Question

what are the steps included in the methods used by plant breeders to produce varieties

Answer 1

(I) Collection of Germplasm:
(ii) Evaluation and Selection of plant Parents
(iii) Cross-Hybridization among Selected Parents
The procedure of hybridisation involves the following steps.

(a) Selection of Parents with Desired Characters
(b) Selfing:
(c) Emasculation
(d) Bagging
(e) Tagging
(f) Artificial Pollination (= Crossing)


(iv) Selection and Testing of Superior Recombinants
(a) Selection in Self-pollinated Crops
(b) Selection in Cross-pollinated Crops

(v) Testing, Release and Commercialisation of New Cultivars

Answer 2

The various steps required for developing new varieties are as follows:

(i) Collection of Germplasm:

Germplasm is the sum total of all the alleles of the genes present in a crop and its related species. The germplasm of any crop species consists of the following types of materials:

(i) cultivated improved varieties,

(ii) improved varieties that are no more in cultivation,

(iii) old local or ‘desi’ varieties, (iv) pure lines produced by plant breeders, and (v) wild species related to the crop species.

The entire collection (of plants/seeds) having all the diverse alleles for all genes in a given crop is called germplasm collection. A good germplasm collection is essential for a success­ful breeding programme.

(ii) Evaluation and Selection of Parents:

The germplasm is evaluated to identify plants with desirable combination of characters. Selection of parents is picking up seeds of only those plants for multiplication which have the desired traits. For example, grain length in rice is variable— longer grains, intermediate grains and shorter grains. If we select the seeds of the longest grains and sow them to grow the next generation, the selected population of rice plants will have on average, longer grains than the original population.

iii) Cross-Hybridization among Selected Parents:

Hybridisation is the most com­mon method of creating genetic variation. Hybridisation is crossing of two or more types of plants for bringing their traits together in the progeny. It brings about useful genetic/ heritable variations of two or more lines together. Line is a group of individuals related to descent and have similar genotype. The individuals or lines used in hybridisation are called parents. Hybridisation takes a lot of time.

As stated earlier a wheat variety HUW 468 took 12 years to develop. Hybridisation may involve a single cross (two plants) or multiple cross (more than two plants). Wheat variety C-306 was developed through multiple cross between C-591 (Reagent 1974 x Ch2-3) and hybrid of P-19 x C-281. Hybridisation may further be:

(i) intravarietal,

(ii) intervarietal (= intraspecific) or

(iii) interspecific and

(iv) intergeneric. Intervarietal hybridisation is the process of crossing individuals of different lines or varieties of the same species to produce hybrid, e.g., different varieties of wheat are mated. Interspecific hybridisation is the process of crossing individuals of two different species to produce a hybrid. Examples of interspecific hybridisation are the development of rice variety ADT-37 from a cross between Oryza japonica and O. indices and all the sugarcane varieties being cultivated today. In intergeneric hybridisation, the cross is between two different genera.

SOURCE: http://www.biologydiscussion.com/plants/plant-breeding-steps-and-methods-of-plant-breeding-for-disea...