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Open access

L. F. Lippert and P. D. Legg

Abstract

Ten cultivars of muskmelon were evaluated in a diallel cross at 3 locations during a single season for net appearance, absence of vein tract depression (sutures), rind thickness, percent soluble solids, percent flesh, and shape index (length/width). Variances among crosses were significant for all traits. Significant heterosis was favorable for percent soluble solids, but unfavorable for net appearance and shape index. General combining ability accounted for a greater portion of the variability among crosses than did specific combining ability, although both effects were highly significant for each of the traits. Crosses correlated favorably with cultivar performance for net appearance, vein tracts, and percent flesh. The combination of certain cultivars into a synthetic population for further improvement of muskmelon is discussed.

Open access

Shivaji Pandey and E. T. Gritton

Abstract

A diallel cross involving 8 pea (Pisum sativum, L.) cultivars and experimental lines was used to study the inheritance of percent crude protein of dry seeds, and selected agronomic traits. The F1’s averaged very near the midparent for percent protein, showing little heterosis. Heterosis and inbreeding depression were observed for plant height, seed yield, and its components. General combining ability for percent protein was of major importance in all experiments. Specific combining ability for percent protein was indicated only in one of the 2 years tested. GCA and SCA variances were significant for days to bloom, plant height, yield, and its components except for seeds per pod. Maternal effects were important for only the 2 traits days to bloom and plant height.

Estimates of broad sense heritability for percent protein ranged between 54 and 67%; and of narrow sense heritability, between 45 and 67%. The highest narrow sense heritability (80%) was observed for wt/seed and the lowest for yield (8%).

Open access

George L. Hosfield, Grant Vest, and C. E. Peterson

Abstract

The diallel cross technique was used to evaluate the performance of onion (Allium cepa L.) inbred lines in F1 combinations and to estimate combining ability of several traits. All possible crosses, including reciprocals, among 10 inbred lines of diverse origin and known horticultural performance were tested at 3 locations in 1973. Cytoplasmic male-sterility was used to insure that all seed from maternal plants was hybrid. Cross variances were highly significant for all traits at all locations. General combining ability effects accounted for most of these differences. Specific combining ability effects were significant at all locations for yield, weight/bulb, firmness, and percent of storage loss. In all instances variance components of general combining ability were larger than those of specific combining ability. Specific rankings of the best and poorest lines for the traits measured according to the effects of their general combining ability were not identical at each location, but the same inbreds were generally in the same positive or negative grouping. Inbreds M728 and M2399 transmitted substantial yield and bulb weight to their progeny, while la163 consistently depressed these traits in the F1's. These results confirm the contribution that inbreds M728, M2399, and la163 make to a hybrid. Significant mean squares for reciprocal effects were apparent at all locations for only yield and maturity. Maternal effects per se influenced reciprocal variation, but were, generally, less important than nonmaternal reciprocal causes.

Open access

George L. Hosfield, Grant Vest, and C. E. Peterson

Abstract

Nine inbred onion (Allium cepa L.) lines of diverse origin and known horticultural performance were crossed in diallel to measure the extent of heterosis for yield and 6 other traits and to evaluate the types of gene action involved in character expression. Parents and the 36 F1 hybrids were compared at 2 locations (Michigan and Wisconsin) in 1975. Average performance of the parents and hybrids showed good agreement between environments for yield and several other traits. The mean performance of F1 hybrids fell within the range of parents for all characters. Although not always significant, F1’s on the average yielded more, were earlier to mature, had greater bulb weights, more centers, fewer rings, and were less firm than the average of the better parents in crosses. Heterosis was significant and favorable at both locations for yield, maturity, and bulb weight, but unfavorable for centers/bulb. Yield heterosis of the hybrids over the mid- and high parent, respectively, were 39 and 20% at Palmyra, Wisconsin and 27 and 12% at East Lansing, Michigan. In general, high F1 yields were associated with crosses involving high yielding parents. Variances of general combining ability (GCA) predominated for all traits. Small but significant specific combining ability (SCA) effects were noted for maturity, bulb firmness, and % of storage loss.

