Variation in degree of pollen exclusion for ga1‐s unilateral cross incompatibility in temperate maize breeding populations

Abstract

Fertilization and kernel development are crucial for breeding and agronomic production of maize (Zea mays L.), which is prone to outcrossing. Because of this tendency, a major issue for organic corn farmers is to maintain genetic purity of their crop. One way to maintain this purity is to use a unilateral cross incompatibility system such as Ga1-s. However, lack of complete pollen exclusion has been reported in Ga1-s heterozygotes, complicating introgression of this trait into breeding germplasm. A systematic, quantitative evaluation of pollen exclusion rates in breeding lines would greatly facilitate use of this system. The purpose of this study is to quantitatively evaluate exogenous ga1 pollen exclusion of a diverse set of Ga1-s/ga1 F 1 hybrids representing the stiff stalk and nonstiff stalk heterotic groups, and the Iowa Synthetic Corn Borer population. Differences between genotypes but not heterotic groups were observed when applying exogenous ga1 pollen onto heterozygotes possessing the same Ga1-s allele, indicating there are epistatic interactions between Ga1-s and modifier loci in the ga1 parents tested.

The maize Ga1-s allele confers protection against ga1 pollen in popcorn and dent corn

“…Hoegemeyer 8 proposed to use the Ga1 system for maintaining the genetic purity of organic corn by preventing unwanted pollinations by GMO corn. Both public 9 , 10 and private breeders have transferred the Ga1-s allele from popcorn into dent corn in order to develop varieties with improved genetic purity for organic corn production.…”

“…The degree to which Ga1-s corn lines can exclude unwanted pollen is complicated by genetic background and zygosity of the Ga1-s locus 9 . In addition, QTL for genetic modifiers have been shown to effect pollen exclusion in popcorn 12 .…”