Management of Urd Bean Leaf Crinkle Virus in Urd Bean (Vigna Mungo L. Hepper)

Six plant extracts viz , Mirabtlis jalapa, Carthamus roseus. Datura metal, Bougainvitlea spectabilis, Boerhaavia diffusa and Azadirachta indica recorded maximum reduction in the incidence of urd bean leaf crinkle virus (ULCV) in urd bean crops at field level Among the antiphytovirat chemicals tested, DHT reduced the transmission to the maximum extent and increased the incubation period of virus in the urd bean plant Fresh buttermilk was significantly superior to fermented buttermilk in reducing the disease spread and increasing the incubation period of the virus in the plant. Casein was found effective in reducing the per cent transmission and increased the incubation period of the virus. Raising barrier crops viz maize, sorghum and pearl millet were equally effective in reducing the spread of the disease in field Spraying of DHT at two intervals. 7 and 22 DAS was found effective in reducing the disease spread when compared with Thuja, buttermilk, ivf jalapa and neem oil

Effect of environmental factors during seed development and maturation on seed quality in Sorghum bicolor (L.) Moench

Studies were conducted to evaluate the effect of environmental conditions on physiological characteristics of seeds of sorghum genotypes viz., CO 24, CO 25, CO 26 and JH 35 during seed development and maturation. In the present study, a steady decline in moisture content of the seed was observed. Length and width of seed increased rapidly between seven to 35 days after 50 per cent flowering. A steep increase in the dry weight of seed was registered between 14 and 35 days after 50 per cent flowering, beyond that the increase was gradual. Water absorption per cent declined from 16.5 to 12.0 per cent between 7 to 28 days and increasing steadily beyond 42 days (22.1 per cent) after 50 per cent flowering. The germination potential of seeds improved with seed development and maturity. The root length, shoot length, dry weight of seedling, field emergence, seed recovery, seed yield and vigour index were highest in seeds harvested at 35 and 42 days after 50 per cent flowering. Seed vigour as estimated through stress tests viz., soaking seeds in ammonium chloride and D-manitol and accelerating ageing and exhaustion tests revealed the superiority of seeds having maximum germinability, vigour and viability at 35 and 42 days after 50 per cent flowering. These stages respectively correspond to physiological and harvestable maturity

Studies on Seed Colouring in Soybean and Tomato

The effects of seed colouring using 25 dyes (i.e. 20 chemical and 5 natural dyes) on the quality of soyabean (cv. JS 335) and tomato (cv. Pusa Ruby) seeds were studied in the laboratory. Data were recorded for seed germination percentage, root and shoot length, whole seedling length, dry weight of seedling, vigour index, speed of germination and electrical conductivity. Rhodamine-B, Fast green and Malachite green for soyabean and Rhodamine-B and Fast green for tomato were the best dyes for seed colouring

Studies on seed colouring in redgram, blackgram and bengalgram

The investigations on the effect of seed colouring of redgram, blackgram and bengalgram seeds encompassing 25 dyes were conducted to identify non-deleterious and deleterious dyes based on their effect on seed quality. The dyes namely Rhodamine-B, Fuchsine and Titan yellow for redgram, Rhodamine-B, Fuchsine and Phenol red and Rhodamine-B, Crystal violet, Titan yellow for bengalgram were found to be the best dyes for seen colouring at 0.75% concentration. In this paper we discuss developing colour standards for redgram, blackgram and bengalgram seeds and their resultant implications for Indian seed industry

Host plant resistance to grain mould in germplasm accessions of pearl millet (Pennisetum glaucum [L.] R. Br.)

The paucity of information on the moulds in Indian pearl millet (Pennisetum glaucum) led to the studies that were conducted at ICRISAT, India to evaluate (a) 447 germplasm accessions of 32 countries for mould reaction in rainy season, (b) threshed grain mould rating (TGMS) and mycoflora on grains of each accession, and (c) mould scores in field and in vitro. Post physiological maturity evaluation showed that 16% of the accessions secured a mould rating of 2. In TGMS, 18% were mould free and 57% secured a rating of 2 on a 1 – 9 scale. Assessment of twenty representative accessions in vitro against individual and mixed conidial suspensions (1610(6) conidia ml(71)) of Fusarium moniliforme, F. pallidoroseum and Curvularia pennisetti indicated significant correlation (r¼0.97) between the overall field and in vitro scores of mixed spores inoculations. The mycoflora for TGMS in blotter test revealed that Fusarium moniliforme, F. pallidoroseum, Curvularia pennisetti, Helminthosporium spp., Alternaria spp. and Colletotrichum spp. to be the major fungi affecting pearl millet grain. It is advisable to harvest panicles at the physiological maturity stage to obtain better quality grains. A strong negative correlation between TGMS and % GS (r¼0.4601) and positive correlation between TGMS and % UGS (r¼0.4654) indicated that, the lesser the threshed grain mould rating higher the % seed germination

