Caracterização molecular de cultivares de cebola com marcadores microssatélites

Abstract

Resumo -O objetivo deste trabalho foi estabelecer padrões alélicos e estimar as distâncias genéticas baseadas em marcador SSR de 44 cultivares de cebola adaptadas às condições de cultivo tropicais e subtropicais do Brasil. Para visualização da similaridade genética, utilizou-se o dendrograma UPGMA gerado da matriz de distâncias do coefi ciente de Jaccard, com base em 40 alelos de 13 locos SSR. O DNA total foi extraído pelo método CTAB 2x, e os produtos de PCR foram analisados em géis de poliacrilamida desnaturante 6% e corados com nitrato de prata. O número de pares de bases foi estimado pelo método da mobilidade inversa, com base em regressão de produtos de tamanho conhecido. A média da heterozigosidade dos locos SSR foi 0,58. Os 40 alelos dos 13 locos SSR foram sufi cientes para distinguir as 44 cultivares de cebola. O maior número de alelos em comum foi observado entre as cultivares Yellow Granex e Henry's Special PRR e o menor, entre as cultivares Baia Periforme Super Precoce e Excel. Os sete grupos principais de cultivares identifi cados no dendrograma apresentaram concordância com a genealogia conhecida e o tipo agronômico das cultivares avaliadas. Os locos SSR selecionados são adequados para melhoramento e proteção de cultivares da espécie.Termos para indexação: Allium cepa, dendrograma, similaridade, SSR. Molecular characterization of onion cultivars using microsatellite markersAbstract -The objective of this work was to establish allelic patterns and to estimate genetic distances based on the SSR marker in 44 onion cultivars adapted to Brazil's tropical and subtropical growing conditions. An UPGMA dendrogram generated from the distance matrix of the Jaccard's coeffi cient, based on 40 alleles of 13 SSR loci, was used for visualizing genetic similarities. Total DNA was extracted according to the CTAB 2x protocol, and the PCR products were analyzed in 6% denaturing polyacrylamide gels and stained with silver nitrate. The number of base pairs was estimated by the inverse mobility method, based on regression of products of known size. The heterozygosity mean was 0.58 for all SSR loci. The 40 alleles of the 13 SSR loci were enough to distinguish all 44 onion cultivars. The highest number of common alleles was observed between Yellow Granex and Henry's Special PRR cultivars, and the lowest was observed between the Baia Periforme Super Precoce and Excel cultivars. The seven main groups of onion cultivars identifi ed in the dendrogram were in agreement with the known genetic genealogy and with the agronomic type of the analyzed cultivars. The selected SSR loci are adequate for breeding programs and for protection of the cultivars of the species.

Assessing the genetic diversity of Spanish Allium cepa landraces for onion breeding using microsatellite markers

“…The EST-SSR markers showed a percentage of amplification (75%) higher than those previously reported (Santos et al, 2010;Khar et al, 2011) using also the EST-SSRs developed by Jakše et al (2005). Only one EST-SSR primer (ACM300) gave monomorphic bands in the Spanish onions but it revealed polymorphism between onions and other Allium species.…”

Microsatellite marker based analysis of genetic diversity in short day tropical Indian onion and cross amplification in related Allium spp.

“…Genomic SSRs were less polymorphic (10%) as compared to the EST derived microsatellite (53.3%). Genomic SSRs require optimization of PCR conditions and amplify rarely in onion and allied Alliums McCallum et al 2008;Santos et al 2010). In contrast, Araki et al (2010) reported their amplification but it was in bulb onion and closely related species of section Cepa and Phyllodon only.…”

Allelic database and accession divergence of a Brazilian mango collection based on microsatellite markers

“…As pointed out by Santos et al (2010) for onion, laboratories that employ systems that use fluorescent initiators and automatic band recording can estimate different numbers of base pairs for the alleles identified in the present study with the expectation that the allelic pattern is maintained if the same protocol for the PCRs and amplifications is adopted. Studies with DNA codominant markers in mango can be important as references for germplasm management studies, controlled hybridizations, and even for the choice of other pollinators of cultivars that present floral abortion.…”

“…This low cophenetic correlation may have been due to the presence of ties in the matrix of similarity, as commented on by Santos et al (2010) in onion.…”