Cassava mosaic disease, caused by cassava mosaic geminiviruses are transmitted by Bemisia tabaci. The B. tabaci adults from colonies reared on virus free cassava plant produced from apical meristem culture was studied to determine their ability to transmit Indian cassava mosaic virus (ICMV) and Sri Lankan cassava mosaic virus (SLCMV) from cassava to cassava. Virus free plants were confirmed by polymerase chain reaction (PCR) using geminivirus degenerate primers. The virus acquisition access period (AAP) of 48 h on virus infected cassava leaves and 48 h virus inoculation access periods on virus free healthy leaves were investigated. Both ICMV and SLCMV were absolutely transmitted by whiteflies reared on cassava. Virus specific primers were designed in the replicase region and used to detect virus in B. tabaci after different AAP. The PCR amplified replicase genes from virus transmitted cassava leaves were cloned the plasmid DNA was isolated from a recombinant colony of E. coli DH5α after their confirmation by colony PCR and sequenced them. The nucleotide sequences obtained from automated DNA sequencing were confirmed as ICMV and SLCMV replicase gene after homology searching by BLAST and found to be a new isolates. The nucleotide sequences of new isolates were submitted in GenBank (accession number JN652126 and JN595785).

Abstract:The goal of our research is to establish a unique portal to bring out the potential outcome of the research in the Casssava crop. The Biogen base for cassava clearly brings out the variations of different traits of the germplasms, maintained at the Tapioca and Castor Research Station, Tamil Nadu Agricultural University. Phenotypic and genotypic variations of the accessions are clearly depicted, for the users to browse and interpret the variations using the microsatellite markers. Database (BIOGEN BASE -CASSAVA) is designed using PHP and MySQL and is equipped with extensive search options. It is more user-friendly and made publicly available, to improve the research and development of cassava by making a wealth of genetics and genomics data available through open, common, and worldwide forum for all individuals interested in the field.

Proteomics is becoming an increasingly important tool for the study of many different aspects of plant functions, such as investigating the molecular processes underlying hostpathogen interaction, plant physiology, development and differentiation. Cassava mosaic disease (CMD), caused by cassava mosaic virus (CMV), is the most serious disease in cassava. However, the molecular mechanisms underlying CMD in cassava during CMV infection is not yet clearly understood. The current study determined and identifies the differentially expressed proteins from cassava leaves during the infection of CMV viz., Indian Cassava mosaic virus (ICMV) and Sri Lankan Cassava Mosaic Virus (SLCMV). 2D gel electrophoresis was used to identify the cassava responsive proteins during the virus infection and the differentially expressed proteins were analysed by matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometry. There are 19 proteins were differentially expressed in cassava leaves by CMV infection. Among them 18 were giving good spectra by MALDI-TOF mass spectrometry. Analysis of Peptide Mass Fingerprint (PMF) data of these 18 proteins revealed the identity of the differentially expressed proteins, which suggest their importance and relevance on plant growth and development, and defence. This work paves the way towards a comprehensive analysis of CMV infection of cassava. Identification of the differentially expressed proteins by their sequence homology to known proteins suggests a possible direct or indirect role on plant defence during CMV infection. This study revealed the differentially expressed proteins, expressed during interaction between cassava and CMV that might play important roles either in viral pathogenesis or resistance.

Cassava, family Euphorbiaceae, is the fifth most important staple food crop. The study of variability and diversity present in diverse cassava accessions maintained at the field genebank of TCRS, TNAU is essential to design the breeding program of cassava in TNAU. Hence, a study was carried out to assess the genetic diversity based on morphological traits and Simple Sequence Repeat (SSR) markers, identifying the SSR markers linked to a cassava mosaic disease-resistant QTL region. Genetic diversity among cassava germplasm accessions was estimated using 28 morphological traits and three SSR markers. The polymorphic information content (PIC) result gives high information for all the SSR markers. Morphological traits revealed 10 clusters and the SSR markers revealed 13 clusters at a similarity coefficient of 2.514 and 0.75, respectively. The SSR marker diversity revealed that the most promising clusters (II and XII) possessing accessions with yield attributing traits and cluster IX were grouped together due to low yield and CMD susceptibility. Morphological descriptors revealed variance for yield contributing traits. The first three principle components accounted for 10.8, 9.1, and 8.4%, respectively. Correlation studies showed significant correlation among yield and yield-attributing traits, which in turn influences yield. The morphological traits diversity reveals that cluster VI was the most promising cluster in which genotypes ME209 and ME460 possess higher yield and starch content with cassava mosaic disease (CMD) resistance. Most of the accessions grouped under cluster X belong to selection from International Centre for Tropical Agriculture (CIAT) collections and the cultivars under clusters I and II were true cassava seed (TCS) selections of India. The CMD-linked SSR marker which is reported in the previous studies have generated eight alleles and each were regressed with CMD resistance and resulted in non-significant linkage to CMD resistance.

No abstract