Belly rot, caused by the fungal pathogen Rhizoctonia solani Kühn., is a severe disease in many regions that produce cucumber (Cucumis sativus L.). Annual crop loss to belly rot is commonly 5% to 10%, but losses as high as 80% can occur in individual fields. There are no resistant cultivars, so fungicides are used to provide partial control. Genetic resistance in an acceptable cultivar would be more desirable and economical. Studies were conducted in Summers 1991 and 1992 to screen promising germplasm for belly rot resistance using field and detached-fruit screening methods. In 1991, 105 cultigens (cultivars, breeding lines, and plant introduction accessions) were evaluated for belly rot resistance. The tests were repeated in 1992 with 63 cultigens, including the most resistant cultigens identified in 1991 and appropriate controls. Several cultigens were identified as potential sources of resistance genes. Pickling cucumbers showing resistance included PI 197085, PI 271328, and an F4 selection of PI 197087 × PI 280096. Slicing cucumbers with resistance included `Marketmore 76' and the F1 of Gy 14 × PI 197087. Belly rot resistance was not correlated with other horticultural traits measured, including fruit type, skin type, spine color, and firmness. The resistant cultigens identified should be useful for developing cucumber cultivars with enhanced resistance to Rhizoctonia solani.
Michael S. Uchneat and Todd C. Wehner
Ralph Scorza and Margaret Pooler
Doubled haploid peach [Prunus persica (L.) Batsch] lines were cross-pollinated to produce F1 hybrids. F1 hybrids were evaluated at 3, 7, 8, and 9 years after field planting for tree growth as measured by trunk cross-sectional area, and for fruit production as measured by total weight, total number, and production per unit trunk cross-sectional area. Fruit quality of most F1 hybrids was within the range of quality observed in progeny of standard peach cultivars, and tree growth and productivity were similar to those of standard cultivars. F1 hybrids present the possibility of developing scion varieties that can be produced from seed, thus eliminating the need for grafting scions onto rootstocks in situations where specific, adapted rootstocks are not necessary. They could also be used to develop genetically uniform seed-propagated rootstocks. The use of doubled haploid-derived F1 peach hybrids, however, would require reliable, efficient production techniques.
Masahiko Yamada, Akihiko Sato, and Yasuo Ukai
Environmental variance components were estimated for calyx-end fruit cracking in pollination-constant and nonastringent cultivars and selections of Japanese persimmon (Diospyros kaki Thunb.). The cracking value of a tree in a cultivar or selection (genotype) (X) was evaluated as the number of fruit that cracked divided by the total number (25) of fruit evaluated from each tree. Because the mean value of X was correlated with the variance of X, analyses of variance were performed using its square root value. The variance associated with genotyp× year interaction was the largest of environmental variance components. The variances associated among years and among trees within genotypes were very small. The mean percentage of cracked fruit in evaluation for 10 years was 3% for `Fuyu', 11% for `Matsumotowase-Fuyu', and 12% for `Izu'. On the basis of the environmental variance components obtained, it is proposed that all offspring genotypes exhibiting a phenotypic cracking incidence of less than 20% and 11% should be selected in single-year and three-year evaluations, respectively, when those genotypes are evaluated using 25 fruits from a single tree, in order to successfully select all genotypes with an genotypic incidence of less than 3%.
Jude W. Grosser*, J.L. Chandler, and R.M. Goodrich
Sweet orange (Citrus sinensis L. Osbeck) is the most horticulturally important and widely grown Citrus species in Florida and worldwide, and `Valencia' is the most important cultivar for processing. Frozen concentrate orange juice has been the primary product of the Florida and Brazilian industries, but recently there has been a strong shift to not from concentrate (NFC) product in Florida. The higher quality NFC has a greater consumer appeal, and brings a higher market price. The development of higher quality oranges with expanded maturity dates will facilitate this change and should increase the competitive ability of the Florida industry. No true sweet orange cultivars have been developed by conventional breeding due to biological impediments, and alternative methods to obtain genetic variation are being investigated, including studies of somaclonal variation. We have produced nearly 1000 somaclones of `Valencia' sweet orange using organogenesis, somatic embryogenesis, and protoplasts. Following several years of fruit evaluation, early and late maturing high quality somaclones have been identified based on juice analytical data (brix, acid, ratio, juice percentage, juice color, and lbs. solids). These clones have also performed exceptionally in taste panel evaluations comparing them with the traditional mid- and late-season cultivars. Second generation trees of the most promising clones have been propagated for further evaluation, and superior processing clones will be released to the Florida industry in the near future. An overview of this program including pilot plant juice quality data and taste panel results will be presented.
Paul Cooper, Robert Stark, Paul Francis, and Charles Allen
Eight tomato varieties were evaluated in 1999 for consumer preference of appearance and taste. Fruits were collected from a tomato yield trial conducted at the Southeast Research and Extension Center at Monticello, Ark. Four of the varieties (`Mountain Spring', `Celebrity', `Better Boy', and `Early Girl') were red-fruited. Three (`Bradley', `Traveler 76', and `Pink Girl') were pink-fruited. One variety, `Mountain Gold', was yellow-fruited. Fruit evaluations were conducted on three separate dates. Varieties were ranked 1–8 by the taste panelists for both outward appearance and for taste. Appearance and taste were not correlated. `Mountain Spring' was ranked best in appearance, followed closely by `Pink Girl' and `Celebrity'. However, the panelists ranked `Mountain Spring' next to last (seventh) for taste. `Pink Girl' was ranked first in taste, followed by `Better Boy', `Bradley', `Celebrity', and `Early Girl'. `Mountain Gold' was ranked last (eighth) for both appearance and taste. These results indicate that consumers should not rely on appearance alone when purchasing tomatoes. The results also indicate that tomato producers should have a thorough knowledge of the market that they are serving.
