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Abstract
Four methods of inoculation with Verticillium were tested for effectiveness in infecting strawberry plants grown in a greenhouse bench. The most severe and early symptoms were produced with a macerated mycelium root dip inoculum. Effect of inoculum aggressiveness on the extrapolation of plant resistance information is discussed.
Abstract
Fifty seedlings each of 8 tetraploid interspecific populations involving 6 Vaccinium species were examined for date of flowering, date of fruit ripening, fruit yield, color, firmness, and size. The 8 progenies contained from 25 to 75% highbush blueberry (V. corvmbosum L.) germplasm. There were significant differences among the 8 populations for all fruit characters and for the number of days from bloom to ripe fruit. Only 2 backcross progeny populations (75% high-bush blueberry) produced significant numbers of seedlings that met the selection criteria for 4 fruit characters.
Abstract
Young highbush blueberry seedlings (Vaccinium corymbosum L.) from 26 crosses of a partial diallel were inoculated with Phytophthora cinnamomi Rands by dipping the roots into a mycelial slurry. The seedlings were grown 90 days in sand in the greenhouse and rated for resistance to root rot damage. Of the 2412 inoculated seedlings, 214 (8.9%) were resistant. The 2 parental clones that produced the largest percentage of resistant seedlings were US 141 and G-164; within their progenies, each produced an average of 18% resistant seedlings. Mean squares for general (GCA) and specific combining ability (SCA) were significant at the 1% and 5% levels, respectively. The mean square estimate for GCA was about 5 times higher than that for SCA, While both additive and nonadditive effects are important, rapid improvement can be made by phenotypic selection. Resistance to P. cinnamomi in blueberry progenies studied appears to be partially recessive and quantitatively inherited. Inoculation of young seedlings by root dipping in a mycelial slurry of P. cinnamomi and growing the seedlings in sand provided rapid identification of resistant plants.
Abstract
Hexaploid Vaccinium hybrid progenies, including F1, F1 intercross, F1 × F2, BC1, BC1 intercross, and BC1 × F2 crosses between V. ashei Reade and V. constablaei Gray, and an intercross between late-blooming V. ashei genotypes, established in the commercial blueberry production area in eastern North Carolina, were compared among themselves and with 2 highbush blueberry (V. corymbosum L.) cultivars for flowering, ripening, primary mummy berry infection, crop, and fruit characteristics. There were significant differences among progenies for all traits, with sufficient variability for selection within most progenies. Differences reflected specific parent combinations rather than type of cross with the V. ashei–V. constablaei derivative progenies. The experiment included both V. ashei and V. ashei–V. constablaei derivative progenies that produced a high percentage of seedlings flowering with or later than highbush blueberries. Two percent of the V. ashei–V. constablaei derivative seedlings bloomed and ripened with the early ripening highbush cultivar ‘Croatan’. Crop ratings were variable in all progenies, and high sds for the cultivars indicated that a high percentage of the variation was environmental. Primary mummy berry infection significantly reduced the crop in several progenies but was not responsible for the poor overall crop performance of most. Mean fruit size of the V. ashei intercross was large enough for hand harvest, while all but the 2 smallest-fruited V. ashei- V. constablaei derivative progenies were large enough for mechanical harvesting. Fruit of most progenies were commercially acceptable for color, picking scar, firmness, and flavor.
In the 1970s, the U.S. Department of Agriculture (USDA) began developing low-chill-adapted highbush blueberry (Vacchizium corymbosum L.) for the southern United States (lat. 29° to 32°N) by using germplasm of the native southern species, V. darrowi Camp. This breeding work resulted in the release of several low-chill southern highbush blueberry (SHB) cultivars in the mid-1980s. These cultivars have been evaluated for yield and adaptation at several locations through the southern regional blueberry germplasm evaluation trials. These trials have shown that organic mulch is required for good performance of SHB. The one-fourth V. darrowi composition of SHB cultivars presents problems of freeze damage at some locations. This problem may be resolved by breeding cultivars through several alternative approaches.
Eight clones with various Vaccinium species in their background were evaluated to determine their potential for improving fruit characteristics in the southern highbush blueberry. One clone was crossed with each of the others to produce seven sets of progenies which were evaluated with the parent clones. Heritability estimates were computed as the regression of progeny on parental means for each character. The progenies ranged from small to average berry size and weight, were above average for picking scar, and were generally less than average for color, firmness, and flavor. Mean of progenies was not significantly different from the parental mean for any character. Very high (0.45-0.85) heritability estimates were found for each character except berry firmness (0.22). These results suggest that considerable improvement in each character except possibly berry firmness should result from phenotypic recurrent selection in a broad based population involving these parents.
Abstract
Most progenies from intercrossed or outcrossed inbred selections of strawberry (Fragaria × ananassa Duch.), germinated as well or better than a control outcross between 2 vigorous noninbred clones. Germination of an S3 progeny was lower than the control. In general, inbreeding reduced seedling vigor while intercrossing or outcrossing of inbreds restored vigor. Germination total and rate as expressed by an index were unrelated to subsequent seedling growth.
Seven highbush blueberry (Vaccinium corymbosum L.) cultivars were evaluated for their photosynthetic heat stability. Ail showed significant reductions in CO2 assimilation rates (A) as leaf temperatures were raised from 20 to 30C, although `Blue-crop', `Jersey', `Elliot', and `Rubel' (22% to - 27%) were significantly less affected than Spartan', `Bluejay', and `Patriot' (-41% to -51%). To determine whether temperature adaptations of highbush types can be broadened through hybridization with native, heat-tolerant species, `Bluecrop' was crossed with the V. darrowi Camp. selection Florida 4B, and F2, BC1, and BC2, populations were generated. This approach showed promise as genotypes were identified in all the derivative populations that were more heat tolerant than `Bluecrop' and had a high A.