Methods of Breeding in Self Pollinated Crops – Introduction
According to Allard (1960) plant introduction is the acquisition of superior varieties by importing them from other areas. Or plant introduction is the process of taking / introducing plants/ genotype or group of genotype into new environment where they were not being grown before.
Introduction may involve new varieties of a crop already grown in the area wild relatives of the crop species or totally new crop species for that area. Plant introduction may within the country between the countries or confirmed between the states or within the state. The plant may be introduced from the country of another coninenet .Ex. Introduction of Ridley wheat varieties from Australia.
Introduction may be classified into two categories:
a) Primary Introduction:
When the introduced variety is well suited to the new environment and is directly released for commercial cultivation without any change the original genotype, known as primary introduction. Ex. Introduction of semi dwarf wheat varieties Sonora, Lerma Rojo and semi dwarf Rice Var. TN-1, IR-8, IR-28, and IR-36.
2) Secondary Introduction:
The introduced variety is subjected to selection, to isolate superior variety or may be hybridized with local variety to transfer one or few desirable characters to the local variety, known as secondary introduction.
Secondary introduction is much more common than primary introduction particularly
in countries having well- organised crop improvement programme. Ex. Kalyan sona and sonalika varieties selected from the material introduced from CIMMYT. Mexico (Centro International de Mejoramieno de maize ‘Y’ Trigo) commonly known as Internation centre for maize and wheat Research.
Procedure of Plant Introduction:
Plant introduction is one of the very old and effective methods of plant breeding. It consists of following steps:
i) Procurement of Germplasm:
Any individual or scientist or institute can introduce germplasm, but the entire introduction must be routed through NBPGR, from the known source of the country or neighbouring countries. While introducing germplasm scientist has to allow two routes. In case of the first route individual make a direct request to individual or institution abroad and in the second route individual submit his requirement to the NBPGR, by giving much detail information about the requirement. Generally, the required materials are obtained through correspondence as gift, an exchange, purchased etc. The plant part to be introduced depend upon the crop species, it may be seed, tubers, runners, suckers, stolons, bulbs, Rhizome, cutting, bud or seedling. The part of the plant used for the propagation of a species is known as propagule. The nature of propagules varies from species to species. Seeds general have more viability than propagules and are packed and transported more easily, while propagules require special packing techniques.
Quarantine means to keep the materials in isolation to prevent the spread of disease, weeds etc. all the introduced material is thoroughly inspected for contamination with weed, disease and insect pests. The material is fumigated or treated to avoid the contamination. If necessary, the materials are grown in isolation for observation of disease, insect, pest and weeds, this entire process is known as quarantine and the rules prescribed them are known as quarantine rules. All the materials being introduced must be covered by an authentic phytosanitary certificate from the source of country i.e the must be declared free from disease, weed and pests. If any country or material does not fulfil the quarantine rules, that materials are likely to be destroyed by NBPGR or would return to the source country.
The quarantine controls is exercised by NBPGR at prescribed part of entry. E.g Mumbai, Calcatta and Madras and this process is required at least three weeks.
The introduced material is entered in assession register and is given on entry number. The information regarding the name of the species, crop variety, and place of ongin, adoption and morphological character are reduced. The plant materials are classified into three groups viz.
a) Exotic Collection (EC)
b) Indigenous Collection (IC)
c) Indigenous Wild Collection (IW)
The introduced material is evaluated to assess the potential of new introduction and their performance. These materials are evaluated at different substation. The material resistance to disease and pest is evaluated under favourable environment conditions, and the promising one is either released as such as a variety or subjected to selection or hybridization.
V) Multiplication and Distribution:
After evaluation promising material from production may be increased by multiplication and released for general cultivation as varieties after necessary trials. Most of there are identified for desirable character and maintain for future use.
The process that leads to the adoption of a variety to a new environment is known as acclimatisation. Generally the introduced varieties perform poorly because they are often not adapted to the new environment. Sometimes the performances of that variety improve in the new environment by growing it for number of generations. Acclimatisation is brought about by a faster growing it for number of generations. Acclimatisation is brought about by a faster multiplication of those genotype that are better adopted to new environment. The population having more variability is easily acclimatised i.e cross pollinated crops are easily acclimatised than self pollinated crop.