Environmental variance components were estimated for calyx-end fruit cracking in pollination-constant and nonastringent cultivars and selections of Japanese persimmon (Diospyros kaki Thunb.). The cracking value of a tree in a cultivar or selection (genotype) (X) was evaluated as the number of fruit that cracked divided by the total number (25) of fruit evaluated from each tree. Because the mean value of X was correlated with the variance of X, analyses of variance were performed using its square root value. The variance associated with genotyp× year interaction was the largest of environmental variance components. The variances associated among years and among trees within genotypes were very small. The mean percentage of cracked fruit in evaluation for 10 years was 3% for `Fuyu', 11% for `Matsumotowase-Fuyu', and 12% for `Izu'. On the basis of the environmental variance components obtained, it is proposed that all offspring genotypes exhibiting a phenotypic cracking incidence of less than 20% and 11% should be selected in single-year and three-year evaluations, respectively, when those genotypes are evaluated using 25 fruits from a single tree, in order to successfully select all genotypes with an genotypic incidence of less than 3%.
In a yellow summer squash (Cucurbita pepo L.) experimental line developed by Seminis Vegetable Seeds, the coat protein gene of an American strain of squash mosaic virus (SqMV-M88), conferred resistance to Arizona, California, New Jersey, and New York strains belonging to the two pathotypes of the virus. An analysis of genetic populations derived from crosses and reciprocal backcrosses of a homozygous SqMV-resistant line A127-1-2 with the susceptible cultivar Butterbar revealed that the high level of resistance mimics the response of a single recessive gene.
Six cross-incompatibility groups, which contain most of commercially important California almond cultivars [Prunus dulcis (Mill.) D.A. Webb, syn. Prunus amygdalus Batch], and their self-incompatibility (S) allele genotypes are identified. Incompatibility groups include `Mission' (SaSb), `Nonpareil' (ScSd), and the four groups resulting from the `Mission' × `Nonpareil' cross: (SaSc), (SaSd), (SbSc), and (SbSd), as represented by `Thompson', `Carmel', `Merced' and `Monterey', respectively. All seedlings from the `Mission' × `Nonpareil' cross were compatible with both parents, a result indicating that these two cultivars have no alleles in common. Crossing studies support a full-sib relationship for these progeny groups and the origin of both parents from common germplasm. Cultivars in these six groups account for ≈ 93% of present California production, a result demonstrating a limited genetic base for this vegetatively propagated tree crop.
Abstract
Resistance to black rot of cabbage (Brassica oleracea L. Group capitata), caused by Xanthomonas campestris pv. campestris in PI 436606, was conditioned by one recessive gene. The data suggested the occurrence of one or two modifying genes for tolerance to black rot in an unrelated line.
Abstract
Some Citrus spp. and cultivars exhibit juice vesicle branching. In this study, we determined that the branching trait is inheritable. The mode of inheritance of this trait was analyzed in progenies from various 2x × 2x and 2x × 4x citrus crosses. No consistent model for inheritance of branching has been found, although some crosses do suggest simple inheritance. We found that if one parent is a pummelo, even if this parent does not exhibit the branching trait itself, branching may be inherited by a substantial portion of the progeny, suggesting that more than one locus is involved in this trait.
Abstract
Twelve cultivars and one breeding line of tomatoes, (Lycopersicon esculentum Mill.) which varied in maturity from early to late cultivars, were crossed in a diallel to estimate general and specific combining ability for earliness, fruit size, and yield using Griffing's method II, model II. General combining ability mean squares for earliness at 3 stages expressed as growing degree days (GDD) (10–32°C); and for number of days were larger than specific combining ability mean squares except for the index of first flowering stage to first fruit set. Days from seeding to first flowering and of first fruit set to first ripe fruit were positively correlated with each other and with total earliness. However, days from first flowering to first fruit set was not correlated either with the period from first fruit set to first ripe fruit or with total earliness. Fruit sizes, measured at the 3 different times were positively correlated with each other and with overall average size. A positive correlation resulted between the September 1st and October 1st yields and total yield. There was no significant correlation between fruit size and yield. General and specific combining ability mean squares were estimated on August 1st, September 1st, and October 1st for fruit size and yield. Broad sense heritability estimates were high and narrow sense heritability estimates were low, for both fruit size and yield.
The search for appropriate white pine blister rust (WPBR) (Cronartium ribicola J.C. Fischer) resistant germplasm to use in black currant (Ribes nigrum L.) breeding programs began in 1935 in Ottawa. Crosses were made in 1938 and 1939 with three different Ribes L. species and two standard black currant cultivars. The resulting seedlings from these crosses were evaluated for rust resistance. Three promising selections resulted from this program and were named `Coronet', `Crusader' and `Consort'.
Frequency of infection, main effects and interactions among four geographic sources of white pine blister rust (WPBR) (Cronartium ribicola J.C. Fisch.) and 10 Ribes-sites (Ribes L. specie × site combinations) was investigated using leaf disk assay. Two clones, one of R. hudsonianum (Dougl.) Jancz. and one of R. viscosissimum Prush., were not infected by any sources of WPBR. One clone of R. viscosissimum that was not infected by two sources of WPBR was susceptible to the other sources. Highly significant WPBR sourc × Ribes-site analysis of variance interaction for incubation period and infection efficiency precluded testing main effects. Profile plots of incubation period interaction means showed orderly interaction by all WPBR sources and plots of infection efficiency showed that aggressively virulent WPBR from Oregon (Champion Mine) ranked near or at the bottom for infection efficiency for all Ribes-sites. Meanwhile, aggressively virulent WPBR from Idaho (Merry Creek) ranked near the bottom for infection efficiency when inoculated onto Ribes obtained from the Cascade Mountains but switched to the highest ranking when inoculated onto Ribes obtained from Idaho. Geographic interaction of white pine blister rust and Ribes for incubation period and infection efficiency may help to explain geographic patterns recently observed in WPBR molecular markers.
Abstract
Six crosses were produced from 8 breeding lines and cultivars of cucumber (Cucumis sativus L.). Within each cross, 11 generations (P1, P2, F1, F2, F3, BC1 5 BC2, BC1×1, BC1×2, BC2×1, BC2×2) were studied. Data were collected on fruit weight/plot, fruit number/plot, average fruit weight and fruit bearing index at 2 locations. Preliminary analyses indicated the adequacy of an additive-dominance model for all characters in most crosses. The model was extended to include environment and genotype × environment interactions. The model was either significant or highly significant for all characters in all crosses. Dominance was a major contributing factor in the inheritance of all 4 characters. This was evidenced by significant dominance effects and substantial amounts of heterosis for all characters in most crosses. Such heterotic effects were large enough to justify the cost of hybrid seed production. Low incidences of dominance × environment interactions provided evidence for the stability of hybrids under different environments. Additive effects were significant for certain characters in some crosses. Significant additive effects suggested the effectiveness of selection for development of superior parental genotypes. Various degrees of additive × environment interactions were obtained. The interactions suggested that effective selection for yield should be carried out under more than one environment.