EMBRAPA Maize and Sorghum

Mapping a novel opaque endosperm mutant using SSR markers --Maki, CS, Carneiro, NP, Guimarães, CT, Lopes, MA, Paiva, E To understand more about the relation among the opaque mutations, zein levels, endosperm hardness and nutritional quality of the maize endosperm we started to characterize native maize opaque endosperm mutants. The opaque mutants described in the literature have in general higher nutritional quality and lower zein levels compared to the wild type genotypes. These novel maize opaque endosperm mutants have soft endosperm, low nutritional quality and zein levels similar to the wild type endosperm (Guimarães et al., Rev. Bras. Genet. 18, 2, 259-264). One of the mutant genotypes (BOL II) was crossed to the wild type genotype (BR-201) and the F2 plants were self-pollinated to F4. DNA pools from homozygous vitreous and opaque plants were analyzed in bulked segregant analysis (Michelmore et al., PNAS 88:9829-9832) to map the locus related to endosperm hardness in this mutant. Four out of 276 primer pairs tested (Research Genetics) showed to be polymorphic when bulks of DNA from individuals of vitreous and opaque endosperm were compared: MAG.T01.D04, bngl125, bngl382 and phi083, located at 2.01-2.02, 2.02, 2.03 and 2.04 respectively. To get more accurate map position, DNA from these individuals was tested separately (Figure 1). We are in the process of refining the data using RFLP markers surrounding this genomic region. The same F4 population will be used in a subtractive hybridization strategy to isolate genes involved in the definition of the soft endosperm trait.

Figure 1. SSR marker analysis showing polymorphism among F4 individuals homozygous for vitreous (Group A) and opaque (Group B) endosperm. Parent A is the novel mutant and Parent B is the wild type.

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