Recurrent Selection for Kernel Weight in Spring Wheat1

Abstract

Successful recurrent selection in cross‐pollinated species is well documented, but few reports of its use in self‐pollinated species are available. Our objectives were to determine the gain from stuctured recurrent selection for kernel weight of wheat (Triticum aestivum L.) and to determine its indirect effects on other traits. Ten lines, selected for high kernel weight from 100 lines screened, were intercrossed to form the initial C0 population. Selection among S1 plants for high kernel weight was used with approximately 22 plants selected each cycle. The selection intensity varied from 1.5 to 2.9% per cycle and averaged 2.2%.Eighty random S3 and S4 lines each from C0 and C2, respectively, were used to compare variances and means. In addition, C1, C2, C3, and C4 were grown as populations for evaluation of gain.Kernel weight increased 3% per cycle from C0 through C2 as measured by the lines, and 7% per cycle from C1 through C4 as measured by the populations. Genetic variance for most measured traits remained as high in the C2 as the C0 population. Two cycles of selection resulted in lines with kernel weight higher than any lines in the C0 population. These results were further confirmed by the results of the population tests which indicated continued gain for kernel weight through Cycles 3 and 4.Negative indirect effects of selection for kernel weight were observed for days to head, spikelets per spike, kernels/cm of spike, and spikelets/ cm of spike. Grain protein increased slightly while plant height, grain yield, and test weight did not differ over cycles of selection.Structured recurrent selection produced a population with much higher kernel weight than did single crossing and selection among segregating progeny, even though the original population was selected for high kernel weight and a high selection intensity was used.