Open access

Aage Krarup and David W. Davis

Abstract

Pea seed yield (W) and its components—pods per plant (X), seeds per pod (Y), and average seed weight (Z)—and also seeds per plant were found to be controlled by an additive genetic system, on the average. The existence of some departure from additivity was indicated by deviation of the F1 from the midparent, especially for X, W, and seeds per plant. This deviation was more likely due to epistasis or linkage than to dominance. Specific Heterosis (specific combining ability) was important for all components, while Variety Heterosis (general combining) was important only for Y and Z. Estimates of heritability were high, ranging from .38 for seeds per plant to .65 for Z. Yield was found to be closely related to X, Y, and Z in descending order. Pods per plant (X) probably is a good selection index for dry seed yield in the pea.

Open access

Safi S. Korban, Dermot P. Coyne, and John L. Weihing

Abstract

A Hunter Color Difference meter and a white-paint color chart were used to determine the degree of whiteness among 8 white-seeded Great Northern (GN) cultivars of Phaseolus vulgaris. A correlation coefficient of +0.84 was found between the 2 methods. The former method provided better separation of cultivars for degrees of whiteness than the latter method. Two genetic studies were conducted, with seed-coat whiteness determined by use of the white-paint color strip. ‘GN Emerson’ had the whitest seed-coat. The inheritance of seed-coat whiteness was investigated in 1978 using parents, F2s of the crosses Plant Introduction (PI) 165078 (bright white) with ‘GN Emerson’ (moderately bright white), ‘GN Valley’ (dull white) and ‘GN UI 59’ (dull white) and in the reciprocal cross ‘Bulgarian White’ (brightest white) × ‘GN UI 59’ (dull white). A quantitative pattern of inheritance was observed. Broad sense heritability estimates for this trait ranged from 46 to 57%. The Gardner and Eberhart model, Analysis II, was used in 1979 to estimate genetic effects for the trait in a 6 parent diallel cross involving ‘GN Emerson’, ‘GN UI 59’, ‘Bulgarian White’, ‘GN Star’ (dull white), ‘GN 1140’ (dull white) and ‘GN D-88’ (dull white). Additive genetic effects were predominant; but heterosis effects were also important, including significant effects for specific combining ability, and reciprocal crosses. ‘Bulgarian White’ showed high combining ability for brighter whiteness. The genetic data indicate that improvement of seed-coat whiteness in dry beans should be relatively easy to accomplish.

Open access

Nicolas E. Valladares-Sanchez, Dermot P. Coyne, and Robert F. Mumm

Abstract

A 6-parent Phaseolus vulgaris diallel cross was produced to determine the inheritance of leaf, external, and internal pod reactions to the bacterial pathogen Xanthomonas campestris pv. phaseoli (Smith) Dye = Xanthomonas phaseoli E.F.S. Dows (X.p.) Nebraska isolate EK-11. The parents and F1 generations were grown in the greenhouse, whereas the F2, along with parents, were also grown in the field at 2 locations (Lincoln and Scottsbluff, Neb.). The Gardner and Eberhart (1966) model, Analysis II, was used to obtain estimates of the genetic effects for the reactions to the pathogen in the different plant parts. Coefficients of variation were high in the greenhouse experiment and low in both field experiments. The increased precision of the field experiments allowed more genetic effects to be detected as being significant. The leaves of ‘Great Northern (GN) Nebraska #1 sel. 27’ and Plant Introduction (PI) 207262 were resistant, ‘Tacarigua’ moderately susceptible, and PI 163117, ‘GN 1140’, and ‘Guali’ were highly susceptible. The pods of the first 3 entries, along with ‘GN 1140’ showed moderate resistance, but the internal reaction of the pods of ‘GN Nebr. #1 sel. 27’ showed more susceptibility than the external reaction. The reaction to X.p. was quantitatively inherited in all experiments. Additive effects were primarily involved in the genetic control of the leaf, external, and internal pod reactions to X.p. Heterosis effects for leaf reaction were detected under field conditions. External and internal pod reactions were highly correlated, but little association between leaf and pod reaction was observed. It is, therefore, necessary to select for resistance simultaneously in both plant parts since correlated responses are not expected to be present. Large positive correlations were detected between the reactions of genotypes observed in the greenhouse with those in the field experiments and between the field experiments, indicating that greenhouse tests should adequately predict field performance. A significant genotype × location interaction for leaf reaction was detected, with ‘Guali’ and ‘Tacarigua’ being more susceptible at Lincoln, under higher night temperatures, than at Scottsbluff, indicating the importance of evaluating the reaction of germplasms to this pathogen in different environments.

