Assessment of genetic diversity in three subsets constituted from the ICRISAT sorghum collection using random vs non-random sampling procedures B. Using molecular markers

The large size of the sorghum [Sorghum bi-color (L.) Moench] landrace colle ction maintained by ICRISAT lead to the establishment of a core collection. Thus, three subsets of around 200 accessions were established from: (1) a random sampling after stratification of the entire landrace collection (L), (2) a selective sampling based on quantitative characters (PCS), and (3) a selection based on the geographical origin of landraces and the traits und er farmers' selection (T). An assessment was done of the genetic diversity retained by each sampling strategy using the polymorphisms at 15 microsatel lite loci. The landraces of each subset were genotyped with three multiplex polymerase chain reactions (PCRs) of five fluorescent primer-pairs each wi th semi-automated allele sizing. The average allelic richness for each subs et was equivalent (16.1, 16.3 and 15.4 alleles per locus for the subsets PC S, L, and T, respectively). The average ge netic diversity was also compara ble for the three subsets (0.81, 0.77 and 0.80 for the subsets PCS, L, and T, respectively). Allelic frequency distribution for each subset was compar ed with a chi-square test but few significant differences were observed. A high percentage of rare alleles (71 to 76% of 206 total rare alleles) was m aintained in the three subsets. The global molecular diversity retained in each subset was not affected by a sampling procedure based upon phenotypic characters.