Graft Success of Hass Avocado Cultivar Under Nursery and Field Environmental Conditions at NaFORRI
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Avocado has gained an immense popularity over the last few decades as a luxurious and important tropical horticultural crop in the modern world. However, production of avocado especially for commercial use is not commonly done through growing avocado seedlings to maturity but rather grafted like most commercial fruit crops, mainly to overcome juvenility. Even then, Hass avocado cultivar is usually more difficult to successfully graft than any other commonly grown cultivars. It requires suitable environmental conditions for the successful establishment of the graft. While environmental conditions are believed to be very crucial in graft success, grafting techniques have to be taken into account too. The aim of this study was to evaluate the graft success of Hass Avocado cultivar under nursery and field environmental conditions. An experiment was carried out where Hass scions obtained from NaFORRI orchard were grafted onto nursery and field rootstocks using splice and top wedge grafting techniques in a Complete Randomized Block Design (CRBD). Data were collected on number of days to first bud sprouts, number of bud sprouts, number of young and green leaves and graft survival percentages for a period of 4 months. Data were entered in Microsoft excel 2007 and further analysis conducted in Minitab software. Significant tests were carried out using a two-way analysis of variance (ANOVA), all statistical tests being performed at 5 % level of significance. The results indicated that a lower mean number of days taken to first bud sprout (04.11±1.08) was recorded under field environmental conditions while top wedge grafting techniques gave a lower mean number of days to first bud sprout (05.90±1.22). Generally, higher graft success in terms of number of bud sprouts (0.43±0.03), number of young (0.92±0.09) and green leaves (0.81±0.09) was exhibited under nursery environmental conditions using splice grafting techniques. Nursery environmental conditions revealed a higher mean survival percentage (32.41±4.15). Among the grafting techniques, splice grafting technique gave a higher mean graft survival percentage (10.52±1.63%). Statistically, the recovery time (number of days to first bud sprouts), graft success (number of bud sprouts, number of young and green leaves) and survival rate of Hass Avocado Cultivar can be significantly influenced by environmental conditions (P<0.05) but not by grafting techniques (P>0.05). This study indicates that in order to enhance grafting success of Hass avocado cultivar, grafts should be made under nursery environmental conditions using splice grafting technique. Commercial avocado farmers and other tree nursery operators should be encouraged to graft Hass avocado cultivar under nursery environmental conditions using splice grafting technique. Further research should be carried out on grafting Hass under nursery and field environmental conditions within the right grafting season (June to August) using other grafting techniques. Grafting of Hass avocado cultivar should be done by experienced grafters to determine if the results of the study will be of any difference from those of the current study. This is expected to provide a better answer to a better grafting techniques and environmental conditions for promoting grafting Hass avocado cultivar in Uganda.