Determinação da variabilidade genética nas populações de seleção recorrente de arroz CNA-IRAT 4 e CNA 12 utilizando marcadores microssatélites / Determination of the genetic variability in rice populations of recurrent selection CNA-IRAT 4 and CNA 12 using microssatellites markers

AUTOR(ES)

Letícia da Silveira Pinheiro

FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

07/03/2008

RESUMO

Recurrent Selection is a population inbreed method that is not traditionally used in autogamous species as rice. However, it is still an interesting methodology to the implementation of recurrent selection populations, due to the possibility of obtaining genotypes with wide genetic base and adequate agronomical traits. It is even more attractive when a great genetic variability is easily available, as it is for rice and could be largely used in the development of more productive elite cultivars and with a better production stability even under low input agricultural systems. Two recurrent selection irrigated rice populations, developed by Embrapa Arroz e Feijão, were synthetized using different recombination methods. The CNA-IRAT 4 population was developed in field conditions using male-sterelity, while the CNA 12 population originated from manual crosses in a circulant partial diallel scheme. The aim of this work was the evaluation of the genetic variability among cycles of the two recurrent selection populations using fourteen SSR markers. Hundred and eighty genotypes of the cycles 1, 2 and 5 of CNA-IRAT 4 population and cycles 1 and 2 of CNA 12, were evaluated. The AMOVA did not indicate any genetic structure among the cycles of selection, meaning that the greater variation was attributed between individuals within cycles, in both studied populations. Unexpected alleles, which means alleles that not belong to the genetic pool of the genitors, were identified in both populations and in all cycles evaluated, mostly of these alleles were observed on CNA-IRAT 4 population. These alleles were probably a result of undesired crosses of genotypes which did not belong to both populations. Parameters Fis and Fit of Wrights statistics indicated that the genetic variability of the manually conducted population (CNA 12) were increased while the population using male-sterelity recombination (CNA-IRAT 4) were reduced. The mean reason for this particular situation was due to the directionally crosses that promoted a greater combination between the alleles of all genitors, while male-sterelity methodology pollination the alleles from plants with major height and more capable of producing more pollen were privileged. To avoid the genetic drift in CNA-IRAT 4, genotypes genetically divergent, with more General Capacity of Combination and with good agronomic attributes, should be introduced on this population.

ASSUNTO(S)

seleção recorrente variabilidade genética marcador microssatélite oryza sativa. genetica e melhoramento florestal recurrent selection genetic variability microssatellite marker and oryza sativa

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