What are the factors that lead to the shape deviation of apple and pear?

Correct fruit shape is an important appearance index of high-quality apple pears. The fruit of Pingguo pear is irregular and oblate, and the fruit shape index is 0.8 1 ~ 0.85. In the process of fruit growth and development, the fruit shape index gradually becomes smaller. The factors that affect the fruit shape are:

(1) Pollination conditions and seed number.

The fruit with good pollination and fertilization conditions has good shape. If pollination conditions are poor, some ventricles will not form seeds, which will easily produce deformed fruits. Whether the fruit shape is correct or not is related to the distribution of seeds in the fruit. If there are many seeds and the seeds are evenly distributed (there are seeds in all five ventricles), the fruit shape is correct. On the contrary, if the seeds are few or concentrated in two or three ventricles on one side of the fruit, the pulp on the seedless side will not fully develop and form deformed fruit. The reason for less seed formation is related to insufficient pollination and fertilization, and deformed fruits mostly appear in pear orchards with few pollinated trees, no artificial pollination or poor artificial pollination. According to Yin (2002), the fruit shape of self-pollinated apples and pears is obviously deformed, and the fruit shape deflection index is large. The reason can be considered as the result of poor pollination and fertilization. From the cross-sectional view of ventricles, the fruit shape of Pingguo pear after self-pollination shows that among the investigated 10 fruits, 6 fruits have hypoplastic ventricular seeds, and only 1 ~ 2 ventricles out of 5 ventricles produce seeds, while other ventricular seeds are hollow and undeveloped, with an average of 4.2 seeds per fruit. On the side where the seeds are well developed and concentrated, the fruit shape is more prominent. On the other hand, on the side where there are no seeds or the ventricles with hypoplasia of seeds are concentrated, the appearance of fruit shape is flat, that is, the development of seeds directly affects the appearance of fruit. However, the fruit shape deviation index of cross-pollination is smaller than that of self-pollination, and the fruit shape is also corrected. From the fruit profile of cross-pollinated apple pear, only 5 fruits 1 room of 60 fruits are undeveloped, and the other 55 fruits have seeds in 5 rooms, which indicates that pollination and fertilization are good. In a word, pollination and fertilization is an important factor for the correct fruit shape. The fruit appearance variation of Chetou pear and Dachangba pear is small, and the fruit shape uniformity is high. Pollination with them has great influence on the fruit shape of apple pear. However, the fruit shapes of Xiaochangba pear, Zaosu pear and Jinfeng pear are quite different, and the improvement of apple pear fruit shape is not obvious, that is, the direct feeling of pollen is the reason that affects apple pear fruit shape. In practice, it is necessary to correctly select the pollinated varieties of apple pear, and comprehensively consider the fruit shape, flowering period and pollen quantity of pollinated varieties, and Chetou pear is the best. The flowering period of Dachang pear is 3 ~ 4 days later than that of Pingguo pear, and there are fewer pollen plants, so it is generally not used as a pollination tree in production. (2) Fruit growth sequence.

Fruit is inserted at the base of inflorescence, with regular shape. The fruit shape index of the outer crown is lower than that of the inner crown in the same order fruit. (3) The bearing capacity of inflorescence.

Apples and pears bloom easily. Each flower bud can produce 6-20 flowers, but it is usually 7-9. If the flowering climate is normal, the fruit setting rate is extremely high. Generally, each inflorescence can bear 3 ~ 4 fruits, many of which have 5 ~ 6. If the flowers and fruits are not thinned, the fruit deflection rate will increase significantly with the increase of fruit retention. According to the investigation results of Li Nan (1997), it is proved that if one single fruit is left in each inflorescence, the deviation rate of fruit shape is12.4%; There are two fruits per inflorescence, and the deviation rate of fruit shape is 44.3%; Leave 3 fruits per inflorescence, and the deviation rate of fruit shape is 62.7%; There are 4 fruits per inflorescence, and the deviation rate of fruit shape is 78.6%. With the increase of fruit retention, the deflection rate of fruit shape also increases, and the fruit is generally smaller. (4) Freezing at flowering stage.

Warm and sunny weather is the best weather for apple and pear pollination. In the northeast and northwest regions, apples and pears are vulnerable to frost from flowering to young fruit. Although pear flowers and young fruits can bear normal fruits after freezing, some frozen fruits have fewer seeds than normal flowers. The appearance shows that the fruit shape is not straight, the head is small, and the deflection fruit increases. Therefore, frost at flowering stage is also one of the factors affecting fruit deflection.