ONTOGENIC EVALUATION OF GRAIN-YIELD AND TIME TO MATURITY IN BARLEY

High grain yield and early maturity are desirable characteristics in m any regions in which barley (Hordeum vulgare L.) is grown. However, ne gative correlation between these traits makes their joint improvement difficult, Previous research quantifying the contribution of traits to grain yield has not included their effects on time to maturity, and o ften has not included important developmental traits related to time t o maturity, The purpose of this research was to quantify the determina tion of grain yield and time to maturity in barley, using a model that included developmental traits such as leaf number, phyllochron, and g rain fill rate, A genetically diverse group of 24 barley genotypes was grown for three years at Palmer, AK, and significant causal relations hips determined using path analysis and stepwise regression, Longer ve getative periods (time to heading) resulted in higher grain yield, but longer heading-to-maturity periods had no effect on grain yield, Fast er grain fill rate resulted in higher grain yield and shorter grain fi lling period. In environments similar to these, the competing objectiv es of high grain yield and acceptably early maturity were realized by cultivars with relatively long preheading periods and relatively short reproductive periods, without exceeding the critical level of early m aturity required by growers, Longer preheading periods appear necessar y to develop an adequate number of kernels per spike and sufficient nu mber of leaves to provide photoassimilate during grain fill, These res ults provide breeders additional insights for decisions involving choi ce of germplasm and selection criteria in breeding programs.