Rootstock induced changes in enzymes activity and biochemical constituents during budbreak in ‘Thompson Seedless’ grapevine

The process of budbreak was monitored in own rooted and grafted vines of 'Thompson Seedless' (Vitis vinifera L.). Vines grafted on 110R rootstock and own rooted vines took a shorter time to achieve maximum percentage of budbreak as compared to those grafted on Dogridge rootstock. The higher starch degradation with corresponding increase in α-amylase activity was observed in buds of own rooted and 110R grafted vines till 9th day after pruning, while the α-amylase activity was least on Dogridge rootstock. In own rooted and 110R grafted vines, activity of peroxidase and polyphenol oxidase enzymes showed drastic reduction from 0-9th day after pruning. The highest phenolic concentration was observed in the buds of vines grafted on Dogridge rootstock from 0-9th day after pruning. Significant and positive correlation was observed for α-amylase activity and percent budbreak while it was negatively correlated with starch concentration in both buds and canes.

Biochemically Induced Variations During Some Phenological Stages in Thompson Seedless Grapevines Grafted on Different Rootstocks

Phenological variation in Thompson Seedless grapevines grafted on different rootstocks and own rootedvines was assessed for two consecutive years and the reasons for such variations were studied throughbiochemical analysis. Uniform and early bud sprouting was recorded in the vines grafted on 110Rrootstock and on own roots, which was attributed to increased peroxidase activity and protein content inthe buds before bud burst. Increased fruitfulness on 110R rootstock and own rooted vines was attributedto the increased phosphorus and protein content of those vines and reduced vegetative vigour measuredin terms of shoot length, cane diameter and pruned biomass. Thompson Seedless grafted on Dogridgerootstock recorded the highest nitrogen content, increased shoot length, cane diameter and increasedpruned biomass attributing to reduced fruitfulness. The highest concentration of phenolic compoundsand amino acids was recorded in the fruits produced on 110R rootstock, while it was least on St. Georgeand own roots. Significant variation in the accumulation pattern of amino acids (especially proline andarginine) was observed, with the least proline/arginine ratio recorded on 110R rootstocks at the time ofharvest, indicating the variation in the days taken for fruit ripening on different rootstocks

Chromium Stress Mitigation by Polyamine-Brassinosteroid Application Involves Phytohormonal and Physiological Strategies in Raphanus sativus L.

Brassinosteroids (BRs) and polyamines (PAs) are well-established growth regulators playing key roles in stress management among plants. In the present study, we evaluated the effects of epibrassinolide (EBL, an active BR) and spermidine (Spd, an active PA) on the tolerance of radish to oxidative stress induced by Cr (VI) metal. Our investigation aimed to study the impacts of EBL (10−9 M) and/or Spd (1 mM) on the biochemical and physiological responses of radish (Raphanus sativus L.) under Cr-stress. Applications of EBL and/or Spd were found to improve growth of Cr-stressed seedlings in terms of root length, shoot length and fresh weight. Our data also indicated that applications of EBL and Spd have significant impacts, particularly when applied together, on the endogenous titers of PAs, free and bound forms of IAA and ABA in seedlings treated with Cr-stress. Additionally, co-applications of EBL and Spd modulated more remarkably the titers of antioxidants (glutathione, ascorbic acid, proline, glycine betaine and total phenol) and activities of antioxidant enzymes (guaicol peroxidase, catalase, superoxide dismutase and glutathione reductase) in Cr-stressed plants than their individual applications. Attenuation of Cr-stress by EBL and/or Spd (more efficient with EBL and Spd combination) was also supported by enhanced values of stress indices, such as phytochelatins, photosynthetic pigments and total soluble sugars, and reduction in malondialdehyde and H2O2 levels in Cr-treated seedlings. Diminution of ROS production and enhanced ROS scavenging capacities were also noted for EBL and/or Spd under Cr-stress. However, no significant reduction in Cr uptake was observed for co-application of EBL and Spd when compared to their individual treatments in Cr-stressed seedlings. Taken together, our results demonstrate that co-applications of EBL and Spd are more effective than their independent treatments in lowering the Cr-induced oxidative stress in radish, leading to improved growth of radish seedlings under Cr-stress

Genomic Approaches to Enhance Stress Tolerance for Productivity Improvements in Pearl Millet

