Flag Leaf Physiological Analysis of Oat Isolines That Differ in Grain Yield from Their Recurrent Parents1

Abstract

An early and a midseason series of oat (Avena sativa L.) isolines were developed for resistance to crown rust Puccinia coronata Cda var. avenae Frazier and Ledingham), but they were significantly higher or lower yielding than their recurrent parent in each series. The purpose of this study was to determineif the isolines in each series had significant differences in physiological characteristics of flag leaves from their respective recurrent parent that may have contributed to the deviant grain yields.Plants were grown in field plots and CO2 exchange rates (CER) and transpiration (T) were measured on intact leaves. In the early series, the two high yielding isolines had higher CER, and in the midseason series the low yielding isoline had a lower CER than the respective recurrent parent. Rates of T and specific leaf weights (SLW) were similar to the recurrent parent T and SLW in each series.Differences in CER between isolines and their recurrent parent were attributable primarily to differences in residual (mesophyll) resistance (rr) to CO2 diffusion in both series. There was no association between CER and SLW within the two sets of closely related lines.