strawberry cultivars has also been observed by Hutton and Gomez (2006) . Information about the heritability of the resistance in strawberry and estimation of the breeding value of individual plants would be beneficial in identifying highly resistant
Michelle L. Paynter, Joanne De Faveri, and Mark E. Herrington
Hiroshi Iwanami, Shigeki Moriya, Nobuhiro Kotoda, Sae Takahashi, and Kazuyuki Abe
, the estimation of the breeding value of the mealy parent is necessary. Narrow-sense heritability or combining ability has been estimated to improve breeding strategies and to evaluate the potential of cultivars for use as parents in fruit breeding
Valdomiro A.B. de Souza, David H. Byrne, and Jeremy F. Taylor
Breeding values (BVs) for four plant (bloom date, fruit development period, fruit density, and blind node propensity) and five fruit (weight, blush, shape, soluble solids, and titratable acidity) traits of 28 peach [Prunus persica (L.) Batsch (Peach Group)] genotypes used as parents in the Texas A&M University peach breeding program were predicted using best linear unbiased prediction (BLUP). Data from seedlings of 108 families developed from 42 peach parents were analyzed by using a mixed linear model, with years treated as fixed and additive genotypes as random factors. The precision of the predictions was high for most parental genotypes, as indicated by the correlations (rTI) between predicted and true BVs and the standard error of the predictions (SEP). In most cases, the higher the number of progeny, the better the agreement between predicted and true BVs for that parent. Parents with observations from more than 30 seedlings had a rTI ≥ 0.90 and smaller SEPs. For all traits analyzed, the lowest precision (low rTI and high SEP) was observed for `Flordaking', whose predicted BVs was based only on pedigree information.
Douglas V. Shaw and Erik J. Sacks
Four sets of selected strawberry (Fragaria ×ananassa Duch.) genotypes were generated from within a single breeding population to evaluate the correspondence between predicted and realized selection response for fresh fruit color traits. Genotypes were selected for extreme phenotypes, dark or light, of either internal or external color value (CIELAB L*). Genotypic selection response was evaluated empirically by scoring fruit from the clonal derivatives of these selected genotypes, and response for breeding value was estimated by scoring the offspring of crosses performed among a subset of the genotypes within each selected set. Realized selection response was slightly larger than predicted for internal and external L* when calculated for selected genotypes. Also, more than half of the selected genotypes had genotypic values for L* outside the range of the original parents, providing evidence for transgressive segregation. Realized selection response for breeding value in exterior and interior color was slightly less than predicted. Compared in a different way, genotypic selection response for external color was significantly greater than selection response for breeding value, whereas genotypic and breeding value responses did not differ for internal color. These observations suggest the presence of some nonadditive genetic variance for external color but support the conclusion that the heritabilities predicted previously were reasonably accurate. Estimates of variance components within each of the offspring populations demonstrated that genetic variances were modified substantially by one generation of selection. Selection for dark fruit color reduced genetic variance to nonsignificant levels, with internal color more affected than external color. The total genetic variances within both of the offspring populations from parents selected for light color were changed little by one generation of selection, but substantial dominance variance was detected that had not been found in the original population. The rapid response to selection and large changes in the distribution of genetic variances may indicate the presence of a few genes with comparatively large effect in strawberry color expression. Additional divergent selection response can be expected, but primarily in the direction of light fruit color.
Douglas V. Shaw and Thomas R. Gordon
Strawberry (Fragaria ×ananassa Duch.) genotypes retained for resistance to Verticillium wilt (Verticillium dahliae Kleb.) after two cycles of a two-stage (TS) selection procedure consisting of full-sib family selection followed by within-family selection of individuals, and genotypes retained for resistance using genotypic mass (GM) selection were crossed to a common set of moderately susceptible genotypes. The relative resistance of the seedlings from these progenies was compared using a resistance score and the percentage of stunted plants. Although the two sets of resistant parents had performed similarly in genotypic comparisons, those genotypes selected using the TS procedure yielded test cross offspring with significantly higher resistance scores (X̄ = 3.84 ± 0.09 vs. X̄ = 3.46 ± 0.09, t = 3.11**) and significantly lower rates of plant stunting (X̄ = 38.1% ± 3.1 vs. X̄ = 50.2% ± 2.9, t = 2.87**) than the parents chosen using GM selection. Further resolution using analysis of variance and general combining ability (GCA) estimates showed that these between-set differences resulted from higher resistance breeding values for parents selected using the TS procedure. The five genotypes with largest GCA for resistance score and four of the five genotypes with minimum GCA for percentage stunting were obtained by TS selection.
