Grafting success of elite clonal Hass avocado rootstocks.

Abstract

Avocado production is constrained by a shortage of improved cultivars, reliance on local cultivars that have led to low yields and low quality. In addition, smallholder farmers, who are the backbone of the country’s agricultural production, usually encounter several challenges while participating in the avocado value chains. The continued use of conventional avocado varieties that are low yielding and susceptible to pests and diseases by smallholder farmers has been due to limited access to clean planting material of high-value Hass avocado varieties. Thus, this study aimed to develop elite clonal rootstocks for enhancing the production of grafted Hass avocado in Uganda. The experiment was conducted at NAFFORI from September 2023 to February 2024. The experiment was laid out in a Randomized Complete Block Design (RCBD) with factorial concept and three replications. Data were collected on the number of days to shoot emergence, the number of young and green leaves, shoot length, and graft survival percentages. Data were entered in Microsoft Excel 2011, and further analyses were conducted in Minitab software. Significant tests were carried out using a two-way analysis of variance (ANOVA), and all statistical tests were performed at 5 % level of significance. The results revealed significant differences (P≤0.05) in mean graft percentage, height, and leaf production among the 12 avocado varieties. Reed exhibited the highest mean graft success percentage (94.1± 0.781%), followed by Esther (88.77±0.79%), while the local variety had the lowest mean graft success percentage (18.87± 0.38%). The analysis of the number of young leaves also indicated significant differences among the varieties (P≤0.05). Semile 43 had the highest mean number of leaves (9.23±2.62) while Fuerte and Esther exhibited the lowest mean number of young leaves of (4.933 ± 0.445) and (4.833 ± 0.536), respectively. Land races were found to be more compatible when grafted onto Hass avocado. Significant differences were observed in days to shoot emergence, success and survival percentages at (P ≤ 0.05). Maximum and significant shoot length and plant height were attained at 10-11 am grafting with 60 cm grafting height (T3H3). Based on the findings, it is recommended that Reed and Rincon, with vigorous growth and high survival rates (40%), can be used as rootstock varieties for grafting Hass avocado. Grafting should be conducted in the mid-morning hours (10–11 am) when environmental conditions are optimal, as this time resulted in the highest graft success rate (76.63% ± 2.93). A grafting height of 60 cm is recommended to maximize shoot length and plant vigor, as it demonstrated significantly better growth performance than lower grafting heights.