Research Projects

North East (NE) region of India has a rich treasure of various Citrus species and among those, sweet orange is most widely grown across the globe while, Khasi mandarin is another citrus variety having high commercial value. Citrus tristeza virus (CTV) is one of the most devastating pathogens which is transmitted by aphid. NE region of India is considered as probable origin of CTV and its vector. Hence there is an urgent need to identify the CTV resistant genotypes, develop CTV disease free planting material in commercial citrus variety and identification of the molecular basis of CTV resistance. Calmodulin-binding Transcription Activators (CAMTAs) are major transcription factors involved in regulation of gene expression under several biotic and abiotic stresses across plant species. Recent studies in citrus depicted involvement of CAMTAs in abiotic stresses only. Present study can decipher the involvement of citrus CAMTA genes and promoters in CTV infestation.

Survey was conducted to assess Citrus tristeza virus (CTV) incidence across Meghalaya, Tripura, and Arunachal Pradesh with Meghalaya showing the highest incidence rate followed by Arunachal Pradesh and Tripura. In Meghalaya, 9 villages across 5 districts were surveyed. RiBhoi district's Sohkhwai village recorded maximum with 100% CTV incidence, while Umsohme village had the lowest (57.14%). In Tripura, eight villages were surveyed, of which, Darjeeling Bari and Thelakumb showed the highest incidence (60%), while four villages reported no CTV presence. In Arunachal Pradesh, Rengging village, East Siang District and Kamba, Anjaw District, exhibiting the highest incidence (54.54%), followed by Bodak, East Siang District and Supliang, Anjaw District. For in vitro micrografting studies, sucrose concentration, scion pretreatment, and rootstock age significantly influenced grafting success, while plant growth regulators had a lesser impact. Among the rootstocks, Rough lemon achieved the maximum grafting success (60.74%), followed by Citron (46.30%), Melanesian Papeda (44.81%) and Pummelo (41.48 %). Cleft grafting proved to be more effective than the inverted-T method across all rootstocks. The standardized protocol can help in the large-scale production of disease-free planting material and exploration of rootstocks indigenous to northeast region which are tolerant/ resistant to biotic and abiotic stress to increase the overall production of Khasi mandarin in the region. The present work identified several important genes involved in the CTV infestation in citrus. This study identified unique CAMTA genes from two different Citrus species. Previous studies identified upto nine different CAMTA genes from citrus but those were redundant or different transcript variant of a single CAMTA gene. Protein modelling and docking experiment clearly revealed the interaction between CAMTA and calmodulins which could be explored further to understand the CAMTA-mediated signalling in more detail. Among the identified CAMTAS, CrCAMTA displayed maximal expression upon exposure to CTV infestation and this finding make it a potential candidate for further research in relation to CTV infestation.