Open access

Hyo G. Park and David W. Davis

Abstract

The inheritance of interlocular cavitation (IC), characterized by rupture of the soft, parenchymatous endocarp tissue between the seed locules in developing snap bean pods, was studied using 6 parental cultivars, all 30 possible F1 progenies grown in the greenhouse, and the 30 F2 families grown at various planting dates at 2 field locations.

IC appeared to be a highly heritable character conditioned by a predominantly additive polygenic system with partial dominance for resistance. Reciprocal effects were negligible. Neither epistasis nor transgressive segregation was detected. Order of susceptibility among genotypes was maintained over the wide range of environments. Genotype × environment interaction was significant, but was relatively small compared to total genetic variability. Association between greenhouse-grown F1 and field-grown F2 plants was high for degree of IC, suggesting that F1 performance might be informative in choosing superior crosses. Breeding progress appears to be feasible in a program designed to utilize the large amount of additive genetic variance.

Open access

George L. Hosfield, Grant Vest, and C. E. Peterson

Abstract

A diallel analysis was used to estimate combining ability of several traits in onion (Allium cepa L.) and evaluate the importance of interactions of general combining ability (GCA) and specific combining ability (SCA) with locations and years. All possible crosses among 7 inbred lines of diverse origin and known horticultural performance were tested for 2 years at the same 3 locations for yield, maturity, bulb traits, and storage quality. Highly significant differences among crosses were detected for all traits. The partitioning of among-cross variation showed that all GCA main effects were highly significant, and SCA main effects were significant for all traits but ring thickness. Cross × environment interactions were primarily due to the interactions of GCA effects with environments. The GCA × year interaction was significant for bulb firmness and centers/bulb, and the GCA × location interaction was significant for yield. While first-order interactions involved only GCA effects, all traits showed significant second-order interactions of both GCA and SCA with years and locations. Variance components of GCA were predominant for all characters, and ratios of GCA to SCA ranged from 2:1 for centers/bulb to 13:1 for % of storage loss. Variance components of GCA × environmental interactions at all levels and for all traits were always smaller than those for GCA main-effect components. For the traits maturity and % of storage loss, the SCA × year × location component was larger than the SCA component. Correlations of GCA effects between environments suggested that significant interactions of GCA were sometimes due to a 1) change in rank of effects from environment to environment and 2) a change in rank and change in variance.

Free access

Chad E. Finn, James J. Luby, Carl J. Rosen, and Peter D. Ascher

Progenies from crosses among eight highbush (Vaccinium corymbosum L.), lowbush (V. angustifolium Ait.), and V. corymbosum/V. angustifolium hybrid-derivative parents were evaluated in vitro at low (5.0) and high (6.0) pH for vitality, height, and dry weight. Succinic acid and 2[N- morpholino]ethanesulfonic acid (Mes) effectively maintained pH in the medium and rhizosphere. The pH regime did not affect percent radicle emergence from seed or survival; however, percent seed germination was slightly lower at high pH. The parental general combining ability (GCA), reciprocal and maternal, but not the specific combining ability (SCA) variance components were significant for plant vitality, height, and dry weight. The GCA variance components were six to 26 times larger than the SCA variance components for the plant growth traits. Variation due to pH regime was significant for vitality and dry weight but not for plant height. The progenies of parents with high percent lowbush ancestry were taller at both pH levels than those with less such ancestry. Little variation was apparent for higher pH tolerance as measured by dry weight; however, the GCA effects suggested that the progenies of some parents performed better than others at high pH. Vaccinium angustifolium parents differed in the extent to which tolerance to high pH was transmitted. In vitro screening in concert with a traditional breeding program should be effective in improving blueberry tolerance to higher pH.