Estimación de efectos genéticos relacionados con el vigor de la semilla y de la plántula en maíces tropicales mexicanos Genetic effect estimation related to seed and seedling vigor in Mexican tropical corns

We determined the genetic components, and the cor- relation between the F 1 and the F 2 generations, for traits like seed and seedling vigor using a diallel crossing design. The study involved six tropical maize inbred lines from the CIMMYT. Crosses were formed in CIMMYT's Maize Research Station in Tlaltizapan, Morelos dur- ing the summer of 2004. In order to produce F 2 seeds, F 1 crosses were grown at Tepalcingo, Mor. and Iguala, Guerrero. This was ac - complished by controlling pollinations (half sibs). Seeds from the F 1 and the F 2 crosses were evaluated at the Colegio de Postgraduados, Montecillo, Mexico. F 1 and F 2 seeds were used to perform a standard germination test. Seed vigor was evaluated after conducting a seed ag- ing treatment, and conductivity and seed weight were also determined. A test for emergence on sand bed was also conducted. Variables re- corded included percentage, speed and index of emergence; canopy dry weight; seedling height and vigor indexes I and II. Significant (p≤0.01) effects of the General Combining Ability (GCA) were ob - served for all traits in both the F 1 and F 2 generations. GCA effects were greater than those of Specific Combining Ability (SCA). The only exception was vigor after the accelerating age treatment for the F 1 seed. Maternal effects in the F 1 generation were significant (p≤0.01) for all characters. However, seedling height, canopy dry weight and vigor indexes I and II were not influenced by the female parent in the F 2 generation. Parents CML 396 and CML 407 had the highest GCA for seed vigor, while 245 CML expressed the same condition for seed- ling vigor traits in both generations for most traits evaluated. These materials might be considered for integrating a program of breeding for seed and seedling vigor. On the other hand, there was no direct and significant association of the GCA in the F 1 versus the F 2 generations for all evaluated traits.