Heritability and Phenotypic Correlations of Six Pecan Nut Characteristics

Abstract

<jats:p>Heritability estimates for pecan <jats:italic>[Carya illinoinensis</jats:italic> (Wangenh.) K. Koch] nut weight, nut buoyancy, nut volume, nut density, kernel weight, and percentage kernel were determined from 8748 nut samples representing 152 families collected during 25 years in the U.S. Dept. of Agriculture (USDA) pecan breeding program at Brownwood, Texas. Measurements were corrected for year-to-year environmental variability using least-squares constants of individual year effects. Adjusted values were then regressed on midparent means. Generally, heritability (h<jats:sup>2</jats:sup>) estimates were low to moderate: nut weight 0.35, nut buoyancy 0.18, nut volume 0.35, nut density 0.03, kernel weight 0.38, and percentage kernel 0.32. The low values are probably due to the extreme alternate bearing tendency of this species, since crop load affects pecan nut characteristics so directly. Phenotypic correlations among these traits showed that larger or heavier nuts had significantly higher kernel weight, buoyancy, and percentage kernel. Nut density increased with higher nut and kernel weight, but decreased with nut volume.</jats:p>

Selecting for Nut Characteristics in Macadamia Using a Genome-wide Association Study

“…The replication of cultivars may have allowed more accurate estimates and smaller error, and hence higher heritability in the study by Hardner et al (2001) compared with the current study. Our estimates of heritability were higher than that of NW and KW in pecan (h 2 = 0.35 and 0.38, respectively) ( Thompson and Baker, 1993). In this study, estimates of narrow-sense and broad-sense heritability were similar for each trait (Table 1), indicating that the model could not detect any dominance.…”

Heritability, variance components and correlation of morphological and phenological traits in hazelnut

“…Comparison with other crops When our results are compared with the same or similar traits in other nut and tree fruit crops, some similarities can be seen. Similarly high heritability estimates were reported for morphological traits in almond (Kester et al 1977, Dicenta et al 1993b) and walnut (Hansche et al 1972a), but lower estimates were reported for pecan (Thompson and Baker 1993). High heritability estimates have been reported for phenological traits in all crops, even though the crops, the studied populations, the growing conditions and types of measurements were dierent (Hansche et al 1966, 1972a, 1972b, Vileila-Morales et al 1981, Dicenta et al 1993a, Tancred et al 1995, De Souza et al 1998a).…”

“…Several authors have addressed this situation by adjusting values based on leastsquares estimates of year eects prior to heritability estimation. This approach was used in peach (Hansche et al 1972b), sweet cherry (Hansche et al 1966), grape (Firoozabady and Olmo 1987), walnut (Hansche et al 1972a) and pecan (Thompson and Baker 1993). In a similar study in almond (Kester et al 1977), however, the year eect was not signi®cant so unadjusted data were used.…”

“…Therefore, the selection of parents based on their phenotypic values is recommended and genetic advance is expected to be rapid. When heritability estimates are low to moderate, selection of parents based on phenotypes may still be eective and genetic advance will be satisfactory (Hansche et al 1972b;Thompson and Baker 1993). When heritability estimates are very low, the development of more precise objective measures and growing under more uniform conditions can reduce measurement error and thus increase heritability (Hansche et al 1966(Hansche et al , 1972b.…”

“…Correlation coecients have been estimated in several fruit and nut crops, including walnut (Hansche et al 1972a), pecan (Thompson and Baker 1993), peach (De Souza et al 1998a,b), sweet cherry (Hansche et al 1966), and grape (Firoozabady and Olmo 1987). Phenotypic correlation coecients have been reported most often.…”