Dry Matter Accumulation and Grain Filling Period in Tropical Maize

Tropical adapted maize inbreds were studied over two locations/seasons with the Dry Matter Accumulation (DMA) rates and Grain Filling Period (GFP) durations calculated and analyzed for future breeding qualities. Assessment of the inbreds response to variations in solar radiation and temperature was also evaluated. Over 100 varieties were selected from a wide resource base of the Maize Inbred Resistance program at the U. of Hawaii. Inbreds were harvested at 4 different dates after pollination (14, 21, 28, and 35 DAP) in addition to a final maturity harvest in order to map the accumulation of dry matter. Linear regression analysis was performed for each variety to determine the DMA rate and GFP duration. The DMA rates significantly decreased from summer to winter, and the GFP durations were significantly extended for the majority of inbreds. Six inbreds were then selected on the basis of fast, slow, and average rates and durations then crossed in diallel form to produce fifteen hybrids. The parents and hybrids were grown and harvested in the previous fashion with the DMA rates and GFP durations assessed. General and specific combining abilities were assessed using Griffing's Method II of diallel analysis on a Lotusl23 spreadsheet. Broad sense heritability was determined to be 83.5% for kernel dry weight at final maturity, 96.8% for rate of dry matter accumulation, and 67.7% for grain filling period duration. Analysis of variance conducted on the parent and hybrid materials indicated that increasing the rate of DMA may have a more significant effect on grain yields than trying to extend the grain filling period. Data implied that effects from breeding for the DMA rate may be easier to determine than selecting for extensions in the filling period. Further studies should be conducted to verify and expand on knowledge gained through these trials and analyses