Seedling vigor characteristics among Chinese and Australian wheats

Successful early establishment and early leaf canopy growth is important fo r high yield in wheat in many regions. In this study, we report variation i n early vigor among 60 contemporary wheats of Chinese and Australian origin , the characteristics that contribute to this variation in vigor and the mo st efficient way to select for early vigor in a breeding program. Vigor was assessed in two environments. One was considered optimal and the other sub -optimal and there was a two-fold difference in leaf area. Early vigor was assessed as total leaf area at the 5th leaf stage and the traits considered to contribute to vigor were: kernel weight, emergence time, the rate of le af appearance, tiller appearance, specific leaf area, leaf area ratio, and the area of the earliest formed leaves. The wheats from China had, on avera ge, greater vigor. However, this was probably due to the greater kernel wei ght in these wheats (44 mg versus 35 mg). The trait most closely associated with vigor was the area of the first two seedling leaves in both the optim al and suboptimal environments. Next important were emergence time and then kernel weight. Rate of leaf appearance, tiller appearance, specific leaf a rea, and leaf area ratio did not contribute to early vigor in the optimal e nvironment. Of these traits, only tiller number was significant in the sub- optimal environment. Spring wheats, despite the lower tiller number, were 1 5% more vigorous than the winter wheats. It is proposed that the area of th e first two seedling leaves could be used to select for improved vigor in w heat.