Recovery of exotic alleles in semiexotic maize inbreds derived from crosses between Latin American accessions and a temperate line

Abstract

Genetic diversity of elite maize germplasm in the United States is narrow relative to the species worldwide. Tropical maize represents the most diverse source of germplasm. To incorporate germplasm from tropical maize landraces into the temperate gene pool, 23 Latin American maize accessions were crossed to temperate inbred line Mo44. During inbred line development, selection was practiced in temperate environments, potentially resulting in the loss of substantial proportions of tropical alleles. Genotyping 161 semiexotic inbreds at 51 simple sequence repeat (SSR) loci permitted the classification of their alleles as either Mo44 or tropical and allowed estimation of the proportion of detectable tropical alleles retained in these lines. On average, the percentage of detectable tropical alleles ranged among lines from 15% to 56%, with a mean of 31%. These are conservative, lower-bound estimates of the proportion of tropical germplasm within lines, because it is not known how frequently Mo44 and the tropical maize accession parental populations shared SSR alleles. These results suggest that substantial proportions of exotic germplasm were recovered in the semiexotic lines, despite their selection in temperate environments. The percent of tropical germplasm in semiexotic lines was not correlated to grain yield or moisture of lines testcrossed to a Corn Belt Dent tester, indicating that the incorporation of a substantial percentage of tropical germplasm in an inbred line does not necessarily negatively impact its combining ability. Thus, tropical maize accessions represent a good source of exotic germplasm to broaden the genetic base of temperate maize without hindering agronomic performance.

Phylogenetic Relationships Among Teosinte, Maize and Its Hybrids

“…Despite being one of the cultivated species with greater genetic diversity, molecular analysis of the maize genome suggests that a single domestication event reduced diversity when compared with teosinte Warburton et al, 2008). Most maize commercial varieties in the world has limited genetic diversity, whereas today the germplasm base in maize breeding programs is relatively narrow (Tarter et al, 2004).…”

Genetic variability in maize and teosinte populations estimated by microsatellites markers

“…As observable by WIETHÖLTER et al (2008), the lowest number of alleles detected in this study may reflect the use of agarose gels, which have lower resolution and may underestimate the number of alleles detected (TARTER et al, 2004). However, although it is know that SSR analysis in agarose gels may result in underestimation of the variability, it is indicated especially because it is a cheap and a quick technique (SENIOR et al, 1998).…”

“…Despite being one of the cultivated species with greater genetic diversity, molecular analysis of the maize genome suggest that a single domestication event reduced diversity when compared with teosinte (VIGOUROUX et al, 2002;WARBURTON et al, 2008). Most maize commercial varieties in the world has limited genetic diversity, whereas today the germplasm base in maize breeding programs is relatively narrow (TARTER et al, 2004;LE CLERE et al, 2005). In general, wild species, such as teosinte, may contain useful allelic variation for genetic breeding.…”

Evaluation of CIMMYT maize (Zea mays L.) germplasm by tropical inbred testers

“…The genetic base of maize germplasm throughout the world has been narrowing because of new maize inbred lines and hybrids or varieties have been derived from intercrossing among existing elite materials (Tarter et al 2004, Goodman 2005. Introducing exotic maize germplasm and the introgression of some useful genes into locally adapted germplasm is an effective way to broaden the genetic base of local maize germplasm and to create new superior inbred lines for hybrid maize development (Albrecht and Dudley 1987, Fan et al 2008.…”