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Loong S. Chang, Amy Iezzoni and Gerald Adams

Heritability and the genetic and environmental variance components of resistance to the canker-causing pathogen Leucostoma persoorrii were estimated in a population of diverse peach (Prunus persica L.)-genotypes. Disease resistance was measured as the length of necrotic tissue, i.e., canker length, following artificial inoculation in the field. Genetic and environmental variations were partitioned as variance components of the linear statistical model. Heritability was estimated by regressing average performance of seedlings on performance of their maternal parent. The genetic variance was highly significant, and the heritability for canker necrotic length was relatively high (0.72), suggesting that it should be possible to select L. persoonii -resistant individuals within the population.

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I-C Wen, W.B. Sherman and K.E. Koch

Peach-to-nectarine mutations are associated with broad pleiotropic effects. The present study addresses the heritability of nectarine-specific effects in three hybrid families. A comparison of peach and nectarine siblings showed that nectarine fruit were smaller (less fresh weight), rounder, darker, redder, and had higher levels of sugars and organic acids. These heritable characteristics are similar to effects of spontaneous peach-to-nectarine mutations described previously.

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J.W. Gonzales, D.P. Coyne, D.T. Lindgren, D. Schaaf and K. M. Eskridge

The potato leafhopper (PLH), Empoasca fabae Harris is the most important Empoasca species attacking dry beans (Phaseolus vulgaris L.) in North America. The objective of this study was to determine the heritability (h2) of PLH injury based on parent-offspring regression analysis of F3 means on individual F2 plants derived from crosses of pinto `Sierra' (resistant) × great northern `Starlight' (susceptible), and black bean `Tacarigua' (resistant) × `Starlight' (susceptible). Low narrow-sense heritability values of 0.29 ± 0.06 and 0.28 ± 0.10, respectively, were obtained for the above crosses. The low narrow-sense heritability estimates indicated large environmental effects on the expression of PLH injury in dry beans. An allelic test showed that both resistant parents possessed the same genes for resistance.

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Qiang Yao, Shawn A. Mehlenbacher and David C. Smith

The Oregon State Univ. breeding program is developing improved hazelnut cultivars for the kernel market. Most traits of interest are quantitative, yet there is little information available on their heritability. In this study, the heritability of 10 morphological and 4 phenological traits was estimated by regression of offspring means on midparent values. Seedlings from 35 crosses among 41 parents made in 1988 and 1989 were used. The parents represented the wide genetic diversity used in the breeding program. Estimates were all high, ranging from 0.56 for amount of kernel fiber and 0.58 for time of catkin elongation to 0.87 for percent kernel and 0.89 for nut depth.

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Valdomiro A.B. de Souza, David H. Byrne and Jeremy F. Taylor

Heritability estimates are useful to predict genetic progress among offspring when the parents are selected on their performance, but they also provide information about major changes in the amount and nature of genetic variability through generations. Genetic and phenotypic correlations, on the other hand, are useful for better planning of selection programs. In this research, seedlings of 39 families resulting from crosses among 27 peach [Prunus persica (L.) Batsch] cultivars and selections were evaluated for date of full bloom (DFB), date of ripening (DR), fruit period development (FDP), flower density (FD), node density (ND), fruit density (FRD), fruit weight (WT), soluble solids content (SS), apical protuberance (TIP), red skin color (BLUSH), and shape (SH) in 1993 and 1994. The data were analyzed using the mixed linear model. The best linear unbiased prediction (BLUP) was used to estimate fixed effects and predict breeding values (BV). Restricted maximum likelihood (REML) was used to estimate variance components, and a multiple-trait model to estimate genetic and phenotypic covariances between traits. The data indicates high heritability for DFB, DR, FDP, and BLUSH, intermediate heritability for WT, TIP, and SH, and low heritability for FD, ND, FRD, and SS. They also indicate year effect as a major environmental component affecting seedling performance. High correlation estimates were found between some traits, but further analysis is needed to determine their significance.

