Eight strawberry cultivars or advanced selections from the Univ. of California, Davis, breeding program were screened for polymorphisms using the polymerase chain reaction (PCR) and 43 random 10-base DNA primers. Over 60% of the primers screened resulted in replicable polymorphic banding patterns (amplification profiles), and a subset of ten primers that exhibited high levels of amplification profile polymorphism was used to identify each of the eight genotypes uniquely. There was also a significant product-moment correlation (r = 0.64, P < 0.01) between number of shared amplification profile phenotypes and pairwise coefficient of coancestry. This technology shows high promise as a means of verifying the identity of cultivars and developing a genetic map of the octoploid cultivated strawberry.
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.
The genetic opportunity for selection of early fruiting strawberry cultivars was evaluated using seedling populations from the Univ. of California (UC) breeding program in three years. Narrow-sense heritabilities for early season yield and for the proportion of an individual's total yield expressed early were moderate (h2 = 0.24-0.53) and broad-sense heritabilities were slightly larger (H2 = 0.31-0.70), suggesting the presence of some nonadditive genetic variance for these traits. These two traits were genetically correlated with each other (rg = 0.78-0.98), but only early yield was consistently genetically correlated with seasonal yield (rg = 0.52-0.82). Selection was performed for each trait using an index on full-sib family means and individual phenotypic values in two of the three years, and predicted response was compared with that obtained using vegetatively propagated runner plants from selected genotypes in the subsequent fruiting season. Statistically significant (P < 0.05) selection response was obtained in one of two years for each trait, and combined analysis demonstrated highly significant (P < 0.01) response for both traits. However, realized response over all traits and years was just 27.3% of that predicted based on the estimated heritabilities and applied selection intensities. These results suggest that selection for early yield should be based at least in part on runner plant evaluations rather than exclusively on seedling performance.
Selfed progenies were generated using 10 day-neutral genotypes from the University of California (UC) strawberry breeding program as parents and their offspring were classified for late-summer flowering response. The grandparents of each selfed progeny included one of four day-neutral genotypes and one of eight short-day genotypes. Under the null hypothesis of genetic control by a single locus with the allele for day-neutrality dominant to the allele for short-day flowering response, all of these day-neutral parent genotypes must be heterozygous and their selfed offspring were expected to fit a 3:1 ratio of day-neutral: short-day phenotypes. The percentage of day-neutral offspring observed over all progenies was 70.9%, and was significantly smaller than the expected value of 75% (χ2 1 = 5.08, P < 0.02). The percentage of day-neutral offspring for individual progenies ranged from 41.4% to 84.8%, and highly significant heterogeneity was detected among progenies (χ2 9 = 40.3, P < 0.01). Selfed progeny means for the cumulative late-summer flowering score calculated using the day-neutral fraction of offspring varied from 1.31 to 2.35 and progeny means for the number of inflorescences per plant ranged from 3.5 to 9.9; these differences among progenies were highly significant (P < 0.01). These observations can be used to conclusively reject the hypothesis that day-neutrality in this domestic strawberry population is controlled by a single locus.
Eighteen strawberry genotypes from the University of California's breeding population were evaluated over two years for yield and fruit size with complete, partial, and no control of natural infestation by Tetranychus urticae Koch. The numbers of mites per leaf accumulated for the entire season or counted at peak infestation, and the number of mite-days accumulated for the season for partial control treatments were 31.7% to 44.0% of corresponding values realized for uncontrolled infestation, and values differed significantly between treatments for all three variables. Yields for the no-control and partial-control treatments averaged 81.6% and 85.0% of the yields obtained with complete spidermite suppression for the 2 trial years; fruit sizes were 95.1% and 92.0% for corresponding comparisons. Yield and fruit size differed significantly between the complete-control treatment and any level of infestation, but statistically significant differences between partial and complete mite control treatments were detected only for fruit size in a single year. Analysis of variance demonstrated significant or highly significant variation due to control level, genotype, and their interactions for both yield and fruit size, but resolution of variance components demonstrated that genetic × treatment interactions explained just 0% to 8% of the phenotypic variance for yield and fruit size in a 2-year evaluation. Genotypic variances, those reflecting genetic effects that were stable across treatments, were at least 9.3 times as large as interaction variances for these traits. There appears to be no evidence for partial resistance that might be expressed at intermediate levels of spidermite infestation.
The cultivated strawberry was originally derived from the accidental hybridization of two wild, octoploid species, Fragaria chiloensis and Fragaria virginiana ( Darrow, 1966 ). The resulting octoploid hybrid, Fragaria × ananassa , is the basis
reconstruction of F . × ananassa using selected genotypes of F. chiloensis and Fragaria virginiana ( Hancock et al., 2010 ; Luby et al., 2008 ). Several wild and domesticated Chilean clones of F. chiloensis have been collected and characterized
in soil and the incidence of strawberry wilt as a basis for disease risk prediction Plant Pathol. 45 106 114 Hortyński, J.A. 1987 Dziedziczenie niektórych cech ilościowych truskawki ( Fragaria × ananassa Duch.). Metody i problemy oszacowań
strawberry ( Fragaria ×ananassa Duch.) estimated by exploring mixed and spatial models and pedigree information Theor. Appl. Genet. 111 256 264 de Souza, V.A.B. Byrne, D.H. Taylor, J.F. 1998 Heritability, genetic and phenotypic correlations and predicted
productivity at different within-season intervals for strawberries ( Fragaria × ananassa ) Theor. Appl. Genet. 85 1001 1009 Shaw, D.V. Bringhurst, R.S. Voth, V. 1987 Genetic variation for quality traits in an advanced-cycle breeding population of strawberries