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  • Author or Editor: James N. Moore x
  • Journal of the American Society for Horticultural Science x
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Abstract

Seven seedling populations of strawberry were analyzed for ascorbic acid content and color intensity. The amount and type of variation found showed both characters to be controlled by quantitative genes. It is postulated that 2 genetic systems control the inheritance of ascorbic acid and that the 2 systems can interact with each other. Partial dominance was exhibited for high color intensity. Heritability estimates of 41% for ascorbic acid and 81% for color intensity were obtained. Flesh color and ascorbic acid content were not correlated characters.

Open Access

Abstract

Eighteen species of Prunus and 4 interspecific hybrids from the 3 main subgenera were used to ascertain the prezygotic mechanisms that maintain reproductive isolation. The percentage of pollen germination of pure species was very high (82% to 97%), and ranged from 1% to 97% for interspecific hybrids. Pollen tube growth rates differed greatly among species and ranged from 3.8 to 8.7 mm/day in vitro, and from 3 to 12 mm/day in vivo. These values were highly correlated with pistil length (r = 0.90) and pollen volume (r = 0.91). Evidence was obtained suggesting the existence of additional incompatibility mechanisms, the 1st preventing interspecific fertilization in the subgenus Cerasus. In P. avium L., the pollen tubes of some species are inhibited and finally arrested before they reach the first half length of the style. In crosses involving P. cerasus L. and P. serotina Ehrh., the use of the latter as the seed parent showed a 10-fold increase in fruit set when compared to the reciprocal. Secondly, differences in pistil length and in pollen tube growth rate among species provide a sound basis for explaining the phenomenon of unilateral incompatibility in Prunus. The use of male-sterile genotypes of P. persica L., which had a prolonged period of receptivity, gave increased fruit set and showed increased potential for overcoming the prezygotic incompatibility barriers.

Open Access

Inheritance of the primocane-fruiting (PF) characteristic was studied in seedling populations of tetraploid (4x) blackberries (Rubus subgenus Rubus). Four selections (A-1836, A-593, A-830, and A-1680) and two cultivars (`Arapaho' and `Shawnee') were used as parents in a full diallel crossing scheme. Selection A-593 was used as the main source for PF due to its origin (`Brazos' × `Hillquist,' the latter an old PF cultivar). All parents except `Shawnee' have A-593 in their parentage; among the parents, only A-1836 fully expresses PF. Selfing of A-1836 resulted in 100% PF offspring, indicating that A-1836 is homozygous for this trait. Selfing of A-593, A-830, and `Arapaho' produced either a 35:1 or a 20.8:1 FF (floricane or summer-fruiting):PF segregation ratio, fitting a tetrasomic inheritance model under either random chromosome assortment (RCSA) or random chromatid assortment (RCTA), respectively, also suggesting that PF is controlled by a single recessive gene and that the parents are duplex (AAaa) for this trait. Selection A-1680 and `Shawnee' selfed did not produce PF progeny, but when crossed with the nulliplex A-1836, gave a 27:1 FF:PF ratio, indicating RCTA and that they are triplex (AAAa) for PF. According to these research, both gametic outputs (RCSA and RCTA) seem to operate in 4x blackberry. The intensity in expression of PF had a negative relationship with time to harvest, with those seedlings showing the highest PF scores producing a crop in early to mid-August. This knowledge will be helpful in implementing breeding strategies to produce PF blackberry cultivars.

Free access

Fruit of four clingstone peach [Prunus persica (L.) Batsch.] seedling populations, 54 advanced selections, and the cultivars Allgold and Goldilocks were analyzed for sugar content, soluble solids concentration (SSC), and acidity. Sucrose, glucose, fructose, and sorbitol were identified and quantified by high pressure liquid chromatography (HPLC) analysis. Variation was found for all the sugars between the seedling populations. Comparison of the means for the advanced selections with `Goldilocks' indicates that progress has already been made toward selection for a sweeter peach. Glucose, fructose, sorbitol, SSC, and acidity (citric) differed significantly for two harvest years, while sucrose and total sugar concentrations showed no significant yearly variation. A fruit maturity study revealed no significant changes in SSC, percentages of glucose, fructose, and total sugar during ripening on the tree. Acidity and percent sorbitol decreased, while the sugar: acid ratio and percent sucrose increased with increasing maturity. Broad-sense heritability of SSC, acidity, and sugar: acid ratio bad values >0.72, while values for individual sugars and total sugars were much lower. Transgressive segregation for each sugar was found in seedling populations.

Free access

A study was conducted to determine how resistance to downy mildew [Plasmopara viticola (Bert. & Curt.) Berl. & de Toni] is inherited in germplasm (Vitis vinifera L., V. labrusca L., V. rupestris Scheele, and V. riparia Michx.) used for breeding table grapes. Crosses, including reciprocals, among parents possessing different levels of downy mildew resistance were evaluated in 1994 and 1995. The proportion of foliar tissue with sporulation, chlorosis, or necrosis was used to measure resistance. All genotypes were rated for these characters on two separate dates in 1994 and 1995. Hypersensitive flecking was also evaluated in the 1995 seedlings to determine its relationship with downy mildew resistance. Crosses with at least one resistant parent had a larger number of resistant offspring than crosses between two susceptible parents. General combining ability (GCA) effects were highly significant for 1994 and 1995. Specific combining ability effects were significant, but were relatively small compared to GCA, suggesting additive gene action was a primary influence on downy mildew resistance. Heritability estimates for sporulation, chlorosis, and necrosis were the highest at the second rating in 1994 (0.88, 0.74, and 0.57, respectively) and 1995 (0.50, 0.60, and 0.60, respectively). Reciprocal crosses indicated that maternal inheritance did not influence downy mildew resistance. A small percentage of progeny with hypersensitive flecking were identified from the germplasm. Seedlings with the flecking characteristic tended to have lower sporulation, chlorosis, and necrosis ratings earlier in the growing season.

Free access