Principles of Plant Breeding (2+1)

Procedure for Pure line selection

First year:
An old variety or landrace is used for pure line selection. Population they selected for pureline selection is homozygous. Single plant is selected and harvested separately superior plants must be selected from the mixed population. About 1000-2000 plants areselected depending on the available resources.

Second year:
The individual progenies are grown separately with proper spacing the top 15-20 progenies are selected and they are bulked. Poor, defective, weak and segregating progenies are discarded. Selection should be based on simply inherited character like plant type, Plant height, grain type , flowering and maturity duration disease resistance this process may be repeated

Third year:
Seed of the individual plant progenies are not enough to conduct a replication trail. So they are grown in unreplicated trial with check. Here yield of progenies are taken as a criteria for selection

Fourth year:
Replicated yield trials are conducted using the best available check variety. This may be repeated for 2-3 year.All the observation are recorded

Fifth to Eighth year:
Promising strains are evaluated at several locations along with strains or check. The best progeny / strain is released as a new variety and its seed multiplication in initiated for distributed to the farmer.

Advantages:
Maximum possible improvement over original variety.Uniform and more attractive, easily identifiable.

Disadvantages:
This method can isolate only superior genotypes, it cannotcreate new genotypes. And not applicable in cross pollinated crop. Poor adaptability due to narrow genetic base vulnarble for new diseases and pests.