TOLERANCE OF GROUNDNUT CUL TIV ARS TO MANGANESE TOXICITY

To investigate the differential response of groundnut genotypes to manganese toxicity, twenty groundnut (Arachis hypogaea L.) genotypes were grown at toxic level of Mn (44.0 ppm) in solution culture. The susceptible genotypes (TCGS 150, TCGS 476 etc) showed severe toxicity symptoms such as inword curling of leaves, isolated rusty brown spots with severe necrosis while the tolerant genotype (TCGS 1709/1518) showed reduced growth but not marked toxicity symptoms. Leaf area, chlorophyll content and shoot and root weight decreased significantly with increase in Mn concentration in the nutrient medium. Relative leaf dry weight (Wt. with toxic level of MnlWt with control level of Mn x 100) was 95% for TCGS 1709 and only 62.6% for TCGS 476. Leaf area and total chlorophyll content were found to be the most sensitive parameters to Mn toxicity. Plant analytical results indicated that the TCGS 1709 genotype tolerate a higher Mn concentration due to reduced translocation ofMn to shoots.