eQTL regulates OsHAK5 in enhancing potassium content under salt stress in rice

To alleviate salt stress in rice, the role of potassium in countering the ill effects of sodium is gaining importance. Towards this, OsHAK5 a member of the high-affinity potassium transporter family was known for enhancing the intracellular potassium under reduced/low K+ availability during salt stress. The full-length cDNA of OsHAK5 was cloned and sequenced from the roots of Pokkali and cv. IR64 however, no nucleotide polymorphism detected. Interestingly, the expression of OsHAK5 in roots of salt-tolerant landrace Pokkali and salt susceptible cv. IR64 revealed a significant upregulation in the former under low K+ (1/4th) condition. Subsequent analysis of the amino acid sequence of CBL-interacting protein kinase (OsCIPK23), the upstream regulator of OsHAK5 revealed two INDELs and one of them turned out to be functionally relevant. The OsCIPK23 variant from salt-tolerant Pokkali should be favorably regulating the expression of the downstream OsHAK5 leading to an increased K+ uptake under salt stress

Effect of temperature and humidity regimes on grain mold sporulation and seed quality in sorghum (Sorghum bicolor (L.) Moench)

Grain mold, induced by a number of non-specific fungi, causes substantial loss to seed/grain yield and quality in sorghum (Sorghum bicolor (L.) Moench). Fungal sporulation and grain mold severity are greatly influenced by temperature and relative humidity (RH) levels. We studied the effects of three incubation temperatures (25, 27 and 28°C) and two sets of RH levels (first set: 85, 90, 95, 98, and 100%, second set: 95, 96, 97, 98, 99 and 100%) on sporulation and grain mold severity in three major mold fungi (Curvularia lunata, Fusarium moniliforme, and Bipolaris australiensis) and on four each of resistant, moderately resistant and susceptible sorghum genotypes for sporulation and mold severity of major fungi. Results indicated that both fungal sporulation and grain mold severity increased on most sorghum genotypes with increasing incubation temperature from 25 - 28°C and RH levels from 95 - 98%. A linear relationship was observed among RH levels, grain mold severity and fungal sporulation. The highest sporulation of all the three fungi occurred at 28°C and 98% RH after 5 days of incubation. Among the three fungi, C. lunata grew and sporulated faster than B. australiensis and F. moniliforme, in that order. Among the sorghum genotypes, IS 25017 supported the least sporulation and had the lowest mold severity, followed by IS 8545 and PVK 801. Seed quality parameters, such as seed germination, seedling vigor index, field emergence potential, dehydrogenase and α-amylase activities declined significantly with increasing temperature and RH levels that supported heavy sporulation and grain colonization

