Plant breeders use different methods depending on the mode of reproduction of crops, which include: The mode of reproduction of a crop determines its genetic composition, which, in turn, is the deciding factor to develop suitable breeding and selection methods.
It is due to such reasons that imposition of self-fertilization on cross-pollinating crops leads to drastic reduction in their performance.
Critical steps in the improvement of self-fertilizing crops are the choice of parents and the identification of the best plants in segregating generations.
Mass selection is only applied to a limited degree in self-fertilizing plants and is an effective method for the improvement of landraces.
One shortage of mass selection is the large influence that the environment has on the development, phenotype, and performance of single plants.
Stratified mass selection for ear size over 22 cycles [clarification needed] has drastically altered plant phenotype in the maize population Zacatecas 58.
Plant species where normal mode of seed set is through a high degree of cross-pollination have characteristic reproductive features and population structure.
Existence of self-sterility,[1] self-incompatibility, imperfect flowers, and mechanical obstructions make the plant dependent upon foreign pollen for normal seed set.
The heritability estimates are reduced by half, since only parents are used to harvest seed whereas the pollen source is not known after the cross pollination has taken place.
A number of full-sib families, each produced by making crosses between the two plants from the base population are evaluated in replicated trials.
This unique characteristic of asexual reproduction helped to develop a number of cultivars of fruits and vegetables including grapes, apples, pears and peaches.
For the best results the selected plant must be evaluated during the next season, when growth-abnormalities, leave disfigurations and virus symptoms are best visualized.