Comparative assessment of SCoT and ISSR markers for analysis of genetic diversity and population structure in some Aegilops tauschii Coss. accessions

Aegilops tauschii, the diploid progenitor of the wheat D-genome, is a valuable genetic resource for wheat breeders. In this study, we compared the efficiency of inter-simple sequence repeat (ISSR) (as an arbitrary technique) and start codon targeted (SCoT) (as a gene-targeting technique) markers in determining the genetic diversity and population structure of 90 accessions of Ae. tauschii. SCoT markers indicated the highest values for polymorphism information content, marker index and effective multiplex ratio compared to ISSR markers. The total genetic diversity (Ht) and genetic diversity within populations (Hs) parameters were comparably modest for the two marker systems. The results of the analysis of molecular variance showed that the genetic variation within populations was significantly higher than among them (ISSR: 92 versus 8%; SCoT: 88 versus 12%). Furthermore, SCoT markers discovered a high level of genetic differentiation among populations than ISSRs (0.19 versus 0.05), while the amount of gene flow detected by ISSR was higher than SCoT (2.13 versus 8.62). Cluster analysis and population structure of SCoT and ISSR data divided all investigated accessions into two and four main clusters, respectively. Our results revealed that SCoT and ISSR fingerprinting could be used to further molecular analysis in Ae. tauschii and other wild species. The high-genetic variability found in this study also indicates the valuable genetic potential present in the investigated Ae. tauschii germplasm, which could be utilized for future genetic analysis and linkage mapping in breeding programmes.

Analysis of Genetic Variability Amongst Polyploid Genotypes of Pteris vittata L. From Various Geographic Locales of India

Pteris vittata L. is very common and a widely distributed species belongs to the family Pteridaceae. Various cytotypes from diploid to octaploid is available in this fern species. The present work has been carried out for genetic diversity in this fern both within and between the cytotypes. The molecular analysis at inter- as well as intra-species has been carried out with 57 accessions of P. vittata as well as of other species of Pteris with Microsorium punctatum considered as an out group taxon. For the present study 48 P. vittata (36 tetraploid and 12 pentaploid) and five of other species (four P. cretica, one P. pellucida, one P. tremula, one P. quadriaurita, and two P. ensiformis) accessions were used. The UPGMA (unweighted pair group method with arithmetic mean) dendrograms were generated for each method separately, as well as for all methods cumulatively, after a 1000 replicate bootstrap analysis. In order to determine the utility of each of the method, a comparative statistical assessment was done and marker index (MI), expected average heterozygosity, fraction of polymorphic loci and effective multiplex ratio (EMR) were calculated in case of each of the methods used in the present study. At the level of individual methods highest MI was obtained for directed amplification of minisatellites DNA (DAMD) method. Our findings of the present study concluded that out of the three methods Random Amplified Polymorphic DNA (RAPD), Inter-Simple Sequence Repeat (ISSR), and Directed Amplification of Minisatellite DNA (DAMD), DAMD was the best in term of polymorphism and heterozygosity as scores exhibited highest MI. The different accessions of P. vittata collected from different phytogeographical regions falls into six groups. Out of six clusters, one cluster is of pentaploid cytotype, four clusters are of tetraploid cytotype and one for outgroup taxon (M. punctatum). The result thus showed that within tetraploid, heterozygosity with variable genomic structure exists.

PENGEMBANGAN METODE PENANDA ISOZYME PADA TREMBESI

Fifty samples of raintree from Sangatta, the capital city of Kutai Timur Regency, East Kalimantan were analyzed using isozyme markers to determine the characteristics of the banding pattern. The use of isozymes was intended as a biochemical marker for genetic diversity analysis. This study aimed to determine the enzyme system that could be used to determine genetic diversity of raintree. The enzyme systems used were diaphorase, esterase, and peroxidase. Polymorphism assessments were carried out on the parameters of expected heterozygosity (H), polymorphism information content (PIC), effective multiplex ratio (E), marker index (MI), discriminanting power (D), and Resolving (R). Among the three enzyme systems used, diaphorase showed consistent performance against each of the parameters assessed, with a value of H =0.475; PIC = 0.362; E =6.1; MI = 2,2; D = 0.63: and R = 4.44. However, esterase had the highest multiplex effective ratio (E = 6.16). Therefore, diaphorase is the best isozyme marker that can be used to analyze the genetic diversity of raintree.

Comparative assessment of DNA fingerprinting techniques (RAPD, ISSR and AFLP) for genetic analysis of cashew (Anacardium occidentale L.) accessions of India

Nineteen cashew accessions were analysed with 50 random primers, 12 ISSR primers and 6 AFLP primer pairs to compare the efficiency and utility of these techniques for detecting variation in cashew germplasm. Each marker system could discriminate between all of the accessions, albeit with varied efficiency of polymorphism detection. AFLP exhibited maximum discrimination efficiency with a genotype index of 1. The utility of each molecular marker technique, expressed as marker index, was estimated as a function of average band informativeness and effective multiplex ratio. Marker index was calculated to be more than 10 times higher in AFLP than in RAPD and ISSR. Similarity matrices were determined based on the data generated by molecular and morphometric analyses, and compared for congruency. AFLP displayed no correspondence with RAPD and ISSR. Correlation between ISSR and RAPD similarity matrices was low but significant (r = 0.63; p < 0.005). The similarity matrix based on morphometric markers exhibited no correlation with any of the molecular markers. AFLP, with its superior marker utility, was concluded to be the marker of choice for cashew genetic analysis.Key words: Anacardium occidentale, DNA fingerprinting, RAPD, ISSR, AFLP, morphometric.

Efficiency of three PCR-based markers in assessing genetic variation among cowpea (Vigna unguiculata subsp. unguiculata) landraces

The main objective of this study was to investigate the efficiency of RAPD, AFLP, and SAMPL marker systems in detecting genetic polymorphism in cowpea landraces (Vigna unguiculata subsp. unguiculata (L.) Walp.) that probably share a similar genetic pool. A second objective was to determine the level of diversity among landraces from a restricted area, to define the most appropriate strategy of on-farm conservation. Each marker system was able to discriminate among the materials analysed, but a clear distinction between all the local varieties was only obtained with AFLP and SAMPL markers. The average diversity index was quite similar for each marker system, but owing to the differences in the effective multiplex ratio values the marker index was higher for the AFLP and SAMPL systems than for the RAPD system. The AFLP and SAMPL techniques appear to be more useful than the RAPD technique in the analysis of limited genetic diversity among the cowpea landraces tested. The significant correlations of SAMPL similarity and cophenetic matrices with those of the other markers, and the lower number of primer combinations required, indicate that this technique is the most valuable. The low genetic similarity detected among landraces suggests that all the cowpea landraces should be maintained on the respective farms from which they came.Key words: landraces, molecular marker, marker index, Vigna.