that selection for high head exsertion would result in smaller heads and reduced yield.
Experiments were developed to study the inheritance of the high level of tolerance to the herbicide bentazon exhibited by the pepper (Capsicum annuum L.) cultivar Santaka. Parental, F1, F2, and backcross populations of the cross `Santaka' × `Keystone Resistant Giant' were evaluated for injury in a greenhouse test using bentazon at a rate of 4.5 kg·ha-1 (1.1 kg×ha-1 is the rate recommended for most applications). Additionally, parental and F1 populations were evaluated for injury under field conditions using sequential bentazon applications of 4.5, 4.5, 6.75, and 9.0 kg·ha-1. A single, dominant gene determined tolerance. F1 hybrid plants (heterozygous at the locus conditioning tolerance) exhibited a high level of tolerance under field conditions. Results of the greenhouse test suggested a possible cytoplasmic involvement in the expression of the tolerance gene, but the results of the field test provided strong evidence that cytoplasm does not play a significant role. We propose that this gene be designated Bentazon tolerance and symbolized Bzt. Chemical name used: 3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide (bentazon).
Monoecious cucumber (Cucumis sativus L.) parents with high, medium, and low percentage of nodes with distillate flowers had a stronger effect on the percentage of gynoecious plants in F1 and F2 progenies than did degree of gynoecious expression in incompletely gynoecious parents. Highest percentages of gynoecious plants were obtained by using both gynoecious and monoecious parents with the highest level of distillate flowering tendency. According to our data, monoecious parents with a low percentage of distillate flowering nodes should be avoided when gynoeciousness is transferred to monoecious cultivars. Self-pollination of gynoecious F2 plants, requiring induction of staminate flowers by chemical treatment, was more effective in obtaining a high percentage of gynoecious plants in F3 progenies than selfing predominately gynoecious plants, or sibmating predominately gynoecious plants.