MOLECULAR AND PHYSIOLOGICAL SCREENING OF SOME MUNGBEAN CULTIVARS UNDER SALT STRESS

Abstract

Four Mungbean (Vigna radiata L.) cultivars (Kawmy-1, V2010, VCIOOO and VC2719) were examined for in vitro response to salinity stress. Epicotyl explants were cultured on MS media containing 2.0 mgll 2,4-D, 0.2 mg/1 6-benzyl adenine (BA), and NaCl or seawater levels of 6,000; 8,000; 10,000 and 12,000 ppm NaCl. The callus responded differently with the salt source and concentration. Friable callus was observed in all cultivars on the control media (without NaCl), while globular callus formed on NaCl­ media. Fresh weight of calli grown on seawater- containing media were higher than those on NaCl-containing media. Calluses of VC2719 was more tolerant to salinity than V20 I 0, VC l 000, and Kawmy-1 cultivars, in a descending order, in agreement with the examined in vivo data for seed germination, morphological traits and physiological parameters Three DNA random primers (out of 12 examined) produced consistent Randomly Amplified Polymorphic DNA (RAPD) patterns. RAPD-based DNA fingerprints were established for the four cultivars using calli grown on salt-free media. Specific DNA fragments characterized salt tolerant cultivars (e.g.1,330 bp in VC2719 with primer OPD-18 and a 1,330bp in V2010 with primer OPA-3). A 1,250 DNA fragment characterized the salt sensitive Kawmy-1 with OPA-3. Salinity treatments of 6,000 and 8,000 ppm NaCl did not result in variation ofPCR amplification products from calli of the four cultivars when compared with the control. Medium containing 12,000 ppm NaCl in seawater resulted in missing RCR products of I ,636 bp and 1,200 bp in Kawmy-1 and VCIOOO with the primers OPD-18 and OPA-3, respectively. ITS-2 primer revealed greater variation in the amplified DNA products of different salinity treatments compared with the control. These results indicate that salt concentrations less than 10,000 ppm did not induce DNA variation in vitro, while 12,000 ppm NaCl was inductive of variation.