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Freddy Mora, Cristóbal M. Concha and Carlos R. Figueroa

, 2014 ; Santos et al., 2011 ). Threshold models have been reported to be useful for the genetic evaluation of categorical traits ( Sorensen et al., 1994 ), enabling the estimation of genetic parameters, including heritability and genetic correlations

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Long Ma, Kevin E. Kenworthy, Huangjun Lu and Ronald Cherry

these two modes of pollination. The objectives of this study were to compare seed set of common carpetgrass under self-pollination and open pollination and to estimate heritabilities of seed set, number of branches per inflorescence, and number of

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Mark E. Herrington, Craig Hardner, Malcolm Wegener, Louella L. Woolcock and Mark J. Dieters

risk and severity of these losses. The studies reported here estimate the genetic control (i.e., heritability) of resistance to rain damage, particularly damage resulting from water soaking and surface etching because initial observations indicated that

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Christopher S. Cramer*

Heritability estimates of bolting percentage (BP), pink root (PR) and Fusarium basal rot (FBR) incidences, and percentage of single centered (PSC) bulbs were calculated for an intermediate-day, open-pollinated onion population using selection response and half-sib (HS) family analyses. BP was determined by counting the number of seedstalks per plot when the population was seeded at an earlier planting date to induce bolting. PR and FBR incidences were determined by rating 30 bulbs/plot for the severity of PR and FBR, and calculated an incidence rate from the number of infected bulbs out of 30 rated. The PSC bulbs was determined by cutting transversely 30 bulbs at the vertical center of the bulb and looking for the presence of a single growing point or multiple growing points within 1.3 cm from the center of the bulb. Families were also evaluated for bulb quality that consisted of shape, size, maturity, firmness, number of scale layers, and dry outer scale thickness, adherence, retention, and color. Families were selected based upon an index that equally weighted BP, PR and FBR incidences, PSC bulbs, and bulb quality. No progress was made for BP even though the narrow sense heritability (h2) estimate was 0.51. PR and FBR incidence was reduced by 18% and 12%, respectively, and realized heritability (RH) estimates of 0.65 and 0.60, respectively, were calculated. h2 estimates calculated through HS family analysis was 0.46 and 0.37, respectively, for these two traits. Very little progress was made for the PSC bulbs and this was reflected in a RH estimate of 0.17. However, the h2 estimate was 0.71, suggesting that progress should be possible.

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W. R. Maluf, S. M. Azevedo and V.P. Campos

Heritabilities for resistance to root knot nematodes (Meloidogyne javanica and Meloidogyne incognita races 1, 2, 3, and 4) were studied in a population of 226 sweetpotato clones of diverse origin. For each nematode isolate tested, 128-cell speedling trays were filled with previously inoculated substrate (30000 eggs/1000 mL substrate). Sweetpotato clones suitably tagged and identified were randomly planted in the cells (one plant/cell), with a total of four plants per clone per isolate. Ninety days after inoculation, sweetpotato plants had their roots washed for substrate removal, and treated with 150 mg·L–1 Phloxine B to stain nematode egg masses. The number of egg masses per root was recorded, and plants were accordingly assigned scores from 0 (highly resistant) to 5 (highly susceptible). Broad-sense heritability estimates were 0.87, 0.91, 0.81, 0.95, and 0.93 respectively for resistance to M. javanica and races 1, 2, 3, and 4 of M. incognita. The frequencies of resistant genotypes were higher for M. javanica and lower for M. incognita race 2. Genotypic correlations (rG) among the resistances to the various Meloidogyne isolates utilized were weak, ranging from 0.11 to 0.57, suggesting independent genetic controls. Clones could be selected, however, with high levels of resistance to all nematode isolates tested. (This work was supported by CNPq, CAPES, FAPEMIG, and FAEPE/UFLA.)