Genomic region linked to gray mold resistance in castor ( Ricinus communis L.)

Gray mold disease caused by Amphobotrys ricini is a prevalent disease in castor, reducing the yield by directly causing damage to the economic parts (inflorescence). Implementing host plant resistance breeding is considered as an effective approach for the management of gray mold. The utilization of molecular markers linked to gray mold resistance will serve as a valuable tool in the breeding program. In this study, a population of 156 F6 recombinant inbred lines (RILs) derived by crossing the susceptible line JC-12 with the moderately resistant line 48-1 was used for identification of Quantitative Trait Loci (QTL) linked to gray mold resistance. A major QTL flanked by the SNP markers Rc_29775-68167 and Rc_2994-41303 was mapped on chromosome-10, which explained 23.5 % of the total phenotypic variance (R2). Additionally, a F2 population derived from the cross RG1673 x 48-1 was used to validate the identified QTL. In the F2 population, the same QTL region was detected with LOD 8.3 and R2 value of 32.5 %. Furthermore, it was discovered that the QTL identified in this study is tightly linked to capsule spininess, which can be used as a surrogate trait for selection. In-silico analysis of genes underlying the QTL region predicted three putative genes namely methyltransferase, pyrroline-5-carboxylate reductase, and pentatricopeptide repeat-containing protein, that may play a potential role in gray mold resistance. These findings provide important insights into the genetic basis of gray mold resistance in castor and opportunities to improve the resistance against gray mold by phenotypic selection.