The role of iron homeostasis in zinc tolerance in Arabidopsis

Zn is an essential micronutrient for plants, but it is toxic in excess concentrations. To avoid Zn toxicity, plants have developed Zn homeostasis mechanism to cope with Zn excess in the surrounding soil. The second chapter of my thesis emphasizes the difference in the cross-homeostasis system between Fe and Zn in dealing with excess Zn in the Zn hyperaccumulator Arabidopsis halleri ssp. gemmifera and non-hyperaccumulator Arabidopsis thaliana. Briefly, A. halleri shows low expression of the Fe acquisition and deficiency response-related genes IRT1 and IRT2 as compared to A. thaliana. In A. thaliana, lowering the expression of IRT1 and IRT2 by adding excess Fe to the medium increases Zn tolerance. Excess Zn induces significant Fe deficiency in A. thaliana and reduces Fe accumulation in shoots. By contrast, the accumulation of Fe in shoots of A. halleri was stable under various Zn treatments. Root FRO activity and expression of FIT are low in A. halleri as compared to A. thaliana. Overexpressing a ZIP family member IRT3 in irt1-1, rescues the Fe deficient phenotype and this system also represents A. halleri in which the IRT3 expression is higher. This result demonstrates the role of other ZIP family members in Fe uptake in Arabidopsis. Thus, a fine-tuned Fe homeostasis mechanism in A. halleri maintains optimum Fe level by Zn-regulated ZIP transporters and prevents high Zn uptake through Fe-regulated metal transporters, and in part be responsible for Zn tolerance. In order to understand the mechanism and various factors involved in Fe-mediated Zn tolerance in A. thaliana, mutant screening was started by using EMS mutant pools. A mutant of zinc tolerance induced by iron 1, designated zir1, was isolated which exhibited a defect in Fe-mediated Zn tolerance and the characterization of this mutant was detailed in the third chapter of this thesis. With map based cloning and genetic complementation, zir1 was identified with a point mutation of glutamic acid residue to lysine on γ-glutamylcysteine synthetase (γ-ECS, GSH1), the enzyme involved in glutathione biosynthesis. The zir1 mutant contains only 10% of the wild-type glutathione level. Blocking glutathione biosynthesis in wild-type plants by buthionine sulfoximine (BSO) a specific inhibitor of GSH1, resulted in the loss of Fe-mediated Zn tolerance. In addition, two other glutathione-deficient mutant alleles of GSH1, pad2-1 and cad2-1, which contain respectively 16% and 33% of wild-type glutathione level, showed comparable decreases in Fe-mediated Zn tolerance. Under conditions of excess Zn and Fe, the recovery of shoot Fe content in pad2-1 and cad2-1 was reduced as compared to the wild-type. Experiments with the phytochelatin (PC)-deficient mutant cad1-3 showed that it possess Fe-mediated Zn tolerance. Furthermore, the induced accumulation of glutathione in response to excess Zn and Fe suggests that glutathione plays a more specific role in Fe-mediated Zn tolerance in Arabidopsis. The fourth chapter of this thesis illustrates the role of glutathione under Fe limited conditions and zir1 was found to be more sensitive to Fe deficient conditions and it grows poorly under alkaline soil. In addition, zir1 showed defect in Fe translocation from root to shoot under Fe limited conditions when compared to wild-type. Analyzing the other glutathione deficient mutant alleles (pad2-1 and cad2-1) also showed more sensitive phenotype under Fe limited conditions. In wild type, the glutathione level was induced under limited Fe supply and blocking glutathione biosynthesis in wild type leads to increased sensitivity to Fe deficiency. Overexpressing GSH1 in wild type leads to increased level of glutathione and showed enhanced tolerance to limited Fe supply. Altogether these data suggest that glutathione is required for the cross-homeostasis between Zn and Fe and glutathione level is associated with tolerance to Fe deficiency and may play a role in Fe mobilization inside the plant.Table of Contents Acknowledgements..……………………………………………………………………........... i Abstract……………………………………………………………………………………….. iii List of Figures………………………………………………………………………………… vii List of Appendices…………………………………………………………………………….. ix Part 1. Mechanisms and molecules involved in the metal homeostasis network of plants………………………………………………….………………………………. 1 Part 2. Differential expression and regulation of iron regulated metal transporters in Arabidopsis halleri and Arabidopsis thaliana - the role in zinc tolerance……...… 8 Abstract………………………………………………………………………………………… 9 Introduction…………………………………………………………………............................ 10 Materials and Methods………………………………………………………………………… 13 Results………………………………………………………………………………………… 19 Discussion……………………………………………………………………………………… 24 Part 3. ZINC TOLERANCE INDUCED BY IRON1 reveals the importance of glutathione in the cross-homeostasis between zinc and iron in Arabidopsis thaliana.………………… 40 Abstract……………………………………………………………………………………….... 41 Introduction…………………………………………………………………………………….. 42 Materials and Methods…………………………………………………………………………. 45 Results………………………………………………………………………………………….. 49 Discussion…………………………………………………………………………………….... 55 Part 4. Importance of glutathione in iron deficiency response in Arabidopsis…………… 73 Abstract……………………………………………………………………………………….... 74 Introduction…………………………………………………………………………………….. 75 Materials and Methods…………………………………………………………………………. 78 Results………………………………………………………………………………………….. 80 Discussion…………………………………………………………………………………….... 83 Part 5. Conclusions and future prospects……………….………………………………...... 92 References…………………………………………………………………………………….. 99 Appendices..………………………………………………………………………………….. 113 Resume………………………………………………………………………………………... 11

Control of Zn uptake in Arabidopsis halleri: a balance between Zn and Fe

Zinc (Zn) is an essential plant micronutrient but is toxic in excess. To cope with excess Zn, plant species possess a strict metal homeostasis mechanism. The Zn hyperaccumulator Arabidopsis halleri has developed various adaptive mechanisms involving uptake, chelation, translocation and sequestration of Zn. In this mini review, we broadly discuss the different Zn tolerance mechanisms and then focus on controlled Zn uptake in A. halleri. Members of the ZRT/IRT-like protein (ZIP) family of metal transporters are mainly regulated by Zn and are involved in Zn uptake. A few members of the ZIP family, such as IRT1 and IRT2, are regulated by iron (Fe) and can transport multi-metals, including Zn, Fe, manganese (Mn), cadmiun (Cd) and cobalt (Co). This mini-review also discusses the differential expression of multiple metal ZIP transporters in A. halleri and A. thaliana, a non-hyperaccumulater, with Zn exposure as well as Fe deficiency and their role in controlled Zn uptake and tolerance