Viability of reciprocal recurrent selection in populations derived from single-cross maize hybrids / Viabilidade da seleÃÃo recorrente recÃproca em populaÃÃes derivadas de hÃbrido simples de milho

AUTOR(ES)

Matheus Costa dos Reis

DATA DE PUBLICAÇÃO

2009

RESUMO

In a recurrent selection program it is primordial to know whether genetic progress has been reached and the existence of genetic variability for future selection cycles. Thus, this work was carried out to evaluate the genetic progress up to C2, on a first stage, and to estimate genetic variance and covariance components, responses to selection and heterosis for populations of C0 and C3 of a reciprocal recurrent selection program, on a second stage. On agricultural season 2005/06 interpopulation crosses of C0, C1 and C2, single-cross parental hybrids and double-cross F1 were evaluated in randomized complete blocks with ten replications. On the next agricultural season only interpopulation crosses of C0 and C2 were evaluated in the same experimental design with 80 replications. For the second stage, one hundred genotypes that produced both intra- and interpopulation half-sib progenies of each population (1 and 2) of C0 and C3 were sampled. On agricultural season 2007/08, each progeny type was evaluated in a 10 x 10 triple lattice at two locations in Lavras, MG. The progenies types from each cycle were arranged in split-blocks. An equal seed sample of each progeny contributed to represent the populations per se and the interpopulation crosses of CO and C3, which were evaluated in randomized complete blocks with ten replications in the same conditions. All the genetic variance and covariance genetics components were estimated from expected mean squares. These genetic components of C3 were used to estimate responses to reciprocal (RRS), intrapopulation (HSS) and test cross half-sib (THS) recurrent selection in interpopulation crosses, populations per se and, to determine heterosis. Realized responses to RRS and heterosis change were also obtained. The estimates of genetic progress up to C2 per cycle were 7.9% (or 0.7 t/ha) for unhusked ear yield, 3.5% for prolificacy, -12.8% for percentage of diseased ears and -3.0% for disease scores. Estimates of additive genetic variance both intra- and interpopulation were of great magnitude for populations of C0 and C3, showing that the selective procedure did not reduce genetic variability. The partitioning of interpopulation additive genetic variance in to genetic variance of deviations from inter- and intrapopulation additive effects ( ) and covariance between of these deviations with intrapopulation additive effects (CovAτ) indicated that populations 1 and 2 are divergent and presence of dominance for unhusked ear yield. For plant height and disease scores these components can be disregarded because most part of variation was explained by intrapopulation additive effect. The estimates of was raised by the selective process as expected. However, the estimates of CovAτ were always negative when it was expected to be positive for the population with higher mean and negative for the population with lower mean. The expected responses to recurrent selection indicated that THS with population 1 as tester would be more appropriated if populations were used for a hybrid breeding programs from inbred lines. RRS showed more efficiency to breed interpopulational hybrid whereas HSS and THS were equally efficient but superior to RSS for improvement of populations per se. The realized response to for unhusked ear yield after three cycles of RRS was 4.5%.cycle-1 in the interpopulation hybrid (direct response), -1.25 and 2.55%.cycle-1 on population 1 and 2 (indirect responses), respectively. Mid parent heterosis elevated from 12.3% on C0 to 24.9% on C3. It was concluded that RRS is efficient in populations derived from single-cross hybrids and the populations used in this study present potential to recurrent selection programs.

ASSUNTO(S)

variÃncia aditiva zea mays l. additive genetic variance quantitative genetics zea mays l. progresso genÃtico genetica e melhoramento florestal genÃtica quantitativa genetic progress variance components componentes de variÃncia

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