1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)

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Subject: search.filters.subject.Sucrose synthase

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    Molecular screening of rice genotypes for submergence tolerance
    (Department of Plant Biotechnology, College of Agriculture, Vellayani, 2018) Aryalekshmi, A S; Veena Vighneswaran
    Rice (Oryza sativa L.) is the most important staple food crop that providing food to about half of the population. One of the major constraints in rice cultivation worldwide is submergence stress. This mainly affects flood prone areas like kuttanadu Pokkali as well as low lying paddy fields in Kerala. Sub1 is a major quatitative trait locus (QTL) representing a cluster of three ethylene responsive factor (ERF) genes: Sub1A, Sub1B and Sub1C that confers submergence tolerance to rice genotype. Submergence tolerant rice variety is credited with maintaining energy and alcoholic fermentation which require high levels of carbohydrates. Sub1 locus contain Sub1A, Sub1B and Sub1C, all of which are encode ethylene responsive factor and are up regulated under submergence, but only Sub1A is responsible for the flash flood tolerance. The near isogenic lines generated by the introgression of the Sub1 from FR13A into to susceptible cultivar shows restricted shoot elongation similar to FR13A. Submergence tolerant plants suppress the expression of gene encoding α- amylase and sucrose synthase, which are involved in sucrose metabolism. Sub1 A enhance the expression of genes encoding SLENDER RICE -1 (SLR1) and SLR1 like 1(SLRL1), which are key repressor of gibberellins (GA) signalling in rice; it also negatively regulate s the GA response in order to restrict shoot elongation under submergence. Rice varieties with the Sub1 gene were shown higher survival rate with better yield even after 2 weeks of submergence stress. The advancement of marker assisted selection (MAS) have striking impacts on developing improved Sub1 varieties that can meet the increasing demands of consumers along with population hike. In the present study, two rice genotypes were observed with Sub1 QTL using SSR markers through molecular characterization in order to find out the best submergence tolerant lines. Moreover this finding lays the foundation for further researches with sub 1 QTL for crop improvement.
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    Photosynthesis and enzyme activities regulating starch biosynthesis in different varieties of sweet potato (Ipomoea batatas Lam.)
    (Department of Plant Biotechnology, College of Agriculture, Vellayani, 2016) Aswini Krishnan, N K; Ravi, V
    The present study entitled “Photosynthesis and Enzyme activities regulating starch biosynthesis in different varieties of Sweet potato (Ipomoeabatatas Lam.)” was conducted at ICAR-CTCRI, Trivandrum during the period 2015-2016. The objective of the work was to the study the relation between photosynthesis, leaf area and enzyme activities involved in regulating starch biosynthesis in different genotypes of sweet potato and to identify the limiting factor(s) in low starch varieties of Sweet potato. The rate of photosynthesis, morphological and biochemical parameters and enzymes activities involved in the starch biosynthesis were recorded at monthly intervals in selected varieties. Morphological parameters such as total number of leaves per plant, leaf area and tuber yield per plant were recorded during 1 to 4 MAP. Rate of photosynthesis was measured using IRGA (infra-red gas analyzer). The leaf area and photosynthetic rate were directly increasing the productivity which was found to be higher in the Sree Arun and Kanhangad variety. Biochemical parameters such as sucrose and starch content were estimated in leaves and tubers of sweet potato varieties. The sucrose content was relatively higher in leaves of Kanhangad variety and in tubers of ST-13 variety. Starch content was higher in the variety Sree Arun which had a direct relation with the photosynthetic rate and tuber yield. Activities of enzymes such as AGPase, starch synthase (SS), sucrose phosphate synthase (SPS), sucrose synthase (SuSy) and invertase were measured in both the leaves and tubers of sweet potato. AGPase and SS were directly involved in the tuberization throughout the development which was observed in Sree Arun variety. SPS was highly active in leaves than tubers. SuSy and invertase are mainly involved in the sucrose metabolism in leaves and highly active during the day time. The increased activity of AGPase and SS in sweet potato tubers will open a new strategy for bioengineering the efficiency of enzymes to improve the starch content in low yielding sweet potato varieties. A detailed molecular study on enzymes involved in starch biosynthesis will be necessary for increasing or improving the starch content in tuber crops.
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    Photosynthesis and enzyme activities regulating starch biosynthesis in different varieties of cassava (Manihot esculenta crantz)
    (Department of Plant Biotechnology, College of Agriculture, Vellayani, 2016) Geethu Krishnan, P R; Ravi, V
    The present study on Photosynthesis and enzyme activity regulating starch biosynthesis in different varieties of cassava (Manihot esculenta Crantz) was conducted during the period of 2015-2016 in the Division of Crop Production, ICAR-CTCRI, Thiruvananthapuram. The objective of the study was to study the relation between photosynthesis, leaf area, crop duration and enzymes activities regulating starch biosynthesis in four varieties of cassava (Manihotesculenta Crantz) and to determine limiting factor(s) for low starch content of tubers in low starch varieties. Four varieties selected for the study are viz., SreeVijaya, SreeAthulya, H165, H226. SreeAthulya, a triploid long duration variety had the maximum starch and sucrose content whereas H165, a short duration variety, had the minimum starch content. The different parameters such as morphological, biochemical, enzyme activity, and photosynthetic activity were recorded / assayed for four cassava varieties. Morphological parameters are number of leaves, leaf area, leaf area index and tuber yield. Maximum noumber of leaves and leaf area was observed in the variety SreeVijaya. Photosynthetic activity was observed maximum in the variety SreeVijaya. The minimum number of leaves and leaf area were observed in the varieties H226 and H165. The maximum tuber yield was observed in the variety H226 and minimum tuber yield was observed in the variety H165. Biochemical parameters like sucrose content and starch content were maximum in in the variety SreeAthulya and minimum in the variety H165. The enzymes activities involved in starch biosynthesis assayed in the present study are viz., AGPase, SPS, SS, SuSy and invertase. SreeAthulya had the highest AGPase activity and SuSy activity and high tuber yield. SreeVijaya had the highest SPS activity. H165 had the lowest tuber yield due to decrease in leaf area, sucrose and starch content, photosynthetic activity, lowest enzymatic activities of SuSy, SS. Generally the photosynthetic activity the activities of AGPase, SS and SuSy enzymes were high in high starch variety SreeAthulya. The present study reveals low activity of enzyme sto be the rate limiting for low starch content of varieties H165. Low starch content varieties can be improved by manipulating the activity of these enzymes.