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James J. Luby, David K. Wildung, and Gene J. Galletta

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James J. Luby, David K. Wildung, and Gene J. Galletta

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Sean B. Fort, Douglas V. Shaw, and Kirk D. Larson

Nine selected strawberry genotypes (Fragaria ×ananassa Duch.) from the University of California, Davis, strawberry improvement program were intercrossed and their seedling offspring evaluated for five production traits. Plants were evaluated in annual hill culture, with and without preplant soil fumigation using a mixture of 67 methyl bromide: 33 chloropicrin (wt/wt, 392 kg/ha). Plant mortality was <1% for seedlings grown in either soil environment, indicating that the main effects of fumigation treatment in this experiment were due to the consequences of sublethal soil organisms. Plants grown in nonfumigated soils measured from 74% to 77% of the diameter of those grown in fumigated soils and yielded 59% as much fruit. Significant cross × fumigation interactions were not detected for fruit yield, fruit size, and weighted fruit appearance. Moreover, genetic correlations for these three traits calculated by comparing seedling performance in fumigated and nonfumigated soil environments were at or near unity, suggesting that the same genes condition genetic variability for these traits in both soil environments. Together, these findings demonstrate that strawberry fruit yield and vigor are increased substantially by fumigation, even in the absence of an identifiable major pathogen problem. Further, there may be little promise for developing cultivars with genetic adaptation specific to the sublethal effects of nonfumigated soils, as selection in either soil fumigation environment is likely to affect the same sets of genes.

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James F. Hancock, Peter W. Callow, Sedat Serçe, and Phan Quynh Son

Variation in 14 horticultural traits of native octoploid Fragaria L. from North and South America was examined in a greenhouse. Significant levels of variation were found for all but a few of the traits at the species, subspecies, regional and genotypic level, with the highest amount of variation generally being partitioned among genotypes. Fragaria chiloensis (L.) Miller was superior to F. virginiana Miller for crown number, fruit weight, soluble solids and seed set, while Fragaria virginiana was superior for runner production, peduncle length, fruit number, fruit color and winter hardiness. Fragaria chiloensis ssp. pacifica Staudt had the highest soluble solids and among the earliest bloom dates, highest crown numbers and highest seed set. Fragaria chiloensis ssp. chiloensis f. chiloensis (L.) Duch. produced the largest fruit and among the earliest bloom dates and longest peduncles. Fragaria chiloensis ssp. chiloensis f. patagonica (L.) Duch. had among the highest crown numbers and the highest percentage seed set. Fragaria virginiana ssp. platypetala (Rydb.) Staudt produced the most crowns and its fruit ripened earliest. Fragaria virginiana ssp. glauca (Wats.) Staudt were the latest flowering, had the darkest fruit color and the most flowering cycles. Fragaria virginiana ssp. virginiana Duch. displayed the most winter dieback, the longest peduncles, and the highest flower and runner numbers. No significant differences were observed in any of the examined traits between F. chiloensis ssp. pacifica and F. chiloensis ssp. lucida, or F. virginiana ssp. grayana and F. virginiana ssp. virginiana. A number of individual genotypes were superior for more than one trait. CFRA 0024 possessed unusually high crown numbers, was extremely early blooming and displayed multiple fruiting cycles. CFRA 1121 had unusually long peduncles and much higher than average values for fruit weight, soluble solids, fruit color and seed set. CFRA 0094 was extremely early flowering and had much darker fruit color than most other F. chiloensis genotypes. CFRA 0368 flowered unusually early and had among the largest fruit. CFRA 0366 possessed unusually long peduncles and the largest fruit of any North American genotype. CFRA 0560 and CFRA 1369 had an unusual combination of multiple flowering cycles and high runner production. CFRA 1170 and 1171 were unusually late fruiting and had high numbers of large fruit on long peduncles. CFRA 1385 and JP 95-3-1 had extremely high flower numbers, long peduncles and large fruit.

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J.F. Hancock, P.A. Callow, and Douglas V. Shaw

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.

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Creighton L. Gupton and Barbara J. Smith

Experiments were conducted to estimate the relative importance of additive and dominance genetic variances and non-allelic interactions in the inheritance of resistance to Colletotrichum spp. in strawberry (Fragaria × ananassa Duch.). Progeny of 40 parents crossed in a Comstock and Robinson Design II Mating scheme were inoculated with three isolates of C. fragariae and one isolate of C. acutatum. Disease development on each plant was rated visually. Variance components were estimated and converted to genetic variances. Estimates of were six to 10 times higher than those for Within-family variance not accounted for by equaled 35% and 38% of the total genetic variance in females and males, respectively, indicating probable epistatic effects. The frequency distribution of disease severity ratings was bimodal in both experiments, suggesting major gene action. Narrow-sense heritability estimates were 0.37 and 0.26, and broad-sense heritability estimates were 0.87 and 0.85 for females and males, respectively. Narrow-sense heritability estimates are probably sufficient to produce gains from recurrent selection. Gains from selection of clonal value should be possible because of the high broad sense heritability estimates. It appears feasible to establish a broad genetic-based population resistant to Colletotrichum spp. from which selections could be evaluated per se and/or recombined to produce improved populations.

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Youngjae Oh, Jason D. Zurn, Nahla Bassil, Patrick P. Edger, Steven J. Knapp, Vance M. Whitaker, and Seonghee Lee

can serve as a training tool and troubleshooting guide for the implementation of existing DNA tests in strawberry breeding programs. To ensure availability, the handbook has been published at the Genome Database for Rosaceae ( Jung et al., 2019 ) and

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Tomas N. Hasing, Luis F. Osorio, and Vance M. Whitaker

representative subset of genotypes in the strawberry breeding program of the University of Florida. By 1) examining the variation for SSC stability in this set of germplasm; 2) exploring the relationship between SSC stability and other traits such as mean SSC and

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David Jesús Gil-Ariza, Iraida Amaya, José Manuel López-Aranda, José Federico Sánchez-Sevilla, Miguel Ángel Botella, and Victoriano Valpuesta

, relatively recent introgressions from wild octoploid species have contributed to improved diversity of the cultivated strawberry ( Bringhurst and Voth, 1984 ; Hancock, 1999 ). Strawberry breeding has become an area of substantial economical importance

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Yanina Perez Cayo, Steven Sargent, Cecilia do Nascimento Nunes, and Vance Whitaker

overripe. Because of the continuous interest in developing new strawberry genotypes with improved quality traits, additional data on chemical composition and postharvest behavior of new strawberry breeding selections are necessary. These data facilitate the