of 0.5 m within a row with 3 m between rows. Parental plants were grown in adjacent fields. Table 1. Fruit softening rate, degree of mealiness at 30 d of storage at ambient conditions, and general combining ability (GCA) for softening rate
Hiroshi Iwanami, Shigeki Moriya, Nobuhiro Kotoda, Sae Takahashi, and Kazuyuki Abe
Cecil Pounders, Tim Rinehart, Ned Edwards, and Patricia Knight
general combining ability (GCA) effects for 10 crapemyrtle parents for four traits (height, leaf out, bloom date, and flower color). z In this study, parental GCA was a very good predictor for SCA means recorded for the families ( Table 5 ). The
Yayeh Zewdie, Paul W. Bosland, and Robert Steiner
The inheritance of capsaicinoid content was studied in five Capsicum pubescens Ruiz & Pav. genotypes using diallel analysis. General combining ability and specific combining ability effects were significant for all capsaicinoids studied, indicating additive and nonadditive gene actions are present. The association of high capsaicinoid contents with high positive general combining ability of the parents also indicates the predominance of additive gene action in capsaicinoid inheritance. Because of the predominant additive gene effect, recurrent selection would be a good breeding method to increase capsaicinoid level in the population studied. Heterosis was observed in hybrids for some of the capsaicinoids, suggesting that F1 hybrids could also be used to increase capsaicinoid content.
Geok Yong Tan
Six Trinitario females of cacao (Theobroma cacao L.) were crossed with nine Amazonian males in a factorial crossing design. The 54 hybrid progenies were used to estimate genetic variability due to general combining ability (GCA) and specific combining ability (SCA) for yield, pod production, pod weight, husk content, number of beans per pod, average bean weight, and pod value. The results demonstrated that GCA differed significantly for all characteristics from all three sources (Le., female + male, female, and male). SCA (female × male) was also significantly different for all characteristics. The ratio of GCA to SCA ranged from 7.1 for number of beans per pod to 25.7 for pod weight. This result suggested that a major portion of the genetic variability was additive in nature for these characteristics. Among the six Trinitarios, KA2-106 was the best female parent; it contributed high yield and all the desirable pod and bean characteristics into the hybrid progenies. Trinitario KA2-101 combined high pod production and yield, but tended to transmit below-average pod and bean characteristics to its progenies. Amazonians KEE6 and KEE12 were the two highest-yielding male parents, but had below-average bean number per pod and average bean weight. KEE42 and KEE43 combined high yield and transmitted good pod and bean characteristics to their progenies. Based on the GCA effects and the mean performance of the hybrid progenies, a multi-line cultivar consisting of 20 high-yielding crosses with good pod and bean characteristics is being produced in seed gardens for commercial planting.
Nicholas P. Howard, Dennis Stimart, Natalia de Leon, Michael J. Havey, and William Martin
diallel excluding parents grown in greenhouse Environments 2 and 3 z at the West Madison Agricultural Research Station in Verona, WI. Table 3. General combining ability (GCA) in Impatiens walleriana for floral longevity in days in a half diallel across
Douglas V. Shaw and Thomas R. Gordon
Strawberry (Fragaria ×ananassa Duch.) genotypes retained for resistance to Verticillium wilt (Verticillium dahliae Kleb.) after two cycles of a two-stage (TS) selection procedure consisting of full-sib family selection followed by within-family selection of individuals, and genotypes retained for resistance using genotypic mass (GM) selection were crossed to a common set of moderately susceptible genotypes. The relative resistance of the seedlings from these progenies was compared using a resistance score and the percentage of stunted plants. Although the two sets of resistant parents had performed similarly in genotypic comparisons, those genotypes selected using the TS procedure yielded test cross offspring with significantly higher resistance scores (X̄ = 3.84 ± 0.09 vs. X̄ = 3.46 ± 0.09, t = 3.11**) and significantly lower rates of plant stunting (X̄ = 38.1% ± 3.1 vs. X̄ = 50.2% ± 2.9, t = 2.87**) than the parents chosen using GM selection. Further resolution using analysis of variance and general combining ability (GCA) estimates showed that these between-set differences resulted from higher resistance breeding values for parents selected using the TS procedure. The five genotypes with largest GCA for resistance score and four of the five genotypes with minimum GCA for percentage stunting were obtained by TS selection.
