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Abstract
California's ․60,000,000.00 annual strawberry business accounts for more than 58% of the nation's strawberry production, although it has only 16% of the United States strawberry acreage.
Abstract
Eight non-everbearing California strawberry cultivars were evaluated under the standard winter planting system (October-November) in comparisons involving differentials in plant harvest and transplanting dates and comparing approximately 30, 15 and 0 days of cold storage conditioning at Santa Ana, a relatively warm-winter south coastal California site. The varieties differed greatly in performance and the results were consistent with that which is known of their varying performance under commercial conditions. ‘Sequoia’ was almost an ideal performer but the fruit lacks firmness. Photoperiod is important in governing the reproductive response under this planting system since the duration of the fruiting period for a given variety was directly associated with how long the plant had grown under short days. However, chilling appeared to be the dominant factor governing acceptable performance in all varieties except ‘Sequoia’. ‘Sequoia’ performed satisfactorily over the entire range of treatments and although it responded to chilling, apparently it has a short rest period. Of the other varieties that are of great economic importance in California, ‘Fresno’ and ‘Shasta’ evidently have relatively long rest periods and cannot be manipulated satisfactorily under the winter planting system whereas ‘Tioga’ is intermediate and responds favorably to manipulation.
Genetic analysis of day-neutral (photo-insensitive) cultivars and their derivatives hybridized to standard short-day clones of octoploid strawberries [Fragaria × ananassa Duchn., F. chiloensis (L.) Duchn., and F. virginiana glauca Staudt., x = 7, 2n = 56] revealed that photo-insensitivity is controlled by a single dominant allele of a Mendelian gene. The dominant genetic trait is expressed in hybrids with other Fragaria spp. Intergeneric hybrids of day-neutral Fragaria and short-day Potentilla glandulosa L. and P. fruticosa L. also express photo-insensitivity. The day-neutral genes in European perpetual flowering (photo-insensitive) diploid `Alpine' F. vesca (2N = 14) apparently have evolved independently, since photo-insensitivity is recessive to photo-sensitivity. Native California diploid F. vesca have diverged considerably from European F. vesca. No photo-insensitive diploids have been found among them. Photo-sensitivity in native California F. vesca is controlled by three dominant genes. The origins of day-neutral cultivars of F. × ananassa and the classification of day-neutrality are discussed.
Abstract
Genetic analysis of phosphoglucoisomerase and leucine amino peptidase allozymes clearly indicated that the octoploid cultivated strawberries Fragaria × ananassa Duch. are highly diploidized. A 4-locus genetic model is proposed for the PGI allozymes in the octoploid strawberries commensurate with the genomic structure. The LAP system needs further investigation in order to establish the number of loci and alleles present. The possible adaptive value of the biochemical diversity found in the Fragaria species is discussed.
Abstract
Field plots of strawberry (Fragaria × ananassa Duch cv. Chandler) were exposed to two 1-hr nighttime simulated fog episodes per week at specific acidities from pH 1.6 to 3.2, or no fog. Small, distinct, irregularly shaped, rust-colored lesions developed on foliage and fruit after a single 1-hr exposure to acidic fog at low pH. Fog episodes at pH 1.6 resulted in death of the plants after 8 weeks. Strawberries tolerated short-term exposure to acidic fog at pH 2.0 or higher, with little or no negative effect on growth, yield, or fruit soluble solids. However, calyx injury from acidic fog reduced marketability at pH levels up to 2.8. ‘Douglas’, ‘Chandler’, ‘Selva’, ‘Parker’, and ‘Soque!’ differed in magnitude of response to acidic fog in greenhouse exposures.
Abstract
Strawberry (Fragaria × ananassa Duch.) seedlings from biparental crosses were planted in two trials at Watsonville, Calif. Sept. 1985 and 1986. The 1985 trial was scored on three dates and the 1986 trial on four dates for leaf spot (Ramularia tulasnei) infection. Individual seedlings were assigned a value of 0 to 5 on each date, with 0 indicating no infection and 5 indicating very severe infection. Average infection scores were lowest for the earliest scoring dates in both years (0.93 and 0.38) and maximum at late scoring dates (2.83 and 1.49). Narrow-sense heritabilities for infection scores estimated using partial diallel analyses were 0.07 and 0.03 for the earliest scoring dates in the two trials and were 0.24 and 0.28 for the latest dates. Early season estimates of broad-sense heritabilities were calculated as 0.13 and 0.03, whereas estimates based on later scorings ranged from 0.32 to 0.52. The low heritabilities for early scoring dates result from incomplete and uneven infection, indicating that selection under field conditions will be most effective under conditions of very high infection. The moderate heritabilities and predicted gains estimated for high-infection conditions suggest considerable opportunity for improvement of leaf spot resistance by recurrent breeding and selection using available quantitative genetic variation.
Abstract
Genetic variation for percent soluble solids, percent titratable acidity, and fruit firmness was analyzed for representative progenies from the California strawberry breeding population. Fruit samples were harvested from individual seedlings from 28 biparental crosses, organized in two factorial mating sets. Individual narrow-sense heritabilities were estimated as 0.07, 0.48, and 0.38 for solids, acids, and firmness, respectively. Broad-sense heritabilities were estimated as 0.35, 0.78, and 0.38 for the same traits, suggesting the presence of dominance variance for soluble solids and acidity, but not for firmness. Opportunities for genetic manipulation of traits with different additive-dominance genetic variation profiles are discussed.
Abstract
Starch gel electrophoresis was employed to distinguish the University of California-released strawberry cultivars. Isozyme patterns of 3 enzyme systems (PGI, LAP, and PGM) were studied. Fourteen of the 22 cultivars studied were classified uniquely by using the 3 enzyme systems. The use of electrophoresis as a tool in breeding clonally propagated crops is discussed.