MSc

The study entitled “Piriformospora indica mediated response in taro (Colocasia esculenta (L.) Schott) with special emphasis to growth and leaf blight incidence” was conducted at the Division of Crop Protection, ICAR- Central Tuber Crops Research Institute (CTCRI), Sreekariyam, Thiruvananthapuram during October 2015- June 2016 with an aim to identify the potential of P. indica colonization in taro plants to promote growth and leaf blight resistance.
Taro is an oldest cultivated crop grown for its edible corms, leaves and also for its broad medicinal properties. Leaf blight caused by Phytophthora colocasiae is the most destructive disease which causes about 50% yield loss. Use of resistant varieties and adopting cultural methods, application of fungicides and use of biological agents are the prevailing management practices to combat taro leaf blight incidence. Piriformospora indica is an endophytic mycorrhiza like fungi which have shown pronounced growth promotional and disease suppressing activities. In present study, the colonization ability of P. indica in taro varieties Sree Kiran and Muktakeshi was studied. The colonization was confirmed by various staining methods, trypan blue staining and chitin specific WGA-AF 488 staining and also by amplifying species specific TEF1 gene. In pot culture experiment to study the growth promotion and disease suppression potential, an increase in all the growth parameters was noted in the colonized plants compared to control plants. There was a substantial decrease in the disease incidence in colonized plants of both the varieties. During the different stages of infection about 57.6, 50.7and 84.3 % decrease in PDI was observed in P. indica colonized Sree Kiran compared to the control plants and in case of Muktakeshi, reduction was 39.9, 56.2 and 72.5 % over control plants. Induction of defense enzymes during pathogen attack in P.indica colonized plants was also studied. Increase in the activity of defence enzymes like chitinase, β-1, 3- glucanase and total phenol was observed in the colonized plants when compared to control plants during the initial hours of pathogen infection. Suppression Subtractive Hybridization was carried out to identify the differentially expressed genes in the colonized plants upon P. colocasiae infection. Various genes that take part in different defense related pathways were identified upon annotation with Blat2Go program. The genes are, Senescence associated genes, cytochrome P450, Delta (12) oleic acid desaturase FAD2 and Calcium-dependent protein kinases (CDPKs) which are expressed in plants during various biotic and abiotic stresses. Thus the study revealed the potential of P. indica as an effective growth promoter as well as potential bio-control agent for taro leaf blight management.