Effect of Self and Cross-Pollination in Some Local Mango Cultivars on Fruit Set and Retained Fruits
Mango (Mangifera indica L.) considered one of the oldest cultivated trees in the world. Low productivity of some mango cultivars is associated with low fruit setting and/or high fruit drop of immature fruits. The self and cross incompatibility has been reported as one of the serious factor affecting fruit set in many mango cultivars. In this respect, four mango cultivars (Alphonse, Ewais, Hindi khassa and Zebda) were used to examine the effective of cross and self-pollination between them on fruit setting and number of retained fruits. The fluorescence microscope was used to determine the growth of pollen tube in the style tissue after pollination. The results of the present study indicated that, open pollination followed by cross-pollination gave the highest initial number of fruitlets per panicle in all cultivars under study than self-pollination. Florescence microscope showed incompatibility symptoms with self-pollination treatments of Alphonse, Ewais, Hindi khassa and Zebda cultivars in most of resulted pollen tubes such as short tubes, which were unable to penetrate the style. Plugs appeared along of the Alphonse, Hindi khassa and Zebda styles when crossed by Ewais pollens, this lagging in pollen tube growth delays its arrival to the base of the style end. Moreover, pollen tubes grew slowly when use Alphonse as a pollinizer for Ewais and Hindi khassa cultivars, this slowly grow in pollen tube delays its arrival to the base of the style end after 7 days from pollination. The germination of Zebda pollen grains on Hindi khassa stigmatic surface, were higher than other combinations and such pollen tubes reached to the base of the style in 4 days after pollination, this is an indication of high cross compatible between these two cultivars. Ewais gave the lowest percentage of pistils with pollen tubes reaching the base of the style 7 days after self-pollination. Generally, self-pollination of each cultivar induced lower number of pollen tubes at style bases compared with crossing by other cultivars. The highest initial number of fruitless per panicle resulted from cross-pollination was observed when Hindi Khassa cv. crossed by Zebda pollen grains, meanwhile, the lowest initial number of fruits per panicle value was noticed when Ewais cv. was selfed. Concerning the number of retained fruits at harvest date, all cross combinations reach the maximum value of fruit drop (100 %) after 15 weeks from pollination treatments except the combination of (Hindi Khassa crossed by Zebda pollen) and the open pollination in the four studied cultivars.