Genetics of resistance to the fungus Helminthosporium sativum in wheat: use of culture filtrates in tissue culture

Abstract

Six wheat genotypes and their F1 and F2 generations were exposed to the action of Helminthosporium sativum culture filtrates to examine the genetics of hexaploid wheat resistance. The objective was to improve the efficiency of breeding programs by identifying the action and number of genes involved in the resistance. The varied response of the tested genotypes to the culture filtrates allowed division of the genotypes into four groups: resistant, moderately resistant, moderately susceptible and susceptible. This variability was detected in the progeny, suggesting that the parents have distinct genetic constitutions. Additive gene action predominated and genetic gain was shown to be possible through selection. The genetic control of the resistance trait seems to be complex because of the presence of gene interaction and the difficulty of eliminating the environmental effects. The inheritance seems to be oligogenic<br>Foram testados seis genótipos de trigo e suas gerações F1 e F2 com o objetivo de compreender a genética da resistência do trigo hexaplóide à ação de filtrados tóxicos de Helminthosporium sativum, através da identificação da ação gênica e do número de genes envolvidos, de modo a tornar possível uma maior eficiência nos programas de seleção. Os genótipos testados apresentaram variabilidade na resposta aos filtrados tóxicos, possibilitando sua caracterização em quatro grupos: resistente, moderadamente resistente, moderadamente susceptível e susceptível. Esta variabilidade foi detectada na progênie, sugerindo que os genitores possuíam constituições genéticas distintas. Foi evidenciado ganho genético através da análise das gerações, onde a ação gênica de maior importância foi a de aditividade. A herança do caráter testado parece ser complexa, devido à presença de interações gênicas e à dificuldade de evitar a participação do ambiente na manifestação do caráter. A herança parece ser oligogênic

Estimates of Genotype x Environment Interactions and Heritability of Black Point in Durum Wheat

“…G x L x Y effects were fairly large (2.32) relative to genotype main effects, and G x L (0.165) and G x Y (0.525) effects were smaller, as estimated by components of variance. These findings are in accordance with those of as Barbieri et al (1997), Sulman et al (2003) and Fox et al (2004). Just as Barbieri at al (1997) reported that the heritability values for the genotypes along the generations analyzed showed that the environment is responsible for 50%.…”

“…These findings are in accordance with those of as Barbieri et al (1997), Sulman et al (2003) and Fox et al (2004). Just as Barbieri at al (1997) reported that the heritability values for the genotypes along the generations analyzed showed that the environment is responsible for 50%. In addition, more recent studies have identified markers for black point.…”

“…It was showed that black point indicated moderate heritability (49%). While developing a breeding program for resistance to black point stem from H. sativum in the field, it is of fundamental importance to have an efficient environmental control through suitable plot size and large number of replications in various years and sites to allow an increase in the trait heritability (Barbieri et al, 1997 **significant at 0.01 probability level. *significant at 0.05 probability…”

“…1 filter paper. The filtrate was concentrated at 45 o C in a steam bath in a vertical flux chamber to 10% of its original volume (Barbieri et al, 1997).…”