Grain yield gains in three recurrent selection cycles in the CNAIRAT 4 irrigated rice population
Paulo Hideo Nakano Range; Orlando Peixoto de Morais and Francisco José Pfeilsticker Zimmermann
One line of research on irrigated rice genetic breeding programs at Embrapa consists of synthesizing wide genetic base populations followed by recurrent selection. This strategy ensures systematic continuous gains for grain yield and other traits of interest. To estimate the gains observed in three recurrent selection cycles in the CNA-IRAT 4 population, the grain yield data from 924 S0:2 families in 14 experiments carried out in various Brazilian states in the 1992/93, 1994/95 and 1997/98 growing seasons were analyzed. A triple lattice (two 10 x 10 and two 8 x 8 lattices) experimental design was used in the first cycle and Federer augmented blocks in the two subsequent cycles. A non -significant gain was observed in the first cycle (only 15.7 kg/ha (0.28%). The gain observed in the second cycle and the mean gain observed due the selection in the first and second cycles were significante and of high magnitude (369.9 kg/ha (6.65%) and 259.9 kg/ha (4.67%), respectively). Results showed that recurrent selection applied to genetically divergent populations can result in
considerable gains for grain yield.