Early identification of graft compatibility through histological studies in mango

Three polyembryonic mango rootstocks namely, Nekkare, Olour and Vellaikolumban grafted with Alphonso were used to investigate grafting success and histological evaluation of graft union. The observations were recorded at 07, 14 and 21 days after grafting (DAG). The results revealed that softwood grafting of Alphonso on to Nekkare rootstock showed significantly higher vegetative growth related parameters for graft union than the rest of rootstocks (Olour and Vellaikolumban). The Olour and Vellaikolumban grafted with Alphonso showed moderate and lesser graft compatibility, respectively. The graft union compatibility was confirmed through histological studies. It was observed on 07^th DAG that the tissue was juxtapose, initiated callus formation, merged union in Vellaikolumban, Olour and Nekkare rootstocks with Alphonso, respectively. Similarly, on 14^thDAG, continuous proliferation of callus in Alphonso/Olour, numerous separation areas in Alphonso/Vellaikolumban were observed, while Alphonso//Nekkare had enough callus and which trigger the progressive development of xylem and phloem cells. Furthermore, on 21^st DAG, graft union between Alphonso and Nekkare had better connection, vascular bundles differentiation, annual thickenings, xylem formation and xylem strands as compared to Olour and Vellaikolumban rootstocks. Histological observations and growth attributes confirmed that Alphonso grafted on Nekkare rootstock showed high graft compatibility than the rest of rootstocks, hence it can be utilized for the production of more mango saplings.