SOMACLONAL VARIATION AND CHILLING TOLERANCE IMPROVEMENT IN RICE - CHANGES IN FATTY-ACID COMPOSITION

The relationship between chilling tolerance of six rice cultivars - Fa cagro 57, Facagro 76, Fujisaka 5, Kirundo 3, Kirundo 9 and IR64 - and the fatty acid composition in total lipids, phospholipids, galactolipi ds and neutral lipids from leaves was studied. Higher double bond inde x and proportions of linolenic acid in the phospholipid and galactolip id classes were related to cultivar chilling tolerance, but this was n ot so for the total lipids nor the neutral lipid class. The somaclonal families derived from Facagro 76, Kirundo 3 and Kirundo 9 that showed enhanced chilling tolerance as compared to their original parental cu ltivar were analyzed for fatty acid composition in phospholipids and g alactolipids from leaves. Altered proportions in fatty acid compositio n in phospholipids, galactolipids or both were found in the somaclonal families derived from Facagro 76 and Kirundo 9, but not from Kirundo 3. These changes most usually resulted in higher double bond index and higher proportions in linoleic and linolenic acids which were related either to lower ratio of C16 to C18 fatty acids or to higher unsatura tion in the C18 fatty acid fraction. Different mechanisms thus seem to be implicated in the altered fatty acid composition of somaclones, wh ich may be related to the chilling tolerance improvement of some somac lonal families.