Mutation breeding for polygenic traits
- M1 and M2:
- M1 and M2 are grown in the same way as in the case of oligogenic traits.
- In M2, vigorous, fertile and normal looking plants that do not exhibit a mutant phenotype are selected and their seeds are harvested separately to raise individual plant progeny rows in M3.
- M3:
- Progeny rows from individual selected plants are grown.
- Careful observations are made on M3 rows for small deviations in phenotype from the parent variety.
- Inferior rows are discarded. Few rows may be homogeneous and would be harvested in bulk.
- Selection in done in M3 rows showing segregation; a majority of M3 rows would show segregation.
- Intensive and careful evaluation of a large number of M3 progeny rows allows identification of mutants with altered quantitative traits.
- g., partial or horizontal disease resistance. Such mutants occur in high frequencies that approach 1% or even high, so that their isolation becomes quite cost effective.
- M4:
- Bulked seed from homogeneous M3 rows may be planted in a preliminary yield trial with a suitable check; superior progenies are selected for replicated multilocation yield trials.
- Individual plant progenies from M3 are critically observed.
- Progenies showing segregation may be subjected to selection only if they are promising.
- Super ior homogeneous progenies are harvested in bulk for preliminary yield tests in M5.
- M5-M8:
- Preliminary yield trials and / or multi-location trials are conducted depending upon the stage when the progenies become homogeneous.
- Outstanding progenies may be released as new varieties.