J.M. Amurrio, A.M. de Ron, and M. Santalla
Twenty sugar pea (Pisum sativum L.) landraces common to northwestern Spain (Pontevedra), and potentially of interest as parental material, were evaluated at two locations and for 2 years to study the diversity among them for plant and pod physical quality traits. The main objective was to identify landraces that could be included in breeding programs. Highly significant differences among landraces were found for most of the pod traits, such as length, width, length/width index, fresh weight, and flowering date. Genotype–environment interactions were demonstrated for only three traits of the 10 investigated. High values for correlation coefficients were mostly found for pod traits, but highly significant ones (i.e., P ≤ 0.01) were found for traits other than for pods. Most of the landraces were variable for qualitative and quantitative traits. PSM-0070, PSM-0113, and PSM-0116 were superior for earliness and pod physical quality, but were heterogenous. PSM-0064, PSM-0066, PSM-0117, and PSM-0118 lacked pod parchment.
Stanisław Pluta, Edward Żurawicz, Marcin Studnicki, and Wiesław Mądry
strategies for gooseberry cultivar production. This process involves the optimal selection of parental material for crossing with the highest breeding values, an effective use of the genotypes of donors with desired traits, choice of the breeding method, and
Agnieszka Masny, Edward Żurawicz, Kris Pruski, and Wiesław Mądry
General combining ability (GCA) and specific combining ability (SCA) effects of 10 strawberry (Fragaria ×ananassa) cultivars (Darselect, Selvik, Elianny, Figaro, Sonata, Susy, Salsa, Albion, Charlotte, and Filon) for severity of verticillium wilt (Verticillium dahliae) were estimated. Progeny consisting of 45 F1 full-sib families from the crosses made in a half diallel mating design according to the IV Griffing’s method was evaluated in two field experiments conducted in 2009 and 2010 on a soil heavily infested with V. dahliae inoculum. Each hybrid family was represented by 60 seedlings (four replicates of 15 plants each). The analysis of variance revealed significant (P < 0.01) GCA and SCA effects of the parental cultivars for the verticillium wilt severity in plants. This suggests that genetic additive and non-additive effects are involved in the inheritance of strawberry tolerance to verticillium wilt. In 2009, a significant negative GCA effect (P < 0.05) for the verticillium wilt severity in plants was found in ‘Selvik’, ‘Filon’, and ‘Sonata’, indicating genetic transmission of tolerance from parents to the offspring. On the other hand, a significant (P < 0.05) and positive for the verticillium wilt severity GCA effect was found for ‘Figaro’ in 2009, indicating the transmission from this parent to its offspring relatively high susceptibility to the wilt. Only in one hybrid family, ‘Albion’ × ‘Charlotte’, was the SCA effect significantly positive (P < 0.05) for verticillium wilt severity in plants, whereas two other hybrid families—‘Selvik’ × ‘Salsa’ and ‘Sonata’ × ‘Albion’—showed significantly negative SCA effects (P < 0.05). Three of 10 evaluated genotypes (i.e., ‘Selvik’, ‘Filon’, and ‘Sonata’) were found to be the most valuable parents to the strawberry breeding program for tolerance to verticillium wilt. The least suitable cultivar for this purpose was ‘Figaro’.
M. Joseph Stephens, Peter A. Alspach, Ron A. Beatson, Chris Winefield, and Emily J. Buck
mixed models and best linear unbiased predictors (BLUP) through the animal model to estimate the additive genetic variance and breeding value of individuals have been outlined by Lynch and Walsh (1998) and Piepho et al. (2008 ). For BLUP estimations
M. Joseph Stephens, Peter A. Alspach, Ron A. Beatson, Chris Winefield, and Emily J. Buck
. Statistical approach. We calculated variance components, best linear unbiased predictors (BLUP), and empirical breeding values (eBV) ( Henderson, 1977 ) for each trait using the mixed model approach ( Lynch and Walsh, 1998 ) described by Stephens et al. (2012