question_answer

(i) How does a breeder ensure the process of cross - pollination in an economically important bisexual flower?

(ii) Emasculation is done in only bisexual flowers. Justify.

Or

(i) IARI has released several varieties of crop plants that are biofortified. Give four examples of such crops and their biofortifications.

(ii) 'Why is the selection process after hybridisation very crucial in breeding programmes?

Answer:

(i) Controlled cross-pollination is one of the major approaches of crop improvement programmer. In such experiments, it is important to make sure that only the desired pollen grains are used for pollination and the stigma is protected from contamination (from unwanted pollen).

Steps of controlled cross-pollination These are as follows

· Selection of parents for desired characters.

· Emasculation is performed in the female parent bearing bisexual flowers before dehiscence of anther.

· It is followed by bagging, i.e. emasculated flowers are covered with a bag of suitable size, generally madeup of butter paper, to prevent contamination of its stigma with unwanted pollen.

· When the stigma of bagged flower attains receptivity, mature pollen grains collected from anthers of the male parent are dusted on the stigma.

· The flowers are rebagged and the fruits are allowed to develop.

(ii) Emasculation is essential only in case of bisexual flowers to prevent self-pollination. In case of unisexual plants, female parent produces usually unisexual flowers.

If the female parent produces unisexual flowers, there is no need for emasculation. The female flower buds are bagged before the flowers open. When the stigma becomes receptive, pollination is carried out using the desired pollen and the flower is rebagged.

Or

(i) The bio fortified crops include

(a) Vitamin-A enriched carrots or spinach.

(b) Protein enriched beans.

(c) Vitamin-C enriched bitter gourd and mustard.

(d) Atlas-66, a wheat variety having a high protein content.

(ii) It is possible by cross hybridising the two parents to produce hybrids that genetically combine the desired characters in a single plant. However, it is not necessary that the hybrids do combine desired characters. The chances of desirable combination is usually only one in few hundred to a thousand crosses carried out. Therefore, selection of superior recombinants after hybridisation is very crucial in breeding programme. In selection process, plants that are superior than both the parents are selected. This is known as hybrid vigour of heterosis. These are self-pollinated for several generations, till they reach a state of uniformity of homozygosity, so that the characters will not segregate in the progeny.