Evaluation of inter-simple sequence repeat (ISSR) markers for genetic mapping of an oil palm interspecific hybrid mapping population

Inter-simple sequence repeat (ISSR) markers were evaluated for mapping onto the genetic linkage map of an oil palm interspecific hybrid mapping population (Elaeis oleifera × E. guineensis). The genetic linkage of the markers was determined using the two-way pseudo-testcross strategy and the parental map was constructed using JoinMap 4.0. A total of 36 informative ISSR markers consisting of 20 singleprimers and 16 double-primers were genotyped and generated 41 scorable polymorphic bands. Of these 41 polymorphic markers, 39 segregated in the E. guineensis male parent (T128) and only two segregated in the E. oleifera female parent (UP1026). As there were insufficient number of markers generated for UP1026, only the linkage map for T128 could be constructed. Twenty-eight of the ISSR markers were successfully mapped on the T128 parental map together with the existing RFLP, AFLP and SSR markers. Overall, 25 linkage groups covering a total map length of 2402.6 cM with an average interval of 7.1 cM were constructed in this study. Eight ISSR markers were incorporated into six of the 18 linkage groups, while 20 ISSR formed seven small groups separately. The ISSR markers were mostly mapped at the distal ends of linkage groups, regions which were generally not accessible by the other marker systems. This study demonstrated that ISSR markers are useful in combination with other markers for genetic mapping in oil palm. The ISSR primers with CT repeats developed from the dinucleotide 3’- anchored sites also showed the highest level of polymorphism. Furthermore, the development of ISSR markers is comparatively simple, fast, cost-effective and shows reproducibility, thus revealing its potential for genetic analyses of oil palm.