Quantitative trait loci associated with resistance to gray leaf spot and grain yield in corn

Abstract

The main objectives of hybrid development programs include incorporating genetic resistance to diseases and increasing grain yield. Identification of Quantitative Trait Loci (QTL) through the statistical analysis of molecular markers allows efficient selection of resistant and productive hybrids. The objective of this research was to identify QTL associated with resistance to gray leaf spot and for grain yield in the germplasm of tropical corn. We used two strains with different degrees of reaction to the disease; the genotypes are owned by GENESEEDS Ltda, their F 1 hybrid and the F 2 population. The plants were evaluated for gray leaf spot resistance, for grain yield and were genotyped with 94 microsatellite markers. Association of the markers with the QTL was performed by single marker analysis using linear regression and maximum likelihood analysis. It was observed that the additive effect was predominant for genetic control of resistance to gray leaf spot, and the dominant effect in that of grain yield. The most promising markers to be used in studies of assisted selection are: umc2082 in bins 4.03 and umc1117 in bins 4.04 for resistance to gray leaf spot; for grain yield umc1042 in bins 2.07 and umc1058 in bins 4.11.Index terms: Maximum likelihood, microsatellites, regression. RESUMOA incorporação de resistência genética a doenças e o aumento na produtividade de grãos estão entre os principais objetivos dos programas de desenvolvimento de híbridos. A identificação de locos de caracteres quantitativos (QTL) por meio de análises estatísticas associadas a marcadores moleculares possibilita a rápida obtenção de híbridos resistentes e produtivos. Nesta pesquisa, objetivou-se identificar locos de caracteres quantitativos (QTL) associados com resistência à cercosporiose e com produção de grãos em germoplasma de milho tropical. Foram utilizadas duas linhagens contrastantes em níveis de reação à doença (genótipos pertencentes à GENESEEDS -Ltda), seu híbrido F 1 e a população segregante F 2 . Essas plantas foram fenotipadas quanto à resistência a doença e quanto a produção de grãos e genotipadas com 94 marcadores de microssatélites. A associação dos marcadores ao QTL foi realizada por meio de análises de marcas individuais, utilizando as metodologias de regressão linear e análise da máxima verossimilhança. Observou-se que o tipo de efeito predominante no controle genético da resistência a cercosporiose foi o aditivo e para o controle genético da produção de grãos foi de dominância. Os marcadores microssatélites mais promissores para serem utilizados em estudos de seleção assistida para resistência a cercosporiose são umc2082 na posição 4.03 e umc1117 na posição 4.04 e para produção de grãos, umc1042 e umc1058 nas posições 2.07 e 4.11.Termos para indexação: Máxima verossimilhança, microssatélites, regressão.

Production and identification of doubled haploids in tropical maize

“…We used 25 primers indicated for the maize crop, according to Veiga et al (2012) in a study of QTLs linked to resistance to cercospora disease and maize grain production. Of the 25 primers, 5 (BNLG 1175, BMC 1714, BNLG 1520, BNLG 1233, and BNLG 1258) were considered to be polymorphic between the parents, whose bands had good size and definition on the gel.…”

Identification of Alleles Conferring Resistance to Gray Leaf Spot in Maize Derived from its Wild Progenitor Species Teosinte

“…To date, many quantitative trait locus (QTL) mapping studies have identified potential resistance alleles on every chromosome of maize. Generally, those alleles identified were quantitative and additive in action (Balint‐Kurti et al, 2008; Benson, 2013; Bubeck et al, 1993; Clements et al, 2000; Gordon et al, 2004; Lehmensiek et al, 2001; Pozar et al, 2009; Saghai Maroof et al, 1996; Veiga, 2012; and Zwonitzer et al, 2010). Estimates of additive effects were also commonly small and explained a small amount of disease variation.…”

“…Many of these studies have used populations derived from two temperate-adapted maize inbreds, one of which was often B73. Some studies have used populations derived from crosses between temperate lines (often B73 again) and unadapted tropical germplasm (Benson, 2013;Bubeck et al, 1993;Gordon et al, 2004;Lehmensiek et al, 2001;Pozar et al, 2009;Veiga, 2012;Zwonitzer et al, 2010). Teosinte, the wild progenitor of maize offers a potential novel source of resistance alleles for further exploration.…”

Preventing Potential Diseases of Crop Plants Under the Impact of a Changing Environment

“…Two markers, umc2082 and umc1117, identified in bins 4.03 and 4.04 are promising for cultivar screening against gray leaf spot (Veiga et al, 2012). A segregating population derived by a cross of highly resistant inbred line Y32 and a susceptible line, Q11, was used for genetic analysis and QTL mapping.…”