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Heidi C. Wernett, Gary J. Wilfret, Thomas J. Sheehan, Paul M. Lyrene, Frank G. Martin, Timothy L. White, Gregory L. Powell, and Charles J. Wilcox

Intensive selection to improve vase life was performed on a sample population of Gerber ×hybrida Hort. from a broad source of germplasm. Progeny of a 5 × 5 diallel cross yielded estimates of narrow sense heritability (h2 = 0.28) and broad sense heritability (H2 = 0.28) for vase life based on a mean of 1.96 measurements per plant. Additive gene action is postulated to control this character since the difference between total genotypic variance and additive genetic variance components was small. Repeatability (r = 0.57) based on a single measurement per plant was moderately high. Heritability estimates were also determined based on 1, 2, 3, 5, and ∞ measurements per plant. Heritability ranged from 22% to 39%.

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Maren E. Veatch-Blohm, Dennis T. Ray, and Valerie H. Teetor

Guayule (Parthenium argentatum Gray) has been difficult to improve through classical plant breeding because of its facultative apomictic reproductive system. Attempts have been made to increase rubber concentration and yield by examining traits correlated with rubber production and their heritabilities. We propose a new way of estimating heritability in guayule that more accurately accounts for the contributions of apomictic and sexual reproduction. At two years of growth, there was a significant relationship between the parents and the progeny for all traits measured, except for rubber and guayulin B concentrations. Due to the facultative apomictic nature of guayule reproduction, heritabilities are more accurately presented as a range of values between the narrow and broad sense heritabilities. Since guayule is more apomictic than sexual, most heritabilities will be closer to the broad sense values. To increase resin and rubber yield in the progeny, selection should focus on height and width in the parents because height and width are highly correlated with rubber yield, with the highest heritabilities (0.65 to 1.00 and 0.97 to 1.0, respectively) of the traits measured.

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Rolland Agaba, Phinehas Tukamuhabwa, Patrick Rubaihayo, Silver Tumwegamire, Andrew Ssenyonjo, Robert O.M. Mwanga, Jean Ndirigwe, and Wolfgang J. Grüneberg

variability in a given population ( Abinasa et al., 2011 ). The objective of this study was to estimate genotypic means, variance components, broad sense heritability, GCV, PCV, and correlations for yield components [i.e., SRFY, SRDY, VNY, FBY, and harvest

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Durel J. Romaine and Don R. LaBonte

Narrow-sense heritability (h2) estimates for sugars were determined to assess the feasibility of breeding for a sweeter baked sweetpotato. Roots of parents and half-sib progeny were baked (190°C for 75 minutes) 16 weeks after harvest. Sugars from 10 gram root samples were extracted in ethanol for HPLC sugar quantification. Alcohol insoluble solid (AIS) residues (starch) were also measured from the samples. Dry matter was determined on a separate 10-g sample. Narrow-sense heritability estimates based on variance components analysis for AIS and percent dry matter were 0.20 and 0.32, respectively. Estimates for sugar data were 0.05 for sucrose, 0.52 for maltose, and 0.52 for total sugars (fructose, glucose, sucrose and maltose). These heritability estimates for maltose and total sugars imply a breeder could expect a moderate gain in sweetness over several cycles of selection.

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Paul E. Hansche

The heritability of fall leaf abscission and spring bloom date were estimated in a peach breeding stock recently infused with genes of divergent evolutionary origin. One of the two recent progenitors of this breeding stock was evergreen. The other had a high chilling requirement. The heritability of full-bloom date in this breeding stock was estimated to be 0.60 ± 0.08 SD, under the assumption of no outcrossing, and 0.67 ± 0.08 s d, under the assumption of 30% random mating. The heritability of the percentage of leaves abscised by 18 Nov. 1988 was estimated to be 0.33 ± 0.08, under the assumption of no outcrossing, and 0.47 ± 0.08, under the assumption of 30% random mating. The heritability of the percentage of leaves abscised, estimated from data collected on 14 Nov. 1989, was 0.49 ± 0.08, under the assumption of no outcrossing, and 0.55 ± 0.08, under the assumption of 30% random mating. The phenotypic correlation between date of full bloom and percentage of leaves abscised in the following November was estimated to be 0.21; 0.18 t(0.05) > 0.21 > 0.26 t(oo.1). Apparently, these traits readily could be genetically manipulated to circumvent the freeze damage that leads to susceptibility to Cytospora and related disease organisms.

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James S. Beaver and Juan Carlos Rosas

Heritability of length of the reproductive period and rate of seed mass accumulation in beans (Phaseolus vulgaris L.) was estimated using 170 randomly derived F6 and F7 lines from three populations evaluated in the field in Puerto Rico and Honduras during two growing seasons. Narrow-sense heritability for length of reproductive period ranged from moderate (0.43) to high (0.83), and transgressive segregation for shorter and longer reproductive period was observed for the three populations. Heritability of rate of seed mass accumulation was low (0.24) to intermediate (0.49). Lines with high yield potential, which matured 4 to 7 days earlier than the later parents L227-1 and `Catrachita', were selected. Most of the superior lines combined earlier maturity with high yield potential by having greater rates of seed mass accumulation than the early parents `Cuarentena' and `Cuarenteño'. Low to intermediate heritabilities for rate of seed mass accumulation suggest that selection for this trait would be more effective by evaluating advanced generation lines in replicated trials. Several lines yielded significantly more than L227-1 or `Catrachita' by combining long reproductive period with fast rate of seed mass accumulation.

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P.G. Thompson, John C. Schneider, and Boyett Graves

Narrow-sense heritability for component traits of freedom from weevil injury and yield of sweetpotato were estimated by parent-offspring regression and variance component analysis. Heritability estimates by variance component analysis based on half-sib families for percent and number of uninjured roots were 0.25 and 0.83, respectively. Individual plant heritability estimates for uninjured root percent and number were 0.03 and 0.13, respectively. Heritability estimates by parent-offspring regression for uninjured root percent and number were 0.35 and 0.52, respectively. Genetic variance was mostly additive for all traits except stem diameter. Genetic correlations between total root number, uninjured root number, and percent uninjured roots ranged from 0.66 to 0.87, indicating that selection for uninjured root number should most effectively increase uninjured root number and percent, as well as total root numbers. Predicted gains in uninjured root percent and number were 8.8% and 0.87 in the progeny derived from intermating the highest four out of 19 families for uninjured root number. The 0.87 gain in uninjured root number equals a 24% increase in one breeding cycle.

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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.

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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.

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Michael Dossett, Jungmin Lee, and Chad E. Finn

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