Oxidative stress and protein profiling in sweet potato (Ipomoeabatatas (L.) Lam.) under abiotic stresses

Abstract

The present study an “Oxidative stress and protein profiling in sweet potato (Ipomoeabatatas (L.) Lam.) under abiotic stresses” was conducted during the period 2014-2015 in the Division of Crop Production, Central Tuber Crops Research Institute (CTCRI) Thiruvananthapuram. The objective of the study was to elicit information on the antioxidative enzyme activity, protein profiling, growth parameter and yield parameter of five varieties / genotypes of sweet potato under irrigated high temperature stress (HTS) (40oC during the day time) and water deficit stress (WDS) ( 2nd and 3rd month after planting) conditions and identify marker physiological parameter which can be used for identifying / developing sweet potato varieties for tolerance to abiotic stress conditions. The study indicated that the vein length of five different sweet potato varieties/ genotypes was not significantly affected by HTS and WDS. The leaf production of five sweet potato varieties was significantly affected by both HTS and WDS. The leaf retention of five varieties / genotype was differentially affected by both heat and water stress. There was negligible difference in yield parameters between stress and control condition. However, there was significant difference in yield observed for parameters among five varieties. The effect of abiotic stress on various physiological parameters like Relative water content (RWC), chlorophyll and carotenoid content significantly differed in control plant. Among the WDS and HTS treatments, the chlorophyll and carotenoid content decreased in all the five varieties. Chlorophyll and carotenoid content were significantly reduced in plants exposed to HTS. RWC of leaves varied under both WDS and HTS conditions. A higher RWC was observed in plants exposed to HTS condition compared to plants was WDS condition. Total soluble protein content of leaf was found to be lower due to presence of high mucilage in leaves. Total soluble protein in tuber is increased in control and WDS conditions. Total soluble protein in tuber forming roots had increased under stress free condition. The effect of abiotic stress on biological parameter like proline status of plants under stress conditions followed an

increasing trend compared to stress free condition. The outcome of abiotic stress on various enzymatic antioxidant such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), ascorbate reductase, glutathione reductase (GR) was studied. Among the five different sweet potato varieties/ genotypes (Sree Arun, S-1464, S-1466, Sree Kanaka and Kanjangad) S-1466 and Sree Kanaka had maximum GR activity under HTS compared to WDS and control condition. Catalase activity of five varieties/ genotypes of sweet potato plant varied among different stress condition (WDS and HTS) compared to control. The GR activity was significantly reduced due to stress condition and SOD activity increased under stress conditions. The APX enzyme activity is more under WDS conditions compared to HTS and control conditions. Ascorbate reductase become there was no change in absorbance therefore the enzyme activity could not be measured. The AA content in sweet potato leaves increased under WDS condition compared to HTS and control. The glutathione content in sweet potato leaves was negligible or below detectable amount under both control and stress condition. Under HTS condition SOD activity increased in Sree Arun and S-1466 alone whereas other varieties/genotypes had increased SOD activity under WDS. Kanjangad had maximum APX activity in HTS whereas S-1464 had higher APX activity in WDS. From the present study, it is inferred that SOD activity can be utilised as biochemical marker for developing HTS tolerant varieties as it showed consistent changes under both WDS and HTS. APX activity can be utilised as marker for identifying WDS tolerant varieties. Detailed molecular biochemical and physiological information will be necessary using different varieties for getting appropriate activities as the marker to screen abiotic stress tolerant varieties.