[Selection of maize lines tolerant to heat and drought for adaptated hybrids to arid summer and irrigated valleys in North East of Mexico] | Seleccion de lineas de maiz tolerantes al calor y la sequia para hibridos adaptados al verano arido y caliente de los valles irrigados del Noroeste de Mexico
1997
Ortega C., A. | Valenzuela V., J.M. | Cota A., O.
Planting maize in the summer-fall cycle in northwest Mexico represents a profitable option, permitting a rotation with wheat and the possibility of producing 10-14 t/ha of grain per year on some 250,000 ha of irrigated land. The environmental conditions in northwest Mexico (with summer temperatures above 35 Grades C) require maize hybrids and synthetics tolerant to extreme heat and drought. The Yaqui Valley possesses the ideal conditions - especially in the spring-summer and summer-fall periods-to evaluate and select parents adapted to such environments. Parent lines were developed by growing out materials in two adjacent nurseries, one with normal and the other with limited irrigation (the latter simulating drought conditions). The following methods were used to identify the parents: (1) progenies with differing levels of inbreeding, as those with full vigor did not express the differences which could be observed in the self-pollinated progenies; (2) simple visual ranking scales to classify the progenies' response to firing and leaf rolling; (3) measurement of the number of plants of each progeny which produced silks before and after irrigation in the drought trial; (4) selection under drought of progenies with erect leaves and without firing or leaf rolling; (5) selection of progenies with reduced anthesis-silking intervals; and (6) advancement of the selected progenies to the next level of inbreeding and selection for other desirable traits, in particular resistance to pathogens in the normal irrigated nursery (especially in the fall-winter cycle). Finally, various lines in this selection process were used to produce synthetics and hybrids H-430, H-431 and PNS-4019, which permit profitable maize production in northwest Mexico. Two of these synthetics formed part of the CIMMYT population DPT1 .
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