C.L. Treat and W.F. Tracy
Goss's wilt is a bacterial wilt and blight that may cause yield losses up to 50% or greater in sweet corn. Ten hybrids from a diallel cross of five sweet corn (Zea mays L.) inbreds were analyzed for resistance to Goss's wilt (Corynebacterium michiganense ssp. nebraskense Schuster, Hoff, Mandel, and Lazar) in 1987 and 1988. The inbreds used to make the diallel were widely used historically and were chosen on the basis of adaptation and relative maturity. Three hybrids were resistant and seven intermediate, while the field corn controls were extremely susceptible. General combining ability (GCA) and specific combining ability (SCA) sums of squares accounted for 94% and 6% of the variation among crosses, respectively. GCA was highly significant (P ≤ 0.01), while SCA was nonsignificant. Year differences were nonsignificant, but date of rating and hybrid × year interaction effects were significant (P 0.05). Resistance to Goss's wilt is available in sweet corn, and recurrent selection should be effective if improvement in resistance is desired.
Ana I. López-Sesé and Jack Staub
Three U.S.-adapted Cucumis sativus var. sativus L. lines and one C. sativus var. hardwickii (R.) Alef.-derived line were crossed in a half-diallel design to determine their combining ability for several yield-related traits (yield components). Six F1 progenies were evaluated in a randomized complete block design with eight replications in 1999 and 2000 for fruit number and length/diameter ratio (L:D), lateral branch number, number of female flowering nodes, and days to anthesis. Combining ability was significantly influenced (p < 0.05) by year for most of the horticultural traits examined. General combining ability (GCA) was significant for all traits in each year. Specific combining ability (SCA) was significant in magnitude and direction for only fruit number and days to anthesis. Data indicate that the C. sativus var. hardwickii-derived inbred line WI 5551 possessed SCA for yield component traits, and thus maybe useful for improving fruit yield in commercial cucumber.
Kevin E. McPhee, Robert S. Zemetra, Jack Brown, and James R. Myers
Common bean (Phaseolus vulgaris L.) is a nutritionally complete food, but contains antinutritional compounds that reduce digestibility. One group of compounds includes the raffinose family oligosaccharides (RFOs) (raffinose, stachyose, and verbascose), which are partly responsible for flatulence after beans are eaten. RFOs stabilize cell membranes during seed desiccation and when the seed rehydrates during germination. While low levels of RFOs are desirable nutritionally, high levels may enhance germination and emergence, particularly in cold, wet soils. Eight landraces selected for high and low sucrose, raffinose, and stachyose content, were crossed in a diallel mating design to investigate genetic control of the RFOs. Derivatized soluble sugars were measured using gas-liquid chromatography. Fructose, sucrose, raffinose, and stachyose were detected. In the F1, fructose varied from 0.1 to 2.5 mg·g-1 dry weight (DW), sucrose from 17.2 to 56.5 mg·g-1 DW, raffinose from 0.1 to 4.1 mg·g-1 DW, and stachyose ranged from 7.6 to 43.7 mg·g-1 DW. Griffing's analysis estimates of general combining ability were on average, 16.5 times larger than specific combining ability for all the RFOs, indicating that additive genetic variance was most important. Significant reciprocal differences were detected in the F1 and F2, but not in the F3. RFO accumulation was partially dominant as indicated by Hayman's analysis. Narrow sense heritability averaged over F2 and F3 generations for sucrose, raffinose, stachyose, total sugar, and total oligosaccharides were 0.22, 0.54, 0.44, 0.17, and 0.27, respectively. Moderate heritabilities indicate that manipulation of RFO accumulation in this set of bean lines would probably need to be done on a progeny row basis with replication.
W.A. Erb, A.D. Draper, G.J. Galletta, and H.J. Swartz
Abbreviations: BS, berry size; CYV, canopy volume; DFR, days to fruit ripe; DIF, differences in canopy volume; #DBF&F, number of days between flowering and fruiting; GCA, general combining ability; SCA, specific combining ability, TFW, total fruit