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.
Abstract
Awareness that the continuous variation of morphological traits in sweet potato can best be explained and studied with quantitative genetics has increased during the last 20 years (10, 16). This paper has 2 purposes: 1) to summarize available heritability estimates for traits of sweet potato and 2) to alert breeders to their use and application in crop improvement.
To assess the variability and heritability of salt tolerance in current rabbiteye blueberry (Vaccinium ashei) germplasm, about 30 plants from each of 15 crosses involving 8 parents were grown in sand culture. All plants were fertilized five days per week with a solution containing essential micro-and macronutrients but having an excess (250 ppm) Na level. After nine weeks, each plant was rated for vigor and chlorosis, dry weights of roots and shoots were recorded, and Na content of the roots and leaves were determined. The regression of progeny means on mid-parent means for leaf Na content produced a regression coefficient of 0.30, an estimate of heritability. There appeared to be little variability for Na content in the leaves of this germplasm so the moderate level of heritability would not be expected to produce much change in leaf Na by selection. Furthermore, there was no correlation between leaf Na content and either plant weight or rating which would facilitate selection of plants with low salt content in the leaves. variability existed for plant response to excess Na (plant rating) but heritability of the plant rating was estimated to be zero.
, 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
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
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
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.
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.)
stage much earlier ( Gitonga et al., 2014 ). With diploid roses, a heat shock treatment (1 h at 44 °C) decreased flower diameter (15.7%), petal number (23.3%), and flower dry weight (16.9%). A genetic analysis indicated that flower size is heritable
Abstract
Variance component estimates were obtained in a North Carolina Design I experiment for several traits in pickling cucumber (Cucumis sativus L.) for a simulated once-over mechanical harvest. The reference population was random-mating and derived from 18 inbred lines obtained from several U.S. breeding programs. Environments sampled were the spring and fall of a single year. Data indicated most of the genetic variance was additive for all traits except fruit color. Evidence for relatively large genotype by environment interaction variances were found for number of fruit, length to diameter (L/D) ratio, and fruit firmness. Heritabilities, based on full-sib families grown in 2 replications in each of 2 seasons, for dollar value and number of fruit, were .19 and .17 respectively. Genotypic and phenotypic correlations for number of fruit and dollar value were high indicating selection for increased number of fruit would be effective in increasing crop value.