Mineral accumulation, carbon isotope discrimination and indirect selection for grain yield in two-rowed barley grown under semiarid conditions

Abstract

Mineral accumulation in vegetative plant parts and in mature kernels has been proposed as an indirect selection criterion, either in addition to, or in substitution of, carbon isotope discrimination ( Δ), to assess grain yield of temperate cereals in Mediterranean areas. However, the association between mineral concentration, in different plant parts, and grain yield is not yet fully understood. In order to study these relationships, four rain-fed trials were established in northeastern Spain involving 10 two-rowed barley ( Hordeum vulgare L.) cultivars. Carbon isotope discrimination and total ash concentration were measured at maturity in kernels and straw. As expected, the Δ values of kernels ( Δ-K) and straw ( Δ-S) were positively correlated within environments. By contrast, Δ-K and ash concentration in kernels were often negatively related within environments, which suggests that mineral accumulation in kernels is not associated with the transpiration efficiency of the plants during grain filling. The lack of a positive relationship between ash concentration in the straw and either Δ-K or Δ-S indicates that ash concentration in vegetative tissues sampled at maturity may be of limited value as a surrogate of Δ. Grain yield correlated positively with either Δ-K or Δ-S, and negatively with ash concentration in kernels, especially in the poorest rain-fed environments. However, the ash concentration in the straw was not consistently associated with grain yield. While our results confirm that Δ traits are valid indicators of grain yield under Mediterranean conditions, the use of ash concentration in kernels for screening purposes is not warranted at this time due to the lack of a more accurate understanding of the physiological mechanisms underlying mineral accumulation in kernels. Prediction of grain yield through multiple linear regression has shown, however, that ash concentration in kernels could be used as a complementary criterion to Δ in poor rain-fed environments.