STRATIFIED MASS SELECTION FOR PERFORMANCE GRAIN AND SPEAR LENGTH IN WHEAT. l. GENETIC ADVANCES

Abstract

Ten cycles of stratified mass selection for grain yield (SMR) and ten cycles for spike length (SMLE) in wheat (Triticum aestivum L.) were evaluated on three locations with different rainfall conditions, in the spring and summer of 1983. The study was conducted in order to know the efficiency in gain of grain yield with the direct (SMR) and the indirect selection (SMLE). The original genetic material was an F₂ balanced composite of seeds from 28 possible single crosses among eight varieties. As an average, the genetic advance per cycle of selection on grain yield (R) was 2.86% on SMR and -4.16% on SMLE; however, in the first five selection cycles of SMLE the genetic advance was positive (3.32% per cycle). From the 5th cycle, R on SMR increased ata higher rate, whereas on SMLE decreased. For spike lenght only SMLE had a positive response (2.88% per cycle). Among environments, the genetic advance for grain yield on SMR and SMLE decreased as the environment was more favorable.