Development of AFLP markers linked to stem nematode resistance gene in sweet potato ( Ipomoea batatas (L.) Lam.)

AFLP markers linked to stem nematode resistance gene were developed in sweetpotato (Ipomoea batatas). Using bulked segregant analysis (BSA), 800 AFLP primer combinations were screened in the resistant and susceptible DNA bulks from the 186 progenies of F1 single-cross population of Xu781 (resistant parent) × Xushu 18 (susceptible parent), and 245 of them showed polymorphic bands between the two bulks. Primer combinations detecting polymorphism between the two bulks were used to screen the parents and eight individuals from each of the bulks. The results showed that E2M23 and E33M20 produced a specific band of about 500 and 200 bp in length, respectively in the resistant plants but not in the susceptible plants, suggesting markers named E2M23500 and E33M20200 linked to a gene for stem nematode resistance. The amplified analysis of the 186 F1 individuals indicated that the genetic distance was 6.9 and 11.1 cM, respectively, between the two markers and the stem nematode resistance gene with Mapmaker 3.0. These two AFLP markers were used to identify 10 sweetpotato varieties widely planted in China and the results were consistent with those of conventional resistance identification, indicating that the two markers can be used in molecular marker-assisted breeding for stem nematode resistance of sweetpotato.