Abstract
Length of the fruit development period in Florida breeding populations of low-chilling peach (Prunus persica L. Batsch) had estimated heritability values of 0.73 to 0.98. High genetic correlations were found between leaf color classes and length of fruit development periods.
Abstract
The inheritance of peroxyacetyl nitrate (PAN) resistance in Petunia hybrida Vilm. was studied using the inbred parents of ‘White Cascade’, a susceptible F1 hybrid, and ‘Coral Magic’, a resistant hybrid. In each of 6 experiments, 4-week-old plants of the parents, their reciprocal F1 hybrids, the F2 generation, and reciprocal backcross generations were simultaneously tested for PAN resistance. Plants were exposed to 742 μg/m3 (0.15 ppm) PAN for 1.5 hours in a controlled environment chamber. The percent area of bifacial necrosis was determined for each leaf on a plant and an average was calculated to yield an injury rating. Significant genetic variation was detected in each experiment, but the best fitting genetic model varied among experiments, indicating large genotype by environment interaction. In the experiment with the most severe PAN injury, genes for susceptibility exhibited almost complete dominance to those for resistance and epistatic effects were not significant. In other experiments with lower levels of PAN injury, resistance was partially dominant to susceptibility and one or more epistatic parameters were significant.
Abstract
Pale green lethal seedlings of apple (Malus spp.) are characterized by yellowish green color, poor growth of lateral roots, of epicotyl and of leaves, early cessation of apical meristematic activity, and death of the whole plant in about 1 month. Lethal seedlings occur in about 25% of the progeny of 2 heterozygous diploid parents. By this test we determined the homozygosity of 107 diploids (LL) and the heterozygosity of 97 diploids (LI). Among tetraploids 12 were quadriplex (LLLL) and 8 were probably duplex (LLll) or triplex (LLLl), but the expected ratios were not obtained.
Abstract
Attempts to select for flower bud chilling requirement (CR) at the seed stage were made in 58 families obtained from crosses and open-pollination of low chill selections and cultivars of peach and nectarine [Prunus persica (L.) Batsch] from the Florida breeding program. A nonsignificant correlation (r = 0.08) between midparent bud CR and family seed CR was obtained. A low significant correlation (r = 0.21**) was obtained between individual seed CR and the CR of the resultant seedling. Seed coat removal had no effect on these correlations. Narrow sense heritability for bud CR as determined by parent-offspring regression was 0.50 ± 0.06. The small range in CR of the seed and pollen parents, 300 to 450 and 200 to 400 chill units, respectively, may explain the low correlation values obtained. The data suggest that it is impractical to screen for seedling CR based on seed CR where the CR for climatic adaptability must be held within a range of less than 300 chill units.
Abstract
A 3rd recessive, male-sterile gene in muskmelon (Cucumis melo L.) is named male sterile-3 and symbolized ms-3. Male sterile-3 is phenotypically distinct from male-sterile genes ms-1 or ms-2.
Abstract
Horizontal starch gel electrophoresis was used to study the inheritance of some isozyme variants in almond seedling and almond-peach hybrid populations. In almond, aspartate aminotransferase (AAT), glucose phosphate isomerase (GPI), and leucine aminopeptidase (LAP) have two zones of activity, one of which is monomorphic in each case. The polymorphic loci, AAT-1 and GPI-2 each had two alleles and behaved as dimers in the electrophoretic analysis. LAP-1 behaved like a monomeric enzyme with two functional alleles, in addition to an hypothesized null allele. PGM behaved like a monomeric enzyme specified by two polymorphic loci, Pgm-1 and Pgm-2. Pgm-1 displayed two alleles, while Pgm-2 apparently had three, although one gave aberrant segregation ratios. Acid phosphatase (AcP), glyceraldehyde-phosphatase dehydrogenase (GAP), and 6-phosphogluconate dehydrogenase (6-PGD) isozymes showed two zones of activity in the almond cultivars assayed and produced no allelic variation. In peach, AAT-1 and GPI-2 had the same Rf values as almond and segregated in typical Mendelian ratios in F1 and F2 almond × peach populations. The alleles for LAP-1 and LAP-2 not only had different mobilities in almond and peach but were tightly linked to each other within each species. Thus, four-banded patterns were produced in the F1, which segregated in the F2 to peach, almond, and hybrid phenotypes with a reduced number of recombinants.
