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

Mineral accumulation in vegetative giant parts and in mature kernels has be en proposed as an indirect selection criterion, either in addition to, or i n substitution of, carbon isotope discrimination (Delta), to assess grain y ield 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 b arley (Hordeum vulgare L.) cultivars. Carbon isotope discrimination and tot al ash concentration were measured at maturity in kernels and straw. As exp ected, the Delta values of kernels (Delta-K) and straw (Delta-S) were posit ively correlated within environments. By contrast, Delta-K and ash concentr ation in kernels were often negatively related within environments, which s uggests that mineral accumulation in kernels is not associated with the tra nspiration efficiency of the plants during grain filling. The lack of a pos itive relationship between ash concentration in the straw and either Delta- K or Delta-S indicates that ash concentration in vegetative tissues sampled at maturity may be of limited value as a surrogate of Delta. Grain yield c orrelated positively with either Delta-K or Delta-S, and negatively with as h concentration in kernels, especially in the poorest rain-fed environments . However, the ash concentration in the straw was not consistently associat ed with grain yield. While our results confirm that Delta traits are valid indicators of grain yield under Mediterranean conditions, the use of ash co ncentration in kernels for screening purposes is not warranted at this time due to the lack of a more accurate understanding of the physiological mech anisms underlying mineral accumulation in kernels. Prediction of grain yiel d through multiple linear regression has shown, however, that ash concentra tion in kernels could be used as a complementary criterion to Delta in poor rain-fed environments. (C) 1998 Elsevier Science B.V. All rights reserved.