Intra-population improvement of maize earliness and drought tolerance [electronic resource].

Includes references.

A total of 400 S'₁s were extracted from the maize open-pollinated cultivar Giza2 (Pop-0) in 2004 season, classified into 4 groups (each of 100 S'₁s) based on divergent selection for early (E) and late (L) silking and maturity. i.e. EE, EL. LE and LL and evaluated in 2005 season under well-watered (WW) and water-stressed (WS) environments. The highest yielding 16% of lines (16) were selected under WW and WS and 8 groups of 16 S'₁s were obtained (EEWW, EEWS, ELWW, ELWS, LEWW, LEWS, LLWW and LLWS). These 8 groups were separately (in isolation) intercrossed in 2006 early season and random mated in 2006 late season to achieve a genetic equilibrium. The resulted 8 populations (Pop-EEWW, Pop-EEWS, Pop-ELWW. Pop-ELWS, Pop-LEWW, Pop-LEWS, Pop-LLWW and Pop-LL WS) along with Pop-0 were evaluated in 2007 season under WW and WS conditions. The main objectives were to develop new population(s) of earlier maturity or silking and/or higher grain yield/fed (GYPF) than Giza-2 and to test the actual progress in earliness and GYPF under WW and WS. WS reduced means and ranges oft he S'₁s for all studied traits, except for barren plants (BP) %, which was increased. Estimates of genetic variance, heritability in broad-sense and predicted genetic advance from selection were, generally higher in the 400 S'₁s than in each group of 100 S'₁s alone. This tendency was more pronounced in earliness and less pronounced in grain yield traits. Grain yield/plant. 100-kernel weight. kernels/row and barrenness showed valuable secondary traits in increasing the efficiency of selection for GYPF under WS. As a result of practicing one cycle of S₁ recurrent selection it was possible to develop new populations that achieved an actual progress in both earliness and high grain yield together which reached in Pop-LEWW to 3.2 and 3.0 days earlier in maturity than Giza-2 and 3.5 ard (22.6%) and 2.3 ard (19.5%) increase in GYPF and in Pop-LEWS to 4.9 and 5.0 days earliness in maturity and 2.0 ard (13.0%) and 1.9 ard (15.7%) increase in GYPF under WW and WS, respectively. In earliness of maturity only, progress reached in Pop-EEWW to 4.9 and 5.0 days and in Pop-EEWS to 5.9 and 6.1 days earlier in maturity than Pop-0 under WW and WS, respectively, but GYPF was reduced than Giza-2 by 7.7 and 14.9% under WW and 14.6 and 20.2% under WS for Pop-EEWW and Pop-EEWS, respectively.

Summary in Arabic.

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