heritability of phenotypic variation are lacking. In addition, previous research and breeding efforts have been focused in the eastern United States, whereas commercial production is centered in Oregon. At present, the black raspberry processing industry is
Michael Dossett, Jungmin Lee, and Chad E. Finn
M. H. Dickson and M. A. Boettger
Semi-hard seed (SHS) in beans is defined as dry seed which does not imbibe water during a 24 hour soak, but which will gain moisture rapidly at high relative humidity within 14 days and then germinate normally. The inheritance of SHS was found to involve several genes. Soft seed was incompletely dominant to SHS. Narrow sense heritability ranged from 20 to 50% in populations studied. SHS was associated with excellent seed quality resulting in unusually vigorous seedlings.
Min Wang and I.L. Goldman
The root-knot nematode (M. hapla Chitwood) poses a threat to carrot (Daucus carota L.) production in the United States. Little information is available concerning the genetic control of nematode resistance in carrot. Crosses between two inbreds, a resistant genotype (R1) and susceptible genotype (S1) identified in previous screening tests of carrot were studied in the F2 and BC1 generations to determine the heritability of resistance to the root-knot nematode. Seedlings of F2 (R1/S1), BC1S1, and BC1R1 generations were evaluated for their responses to infestation of M. hapla Chitwood based on gall number per root, gall rating per root, and root rating per root in a greenhouse experiment conducted during 1994. Narrow-sense heritabilities were calculated according to the method of Warner (1952). Narrow-sense heritability was 0.16 for resistance based on gall number, 0.88 for resistance based on gall rating, and 0.78 for resistance based on root rating. This information may be of importance to geneticists and carrot breeders for the development of nematode-resistant carrot cultivars.
Bong-kyoo Kim, Don R. La Bonte, Christopher A. Clark, and Mario I. Buteler
Narrow-sense heritabilities for reaction to chlorotic leaf distortion (CLD), incited by Fusarium lateritium Nees: Fr., were estimated in sweetpotato [Ipomoea batatas (L.) Lam] by variance component analysis and parent–offspring regression. Visually rated severity reactions to CLD varied greatly among the 20 parents used to generate half-sib progeny from open-pollinated nurseries in 1990 and 1991. Progeny from each nursery were evaluated along with parents in a completely randomized design in two consecutive years. Narrow-sense heritability (h 2) estimates based on variance components were moderate on an entry mean basis at 0.61 in 1990, 0.38 in 1991, and 0.33 for the two years combined. Slightly higher, but still moderate, estimates were obtained on an individual plant basis. Narrow-sense heritability estimates using parent–offspring regression were 0.35 in 1990, 0.33 in 1991, and 0.33 for the two years combined. Predicted next-generation response was highest using a half-sib family recurrent selection among three schemes compared at a 10% selection intensity. Our data indicate –0.63 improvement in the half-sib family CLD severity rating in one breeding cycle.
L.F. Lippert and M. O. Hall
Data from 14 traits in muskmelon (Cucumis melo L.) were analysed by parent-offspring regression to produce estimates of heritability and phenotypic, genotypic, and environmental correlations. Heritability estimates determined from correlation coefficients (h2 = r), equivalent to regression analysis on data coded in standard deviation units (h2 = b1), were low (5–13%) for maturity and yield traits, and moderate (53–71%) for fruit appearance and quality traits. Soluble solids content at h2 = 16% was the exception. Heritabilities calculated by intraclass correlations of half-sib progenies (h2 = 4ths) provided many values which exceeded 100%. Phenotypic, genotypic and environmental correlations among paired traits indicated many significant and desirable relationships which could be used to reduce numbers of observations on breeding materials as well as provide guidance for selection within future muskmelon populations. Correlated responses were predicted for all traits from single-trait selection of several fruit quality characters. Predicted and realized responses in the offspring generation by simulated direct selection (10%) for each character within the parent population are presented. Priorities for trait selection and choice of breeding procedures for improvement in muskmelon are discussed. External fruit characters such as net appearance and nonindented vein tracts, or intermediate fruit size, each of which can be scored visually and rapidly, appear most suited for selection within these populations.
