Resistance gene analogues in sugarcane and sorghum and their association with quantitative trait loci for rust resistance

Abstract

Fifty-four different sugarcane resistance gene analogue (RGA) sequences were isolated, characterized, and used to identify molecular markers linked to major disease-resistance loci in sugarcane. Ten RGAs were identified from a sugarcane stem expressed sequence tag (EST) library; the remaining 44 were isolated from sugarcane stem, leaf, and root tissue using primers designed to conserved RGA motifs. The map location of 31 of the RGAs was determined in sugarcane and compared with the location of quantitative trait loci (QTL) for brown rust resistance. After 2 years of phenotyping, 3 RGAs were shown to generate markers that were significantly associated with resistance to this disease. To assist in the understanding of the complex genetic structure of sugarcane, 17 of the 31 RGAs were also mapped in sorghum. Comparative mapping between sugarcane and sorghum revealed syntenic localization of several RGA clusters. The 3 brown rust associated RGAs were shown to map to the same linkage group (LG) in sorghum with 2 mapping to one region and the third to a region previously shown to contain a major rust-resistance QTL in sorghum. These results illustrate the value of using RGAs for the identification of markers linked to disease resistance loci and the value of simultaneous mapping in sugarcane and sorghum.

Presence of defeated qualitative resistance genes frequently has major impact on quantitative resistance to Melampsora larici-populina leaf rust in P. × interamericana hybrid poplars

“…Even though distinguishing between the two hypotheses is not straightforward as it requires very precise control of the genetic background (Anderson 1982), the "residual effect" hypothesis was clearly favored in many studies (Nass et al 1981;Pedersen and Leath 1988;Chantret et al 1999;Li et al 2001). The linkage hypothesis follows that most qualitative resistance genes belong to tightly linked gene families in plant genomes (Hulbert et al 2001) and that resistance gene analogs are frequently found in the vicinity of QTLs for quantitative resistance (Geffroy et al 2000;Zimnoch-Guzowska et al 2000;Calenge et al 2005;McIntyre et al 2005;Muylle et al 2005). This may indicate that qualitative and quantitative resistances are encoded by the same classes of genes rather than by the same genes.…”

Assessment of genetic diversity of wheat genotypes by resistance gene analog-EST markers

“…This could include genes for broad-spectrum, qualitative disease resistance, because recent studies in different plant species (Wisser et al, 2005;McIntyre et al, 2005) found that in some instances there was a significant association between RGA genes and quantitative resistance traits. In previous studies, several RGAP markers were coincident with resistance to different diseases (Chen et al, 1998(Chen et al, , 1999.…”

Mechanisms of Resistance to Pests and Pathogens in Sugarcane and Related Crop Species

“…In the case of brown rust, McIntyre et al (2005a) amplified sugarcane NB-LRR fragments from cDNA and used these fragments to produce eight RFLP markers that were significantly associated with quantitative resistance in the progeny from parents lacking any apparent major gene resistance. Each marker was associated with less than 10% of the variation in rust resistance which is consistent with multigenic determination of rust resistance in this population.…”