DIALLEL ANALYSIS OF FLOWERING-TIME IN CORN (ZEA MAYS) USING A CORN HEAT UNIT TRANSFORMATION

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Abstract
A set of 8 corn (Z. mays L.) inbreds was studied in a diallel cross over 2 yr and in a growth room to investigate general and specific combining ability for flowering time. Diallel analysis of days from emergence to flowering revealed a failure of the joint Wr/Vr regression in 1 of the years, indicating a lack of agreement with the simple additive-dominance model of inheritance. The array position changed across the years and environments, complicating genetic interpretation. Transforming data of flowering time to cumulative corn heat units (CHU) to flowering gave a better fit. Joint regression was satisfactory and array position was more consistent across years and environments. Dominance was incomplete for low CHU to flowering. Positive (increasing CHU) and negative, as well as dominant and recessive, alleles were in about equal frequencies. Heritability estimates in the broad- and narrow-sense were high. The estimates of general combining ability were higher than the estimates of specific combining ability in all studies.