Genetic Purity Assessment of Castor Hybrids Using Est-ssr Markers

Maintenance of genetic purity of a hybrid is essential to exploit its full potential. Genetic purity is generally assessed by conducting grow out test (GOT) where morphological and floral characters are analyzed, however results may be influenced by the environment. Further, it is expensive and time consuming. DNA based markers are rapid, reliable and cost effective for hybrid purity assessment. Several molecular markers such as RAPD, ISSR, AFLP, SSR, ESTSSR are being used for purity determination. Co-dominant markers are preferred over dominant markers as they reveal the heterozygous condition of the hybrid accurately. SSR markers are reliable markers for purity assessment. Because of inherent limitations of SSR markers, EST-SSR markers are considered as high quality markers as they give sharp, clear, and robust amplification. In this study, the parents (DPC-9, CS-1 and CS-18) of the two castor hybrids PCH-111 (DPC-9 x CS-1) and PCH-222 (DPC-9 x CS-18) were screened using 283 EST-SSR markers, nine markers showed polymorphism between DPC-9 and CS-1 and 10 between DPC-9 and CS-18 whereas 3 expressed polymorphism among 3 parents. As castor is highly cross pollinated crop and cytoplasmic male sterility system is not yet reported, the possible impurities in hybrid seed are selfing of female parent and pollination of female parent by unknown pollen parent. Selfed seed of female parent can be identified using single polymorphic marker, however contamination of female parent with unknown male parent can be detected reliably by using more number of polymorphic markers.