Vegetative propagation of magnifera indical: effects of grafting technique, shade intensity and age of rootstocks on grafting success at Namanve, Uganda.
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Plant propagation studies are important to plant conservation and have led to the invention of grafting and budding methods that have enabled the improvement of commercial mango cultivars. Although grafting techniques have led to the production of various cultivars in tree nurseries, mango fruit tree production is limited by poor grafting skills, insufficient planting material and variation in agro – ecological regions. The aim of this study was to improve on the grafting success of Mangifera indica by evaluating low technology conditions of mango propagation in tree nurseries. The specific objectives of the study were to assess the effectiveness of selected shading intensities, grafting techniques and ages of rootstocks to grafting success and to determine the hardening off time of grafted mango seedlings. To that effect, two experiments were set up at the Tree Seed Centre nursery in Mukono (Uganda) between August and December 2008. The first experiment that evaluated the influence of shade intensities and grafting techniques was set in a 5 x 3 x 3 factorial treatment structure with five cultivars of mangoes(‘Apple’, ‘Alphonso’, ‘Bire’, ‘Ssejjembe’ and ‗Tommy atkins’), three grafting techniques (Side, Top wedge and Whip& tongue) three shading intensities (90%, 70% and 50%) with three replicates. The second experiment evaluated the effect of two rootstock ages on survival rate of five mango cultivars. This experiment was laid out in a Complete Randomised Block Design with a 5 x 2 x 3 factorial treatment structure of the same mango cultivars grafted on to two and four months rootstock ages. The grafts were then subjected to the same shading intensities with three replicates. Analysis of Variance (ANOVA) was used to examine the effect of cultivar, grafting technique and shade intensity on grafting success. Tukey‘s LSD test was used to separate mean cultivar survival percentage under the three shade intensities in both experiments. Unbalanced ANOVA was used to assess the effectiveness of hardening off time of the grafted cultivars. In experiment 1, selected mango cultivars showed significant differences in mean survival percentage (F= 3.40; P =0.011) across shade intensities. Bire cultivar had the highest mean survival percentage (80.4±0.717%) while Tommy atkins had the lowest mean survival percentage (59.3± 0.665%). Within shade intensities, mean survival percentage differed only under the 90% (F=3.83, P=0.01) shade intensity, but not under the 50% and 70% shade intensities. Mango cultivar Bire had the highest survival percentage (91.1±2%) while Tommy atkins had the lowest mean survival percentage (57.8 ± 10.1%) Mean survival percentage of grafts at two months did not differ from that of four month old rootstock although this result has significant implications on nursery operational costs and profits. Grafting technique significantly (F= 3.58; P= 0.033) affected the hardening-off time of grafts with Whip and tongue being the fastest at 91 days. Mango cultivar Bire being the highest surviving cultivar should be grafted on to two months old rather than four month old rootstocks under 50% shade intensity. This is expected to save on input costs and improve on profits. The findings from this study, thus strengthens the idea that grafting techniques and shade intensities can play a central role in grafting success. Although percentage survival of the grafted mangoes is influenced by mango cultivar and grafting techniques, a more extended study is still needed to elucidate survival percentage of the grafted seedlings in the field. Further studies should also be conducted, specifically to evaluate the effects of dry and wet seasons on grafting success and establishment of grafts in the field.