Breeding and Genetics of Field Dry Down and Test Weight in Short-Season Elite Maize Hybrids.

Fast field dry down after physiological maturity is a very important feature for maize (Zea mays L.) hybrids. Test weight is economically a very important trait and accounts for the packing densities of grain. Both traits are related. The objectives of this research are to better understand the genetic basis controlling the expression of test weight and dry down rate and to identify elite inbred lines and hybrids with high test weight and fast rate of dry down. Three North Carolina II mating designs made of elite North Dakota State University (NDSU) and industry lines were used for seed production. Experiments were arranged in 12 x 12 partially balanced lattice designs and evaluated hybrids across four environments in 2007 and 2008. Data were collected for flowering (DS), ear moisture at four 7-day intervals starting 45 days after pollination (D1, D2, D3, and D4), test weight (TWT), and grain yield. Area under the dry down curve (AUDDC) represented field dry down rate. There was a positive relationship between DS and AUDDC (r = 0.80), indicating that earlier materials tend to have lower initial moisture content and contribute to lower AUDDC. A negative correlation was detected between AUDDC and TWT (r = -0.49), implying that field drying rate has an important impact on test weight. AUDDC was strongly correlated with harvest moisture (r = 0.83). Both additive and non-additive genetic variance were important for field dry down and test weight, but additive effects were more prevalent, particularly for dry down rate. NDSU lines ND05-73, ND06-85, and ND06-211 seem to be promising sources of fast drying hybrids; ND06-244, ND06-50, and ND05-126 showed potential for grain yield, while ND05-117, ND05-96, and ND290 seem to have potential for test weight. Industry line AGR3 and AGR4 were a good source for fast dry down and higher test weight, while AGR2, AGR6, and AGR11 were good for grain yield. Mapping populations will be produced through double-haploid breeding of top hybrids for further genetic dissection at molecular level.