Lakshminarayana R. Vemireddy

Molecular Genetic Diversity of Major Indian Rice Cultivars over Decadal Periods

Genetic diversity in representative sets of high yielding varieties of rice released in India between 1970 and 2010 was studied at molecular level employing hypervariable microsatellite markers. Of 64 rice SSR primer pairs studied, 52 showed polymorphism, when screened in 100 rice genotypes. A total of 184 alleles was identified averaging 3.63 alleles per locus. Cluster analysis clearly grouped the 100 genotypes into their respective decadal periods i.e., 1970s, 1980s, 1990s and 2000s. The trend of diversity over the decadal periods estimated based on the number of alleles (Na), allelic richness (Rs), Nei’s genetic diversity index (He), observed heterozygosity (Ho) and polymorphism information content (PIC) revealed increase of diversity over the periods in year of releasewise and longevitywise classification of rice varieties. Analysis of molecular variance (AMOVA) suggested more variation in within the decadal periods than among the decades. Pairwise comparison of population differentiation (Fst) among decadal periods showed significant difference between all the pairs except a few. Analysis of trends of appearing and disappearing alleles over decadal periods showed an increase in the appearance of alleles and decrease in disappearance in both the categories of varieties. It was obvious from the present findings, that genetic diversity was progressively on the rise in the varieties released during the decadal periods, between 1970s and 2000s.

Assessment of genetic diversity in sesame (Sesamum indicum L.) genotypes, using EST-derived SSR markers

A total of 16,619 ESTs sequences (SSRs) of sesame (Sesamum indicum L.) were mined from Genbank. From sequences, 156 primer pairs were designed and characterized to determine the diversity among 49 sesame accessions. Twenty SSRs were found to be polymorphic and the number of alleles ranged from two to five per locus. The allele size varied from 101 to 399 bp. The average PIC value of the 20 SSR loci was 0.72 ranging from 0.49 (SEM-12-68) to 0.90 (SEM-12-27). Dendrogram analysis grouped the 49 genotypes into five separate clusters exhibiting a genetic similarity coefficient from 0.59 to 1.0. Hence, these EST-derived SSRs markers could be useful in assessing the diversity of sesame accessions and could also help in identifying diverse parents for sesame improvement programs.

Genetic Variability and DNA Fingerprinting of Elite Mango Genotypes of India Using Microsatellite Markers

Genetic variability of 20 promising Indian mango genotypes which include juicy and table types was studied employing 143 simple sequence repeats (SSRs). Of 143 SSRs, 80 were found to be polymorphic among the genotypes. Characterization of the 20 genotypes resulted in the detection of 236 alleles from 80 polymorphic loci with an average of 2.87 alleles per locus and polymorphism information content (PIC) of 0.63. UPGMA cluster analysis grouped all the genotypes into two major groups with a genetic similarity range of 37–66%. The genotypes were grouped into clusters based on the utility type. DNA fingerprinting of 20 genotypes was done using four hyper-variable SSRs, viz. SSR1, SSR11, SSR58 and SSR78, because of their unique cultivar-specific allele sizes that distinguish all the 20 popular mango genotypes by capillary electrophoresis. Cultivar-specific codes were developed based on allelic size of the amplified products for identification of the 20 genotypes. The study shows high genetic variability among promising genotypes and allele codes assigned for each mango genotype to confirm the genetic identity and genetic purity of variety. The authors conclude that this study developed unique allele-specific codes for the 20 mango genotypes in India.