Sexual and Apomictic Seed Reproduction in Aronia Species with Different Ploidy Levels

The genus Aronia Medik., also known as chokeberry, is a group of deciduous shrubs in the Rosaceae family, subtribe Pyrinae. The four commonly accepted species include A. arbutifolia (L.) Pers., red chokeberry; A. melanocarpa (Michx.) Elliott, black chokeberry; A. prunifolia (Marshall) Reheder, purple chokeberry; and A. mitschurinii (A.K. Skvortsov & Maitul). Wild and domesticated Aronia species are found as diploids, triploids, and tetraploids. Genetic improvement of polyploid Aronia genotypes has been limited by suspected apomixis, which may be widespread or distinct to tetraploids. The objectives of this study were to elucidate the reproductive mechanisms of Aronia species and reveal the occurrence of apomixis within the genus and along ploidy lines. Twenty-nine Aronia accessions [five A. melanocarpa (2×), five A. melanocarpa (4×), eight A. prunifolia (3×), four A. prunifolia (4×), six A. arbutifolia (4×), and one A. mitschurinii (4×)] were used in this study. Intra-accession variability was evaluated by growing out progeny from each open-pollinated maternal accession and comparing plant phenotypes, ploidy levels, and amplified fragment length polymorphism (AFLP) marker profiles between the progeny and maternal accession. Progeny of diploid and tetraploid maternal plants had ploidy levels identical to maternal plants, except for UC009 (A. melanocarpa, 2×) which produced a mix of diploids and tetraploids. UC143 and UC149 (A. prunifolia, 3×) produced all triploid offspring, whereas all other triploid accessions produced offspring with variable ploidy levels including 2×, 3×, 4×, and 5×. Pentaploid Aronia has not been previously reported. Diploid accessions produced significant AFLP genetic variation (0.68–0.78 Jaccard’s similarity coefficient) in progeny, which is indicative of sexual reproduction. Seedlings from tetraploid accessions had very little AFLP genetic variation (0.93–0.98 Jaccard’s similarity coefficient) in comparison with their maternal accession. The very limited genetic variation suggests the occurrence of limited diplosporous apomixis with one round of meiotic division in tetraploid progeny. Triploid accessions appear to reproduce sexually or apomictically, or both, depending on the individual. These results support our understanding of Aronia reproductive mechanisms and will help guide future breeding efforts of polyploid Aronia species.

Characterization and genetic diversity of cowpea (Vigna unguiculata L.) genotypes linked to Cowpea yellow mosaic virus

The present research was carried out to investigate the genetic diversity among cowpea tolerant and susseptibe genotypes. For which the fifteen cowpea genotypes were manually infected with Cowpea yellow mosaic virus(CYMV) inoculum and to detect virus by a serological technique. The five most tolerant and sensitive each genotypes had been taken for genetic diversity study in which JCPL-2 and JCPL-11 was found most susceptible and tolerant genotype, having absorbance at 405nm 2.172 and 0.167 respectively. The RAPD, ISSR and SSR marker system were applied to the ten cowpea genotypes. For the RAPD data, based on PIC value, it can be said that primer OPAI-15 was the best primer resulting good amplification with maximum PIC value (0.764).Dendrogram constructed using the RAPD data clearly distinguished all genotypes. It revealed that JCPL-44 and JCPL-45 found in one cluster and shared maximum 96.00% similarity; however, genotype JCPL-2 have out grouped from other 9 genotypes and shared minimum 41.00% similarity. In case of ISSR data, based on PIC value it can be said that the primer 835 was the best primer resulting good amplification with maximum PIC value (0.837). Jaccard’s similarity coefficient ranged from 0.625 and 0.906. The ISSR results indicated that maximum similarity 90.60% was found between JCPL-2 and JCPL-18, while minimum similarity 62.50% was obtained between JCPL-2 and JCP- 87. For the SSR data, based on PIC value it can be said that the primer VM-13 was the best primer resulting good amplification with maximum PIC value (0.668). Jaccard’s similarity coefficient ranged from 0.500to 1.000. So SSR data revealed that JCPL-2 showed maximum variability compared to other nine genotypes. The combined RAPD, ISSR and SSR analysis revealed that out of ten genotypes JCPL-44 and JCPL-45 were showed maximum (91.0%) similarity. The lowest similarity of 58.30% was found between JCPL-2 and JCP-45.

Genetic diversity in tomato (Solanum lycopersicum L.) genotypes revealed by simple sequence repeats (SSR) markers

Twenty five tomato (Solanum lycopersicum L.) genotypes were subjected to genetic diversity analysis using twenty SSR markers. Out of 20 markers used, 14 SSRs were polymorphic and a total numbers of 22 SSR alleles were generated by 14 SSR markers, out of which 19 were polymorphic and 3 were monomorphic, with an average of 1.57 alleles per locus. The range of amplified products was 100-400bp approximately. Jaccard’s similarity coefficient varied from 0.65 between germplasm EC519821 and CO-3 to a maximum of 1.0 between genotypes EC519769 and DARL-66, with an average value of 0.83. Cluster analysis based on Jaccard’s similarity coefficient using the unweighted pair-group method with arithmetic mean (UPGMA) revealed 2 distinct clusters, A and B, comprising 1 and 24 genotypes respectively and at 75 and 78 per cent similarity, respectively. The genotypes which showed similar morphological and genetic trends were grouped more or less together in both these cases were a few. Cluster A comprised most diverse germplasm (EC519821)belongs to pimpinellifolium wild species with similarity coefficient 0.65% and differentiated with other cultivated species.Cherry Tomato and Cherry-2 were trends in similar cluster similar with approximately 96% similarity.SSR markers were able in in differentiating the genotypes based on morphologically and genotypically.However, the grouping of 25 genotypes were independently of geographic distribution.The genetic distance information found in this study might be helpful to breeder for planning among these genotypes.