Monday, November 5, 2007
66-1
Water Stress Response in Inbred Lines and Their Related Hybrids of Maize.
Santiago Cabada, INTA Paraná, Oro Verde, Argentina, Oscar Valentinuz, INTA Paraná - Facultad de Ciencias Agropecuarias (UNER), Ruta 11 km 12.5, Oro Verde-Entre Ríos, Argentina, Guillermo Eyherabide, INTA, Pergamino, Argentina, and Cesar Lopez, Universidad Nacional de Lomas de Zamora, Lomas de Zamora, Argentina.
Grain yield under water-stress conditions is a primary trait for selection in maize breeding. This study examines plant growth rate (PGR) during reproductive stages and plant grain yield of maize hybrids and their parental lines grown under both full irrigated and water stress conditions. Experiments were conducted during 2006-7 growing season at Paraná Research Station of INTA, Argentina. Three hybrids and five inbred lines developed by INTA Pergamino maize breeding program were grown in 20-L pails placed in the field and irrigated by water and nutrients. Treatments were i) well-watered, ii) water deficit during R1+15 days after silking and iii) water deficit 20-35 days after silking. Water deficit treatment were created by supplying 50% of daily transpiration from 2-4 days before starting the stress treatments. Measurements included anthesis-silking interval (ASI), plant grain yield (PY), kernel number per plant (KNP), and harvest index (HI). Plant growth rate (PGR) was estimated from allometric relationship determined by destructive sampling.
Stress conditions reduced PY (42%), KNP (22%), and HI (16%) in hybrids and hybrid x treatment interaction was significant for PGR (p<0.05). Significant inbred x treatments interactions were observed for PY, KNP, HI and PGR. PGR ranged between 0.89 and 2.31 g plant-1 day-1 for hybrids and between 0.12 and 1.15 g plant-1 day-1 for inbred lines. ASI values increased under water stress only in inbred lines. The response of kernel number per plant to PGR was curvilinear for hybrids and linear for inbred lines. A linear relationship between grain yield per plant and total dry matter per plant was found for hybrids and inbred lines. However hybrids showed a greater (15%) ear partitioning and lower (18%) threshold of total biomass for setting kernel than inbred lines. Compared with hybrids, inbred lines were more sensitive to water stress during reproductive stages.
Stress conditions reduced PY (42%), KNP (22%), and HI (16%) in hybrids and hybrid x treatment interaction was significant for PGR (p<0.05). Significant inbred x treatments interactions were observed for PY, KNP, HI and PGR. PGR ranged between 0.89 and 2.31 g plant-1 day-1 for hybrids and between 0.12 and 1.15 g plant-1 day-1 for inbred lines. ASI values increased under water stress only in inbred lines. The response of kernel number per plant to PGR was curvilinear for hybrids and linear for inbred lines. A linear relationship between grain yield per plant and total dry matter per plant was found for hybrids and inbred lines. However hybrids showed a greater (15%) ear partitioning and lower (18%) threshold of total biomass for setting kernel than inbred lines. Compared with hybrids, inbred lines were more sensitive to water stress during reproductive stages.