Fine mapping of Co-x, an anthracnose resistance gene to a highly virulent strain of Colletotrichum lindemuthianum in common bean

Abstract

The Co - x anthracnose R gene of common bean was fine-mapped into a 58 kb region at one end of chromosome 1, where no canonical NB-LRR-encoding genes are present in G19833 genome sequence. Anthracnose, caused by the phytopathogenic fungus Colletotrichum lindemuthianum, is one of the most damaging diseases of common bean, Phaseolus vulgaris. Various resistance (R) genes, named Co-, conferring race-specific resistance to different strains of C. lindemuthianum have been identified. The Andean cultivar JaloEEP558 was reported to carry Co-x on chromosome 1, conferring resistance to the highly virulent strain 100. To fine map Co-x, 181 recombinant inbred lines derived from the cross between JaloEEP558 and BAT93 were genotyped with polymerase chain reaction (PCR)-based markers developed using the genome sequence of the Andean genotype G19833. Analysis of RILs carrying key recombination events positioned Co-x at one end of chromosome 1 to a 58 kb region of the G19833 genome sequence. Annotation of this target region revealed eight genes: three phosphoinositide-specific phospholipases C (PI-PLC), one zinc finger protein and four kinases, suggesting that Co-x is not a classical nucleotide-binding leucine-rich encoding gene. In addition, we identified and characterized the seven members of common bean PI-PLC gene family distributed into two clusters located at the ends of chromosomes 1 and 8. Co-x is not a member of Co-1 allelic series since these two genes are separated by at least 190 kb. Comparative analysis between soybean and common bean revealed that the Co-x syntenic region, located at one end of Glycine max chromosome 18, carries Rhg1, a major QTL contributing to soybean cyst nematode resistance. The PCR-based markers generated in this study should be useful in marker-assisted selection for pyramiding Co-x with other R genes.

Transcriptome Profiling of the Phaseolus vulgaris - Colletotrichum lindemuthianum Pathosystem

“…The resistant NIL in the present investigation possesses the Co-1 gene that was recently fine-mapped to the distal end of Pv01 [23]. A second gene, Co-x that resides in the vicinity of the Co-1 was also fine mapped and reported to contain eight putative genes [25]. Among the eight candidate genes identified within the 58 kb region of the Co-x , our findings revealed that only two kinases and one cytochrome P450 were up-regulated (Table 4).…”

“…Hs1 Pro-1 contains LRR and putative transmembrane domain [91] and is known to impart resistance to cyst nematodes in sugar beet on a gene-for gene basis. This is particularly interesting because the region around the Co-x and Co-1 genes on Pv01 is syntenic with a region on chromosome Gm18 in soybean that possesses a major gene, Rhg1 that conditions resistance to soybean cyst nematode from the same Heterodera genus [25]. There are many reports of dual nature of resistance imparted by plant resistance genes for example in tomato nematode resistance gene Mi also confers resistance to aphids [92].…”

“…These DEGs were considered as both positional and expression candidates, making their candidacy stronger. For the Co-1 and Co-x loci we investigated a 400 kb region spanning 50.0–50.4 Mb on Pv01, which contains the genomic regions identified by Richards et al [25] and Zuiderveen et al [23] who mapped the Co-x and Co-1 genes, respectively. In the case of the Co-4 locus the 325 kb region on Pv08 proposed by Oblessuc et al [28] was searched as the most probable region for Co-4 gene.…”

“…Anthracnose resistance is dominant at all loci except the Co-8 locus, and multiple alleles have been identified at the Co-1 , Co-3 , Co-4 , and Co-5 loci. Fine mapping of some of these resistance genes, Co-x [25]; Co-1 [23]; Co-1 2 [26] and the Co-4 2 [27, 28] has been conducted and candidate genes associated with resistance identified. The Co-x gene was fine mapped to Pv01, adjacent to the Co-1 locus [25] and fine mapping of the Co-4 ( COK-4 ) locus revealed 18 copies of the COK-4 gene in a 325 kb segment of Pv08 [28].…”

“…Fine mapping of some of these resistance genes, Co-x [25]; Co-1 [23]; Co-1 2 [26] and the Co-4 2 [27, 28] has been conducted and candidate genes associated with resistance identified. The Co-x gene was fine mapped to Pv01, adjacent to the Co-1 locus [25] and fine mapping of the Co-4 ( COK-4 ) locus revealed 18 copies of the COK-4 gene in a 325 kb segment of Pv08 [28]. Using this information, breeders have been developing anthracnose resistant cultivars for both subsistence and commercial producers [13].…”