Xurong Tang and Peter M.A. Tigerstedt
Eight characters relating to flowering and maturity, berry yield, and winter hardiness were estimated on the basis of intersubspecific or interprovenance hybrids to determine heterosis, heritability, and genetic and phenotypic correlations in sea buckthorn (Hippophae rhamnoides L.). Two provenances of ssp. rhamnoides, one of Finnish (Fin) and one of Danish (Dan) origin, were dominant to ssp. sinensis and Russian derived provenances (ssp. turkestanica) for most characters related to flowering or maturity. This tendency for dominance or overdominance also extended to berry yield and winter hardiness, except for hybrids between Finnish origins and Siberian (ssp. mongolica) origins. The start of maturity (Ms) and half maturity (Mh) showed the highest heritabilities (h2 = 0.88 and 0.81, respectively). The hybrids were matroclinal, suggesting that Ms and Mh may be sex-linked or cytoplasmically inherited characters. Winter hardiness was the trait with the lowest heritability (h2 = 0.02), suggesting that the climate at the testing site was not severe enough to differentiate variation among half sibs or full sibs derived from Fin x Dan, which on average proved hardier than the native parental provenance Fin. Full maturity (Mf) showed a moderate heritability but was stable across 2 years (rB = 1). High genetic correlations among Mf, Ms, and Mh (rG = 0.94, 0.96, and 1.00, respectively) suggest that these characters were controlled by the same genes. Yield showed a negative genetic correlation with all characters pertaining to flowering and maturity, indicating that selection for early flowering or early maturity should result in a gain in yield.
W. L. Summers and S. Honma
A comparison of inheritance patterns and heritability estimates from a NCII crossing model which included green and red cabbage, Brassica oleracea L. (Capitata group) indicated differences between green × green and red × green crosses. Green × green crosses exhibit dominance for early maturity, large head weight, small non-wrapper leaf weight and small stalk weight while red × green crosses exhibit the opposite dominance pattern.
Carlos D. Fear, F. I. Lauer, J. J. Luby, R. L. Stucker, and Cecil Stushnoff
Genetic variance components, narrow sense heritability, and combining ability effects of parents were determined for several traits from analysis of a partial diallel cross involving 17 parents. Parents included several Vaccinium species and interspecific hybrids. For fall growth cessation, general combining ability (GCA) effects were variable from year to year, and heritability was low. Variance due to GCA was more important than specific combining ability (SCA) variance for winter injury in each of the years. The heritability estimate over years was low for winter injury, although individual year estimates were higher. Lowbush parents had high GCA effects for winter injury in years with snow cover but low estimates for years without snow cover. Off-season flowering was observed in some progenies in both years studied. Certain V. angustifolium Ait. parents had high GCA effects for the occurrence of off-season flowering. The heritability estimate for off-season flowering in combined years was 0.47. Variation due to years and to GCA × year interaction was significant for all characters studied.
W. L. Summers and S. Honma
A comparison of inheritance patterns and heritability estimates from a NCII crossing model which included green and red cabbage, Brassica oleracea L. Capitata group, indicated differences between green × green and red × green crosses. Green × green crosses exhibited dominance for few non-wrapper leaves, greater efficiency index, and smaller leaf size while red × green crosses showed the opposite dominance pattern.
John R. Stommel and Kathleen G. Haynes
Inheritance of resistance to tomato anthracnose caused by Colletotrichum coccodes (Wallr.) S.J. Hughes was evaluated in parental, F1, F2, and backcross populations developed from crosses between adapted resistant (88B147) and susceptible (90L24) tomato (Lycopersicon esculentum Mill.) breeding lines. Resistance was evaluated via measurement of lesion diameters in fruit collected from field-grown plants and puncture inoculated in a shaded greenhouse. Backcross and F2 populations exhibited continuous distributions suggesting multigenic control of anthracnose resistance. Anthracnose resistance was partially dominant to susceptibility. Using generation means analysis, gene action in these populations was best explained by an additive-dominance model with additive × additive epistatic effects. A broad-sense heritability (H) of 0.42 and narrow-sense heritability (h2) of 0.004 was estimated for resistance to C. coccodes. One gene or linkage group was estimated to control segregation for anthracnose resistance in the cross of 90L24 × 88B147.