Phenotypic Epistasis for Ten Quantitative Characters in Maize¹

Abstract

S INCE there has been no general agreement on an adequate explanation of heterosis, Sprague (12) has stated that studies which will contribute information about gene action involved in heterosis should be vigorously explored. This study was undertaken to gather information with currently useful breeding materials relative to the prevalence of epistatic gene action and its interactions with environments. Additional knowledge along these lines should be valuable in planning future fundamental studies, in practical breeding efforts, and in interpreting maize inbred and hybrid performance experiments in diverse environments.REVIEW OF LITERATURE Hollander (4) and Kempthorne (8) have defined epistasis as involving interactions of non-allelic genes including multiplicative gene action. Jinks (7) concluded, in a review of diallel cross data, that measured overdominance for yield was partially spurious and in reality epistasis. A significant positive correlation existed between yield and intensity of non-allelic interaction. Gamble (3), using a factorial gene model analysis for inheritance of yield, plant height, kernel row number, ear length, ear diameter, and kernel weight in four environments, concluded that epistasis was important in the inheritance of the characters studied and was subject to environmental influences. Robinson et al. (l) found the complementary type of non-allelic interaction to be of importance in determining maize yield. Horner et al. (5) pointed out that work demonstrating step-like sequential biochemical reactions in the formation of genetically controlled products was very suggestive of complementary gene action.Bauman (1, 2) described the basic method used with extensions in this study to detect epistatic gene action. Inbreds A and B and their Fi hybrid were crossed with a common inbred tester. A significant positive or negative deviation of the single cross X tester from the mean of the two inbreds X tester would necessarily be due to epistasis. He pointed out the following: (A) epistasis, even if present, may not be detected; (B) only a minimum amount of epistasis present will be detected; (C) the direction of the deviation is dependent on the distribution of alleles within the parents; (D) the type of epistasis will not be determined; (E) linkage will reduce the estimate of epistasis; (F) cancelling effects will reduce the estimate so that only a net effect is measured; (G) the tester genotype will influence the estimate; (H) the test is qualitative and not quantitative; and (I) significant deviations must be due to epistasis. Normal meiosis and segregation are assumed. MATERIALS AND METHODSSix double cross hybrids were used as the basis of this study:Pa 444 (Pa 54 X Pa 11) (Pa 32 X Pa 33) Pa 507 (Ind Wf9 X Oh 5IA) (Pa 32 X Pa 33) Pa 525 (Ind Wf9 X Oh 51A) (Pa 54 X Pa 11) Pa 511 (Ind Wf9 X Oh 51A) (Pa 54 X Pa 32) Pa 602A (Ind Wf9 X Oh 5lA) (Pa 54 X W 22) Pa 602 (Ind Wf9 X Oh 51A) (111 A X W 22)The single cross parents of each of these double crosses were studied by Bauman's (1, 2) method to...

The mode of gene action in flue-cured tobacco

“…In another study, observed that practically all the genetic variance resulted from additive effects of genes, with essentially no dominance or epistatic variance . GoRSLINE (1961), however, established epistasis for all the ten characters which he studied in corn . BRIM and COCKERHAM (1961) in their studies on inheritance of quantitative characters in soy beans indicated that the partitioning of genetic variability into additive, dominant and epistatic effects of genes throw light on the mode of inheritance of the various characters to formulate breeding procedures .…”

Genetic covariances between inbred progenies and their testcrosses

“…However, it has been reported in the literature that epistatic effects are important for specific combinations of inbred lines (Jinks, 1955;Bauman, 1959;Gorsline, 1961;Sprague et al 1962;Gamble, 1962a, b;Darrah and Hallauer, 1972;Lamkey et al, 1995;Wolf and Hallauer, 1997…”

Epistasis for agronomic traits in elite maize hybrids

“…Many studies have found epistasis to be generally less important than additive and dominance variation in maize populations (Chi et al, 1969;Eberhart et al, 1966;Darrah and Hallauer, 1972;Silva and Hallauer, 1975;Wolf et al, 2000a). Some of these studies and others have also reported that epistasis is an important component of genetic variance in specific maize lines under certain conditions (Jinks, 1955;Bauman, 1959;Gorsline, 1961;Darrah and Hallauer, 1972;Sprague et al, 1962;Wolf and Hallauer, 1997). So, there is still confusion and no definite answer for the importance of gene interaction in maize.…”

“…These means are compared and deviations from zero indicate epistasis. Sprague et al (1962) attempted to estimate epistasis using a comparison of population means in a study similar to those performed by Bauman (1959) and Gorsline (1961). These 10 are among the first studies evaluating means rather than the more common procedure using the partitioning of variance.…”