Detection of Epistatic, Additive, and Dominance Variation in Winter Wheat (Triticum aestivum L. em Thell.)¹

Abstract

The objectives of this study were to determine whether epistasis plays a significant role in the genetic systems for selected traits among several winter wheat (Triticum aestivum L. em Thell.) cultivars and to evaluate the importance of additive vs. dominance gene action for traits not influenced by epistasis. In each of two replicated experiments, two cultivars (referred to as testers L1 and L2) and their F1 (L3) were crossed to each of 10 other cultivars and evaluated in a single field experiment. The deviations (cultivar ✕ L1 + cultivar ✕ L2 — 2 cultivar ✕ L3) were analyzed to provide a test for epistasis. An additive‐lominance model was fitted to the data for those characters not affected by gene interactions.Results of the two experiments were generally consistent with respect to the detection of epistasis. Epistasis affected the expression of heading date, kernels/spikelet, and grain yield, but not of plant height, protein content, tiller number, spikelets/spike, and kernels/spike in both experiments. Epistasis was indicated for kernel weight in one experiment but not the other. Expression of epistasis was influenced by particular cultivars, indicating that a limited number of cultivars may not be sufficient to detect nonallelic interactions for a character within this species.Additive gene action was predominant in both experiments for protein content, spikelets/spike, and kernels/spike, suggesting that improvement of those characters can be achieved through standard selection procedures. Evidence for dominance gene action was obtained for plant height and kernels/spike in one experiment.The results of this study indicated that epistasis may be a nontrivial factor in the inheritance of agronomic traits. Genetic models neglecting epistasis may result in biased information.

Epistasia para a produção de grãos em soja

“…ARAÚJO (2006) estudou a epistasia em soja por m e i o d o d e l i n e a m e n t o T T C m o d i f i c a d o , e detectou a ocorrência de variância epistática para os caracteres produção de grãos, dias para florescimento e dias para maturação, e concluiu q u e a s e s t i m a t i v a s d e v a r i â n c i a s g e n é t i c a s aditivas e dominantes normalmente obtidas para estes caracteres podem estar viesadas, pelo fato de serem estimadas com base em um modelo a d i t i v o -d o m i n a n t e . E f e i t o s s i g n i f i c a t i v o s d a e p i s t a s i a p a r a p r o d u ç ã o d e g r ã o s f o r a m relatados também para outras espécies: em trigo (KETATA et al, 1976); em milho (WOLF e HALLAUER, 1997;PARVEZ et al, 2006), em feijão moyashi (KHATTAK et al, 2001(KHATTAK et al, , 2002; em algodão (BHATTI et al, 2006); em amendoim (UPADHYAYA e NIGAM, 1999); e, em arroz (SALLEM et al, 2005). Na tabela 2, são apresentadas as médias do caráter produção de grãos, separadamente para os três grupos: para Linhagens (P i ) a média geral foi de 195,6 g/parcela; para Linhagens cruzadas com o Testador 1 (P i x L 1 ) a média geral foi de 220,1 g/ parcela; e para Linhagens cruzadas com o Testador 2 (P i x L 2 ) a média geral foi de 195,6 g/parcela.…”

“…A epistasia foi detectada ou quantificada para a produção de grãos em diversas espécies, utilizando o "Triple Test Cross": em milho (WOLF e HALLAUER, 1997;PARVEZ et al, 2006); em trigo (KETATA et al, 1976;ESMAIL, 2007); em feijão moyashi (KHATTAK et al, 2001(KHATTAK et al, e 2002; em arroz (SALLEM et al, 2005); em tomate (SINGH e SINGH, 1985); e em soja (ARAÚJO, 2006). Em soja, porém, existem poucos trabalhos relacionados a este assunto.…”

Genetic Architecture of Secondary Yield Components in Mungbean (Vigna radiata (L.) Wilczek).

“…The individual contribution of each line to total epistasis was determined and tested for significance according to the method of Ketata et al (1976) for those traits in which the total epistasis was significant. The mean value (where r corresponds to total 3 replications,) of each genotype for a trait was tested using a 't' test with 20 degrees of freedom as follows:…”

“…The influence of lines on non-allelic interaction of these traits indicated that the manifestation of epistasis is determined to some extent by the lines employed for the study. The limited number of lines used in the study might fail to detect nonallelic gene action when in fact it is a part of the genetic system (Burton 1968a, Ketata et al 1976). The optimal experimental sizes required to detect epistasis through TTC depend largely on the gene dispersion in the tester parents (Pooni et al 1980).…”

“…In the present studies, the detection of epistasis, and estimates of additive and dominance components of variation for secondary yield components in a set of mungbean genotypes were carried out in two seasons using the TTC model proposed by Ketata et al (1976) in which the testers L 1 , L 2 , and L 3 , were crossed to a number of varieties instead of random F 2 individuals, as suggested by Kearsy and Jinks (1968).…”