USING FREE PROLINE CONCENTRATION AS AN INDICATOR FOR IDENTIFYING SUGAR BEET VARIETIES RELATIVELY TOLERANT TO SALINITY

Two pot experiment were conducted during two successive sea‌sons 1996/1997 and 1997/1998 to investigate the effect of different levels of saline irrigation water on nine sugar beet varieties (Beta vulgar-is L.). The results indicated that Ras poly and Oscar poly multigerm va-rieties and Eva monogerm variety could withstand a salinity level up to 6260 mgm/liter without a significant adverse effect on quality, weight and sugar yield of the root, however their praline concentration signifi‌cantly increased with each increase in salt concentration of irrigation wa‌ter. These varieties selected as very tolerant to salinity stress. On the other hand, all the studieded criteria except proline concentration of Ga‌zelle stress. On the other hand, all the studieded criteria except praline concentration of Gazelle andDelitzsch poly varieties were affected by sa‌linity treatments. Therefore they may be considered as the most sensi‌tive varieties to salinity stress. Observations over the Monte Bianco, Delamon, Vede and Top va-rieties showed that they were affected, to some extent by salinity, how‌ever no differences were detected between their praline concentration under 4260 and 6260 mgm/I salinity levels. They were moderatly toler‌ent to salinty stress. Results indicated that, there were high and positive signifficant correlation detected between salinity level and praline concentration in moderate and very tolerant sugar beet varieties. In sensitive varieties no correlation between salinity level and their praline accumulation was ob-served. Thus the results suggest that the concentration of amino acid praline in sugar beet leaves can be used as suitable indicator in screen‌ing varieties of sugar beet according to their tolerance to salinity and can be grown and produce a profitable yield under saline conditions.