Identificação molecular do locus restaurador da macho-fertilidade (Ms), tipo de citoplasma e viabilidade de pólen em acessos de cebola (Allium cepa L.)

Abstract

In this study was accomplished the identification of cytoplasmic types and genotyping of Ms locus in 59 onion genotypes of the Embrapa germplasm collection, as well as association of molecular observations with pollen viability tests, aiming to reduce time for identification of male-sterile lines („A‟) and their maintainers („B‟), for the development of hybrids adapted to the edafoclimatic conditions of the São Francisco Valley. 5‟cob/orfA501 and orf725 markers were used for cytoplasmic identification, whereas AcSKP1 and AcPMS1 for genotyping of Ms. The pollen viability was estimated with acetocarmine 2%, Alexander‟s staining and in vitro germination. In the molecular identification two types of male-sterile cytoplasmic („S‟ and „T‟), as well as fertile cytoplasmic („N‟) and Ms and ms alleles, both in homozygosity and heterozygosity, were identified in the evaluated genotypes. The frequencies with 5‟cob/orfA501 and orf725 and AcSKP1 and AcPMS1 markers were approximate the evaluated accessions. For Brazilian germplasm, the cytoplasmic frequencies of „N‟, „S‟ and „T‟ were approximately 0,47, 0,28 e 0,25, respectively, while the allelic frequencies were 0,52 and 0,48 for Ms and ms, respectively. The accessions Régia, EHCEB 20146, EHCEB 201427, Alvorada, Serrana, Crioula Mercosul, EHCEB 20142, BRS 367, Rainha, Juporanga and Alfa SF C-XI exhibit potential for identification of „A‟ and „B‟ lines because show mixtures of type of cytoplasmic and different Ms allelic frequencies. The accessions EHCEB 20142040/EHCEB 20141040, EHCEB 20142028/EHCEB 20141028, EHCEB 20112006/EHCEB 20111006, EHCEB 20142027/EHCEB 20141027, EHCEB 20102019/EHCEB 20101019 and Alfa SF „B‟/Alfa SF „A‟ presented all evaluated plants in the Nmsms and Smsms or Tmsms conditions. Molecular selection and pollen viability tests showed complete agreement for Alfa SF (Nmsms), BRS 367 (Tmsms), BRS 367 (Nmsms), Cascuda T7 (Nmsms), Cascuda T5 (Smsms), EHCEB 20102017 and EHCEB 20142027. For Alfa SF (Tmsms), EHCEB 20142028 (Nmsms), EHCEB 20141028 (Smsms), EHCEB 20141027 (Tmsms) and EHCEB 20141017 (Tmsms) there was no validation of molecular selection by pollen viability tests for some plants. The pollen viability evaluation methods did not present sterile and fertile classification agreement for the accessions EHCEB 20142028, EHCEB 20141028, EHCEB 20141027 and EHCEB 20141017. Six pairs of „A‟ and „B‟ lines identified in the present study, Alfa SF (Tmsms ) x Alfa SF (Nmsms), BRS 367 (Tmsms) x BRS 367 (Nmsms), Cascuda T7 (Nmsms) x Cascuda T5 (Smsms), EHCEB 20142027 (Nmsms) x EHCEB 20141027 (Tmsms), EHCEB 20102017 (Nmsms) x EHCEB 20141017 (Tmsms) and EHCEB 20142028 (Nmsms) x EHCEB 20141028 (Smsms) demonstrated potential for the development of hybrids.