Scientist Profile

Quantitative Genetics, Genomics, Plant-microbe interactions.

Research Associate, Centre for Genetic Manipulation of Crop Plants, University of Delhi, India (November 2016 – September 2018)

• We described a near-complete genome assembly of Alternaria brassicae using Nanopore sequencing. We identified various secondary metabolite clusters, effectors, and carbohydrate-active enzymes with putative roles in pathogenicity.
• We carried out a whole-transcriptome analysis of different Arabidopsis accessions (resistant, intermediate, and susceptible) upon pathogen infection and discerned some of the pathways involved in resistance against A. brassicae.

Ph.D., Department of Genetics, University of Delhi South Campus, India (August 2010 – October 2016)

• We identified several candidate QTLs and genes responsible for resistance to A. brassicae (a major pathogen of Brassica species) in Arabidopsis thaliana using association mapping and QTL mapping.
• We also deciphered some of the cellular and molecular mechanisms underlying resistance or susceptibility to A. brassicae.

1. Established the Alternaria brassicae-Arabidopsis pathosystem to study pathogenesis of A. brassicae, for which no resistance exists in the cultivated Brassicas.
2. Identified some key candidate genes in Arabidopsis thaliana that confer resistance to A. brassicae.
3. Sequenced and reported a high-quality genome sequence for A. brassicae.

Food security and global food production are major challenges facing the human population. Plant diseases have devastating effects on food availability, thus leading to a bottleneck in supporting the growing world population. Oilseeds of the Brassica genus are significant contributors to the total edible oil consumed worldwide, second only to soybean oil. Brassica juncea (Indian Mustard) is a major oilseed crop grown worldwide contributing 21.7% and 10.7% in world acreage and production. In India, it is the second major oilseed crop, cultivated in around six million hectares of land. Fungal diseases are major destabilisers with respect to growth and yield of mustard. Among various diseases, four diseases viz. Alternaria blight (Alternaria brassicae), white rust (Albugo candida), Stem rot (Sclerotinia sclerotiorum) and powdery mildew (Erysiphe cruciferarum) are of great economic importance. Alternaria blight or black spot, a widespread and destructive disease is caused mostly by A. brassicae (Berk.) Sacc. infecting all above-ground parts of the plant.

Our research focusses on Alternaria brassicae, a necrotrophic pathogen for which no source of resistance is available in any of the cultivated species. We aim to decipher the genetic underpinnings of Brassica-A. brassicae interactions in order to develop disease resistance varieties/cultivars. We have undertaken a two-pronged approach to the problem viz. 1) Screening the landraces and wild germplasm of Brassicas and related species for resistance to prospect for resistance genes; 2) exploring the genetic diversity of A. brassicae across India and utilizing the variation within the pathogen’s population to gain insights into the host resistance genes.

Identification of resistance genes would involve a combination of genetic mapping (QTL and GWAS) and protein-protein interactions (host-pathogen) approaches. Once characterized, strategies can be determined to utilize the resistance genes in breeding programmes through the use of marker-assisted breeding/gene-editing technologies.

For more details, please visit – https://siva5.github.io

1. Rajarammohan S, Pental D, and Kaur J (2019) Near-complete genome assembly of Alternaria brassicae - a necrotrophic pathogen of Brassica crops. Molecular Plant-Microbe Interactions. doi: https://doi.org/10.1094/MPMI-03-19-0084-A.

2. Mandal S, Rajarammohan S, and Kaur J (2019) ROS accumulation and associated cell death mediates susceptibility to Alternaria brassicae in Arabidopsis accessions. bioRxiv 581025; doi: https://doi.org/10.1101/581025.

3. Mandal S, Rajarammohan S, and Kaur J (2018) Alternaria brassicae interactions with the model Brassicaceae member Arabidopsis thaliana closely resembles those with Mustard (Brassica juncea). Physiology and Molecular Biology of Plants, 24:51. doi: 10.1007/s1229/8-017-0486-z.

4. Rajarammohan S, Pradhan AK, Pental D, and Kaur J (2018) Genome?wide association mapping in Arabidopsis identifies novel genes underlying quantitative disease resistance to Alternaria brassicae. Molecular Plant Pathology, 19: 1719-1732. doi:10.1111/mpp.12654.

5. Rajarammohan S, Kumar A, Gupta V, Pental D, Pradhan AK, and Kaur J (2017) Genetic Architecture of Resistance to Alternaria brassicae in Arabidopsis thaliana: QTL Mapping Reveals Two Major Resistance-Conferring Loci. Frontiers in Plant Science, 8:260. doi:10.3389/fpls.2017.00260.

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1. DST-INSPIRE Faculty - Department of Science and Technology (DST), Government of India (2018)
2. Junior Research Fellowship – University Grants Commission (UGC), Government of India (2011)
3. Senior Research Fellowship - University Grants Commission (UGC), Government of India (2013)
4. Graduate Aptitude Test in Engineering (GATE) - 97.5 percentile, conducted by Ministry of Human Resource Development, Government of India (2010)
5. Dean’s List (Top 2% of students), SASTRA University, India. (2007-08)
6. Dean’s List (Top 10% of students), SASTRA University, India. (2006-07, 2008-09, 2009-10)