Sunil Kumar Chattopadhyay

Genetic Diversity and Relationship of Mulberry Genotypes Revealed by RAPD and ISSR Markers

ABSTRACT To improve mulberry (Morus spp.) foliage productivity, assessment of relatively underexploited genetic resources is essential. A core panel of 14 mulberry genotypes, shortlisted from 45 lines based on molecular profiling, was screened using random amplified polymorphic DNA (RAPD) and inter simple sequence repeat (ISSR) markers, to assess genetic diversity among them. Out of 25 primers each of RAPD and ISSR screened, 20 polymorphic primers (8 RAPDs and 12 ISSRs) were used in this study. Amplification of genomic DNA of the 14 genotypes, using RAPD analysis, yielded 67 fragments, of which 87.5% were polymorphic. The number of amplified fragments ranged from 6 to 11, with the size of amplicons ranging from 300 to 1,300 bp. The 12 ISSR primers produced 106 bands across 14 genotypes, of which 93% were polymorphic. The number of amplified fragments ranged from 5 to 12, with the size of amplicons ranging from 200 to 1,100 bp. Similarity coefficient ranged from 0.29 to 0.90 for RAPD and 0.36 to 0.81 for ISSR. For RAPDs the polymorphic information content (PIC) values ranged from 0.280 to 0.496, with an average of 0.351. For ISSRs, the PIC values ranged from 0.325 to 0.428, with an average of 0.375. There was a slight difference between RAPDs and ISSRs in their average resolving power (Rp). Using unweighted pair group method with arithmetic mean (UPGMA), a process of hierarchical clustering by Numerical Taxonomy and Multivariate Analysis System (NTSYS-pc), RAPD-, and ISSR-derived results were grouped the 14 genotypes into 2 and 5 clusters, respectively. Principal coordinate analysis also showed gross similarities with UPGMA-based dendrograms, with minor deviations. Morus indica L. (C-2016) exhibited highest divergence in cluster and lowest similarity coefficient value. This identified elite line may be utilized in mulberry improvement programs. The RAPD and ISSR markers were successfully used in assessing the genetic diversity among the tested mulberry genotypes.

Combining Ability Analysis for Bacterial Leaf Spot Resistance, Leaf Yield, and Agronomic Traits in Mulberry Clones

Combining ability effects for disease resistance, yield, and agronomic traits help in devising appropriate breeding strategies. Bacterial leaf spot (BLS) [Xanthomonas campestris pv.mori] is a destructive foliar disease of mulberry (Morus spp.). We evaluated crosses of useful mulberry clones to select good general combiners for resistance to BLS and to determine the genetics of important agronomic traits for mulberry improvement. Combining ability of six parents was estimated following a line × tester mating design. Established full-sib segregating progenies (440) derived from eight crosses, along with parents, were field-evaluated for leaf yield, agronomic traits, and resistance to BLS across two years. Significant negative (p < 0.01) general combining ability (GCA) effect of disease severity was found in genotype M. rotundiloba, which is desirable for BLS resistance; whereas significant positive GCA for leaf yield was observed in two parents, namely, M. multicaulis and C-2016. Moderately high narrow-sense heritability estimates (≥0.46), continuous frequency distributions, and moderately high genetic gains (19%–22%) were observed for traits such as primary shoot length, internodal distance, and petiole width. M. rotundiloba appeared to be a good general combiner for BLS resistance. Selection for primary shoot length, nodal distance, and petiole width should be effective for improving mulberry.