Genetic variation of 12 rice cultivars grown in Brunei Darussalam and assessment of their tolerance to saline environment

Genetic variations of 12 different rice cultivars in Brunei Darussalam were studied using 15 different SSR markers and their salinity tolerance mechanism was also assessed. Eight SSR markers, RM 151, 187, 206, 226, 276, 310, 320 and 334, showed polymorphic alleles while the other seven were monomorphic. A total of 158 alleles were amplified for all these rice cultivars using 15 SSR markers, with an average of 10.53. The allele frequencies per locus or marker range from 0 in RM 307 to five alleles in RM 226. PIC values varied from 0.00 to 0.7521. Similarity distance varied from 0.00 to 1.00. Dendrogram showed three distinct clusters, where both Kuaci and Sp1 significantly diverted from the other ten rice cultivars. Bandul berminyak was the most tolerant to salinity. Quantum yield for B. berminyak were unaffected and it showed the least reduction in growth parameters studied when expose to salinity stress. From both salinity tolerance and genetic variation investigations for these 12 cultivars, it may probably be better to intercross between Arat (moderately tolerant) and Sp1 (susceptible) as both are from different clusters, showed low genetic similarity with 0.33 and different salinity tolerance level.  Key words: Genetic variability, rice cultivars, SSR markers, salinity. Abbreviation:  RFLP, Restriction fragment length polymorphism; RAPD, random amplified polymorphic DNA; AFLP, amplified fragment length polymorphism; ISSR, inter-simple sequence repeat ; SSR, single sequence repeats; PIC, polymorphism information content; RM, rice marker.