MSc

The season of epicotyl grafting, age of root stock and scion and precurring of scions were standardised by Dhungana (1984) in the earlier studies. The present series of experiments were undertaken with the objective to enhance the grafts ‘take’ by different methods.
Studies reported in this thesis were carried out during the period from June 1983 to March 1985 and consisted of experiments on standardisation of the height of root stock, length of scion, effect of covering material, effect of different plant growth regulators and different fungicides on dieback disease. Anatomical studies were also undertaken to find out the possible reasons of graft failures.
The results of the experiments on the influence of the height of rootstocks (2 to 4 cm, 4 to 6 cm, 6 to 8 cm and 8 to 10 cm) and the length of scion (5 cm, 6 cm and 8 cm) indicated that the height of rootstock and length of scion had significant effect on the success of epicotyl grafting in mango. It was observed that when mature 3 to 4 months old, ten days procured scion of 8 cm were grafted on five to ten days old rootstock at 6 to 8 cm height gave maximum percentage of sprouting and survival during July-August.
In the experiments to find out the influence of covering the grafts with polythene bags both transparent and black polythene bags were used. The grafts were covered with bags (15 x 20 cm) leaving sufficient space at the top. It was observed that covering the grafts with transparent polythene bags and retaining them for one month gave maximum percentage of success as well as final survival compared to control. Black polythene material was detrimental for graft ‘take’.
In another experiments the grafts were sprayed with IAA and GA each at 100, 250 ppm immediately after grafting in order to find out whether these growth regulators would help to increase the graft ‘take’. Although no significant effect could noticed, it appeared that IAA at 100 ppm had some beneficial effect.
The dieback disease of grafts was found to be caused by colletotrichum gloeosporioides and the disease was more sever during August to October. The trials with different fungicides viz., Bordeaux mixture at 1%, Thiram at 0.2% and Caftafol at 0.2%, revealed that Bordeaux mixture was the most effective in controlling the disease when applied one month after grafting and subsequently sprayed at an intervals of 15 days till 90 days.
Anatomical studies of the successful and failed grafts were also studied in order to understand the possible reasons for graft failures. It was observed that in successful grafts callus proliferation commenced from 5th day onwards and the completion of cambial bridge of the stock and scion was attained 15 days after grafting. The completion of cambial union was indicated by sprouting of grafts. There were four district stages in the healing of the grafts.
In unsuccessful grafts there was no indication of callus proliferation. Thicker necrotic layers were also formed in the region of graft union.
In grafts which remained alive up to 60 days, but did not sprout there were wide gap between stock and scion which perhaps inhibited sprouting of the scions.