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 s weet potato (Ipomoea batatas (L.) Lam. ) is complicated owing to the l arge spatial variations in the soil salinity level, differential ontog enic reactions of the plant to salinity and a large genotype X environ ment interaction. Testing micro-propagated plantlets in in-vitro salin e media can overcome some of these in-vivo problems of variability and repeatability. A series of laboratory experiments was conducted to te st the hypothesis that a vigorous plantlet surviving in a saline mediu m would be tolerant owing to a higher competitive ability and a lower growth retardation. The results showed significant variations among th e existing cultivated Ipomoea germplasm and some breeding lines for sa lt tolerance based on plant growth characters, percentage of survival and fibrous root formation. In-vitro techniques were shown to be usefu l in identifying relatively salt-tolerant genotypes. In-vitro clonal b ehavior in a saline medium and the thick root yield potential in salin e field sites need further study.