Heritability of shoot die-back and root biomass in sixteen Pterocarpus angolensis (Fabaceae) half-sib families from Malawi, Namibia and Zambia.

摘要

The experiment was conducted to ascertain narrow-sense heritability (h2) and the family-within-provenance variation in shoot die-back, taproot length and root biomass of half-sib Pterocarpus angolensis families from Malawi, Namibia and Zambia. Provenances differed significantly in shoot dieback for both shoot dieback seasons. A within provenance family effect was not significant in the first shoot dieback season but was significant in the second shoot dieback season. An increase in the proportion of seedling mortality, to 91%, for a Malawi family was observed in the second shoot dieback season. Provenance and within provenance family effects may be due to latitudinal differences between the provenances. The h2 of shoot dieback was 0.07 (SE=0.07) in the first shoot dieback season and 0.42 (SE=0.27) in the second shoot dieback season. Narrow-sense heritability for root biomass was 0.81 (SE=0.45). The h2 for the second dieback season and root biomass suggest the traits are heritable. Random selection of individual families for assessing shoot dieback is important since this trait is only restricted to seedlings and saplings and not mature trees. Within provenance family effects for root biomass were significant, indicating differences between families. Two families from the most northerly provenances of Phalombe and Skull Rock in Malawi were significantly different from other southern families. Non-significant phenotypic correlation between shoot dieback and root biomass shows that shoot dieback is not likely to be determined by root size nor taproot depth. Although a non-significant negative phenotypic correlation (-0.15) between the second shoot dieback season and root biomass was obtained, a family from Malawi that had the highest mean shoot dieback in the second shoot dieback season had the smallest root biomass. Half-sib families with post shoot dieback growth potential, in the first shoot dieback season, are likely to have a better chance of post shoot dieback growth later.