Heritabilities of the pungency and single-center traits were estimated in onion breeding lines using selection response and half-sib family analyses. Pungency was determined by measuring enzymatically produced pyruvic acid in individual bulbs. After one generation of selection, pungency was lowered by 0.37 and 0.42 μmol pyruvic acid/gram fresh weight in the breeding lines 90-61-1 and 89-69-8, respectively, and realized heritabilities of 0.21 and 0.51 were estimated. Heritability estimates calculated through half-sib progeny analysis were 0.53, 0.48, and 0.25 for pungency in the breeding lines 90-61-1, 90-62, and 89-69-8, respectively. The number of single-centered onions was increased by 19% and 22% in the lines 90-62 and 89-69-8, respectively, after one generation of selection, and the realized heritability estimates were 0.37 and 0.34, respectively.
Marisa M. Wall, Ayaz Mohammad, and Joe N. Corgan
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%.
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.
Jan de Jong and S. Honma
Estimates of heritability and general and specific combining ability for resistance of tomato to Corynebacterium michiganense (E. F. Sm.) H. L. Jens, were made, using a half diallel with 6 parental entries. Both the general and the specific combining abilities of the parents differed. Additive variation accounted for 74% (narrow sense heritability) of the total variation, suggesting that a large part of the observed variation is fixable in true-breeding strains.
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.
D. E. Kester, P. E. Hansche, V. Beres, and R. N. Asay
Means and variance components were estimated for genotype, environment (year), and genotype-year interactions for 28 nut and kernel traits of almond (Prunus amygdalus Batsch). The analysis involved over 2,500 genotypes and 20 years of observations. Estimates of heritability were obtained for 19 traits. The latter analysis involved some 100 families. The genetic component of variance and heritabilities tended to be large for shell type, size, shape, double kernels, bitterness, and crease. Year and genotype-year effects were large for quality factors such as shell and kernel color, callus, shriveling, pubescence, grade, blanks, smoothness, gumminess, and broken and split kernels.
Thomas Byrne, Dana Drennan, and James Harding
Statistics were developed to measure the relative importance of genotype × environmental (GE) interactions. Estimates indicate that as much as half of the genetic variance for cut-flower yield in the Davis Population of Gerbera may be attributable to GE interactions. The bias this causes in broad-sense heritability estimates averaged 10.3% ± 2.97% for single-factor interactions; 15.6% ± 3.52% for 2-factor interactions, and 26.8% ± 3.45% for 3-factor interactions. The mean unadjusted broad-sense heritability for cut-flower yield in the same experiments was 37.1% ± 6.54%. Therefore, response equations that do not take interaction bias into account will overestimate selection potential.
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.
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.
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.