Environmental Variance and Broad-sense Heritability of Nut Traits in Japanese Chestnut Breeding

Abstract

<jats:p>We evaluated the nut harvesting date (NHD), nut weight (NW), pericarp splitting (PS), and infestation by insects (II) in eight cultivars/selections of Japanese chestnut, including a Japanese–Chinese hybrid, over 6 years. Data were analyzed by analysis of variance (without transformation for NHD, after log-transformation for NW and PS, and after square root transformation for II). The among-tree variance accounted for only 1.1% to 8.5% of the total variance. The variance component resulting from residual factors for the tree × year interaction and sampling errors was the largest component for NW, PS, and II, accounting for 46% to 54% of the total environmental variance. Because tree replication is costly and time-consuming in chestnut breeding, increasing the number of yearly repetitions is more efficient than increasing the number of tree replicates. Broad-sense heritability was 0.84 for NHD, 0.27 for NW, 0.48 for PS, and 0.17 for II in evaluations with one tree without yearly repetition. It increased to 0.91 for NHD, 0.40 for NW, 0.62 for PS, and 0.29 for II in evaluations with one tree in 2 years. For NHD, the heritabilities are sufficiently high to distinguish genetic differences among cultivars/selection. In contrast, the low heritability of II suggests that this trait should not be evaluated with an emphasis on the initial selection stage but rather with an emphasis on the secondary selection stage based on testing at several locations with a large number of yearly and tree replications.</jats:p>

Environmental Variances of Fruit Traits in a Mandarin-related Population Used in Citrus Breeding in Japan

“…These results are in line with those of the studies of FW and SSC of Japanese pear (Machida and Kozaki, 1975), Japanese persimmon (Yamada et al, 1993), and grape (Sato et al, 2000). Increasing yearly repetition is more reasonable than increasing the number of tree replications if both increase h B 2 similarly, because the latter requires more space and effort (Nishio et al, 2014). Variance by year could be decreased not only by yearly repetition as above, but also by a yearly adjustment procedure using the mean performance of the control genotype over several years (Yamada et al, 1994).…”

“…Analysis of variance (ANOVA) has been used to estimate the contributions of genetic and environmental variance components for fruit traits of Japanese persimmon (Yamada et al, 1993(Yamada et al, , 2002, grape (Sato et al, 2000), Japanese pear Kozaki, 1975, 1976;Nishio et al, 2011), chestnut (Nishio et al, 2014) and for carotenoid contents of citrus (Nonaka et al, 2012). These estimates provide information on optimal yearly repetition, tree or vine replication, and fruit sample size.…”

Genotypic Variation in and Environmental Variance Components of Sugar Composition in Japanese Pear Fruit

“…The reason why the increase in h B 2 with yearly repetition was slightly higher than with tree replication for FRU was that the environmental variance associated with s gy 2 , which was the largest environmental variance component for FRU, was not decreased by tree replication, but by year repetition. Increasing the yearly repetition seems more reasonable than increasing the number of tree replications if both increase h B 2 similarly, because the latter requires more space and effort (Nishio et al, 2014;Sato et al, 2000). Increasing the number of fruits within a tree to five for single year measurements increased h B 2 from 0.33 to 0.46 for TSC, 0.64 to 0.78 for SUC, 0.69 to 0.76 for FRU, 0.71 to 0.82 for GLU, and 0.76 to 0.82 for SOR.…”

“…An analysis of variance (ANOVA) has been performed to estimate the contribution of genetic and environmental variance components to the determination of fruit traits of sweet cherry (Hansche and Beres, 1966;Hansche and Brooks, 1965), Japanese pear fruit (Kozaki, 1975(Kozaki, ,1976Machida and Nishio et al, 2011), Japanese persimmon (Yamada et al, 1993(Yamada et al, , 2002, grape (Sato et al, 2000), citrus (Hamada et al, 2016;Nonaka et al, 2012), and chestnut (Nishio et al, 2014). These estimates provide information regarding the optimal yearly repetition, tree or vine replication, and number of fruits.…”

Signatures of Selection in the Genomes of Chinese Chestnut (Castanea mollissima Blume): The Roots of Nut Tree Domestication

“…A study in Japanese chestnut (Nishio et al, 2017 ) recently revealed quantitative trait loci associated with a set of traits including harvest date, nut weight, and pericarp splitting. Broad-sense heritability estimates for these traits ranged from 0.40 (nut weight) to 0.91 (harvest date) (Nishio et al, 2014 ).…”