PHENOLOGICAL DEVELOPMENT-YIELD RELATIONSHIPS IN SPRING BARLEY IN A SUB-ARCTIC ENVIRONMENT

Barley (Hordeum vulgare L.) producers in northern, marginal agricultur al areas require cultivars that are both early maturing and high yield ing. However, negative relationships between these two characteristics limit their simultaneous improvement. A better understanding of the r elative contribution of the developmental stages to grain yield would assist breeders' selection. This study was undertaken to assess the re lationships between patterns of phenological development and grain yie ld in barley grown in a subarctic environment. Sixteen genetically div erse spring barley cultivars were grown for 3 yr at Palmer, Alaska, an d evaluated for grain fill rate, grain full period, growing degree day s (GDD) to heading, GDD from heading to physiological maturity, and GD D from physiological maturity to ripe maturity. Cultivars developed in temperate regions tended to have slower grain fill rates than those d eveloped in subarctic regions. Rapid grain fill rate was associated wi th high kernel weight, but not with grain fill duration or grain yield . Increasing GDD to heading would result in higher grain yield, while increasing grain fill duration would have little effect. These results indicate that northern-adapted cultivars should have pre-heading peri ods lasting as long as possible, followed by short grain-fill periods. Simultaneous selection for early maturity and relatively long time to heading is recommended for the development of early-maturing, high-yi elding cultivars adapted to northern conditions.