Standardization of grafting techniques in african marigold (tagetes erecta L.) for combating bacterial wilt

Abstract

The present study entitled “Standardization of grafting techniques in African marigold (Tagetes erecta L.) for combating bacterial wilt” was taken up in the Department of Floriculture and Landscaping, College of Horticulture, during the year 2017-2018. The work was carried out under three experiments viz.,standardisation of grafting techniques, assay of enzyme activity and histological studies. The rootstock used in the study was the bacterial wilt resistant local collection M- and the wilt susceptible F1hybrid Maria 91 was used as scion. Grafting was done in the month of January. Three methods of grafting viz., cleft, splice and hole insertion were tried at different ages of rootstock (4, 5, 6 and 7 weeks after sowing) and different ages of scion (3, 4 and 5 weeks after sowing). Observation of graft survival was taken at 15 DAG (Days after grafting). It was observed that cleft grafting four week old scion on to six week old rootstock was found to be the best with a graft survival of 61 percent. It was also observed that there was no survival when grafting was done on four week old rootstock irrespective of age of scion and grafting method followed. Estimation of catalase and peroxidase was carried out to study the activity of these enzymes in graft union formation. Sampling was done at 4,8 and 15DAG. It was observed that, activities of both the enzymes increased from 4DAG to 15DAG. Highest catalase activity at 4th (0.85 EU/g), 8th (1.39 EU/g) and 15th (1.60 EU/g) DAG was observed in cleft grafting of four week old scion on to six week old rootstock. Similar results were also observed in peroxidase activity. Correlation of catalase and peroxidase activity with survival of grafts indicated that both the enzymes are positively correlated with graft survival. Histological studies of the grafts consisted of both anatomical studies and histochemical staining for lignin. It was observed that there was an intensification of the stain from 4DAG to 15DAG with advancement of lignification process in graft union. Histological studies also revealed the formation of necrotic layer in the graft union, as a result of wound repair and cell proliferation. Cleft grafting of four week old scion on six week old wilt resistant rootstock is the best method in African marigold for combating bacterial wilt.