Genetic analysis of karnal bunt resistance in 14 Mexican bread‐wheat genotypes

Abstract

Fourteen Mexican genotypes of bread wheat {Triticum aestivum L.) with good to moderate levels of resistance to Karnal bunt {Tilletia indica (Mitra)) were crossed with the highly susceptible cultivar WL711 to determine the genetic basis of resistance. The parents, F,, Fj and backcross populations of the 14 crosses were evaluated under artificial epiphytotic conditions during the 1993-94 season for Karnal bunt resistance. The Fi data suggested that the resistance was dominant to partially dominant over susceptibility. The x^ analysis of the segregation ratios in the F2 and backcross generations indicated that the resistance in the wheat genotypes Luan, Attila, Vee # 7/Bow, Star, Weaver, Milan, Sasia and Turacio/Chil is controlled by two genes. The resistance in genotypes Cettia, Irena, Turaco, Opata, Picus, and Yaco was found to be conditioned by a single dominant gene. The genotypes with two genes for resistance expressed a higher level of resistance than those with a single gene and, therefore, are better sources of resistance to Karnal bunt.

Mapping of a resistance gene effective against Karnal bunt pathogen of wheat

“…Previous genetic studies on KB resistance in wheat indicated that one to six major genes condition resistance in various wheat germplasms (Morgunov et al 1994;Fuentes-Dávila et al 1995;Singh et al 1995aSingh et al , b, 1999Villareal et al 1995). Six wheat chromosomes (1D, 2A, 3B, 3D, 5D and 7A) were identified as influencing reaction to the pathogen (Gill et al1993;Singh et al 1994).…”

Karnal Bunt: A Re-Emerging Old Foe of Wheat

“… Fuentes-Dávila et al (1995) observed higher resistance in lines from the cross “Shanghai#8” and “CMH77.308” possessing three genes with dominant/partially dominant relationship than those with two or with only one gene(s). On a similar note, Singh et al (1995a) reported that digenic genotypes such as “Luan,” “Attila,” “Vee 7/Bow,” “Star,” “Weaver,” “Milan,” “Turacio,” “Opata,” “Picus,” and “Yaco” had a higher level of resistance to KB compared with those with a single gene. These findings imply that pyramiding of multiple genes should lead to expression of KB-free trait and selection for resistance under low levels of disease in artificial epiphytotic conditions should ideally result into the accumulation of resistance genes ( Singh et al, 1995a ).…”

“…On a similar note, Singh et al (1995a) reported that digenic genotypes such as “Luan,” “Attila,” “Vee 7/Bow,” “Star,” “Weaver,” “Milan,” “Turacio,” “Opata,” “Picus,” and “Yaco” had a higher level of resistance to KB compared with those with a single gene. These findings imply that pyramiding of multiple genes should lead to expression of KB-free trait and selection for resistance under low levels of disease in artificial epiphytotic conditions should ideally result into the accumulation of resistance genes ( Singh et al, 1995a ). Given this, the marker assisted selection (MAS) seems to be a technique of choice for accumulating resistance genes in a single cultivar for durable and multi-pathotype resistance not dependent upon creation of artificial epiphytotic conditions.…”

“…The kind of genetic interactions mentioned above to be present in inheritance of KB resistance trait also imply that the trait should ideally be highly responsive to selection. Also, the genotypes with a higher number of resistance genes should ideally be the better resistance source ( Singh et al, 1995a ) to utilize in a KB-free trait introgressive breeding program. Therefore, different wheat genotypes may harbor a different number of KB resistance genes and knowing their number is of very high importance to decide their inclusion/exclusion in a breeding program.…”

“…As far as number of genes conditioning KB resistance is considered, most of the genetic studies have reported one to six major genes ( Morgunov et al, 1994 ; Fuentes-Dávila et al, 1995 ; Singh et al, 1995a ; Singh et al, 1995b ; Singh et al, 1999 ; Swati and Goel, 2010 ). However, Sharma et al (2005) reported that the number of loci conditioning the KB resistance may be up to nine in “HD29,” “W485,” “ALDAN’S”/”IAS58,” and “H567.71/3∗PAR.” It was concluded that genetic heterogeneity of parental genotypes had no contribution to the observed deviations.…”