The use of somaclonal variation and in vitro selection for improvement of plants to environmental stresses

Summary

The programme was established for the development of rice culture at high altitude. Somaclonal variations and in vitro selection were proposed for improving cold tolerance and resistance to a disease, bacterial brown sheath rot due to Pseudomonas fuscovaginae, which is prevalent in cool and humid conditions of tropical mountains. The rice varieties used for investigations and in vitro cultures were obtained from IRRI germplasm and from regional or national breeding programs, mainly from West Africa, Burundi and Madagascar. Many different in vitro selection procedures were used. In general, more drastic treatments reduced the number of surviving calli and regenerated plants and improved the frequency of aberrant phenotypes, but the consequences of the selection were different according to the parent varieties. Application of strong selection pressures for abiotic stresses, reduce drastically the number of regenerated plants while lower pressures are not very efficient. Many plants and progenies resistant to the different constraints have been found without application of any in vitro selection and they can be screened in large populations on the field or in controlled conditions. The experimental results confirmed the frequent occurrence of variations in plants derived from callus culture in rice and the broader variability in the regenerated populations. The new characters were generally transmitted to the next generations. Somaclonal mutations involved many morphological, agronomical, physiological and biochemical modifications in comparison to the parent varieties.