Suvendu Mondal

Peanut rust (Puccinia arachidis Speg.) disease: its background and recent accomplishments towards disease resistance breeding

The peanut rust disease is an economically important biotic stress that significantly reduces the pod and fodder yield and oil quality. It is caused by the basidiomycete fungus Puccinia arachidis Speg. which belongs to class Pucciniomycetes like other rust fungus but has fewer occurrences in teliospore form. The P. arachidis predominantly spreads by the repeated cycle of uredospores in the field. The disease is prevalent in most of the countries where peanut is cultivated and favored by warm and humid climatic conditions. Despite its economic importance, very limited work has been carried out on host-fungus interaction, fungal genetic diversity, and physiological specialization. The present review describes different aspects of P. arachidis especially its symptomatology, cell biological aspects of pathogenesis, epidemiology, and physiology of resistance as well as developments on genetics and genomics of host resistance, and resistance breeding. The review will help to understand the behavior of this causal organism and the host resistance and subsequently design the breeding approaches to check the spread of the disease.

Characterization of histone modifications associated with DNA damage repair genes upon exposure to gamma rays in Arabidopsis seedlings

Dynamic histone modifications play an important role in controlling gene expression in response to various environmental cues. This mechanism of regulation of gene expression is important for sessile organisms, like land plants. We have previously reported consistent upregulation of various marker genes in response to gamma rays at various post-irradiation times. In the present study, we performed various chromatin modification analyses at selected loci using the standard chromatin immunoprecipitation procedure, and demonstrate that upregulation of these genes is associated with histone H3 lysine 4 tri-methylation (H3K4me3) at the gene body or transcription start sites of these loci. Further, at specific AtAgo2 loci, both H3K4me3 and histone H3 lysine 9 acetylation (H3K9ac) are important in controlling gene expression in response to gamma irradiation. There was no change in DNA methylation in these selected loci. We conclude that specific histone modification such as H3K4me3 and H3K9ac may be more important in activating gene expression in these selected loci in response to gamma irradiation than a change in DNA methylation.

Genetic diversity in groundnut ( Arachis hypogaea L.) genotypes and detection of marker trait associations for plant habit and seed size using genomic and genic SSRs

Groundnut (Arachis hypogaea L.) an important oilseed crop in India is known to have narrow genetic base. Therefore, the assessment of genetic diversity and detection of marker-trait association are important objectives for the genetic improvement of groundnut. The present study involved the development of 192 SSR markers from Arachis genomic survey sequences. From these, seven polymorphic SSRs along with 15 other genomic SSRs, 19 genic SSRs, and three STS markers were used to detect genetic diversity among 44 groundnut genotypes. These polymorphic SSR markers amplified 155 bands (76 genomic and 79 genic), of these 128 bands (67 genomic and 61 genic) were polymorphic. The genomic SSR exhibited 88.1% and genic SSRs displayed 77.2% allelic polymorphism. The polymorphic information content (PIC) of the markers ranged from 0.04 to 0.95. The pair-wise genetic similarity ranged from 24.2 to 90.7% for genomic SSR and 32.9 to 97.9% for genic SSR markers. Cluster analysis based on the pooled data from both genomic and genic SSRs revealed a dendrogram which could distinguish all the genotypes. Further, the AMOVA analysis detected 16.7% genetic variation due to differences in seed size and 13.0% due to plant habit. Based on locus-by-locus AMOVA and Kruskal-Wallis ANOVA and further confirmation by discriminant analysis and general linear model, six markers were found to be associated with plant habit and four markers with seed size.

Electron beam irradiation revealed genetic differences in radio-sensitivity and generated mutants in groundnut (Arachis hypogaea L.)

Electron beam accelerators are being used for many industrial applications including food and agriculture. A 10MeV linear accelerator facility was standardized for low dose application 0.1-1 kGy) in pulse mode using unscanned scattered beam for irradiation of groundnut seeds for mutation breeding. Using this facility, 50% growth reduction (GR50) dose was standardized in five groundnut genotypes. There were significant differences for radio-sensitivity among these genotypes. Seed mutagenesis of two groundnut genotypes, TG 26 and TG 68 with electron beam has generated one large seeded and four high yielding mutants in preliminary field trials.