Séverine Morel, Richard E. Harrison, Donald D. Muir, and E. Anthony Hunter
Fruit from three red raspberry (Rubus idaeus L.) cultivars—`Glen Clova', `Glen Lyon', and `Glen Moy'—were harvested from four sites on two harvest dates and evaluated fresh or following storage at -20 °C to determine the relative importance of genotype, harvest date, location and freezing effects on 19 sensory attributes using a trained sensory panel. Freezing and cultivar × freezing interaction effects were relatively large while site, harvest date, and other interactions were of minor importance. The cultivar × freezing interaction was caused by differential responses among cultivars for the sensory attributes purple, juicy, sweet, and raspberry aroma with less discrimination among cultivars postfreezing. `Glen Clova' fresh fruit received the highest values for juicy, fruity, sweet, and raspberry aroma; `Glen Moy' fresh fruit received the highest values for purple; `Glen Lyon' fresh fruit received the lowest values for juicy, postfreezing, `Glen Lyon' received the highest values for purple and sweet and all three cultivars were similar for the other attributes. These data suggest that selection for improved postfreezing sensory characteristics should not rely solely on fresh fruit evaluations although further study of a more genetically diverse group of genotypes would be beneficial. The significant cultivar and minimal harvest date and location effects suggest that these fruit sensory analysis methods should be useful in selecting raspberry genotypes with superior fruit quality.
Daniel S. Kirschbaum, Kirk D. Larson, Steven A. Weinbaum, and Theodore M. DeJong
The pattern of total nonstructural carbohydrate [starch and soluble sugars (TNC)] accumulation in strawberry (Fragaria ×ananassa Duch.) nursery runner plants, cv. Camarosa, was determined for three growing seasons. A similar study was conducted on `Selva', but for only one year. Growth, development and fruit production patterns of plants transplanted to growth chambers (GC) or fruiting fields were also evaluated. The experiments were carried out on plants propagated in high latitude (41°50' N) nurseries in California (Siskiyou County). Plants were sampled beginning late summer through early autumn and analyzed for dry mass (DM) and TNC. Plants from different digging dates were established in GC or fruit evaluation plots in Irvine, Calif. (33°39'N). Initial TNC concentration in storage tissues at the time of nursery digging increased steadily from the second week of September to the third week of October. Crown and root TNC concentration and content were correlated positively with the accumulation of chilling units (CU = hours ≤7.2 °C) in the nursery. Root TNC concentration consistently increased from 6% to 10% DM in `Camarosa' (a short-day cultivar), and from ∼4% to 14% DM in `Selva' (a day-neutral cultivar) from mid-September to the first week of October. The root TNC content increased ∼2.5 times in `Camarosa' and ∼3.7 times in `Selva' during the same period. Transplant growth, development, and fruiting pattern were affected by digging date. Root TNC concentration and content were more sensitive to CU accumulation than crown TNC concentration and content. Therefore, root sampling appeared to be more appropriate than crown sampling for assessing the carbohydrate status and optimal digging dates of strawberry nursery runner plants early in the fall.
Sogo Nishio, Masahiko Yamada, Yutaka Sawamura, Norio Takada, and Toshihiro Saito
The effectiveness of detected quantitative trait loci (QTLs) and molecular markers associated with them in tree fruit breeding is measured by the percentages of the variance associated with detected QTL effects accounting for not phenotypic variance, but genetic variance of the trait. The genetic variance can be obtained by subtracting environmental variance from the phenotypic variance. Once accurate environmental variance components are obtained for a given selection field, environmental variances under any number of replications and measurement repetitions can be estimated. We estimated environmental variance components of fruit ripening date measured by days in a Japanese pear (Pyrus pyrifolia Nakai) breeding field in the National Institute of Fruit Tree Science, Tsukuba, Ibaraki, Japan. We estimated variance among fruits within a tree (σf 2) as 25.6, among trees within a genotype (σt 2) as 0.2, among years (σy 2) as 9.4, associated with genotype × year interaction (σgy 2) as 7.9, and associated with tree × year interaction (σty 2) as 1.2. Because σf 2 was the largest environmental variance component, increasing the number of fruit evaluated would most effectively reduce the environmental variance, and tree replication would not because of very small σt 2 and σty 2. The 95% confidence limit of a genotypic value was ± 10 days in the evaluation of five fruits on a single tree in a year and ± 7 days over 2 years. Broad-sense heritability in a family, each offspring in which was evaluated using five fruits on a single tree in a single year, was estimated at 0.83 for three full-sib families analyzed.
Jeong Ho Roh, Youn Young Hur, Sung Min Jung, Kyo Sun Park, Hae Keun Yun, Jong Chul Nam, Hae Sung Hwang, Dong Jun Im, and Kyong Ho Chung
pruning, mechanical weed control, and drip irrigation. Annual fruit evaluation data collected from ‘Hongju’, ‘Italia’, and ‘Campbell Early’ grapevines from 2011 to 2013 in Suwon, Korea, included vine yield, cluster characteristics, and berry weight
Chad E. Finn, Bernadine C. Strik, Brian Yorgey, Robert R. Martin, and Margaret M. Stahler
harvested ( Table 1 ). Subjective fruit evaluations were made during the 1997 to 1999 fruiting seasons using a 1 to 9 scale (9 = the best expression of each trait). The fruit ratings included sterility (subjective rating of drupelet set), firmness (as