Evaluation of Graft Success in Fuerte Avocado Cultivar under Nursery and Field Environmental Conditions
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Fuerte avocado cultivar is an important commercial avocado cultivar in Uganda both for local and export markets (because of its good taste). Since its cultivation is limited due to long juvenile period, grafting technique has been adopted in many countries not to only shorten the juvenile period but also to improve its quality and yield. Even then, grafting success has been reported to be low due to inappropriate grafting environment/grafting techniques in addition to low skilled grafting personnel. The aim of this study was to evaluate graft success of Fuerte avocado cultivar under nursery and field environmental condition using splice and top wedge grafting techniques in order to come up with a suitable environmental condition and grafting technique that can boost avocado production in Uganda. The specific objectives were to: compare time taken to first bud sprouting and leafing, determine graft survival percentage and ascertain the most effective grafting technique for Fuerte avocado cultivar with splice and top wedge grafting techniques under both nursery and field conditions. Fuerte avocado scions were collected from NaFORRI seed orchard and grafted using splice and top wedge grafting techniques under both nursery and field environmental conditions. The experiments were set in Completely Randomized Block design (CRBD) with three replicates. Data were collected on time taken to first bud sprouting and to leafing, number of bud sprouts, number of young and green leaves and graft survival percentage over a period of 120 days. Data were in MS Excel/Minitaba, Descriptive statistics were computed and a two way –ANOVA carried out at 5% significance level. The results indicated that field environmental condition exhibited the lower mean number of days to first bud sprouting (8.08±1.39) and to leafing (7.03±1.38). While splice grafting technique exhibited the lower mean number of days to first bud sprouting (17.04±1.56), top wedge grafting technique exhibited the lower mean number of days to leafing (20.52±1.93). Nursery environmental condition revealed a higher mean number of bud sprouts (2.52±0.04), young leaves (4.12±0.13) and green leaves (5.40±0.140) compared to field environmental condition with mean of bud sprouts (0.38±0.02), young leaves (1.56±0.10) and green leaves (1.42±0.11). Of the two grafting techniques, splice grafting technique performed better in terms of mean number of bud sprouts (1.66±0.04) and green leaves (3.45±0.12) but the higher mean number of young leaves was recorded in top wedge grafting technique (2.98±0.13). Grafts under nursery environmental condition exhibited a higher mean graft survival percentage (78.95±1.99) compared to those under field environmental condition (16.64±1.37). Of the two grafting techniques, splice grafting technique gave a higher mean graft survival percentage (48.98±4.89) compared to top wedge grafting technique (46.60±4.33). Generally all the parameters in this study: time to first bud sprouting, leafing, number of bud sprouts and leaves and graft survival were significantly influenced by environmental conditions (P=0.000) unlike grafting techniques which only significantly influenced number of bud sprouts (P=0.000). This study provides preliminary results concerning grafting success of Fuerte avocado cultivar in which splice grafting technique and nursery environmental condition appear to be the most effective. Commercial Fuerte avocado farmers should be encouraged to use splice grafting technique under nursery conditions to propagate Fuerte avocado cultivar; after which the hardened successful grafts should be transplanted into the field. Further research should be carried out using other grafting methods like side wedge, whip and tongue under other environmental conditions like green house, polyhouse and in different grafting seasons to determine their survival rates in order to give a better insight of the best environmental condition and grafting technique for grafting Fuerte avocado cultivar in Uganda.