Heritability of Yield and Secondary Traits in two populations of Para Rubber Tree (Hevea brasiliensis)

摘要

Heritability and interactions of yield and growth traits were assessed in Hevea brasiliensis using full-sib progenies and clonal populations. Using parent-offspring regression, annual mean rubber yield (ARY) and summer yield (SY) showed moderate to high heritability (ARY, h2 =34-56%; SY, h2 = 36-52%). Among the yield components, girth exhibited low to moderate heritability ih2 = 17-36%) while branching height showed low heritability (H~2 = 18%). Using forty clonal genotypes, annual mean rubber yield(H~2 = 48%), rubber yield during peak period (H~2 = 47%) and rubber yield during stress (or summer yield) (if2 = 44%) showed high estimates of heritability. Among the other yield components, except volume of latex during stress period (H~2 = 40%), remaining yield components showed moderate estimates for heritability (H~2 = 29-37%). Dry rubber content (DRC) based on annual mean showed very high heritability (H~2 = 68%), followed by DRC during stress (H~2 = 51%) and peak (H~2 = 50%) periods. Latex flow rate based on annual mean and peak period data showed high heritability (H~2 = 51%) followed by latex flow rate during stress period (H~2 = 42%). Plugging indices of annual and stress period showed high heritability (H~2 = 43%) than that of peak period (H~2 = 25%). Regarding growth traits, girth showed high heritability (H~2 = 50%) than girth increment (H~2 = 32%). While bark thickness showed high heritability (H~2 = 40%) length of tapping panel showed moderate heritability (H~2 = 27%). Total chlorophyllcontent exhibited moderate heritability (H~2 = 22%); chlorophyll pigment ratio showed low heritability (H~2 = 5%). Based on parent-offspring analysis, annual mean rubber yield exhibited high genetic correlation with summer yield and girth. Annual mean rubber yield and summer yield were negatively correlated with branching height. Regarding phenotypic correlations among the forty clonal genotypes, annual mean rubber yield exhibited high correlation with latex volume, latex flow rate, DRC, girth and barkthickness. However, annual mean rubber yield was negatively correlated with yield depression under stress and plugging index. Rubber yield, volume and rate of flow of latex over the three periods, yield depression under stress, girth increment, annual mean plugging index and plugging index under stress showed high estimates of genetic advance. The high estimates of heritability for yield and its components coupled with their high genetic gain indicated that considerable improvement can be achieved for these traits through selection. Estimates for indirect selection efficiency were not optimal for indirect selection for yield using girth and summer yield.