Proline status of genetically stable salt-tolerant Brassica juncea L. somaclones and their parent cv. Prakash |
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Authors: | Sunita Jain H. S. Nainawatee R. K. Jain J. B. Chowdhury |
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Affiliation: | (1) Department of Chemistry & Biochemistry, Haryana Agricultural University, 125004 Hisar, India;(2) Department of Genetics, Haryana Agricultural University, 125004 Hisar, India |
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Abstract: | Three Brassica juncea L. somaclones (SR-1, -2 and -3) selected in vitro for NaCl-tolerance, non-selected somacone (CP-5) and parent cv. Prakash were characterized for their free proline contents in the absence of stress and as a function of increasing salt stress. In the R0 generation, SR-3 somaclone had ca. three times higher free proline as compared to parent Prakash and other somaclones. Somaclone, SR-1, turned out to be sterile. The other somaclones were carried forward to the R2 generation after making selections for yield and yield components in the R1 generation. SR-3 bred true for its high proline accumulating characteristic. The somaclone SR-3 thus had a stable genetic variation for proline overproduction. Free proline content in 7-day-old whole seedlings and 6-week-old plant leaf tissue, increased with the increase in salt stress in all the lines but at differential rates. The magnitude of increase in free proline was much higher in SR-3 lines as compared to parent Prakash and SR-2 salt-tolerant somaclones. Under salt stress, in leaf tissue, one of the SR-3 derived lines (SR3P6-2) accumulated as much as 269 moles of free proline as compared to ca. 20 moles per g dry weight in parent Prakash and SR-2 line. It was interesting to note that there was a critical point concentration of NaCl beyond which the endogenous level of free proline rose sharply. Somaclonal lines (SR3P6-2, SR2P1-2 and CP5-2) which were found to have higher salt-tolerance indices, also had higher critical points as compared to the other relatively salt sensitive genotypes. The relationship between relative water content and osmotic potential of leaves under saltstress also showed a relatively higher degree of osmotic adjustment in the selected somaclones, the maximum being in SR-3 derived lines. |
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