A comparative study of maturity indices and grain filling period in relation to yield in corn single crosses and their constituent inbreds
The conclusion from this study is that three criteria, moisture percentage, GDD and black layer formation, are not adequate to measure corn maturity, although they differ in suitability. The close association of ELF with maximum dry weight, and hence the physiological maturity and the ease of detection, gives it an advantage over the other two. However, cases of premature black layer formation are a pitfall and care should be taken in using this criterion of maturity. A combination of the determination of moisture content after black layer detection would save unnecessary sampling when nnisture content is high and filling is not complete. Further, the growing degree days would support the other two in guiding the planning of the crop growing in a given environment, so that on the basis of expected temperature (GDD), a rough estimate of a sampling date could be made. The data indicate a relatively small GDD variation within an inbred or hybrid in a specific environment. Thus, this third criterion would support a combination of the first two. The negative association of GDD from planting to pollination with GDD in the filling period suggests genes causing an increased GDD for filling period also would decrease GDD from planting to pollination. If indeed the 77 extension of the filling period would increase the yield, this would look like a favorable situation. However, further studies are required to support this view. From this study it is also clear that there is a positive correlation between the grain filling period and yield in hybrids, but a negative relationship in inbreds. It appears that selection for longer grain filling period may be beneficial, but there is need to study this relationship in several environments and years as well as establish its genetic basis. Days to silk were also found highly indicative of yield in the hybrids used in this study.