Genetic variability for manganese concentration in Phalaris aquatica growing in acid soil

Abstract

High levels of manganese in forage can retard the growth of livestock. The feasibility of breeding for lower manganese concentration in shoots of phalaris was examined in a variable population growing in acid, manganiferous soil. Sampling leaves of a particular physiological age in a field-growing breeding population provided an adequate indicator of manganese concentrations in whole shoots. Significant family differences were demonstrated. When transferred to sand culture, high manganese selections maintained consistently higher tissue manganese concentrations than low manganese selections over a wide range of manganese treatments. However, the range of variation was much smaller than in the field. Inheritance of manganese concentration was studied in 52 field-grown half-sib families and their parents from the breeding population. Mean family leaf sample concentrations ranged from 179 to 331 8g Mn g-1. Narrow-sense heritability estimates were 0.72 from the half-sib analysis and 0.40 from the parent-offspring relation. The former estimate is considered the more accurate, because the parent-offspring estimate was depressed by high random variation in some parent means. The mean manganese concentration of the population is predicted to decrease by approximately 80 8g g-1 in each generation in which progeny are raised only from those 25% of plants with the lowest manganese concentration. Although this estimate may have been influenced by available soil aluminium, it indicates that breeding for lower manganese concentration in phalaris is feasible.