Retrocruzamento assistido por marcadores SSRs em milho

Abstract

The present work was carried out with the objective of testing the possibility to use microsatellite markers as selection tools in maize backcross. The chosen characteristic was hight ofear insertion (HEI) where two contrasting maize inbred lines were selected. Line LI 1 was chosen as recurrent parent due to its high general combining ability for grain yield and a high ear insertion, and line LI3 was chosen as the donor parent due to its low ear height. The Fl generation and the first backcross cycle were obtained and the RCi plants were phenotypically evaluated for the trait HEI. One standard deviation below the average for HEI was applied as criterion for phenotypic selection. Thirty five plants were selected and genotyped with twenty-seven previously selected microsatellite markers. Five plants with one standard deviation above the recovery mean ofthe recurrent parent were selected. Two hundred and forty one RC2 plants were obtained from them and were subjected to the same phenotypic and genotypic analysis described above. Thirty-one RC2 individuais were phenotypically selected for their higher ear insertion and among them 7 were genotypically selected for presenting the higher proportion of recovery of the recurrent parent. In each backcross generation around eight plants were selected to be used in a topcross, where inbred line LI61 was used as the male tester. Thirty-three topcross hybrids were evaluated in Goiânia, Janaúba and Sete Lagoas, using a randomized complete block design, with three replications and a common check (P30F33) intercalated at ever seven rows. HEI and grain yield, data were also collected. Ali the experimental hybrids outyielded the check (P30F33) at all the environments tested, showing up theirs high yielding potential. It was showed that assisted backcross in maize by microsatellite markers is a viable strategy for time saving and increasing selection efficiency. The assisted maize microsatellite backcross allowed the identification of plants with high degree of recovery of the recurrent parent at the beginning cycles of the backcross process.