Usually, some fruits we eat have seeds, but why only bananas have no seeds? How do bananas blossom and bear fruits? Let's have a look~
Bananas taste soft, waxy, fragrant and sweet, and are deeply loved by people. In Africa and Southeast Asia, people in some places eat bananas as a staple food, boiled or dried. When eating bananas, many people will wonder why this fruit has no seeds and how do these seedless bananas reproduce?
Banana originated in Asia, Malaysia and southwest China. It is one of the oldest cultivated fruit trees in the world. Today's banana cultivated species originated from the wild banana pointed leaf and long stem banana. There are two groups of chromosomes in these two wild banana varieties, which are diploid, 2n in short, and composed of 22 chromosomes. They can produce seeds, carry out sexual reproduction and grow normally. However, Jianye banana has small fruit and good flavor, but it has poor resistance to harsh environment and is not easy to grow; while Changgeng banana has strong adaptability but poor taste. Therefore, these two wild banana varieties are not suitable for cultivation.
The chromosome composition of C. acuminata is called AA genome, and that of C. longipes is called BB genome. Most of the banana varieties cultivated at present are modified Jianye banana. Their chromosome composition is AAA, which is triploid. This is the use of wild banana in the process of reproduction chromosome meiosis
The diploid gametes are formed, and the chromosome composition is AA. When these gametes are combined with haploid gametes with normal genome a, triploid banana varieties with genome AAA will be produced. This kind of banana has big fruit, good taste and high yield. It is the main cultivated banana in modern times.
The change of chromosome composition has greatly changed the reproduction mode of triploid banana and wild diploid banana. When normal diploid banana propagates, 22 chromosomes undergo meiosis to form female gametes or male gametes with 11 chromosomes. The combination of male and female gametes produces diploid banana. These bananas have normal seeds. However, most of the cultivated bananas are triploid genomes. When they form gametes, the triploid lines composed of 33 chromosomes undergo meiosis, and the distribution of chromosomes is unbalanced. It is difficult to form a set of active gametes containing 11 chromosomes, so normal seeds cannot be produced. So, the bananas we usually see are seedless. Because there is no seed, triploid banana can not be reproduced by sexual reproduction, only by asexual reproduction.