DIFFERENTIAL CHROMIUM TOLERANCE AMONG 8 MUNGBEAN CULTIVARS GROWN IN NUTRIENT CULTURE

Eight mungbean (Vigna radiata L.) cultivars were evaluated for their t olerance to different levels of chromium (Cr+6) (0, 24, 48, 96, 192, a nd 384 mu M) in nutrient solutions at pH 6.8. Seeds were germinated an d grown in the presence of chromium under controlled environmental con ditions. Standard growth parameters such as root length, shoot length, root/shoot dry matter production, and root/shoot tolerance index were used as indicators of chromium toxicity. Measurements as early as 24 h after the beginning of the treatments did not yield consistent resul ts. However, root measurements at 48, 72, and 96 h after the beginning of treatments yielded significant differences among the cultivars whi ch were similar to field performance observations made for mungbean gr owing in chromium-rich soils. The cultivars, TARM-22 and K-851 had enh anced root growth while PDM-54, Sujata, TARM-21, LGG-407, and PDM-116 showed a reverse trend in root growth in the presence of chromium. The root tolerance index (RTI) and the shoot tolerance index (STI) with r espect to the cultivars TARM-22 and K-851 were high indicating their t olerance to chromium, while the cultivars PDM-54 and Sujata showed a l ow RTI and STI. Based on the growth parameters of the eight mungbean c ultivars, they were ranked with respect of their tolerance to chromium as follows: TARM-22>K-851>Dhauli>PDM-116>LGG-407>TARM-21> Sujata>PDM- 54. Therefore, the nutrient culture method was able to quickly screen the mungbean cultivars for their tolerance to chromium.