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Abstract
Irregular germination and delayed emergence of blueberry, strawberry, blackberry and raspberry seedlings have been noted by various investigators. Seed treatments such as afterripening (1) and acid scarification of strawberry seed (2) improved rapidity of germination, but neither treatment fully overcame the delay in seed germination. In a study with blueberry seed, after-ripening did not improve germination (2). Sporadic germination and delayed emergence of seedlings complicates a breeding program when uniform size of seedlings is desired.
Abstract
Three blueberry progenies from crosses of large-fruited X large-fruited parents were significantly larger in fruit size than 3 progenies from crosses of large-fruited X small-fruited parents. Mean fruit sizes of the 3 large-fruited X small-fruited populations were equal to the fruit size of the smaller fruited parents in each cross, indicating that small fruit size is a dominant character. Large fruit size is not linked with low yield.
Abstract
In a germination test with strawberry seed of different ages stored at 40°F, 23-year-old seed germinated as well as 1-year-old seed. Germination was relatively high for all of the seed lots, despite differences in age.
Abstract
In a study of breeding of strawberry (Fragaria × ananassa Duch.) for resistance to red stele root rot caused by Phytophthora fragariae Hickman, two different composites of races of the fungus were used to screen seedlings, one with and one without race A-5. In the absence of race A-5, all resistant parents produced between 28.6 to 72.0% resistant seedlings depending upon parental combinations. When race A-5 was included in the composite, two breeding selections that were derived from Fragaria chiloensis Yaquina A clone transmitted more resistance to their seedlings than three other parents in a diallel comparison. Mean squares and variance components were higher for general than for specific combining ability. Resistance is partially dominant for the races involved in this study.
Abstract
Inheritance of albino seedling was studied in progenies of 3 tetraploid cultivated highbush blueberry clones. This mutant character was found to be controlled by a recessive gene at a single locus. All 3 parental clones appeared to be duplex (AAaa) for the marker gene and upon crossing and selfing segregated with ratios that are most likely to occur with tetrasomic inheritance. They segregated approximately 43 normal : 1 albino which is a significant deviation from the expected 35:1 ratio. This deviation is probably due to nonrandom pairing at meiosis of the 4 homologous chromosomes bearing the marker gene.
Abstract
Strawberry (Fragaria × ananarsa Duch.) plants treated with methyl 1-(butylcar bam oyl) 2-benzimidazolecarbamate (benomyl) before removal from the field were in better condition after 7 months of storage, survived better in the field after planting, and produced higher yields than those not treated with fungicide. Fungicide application dates ranged over 6 weeks in the fall. The time of application made no significant difference in the condition of the plants during storage, however, fruit yield data in some cultivars indicated that late treatment was more beneficial than early treatment for maintaining overall plant quality. Treated plants stored at 1°C for 7 months were of very good quality, while those at 3° were mediocre to poor. Poor quality and high mortality characterized all nontreated plants regardless of storage temperature.
Abstract
The effects of temperatures, before digging and during storage, on the physical condition of cold-stored strawberry plants and their field response are given. Results for 3 of 4 varieties tested under Maryland conditions indicate that most strawberry plants dug in the fall can be stored successfully for 5 months at 30° F. Early digging of non-dormant plants is a feasible method of avoiding winter injury without causing loss of salable plants. Removing leaves from certain varieties before storage had no detrimental effect and probably should be done to avoid the development of decay in storage.
Abstract
The U.S. Department of Agriculture strawberry breeding program has introduced 61 cultivars from 6 breeding locations in its 61-year history. Fifteen to 20 of these cultivars have been widely grown, and 5 of the recent releases show exceptional promise. From its inception, the program has been aimed at producing high-quality, multipurpose cultivars with disease resistance and broad regional adaptation. Because of disease pressures, genetic resistance has been emphasized, especially for red stele root rot. The USDA has become the principal source of red stele-resistant germplasm for breeding pruposes, and has constantly refined and improved its disease-screening techniques. Red stele and Verticillium resistance have now been incorporated into everbearing strawberries adapted to the eastern United States. Investigations concerning virus detection and eradication and the propagation of virus-free stocks have led to state virus-free plant certification programs, which assure the public of production of the cleanest possible strawberry nursery stocks. The work of the USDA and cooperating state stations has played a significant role in the improvement of strawberry cultivars and the development of modern strawberry production in the United States.
Abstract
Young strawberry (Fragaria × ananassa Duch.) seedlings were screened over a 4-year period for resistance to a composite of races of the red stele root rot causal organism, Phytophthora fragariae. A mixture of mycelia of 5 races of the organism, agar and water used as a root dip at the time of planting into sand on 6- to 8-week-old seedlings gave uniform results in the elimination of susceptible seedlings approximately five months later. The technique lends itself to efficient and effective mass screening of strawberry seedlings for relative resistance to P. fragariae.
Abstract
A clone of the diploid blueberry species Vaccinium atrococcum Heller, was previously found to be highly resistant to the fungus tetraploid highbusy blueberry. The tetraploid V. atrococcum was highly root-rot resistant in a greenhouse study. It was crossed with ‘Earliblue’ and 85 seedlings were obtained. In general, the seedlings were fertile, had small, dark fruit with mild flavor, good scars and quite soft flesh consistency.
Blueberry selections Me-US 32 and Michigan Lowbush 1, and cultivars ‘Berkeley’, ‘Bluecrop’, ‘Earliblue’, and ‘Dixi’ were screened in the greenhouse for resistance to P. cinnamomi. Michigan Lowbush 1 was highly resistant to the root-rot fungus. Me-US 32 was resistant, but all the cultivars were susceptible. Michigan Lowbush 1 is a grandparent and probably the source of resistance of Me-US 32.