GENETIC-VARIABILITY IN RECOVERY GROWTH AND SYNTHESIS OF STRESS PROTEINS IN RESPONSE TO POLYETHYLENE-GLYCOL AND SALT STRESS IN FINGER MILLET

Marked differences were found among 28 finger miller genotypes (Eleusi ne coracana Gaertn.) in acquired tolerance to osmotic stress as assess ed by the recovery of root growth from severe stress [-1.2 MPa polyeth ylene glycol, (PEG) or 400 mM NaCl]. However, these differences in tol erance were observed only when the seedlings were subjected to a prece ding mild induction stress (-0.6 MPa PEG or 200 mM NaCl). In two contr asting genotypes, synthesis of stress-induced proteins was studied. Pr oteins with apparent molecular weight of 70-72, 52, 37, 34 and 23 kDa were synthesized in the highly responsive genotype (GE 415) and poorly responsive (VL 481) genotype following a mild induction stress (200 m M NaCl). However, GE-415 synthesized a 54 kDa protein that was not obs erved in VL-481. Addition of abscisic acid (ABA) to the induction medi um containing 200 mM NaCl enhanced the acquired tolerance of finger mi llet seedlings over those without ABA in association with the appearan ce of several ABA-responsive proteins. GE-415 required much less ABA t han VL-481 to obtain the same response. With 10 mu M ABA+ 200 mM NaCl induction stress, GE-415 had significantly higher endogenous ABA. In a ssociation with higher levels of ABA, GE-415 had greater recovery root growth following severe stress from 600 mM NaCl. Pretreatment with 10 mu M ABA + 200 mM NaCl induced several proteins with apparent molecul ar weights of 70-72, 54, 45, 36, 29 and 21 kDa in both genotypes. Qual itatively, GE-415 synthesized a unique 23-24 kDa protein and quantitat ively there was significantly more of the 21 kDa protein in GE-415 com pared to VL-481. The results indicate that the synthesis of stress pro teins is correlated with the observed variation in acquired tolerance of the two genotypes. (C) 1995 Annals of Botany Company