Inheritance of nitrogen and phosphorus utilization efficiency in spring barley at the vegetative growth stages under high and low nutrition

Inheritance of the nitrogen and phosphorus utilization efficiencies (NUE and PUE, respectively) and that of the tolerance (T) to limited NP nutrition was investigated in spring barley crosses at the vegetative growth stages. Plants were grown in sand-vermiculite cultures under high and low NP nutrition. In a diallel set (Ps and F₂s), both general combining ability (GCA) and specific combining ability (SCA) effects were significant for the variation in NUE and PUE, while the variation in T was mainly associated with GCA effects. The contribution of nonadditive genes for the utilization efficiencies was found to increase under nutrient shortages. Overdominance of genes was detected. The characters exhibited low heritabilities (0.10-0.42). Generation means analysis in two cross-combinations revealed significant effects of epistatic gene interactions. It was assumed that the involvement of both the dominance effects and epistatic interactions would not facilitate selection efforts to improve the characters in spring barley at its vegetative growth. Such selection should be performed among families of later generations. The genotype-nutrition interactions observed suggest that selection under diverse nutrition rates would be necessary for the more precise evaluation of barley efficiency under less favourable soil fertility.