IN-VITRO TESTING FOR THE EFFECTS OF SALT STRESS ON GROWTH AND SURVIVAL OF SWEET-POTATO

Field screening in saline sites to select salt-tolerant genotypes of sweet potato (Ipomoea batatas (L.) Lam. ) is complicated owing to the large spatial variations in the soil salinity level, differential ontogenic reactions of the plant to salinity and a large genotype X environment interaction. Testing micro-propagated plantlets in in-vitro saline media can overcome some of these in-vivo problems of variability and repeatability. A series of laboratory experiments was conducted to test the hypothesis that a vigorous plantlet surviving in a saline medium would be tolerant owing to a higher competitive ability and a lower growth retardation. The results showed significant variations among the existing cultivated Ipomoea germplasm and some breeding lines for salt tolerance based on plant growth characters, percentage of survival and fibrous root formation. In-vitro techniques were shown to be useful in identifying relatively salt-tolerant genotypes. In-vitro clonal behavior in a saline medium and the thick root yield potential in saline field sites need further study.