Abstract
F1 progenies from a cross between Lactuca sativa L. breeding line 54671 and L. serriola L. PI 274372 (resistant to the cabbage looper, Trichoplusia ni (Hubner), averaged 42 ± 6 looper eggs per plant, compared to 213 ± 25 for the 54671 parent and 17 ± 4 for PI 274372. Two F2 populations varied widely in plant damage inflicted by the resulting larvae when they were exposed to 4 releases of adult loopers but the damage distribution was skewed towards the resistant parent. Antixenosis of 16 F3 progenies was independent of plant size (r ranged from 0.02 to 0.52) and of plant type (r ranged from 0.00 to 0.57).
Abstract
Ozone sensitivity was compared in F1 and F2 populations from crosses between 2 ozone-sensitive bean cultivars, ‘Spurt’ and ‘Blue Lake Stringless’, and 2 ozone-resistant cultivars, ‘Black Turtle Soup’ and ‘French’s Horticultural’, under controlled environmental conditions. F1 plants were as sensitive as the sensitive parent. About 10% of the F2 progeny obtained by selfing F1 plants appeared to be as resistant as the resistant parent and 90% of the progeny could be divided equally between a group as sensitive as the sensitive parent and a group intermediate in sensitivity between the parent plants. However, precise separation of F2 progeny was not possible because of the variability in injury expression. The average injury on the F2 plants was greater than the parental midpoint value and the variance in injury on the F2 plants was about 3.5x greater than that for the parents. The heritability of resistance to ozone was estimated to be 0.83. It was concluded that ozone resistance is recessive in P. vulgaris and appears to be regulated by a few major genes.
Abstract
Inheritance of an indehiscent anther (ia) mutant in the common bean (Phaseolus vulgaris L.) was studied. Dehiscence was incompletely dominant in heterozygotes making classification difficult in backcross and F2 populations. Progeny tests were necessary to determine that the character was conditioned by a single recessive gene. The symbol ia is proposed to denote the indehiscent anther gene.
Abstract
The inheritance of resistance in butternut squash (Cucurbita moschata Poir) to powdery mildew (Erysiphe cichoracearum DC) was studied under greenhouse and field conditions using F1 F2, and BC1 generations derived from crosses of ‘La Primera’ (resistant) (calabaza type) with 2 butternut cultivars ‘Ponca’ (susceptible), and ‘Waltham’ (susceptible), and ‘Ponca’ x ‘Seminole Pumpkin’ (intermediate resistance). The breath-blowing method of inoculation was effective in greenhouse tests. Petiole and stem reactions of plants in both field and greenhouse trials and leafblade reactions of plants in the field tests indicated that 3 alleles at a single locus determined resistance reactions in crosses involving ‘Ponca’, ‘Waltham’, and ‘La Primera’. Proposed genotypes for the susceptible ‘Ponca’ and ‘Waltham’ butternut squash are pm – lp pm – lp and pm – lw pm – lw , respectively, and for the resistant ‘La Primera’, pm – lL pm – lL . The partial and complete dominance relations of these alleles for the leaf-blade (field) and petiole/stem reactions (field/greenhouse), respectively, are pm – lp > pm – lL > pm – lw . A different gene, pm – 2s , controlled the intermediate resistance of ‘Seminole Pumpkin’. However, a quantitative inheritance pattern of disease reactions of leaf blades was observed in the greenhouse trials in all crosses, presumably because of the higher inoculum load and the increased intermediate ratings of the heterozygotes under these conditions. Leaf-blade and stem/petiole resistance was completely associated in segregating progenies in the field but not in the greenhouse because of the intermediate susceptibility of the leaf blades of heterozygotes under those conditions. Scanning electron micrographs of powdery mildew on compatible and incompatible hosts showed that differential compatibility occurred in conidial germination. Resistance in ‘La Primera’ involved delayed conidia germination, retarded hyphal growth, shorter conidiophores, and weak sporulation.