Phenotypic variations of maize cms populations and subpopulations : 1-agronomic traits

Abstract EN

To assess the contributions of selection and selfing in changing gene frequencies and genetic distinctness, eighteen cms maize (Zea mays L.) populations were grown for six seasons during 2008-2010 at the field of Crop Science Dept.

/ College of Agriculture.

After three cycles of selection and selfing subpopulations retained significant reduction in, c.

v and σ values for most of the studied traits.

Inbreeding depression was greater in populations with a wider genetic base, especially R-lines, probably because they had been exposed to less inbreeding, which implies low level of DNA methylation.

Rs were the most heterozygous populations, and their descended population showed the highest reduction in most studied traits.

Populations showed highly significant differences for all studied traits.

Selection was efficient in increasing hybrid vigor showed by some parental combinations, while it was acted differently as it reduced the ability of some populations to combine positively.

However, hybrid vigor effects regarding the best parent were significant and the hybrid A5oxR6o showed the lowest negative value for early parent hybrid vigor for AD which was -13.08 %, while for SD was the hybrid combination A2sxR6o of -14.45 %.

The hybrid A1sxR1s showed the highest hybrid combination over its best parent for both leaf number and area with the values of 30.08 % and 59.39 %, respectively.

Therefore, selection can serve as effective tool in modifying populations genetic structure, and hence their performance