Pearl millet [Pennisetum glaucum (L.) R. Br.], the sixth most important cereal crop (after rice, wheat, maize, barley, and sorghum), is grown as a grain and stover crop by the small holder farmers in the harshest cropping environments of the arid and semiarid tropical regions of sub-Saharan Africa and South Asia. Millet is grown on ~31 million hectares globally with India in South Asia; Nigeria, Niger, Burkina Faso, and Mali in western and central Africa; and Sudan, Uganda, and Tanzania in Eastern Africa as the major producers. Pearl millet provides food and nutritional security to more than 500 million of the world’s poorest and most nutritionally insecure people. Global pearl millet production has increased over the past 15 years, primarily due to availability of improved genetics and adoption of hybrids in India and expanding area under pearl millet production in West Africa. Pearl millet production is challenged by various biotic and abiotic stresses resulting in a significant reduction in yields. The genomics research in pearl millet lagged behind because of multiple reasons in the past. However, in the recent past, several efforts were initiated in genomic research resulting into a generation of large amounts of genomic resources and information including recently published sequence of the reference genome and re-sequencing of almost 1000 lines representing the global diversity. This chapter reviews the advances made in generating the genetic and genomics resources in pearl millet and their interventions in improving the stress tolerance to improve the productivity of this very important climate-smart nutri-cereal

Systems biology-based approaches toward understanding drought tolerance in food crops

Economically important crops, such as maize, wheat, rice, barley, and other food crops are affected by even small changes in water potential at important growth stages. Developing a comprehensive understanding of host response to drought requires a global view of the complex mechanisms involved. Research on drought tolerance has generally been conducted using discipline-specific approaches. However, plant stress response is complex and interlinked to a point where discipline-specific approaches do not give a complete global analysis of all the interlinked mechanisms. Systems biology perspective is needed to understand genome-scale networks required for building long-lasting drought resistance. Network maps have been constructed by integrating multiple functional genomics data with both model plants, such as Arabidopsis thaliana, Lotus japonicus, and Medicago truncatula, and various food crops, such as rice and soybean. Useful functional genomics data have been obtained from genome-wide comparative transcriptome and proteome analyses of drought responses from different crops. This integrative approach used by many groups has led to identification of commonly regulated signaling pathways and genes following exposure to drought. Combination of functional genomics and systems biology is very useful for comparative analysis of other food crops and has the ability to develop stable food systems worldwide. In addition, studying desiccation tolerance in resurrection plants will unravel how combination of molecular genetic and metabolic processes interacts to produce a resurrection phenotype. Systems biology-based approaches have helped in understanding how these individual factors and mechanisms (biochemical, molecular, and metabolic) ``interact'' spatially and temporally. Signaling network maps of such interactions are needed that can be used to design better engineering strategies for improving drought tolerance of important crop species

Characterization of rhizosphere fungi that mediate resistance in tomato against bacterial wilt disease

Plant immunization for resistance against a wide variety of phytopathogens is an effective strategy for plant disease management. Seventy-nine plant growth-promoting fungi (PGPFs) were isolated from rhizosphere soil of India. Among them, nine revealed saprophytic ability, root colonization, phosphate solubilization, IAA production, and plant growth promotion. Seed priming with four PGPFs exhibited early seedling emergence and enhanced vigour of a tomato cultivar susceptible to the bacterial wilt pathogen compared to untreated controls. Under greenhouse conditions, TriH-JSB27 and PenC-JSB41 treatments remarkably enhanced the vegetative and reproductive growth parameters. Maximum NPK uptake was noticed in TriH-JSB27-treated plants. A significant disease reduction of 57.3% against Ralstonia solanacearum was observed in tomato plants pretreated with TriH-JSB27. Furthermore, induction of defence-related enzymes and genes was observed in plants pretreated with PGPFs or inoculated with pathogen. The maximum phenylalanine ammonia lyase (PAL) activity (111U) was observed at 24h in seedlings treated with TriH-JSB27 and this activity was slightly reduced (99U) after pathogen inoculation. Activities of peroxidase (POX, 54U) and β-1,3-glucanase (GLU, 15U) were significantly higher in control plants inoculated with pathogen after 24h and remained constant at all time points. A similar trend in gene induction for PAL was evident in PGPFs-treated tomato seedlings with or without pathogen inoculation, whereas POX and GLU were upregulated in control plus pathogen-inoculated tomato seedlings. These results determine that the susceptible tomato cultivar is triggered after perception of potent PGPFs to synthesize PAL, POX, and GLU, which activate defence resistance against bacterial wilt disease, thereby contributing to plant health improvement

Enhancement of downy mildew disease resistance in pearl millet by the Gapp7 bioactive compound produced by Ganoderma applanatum

Pearl millet (Pennisetum glaucum) stands sixth among the most important cereal crops grown in the semi-arid and arid regions of the world. The downy mildew disease caused by Sclerospora graminicola, an oomycete pathogen, has been recognized as a major biotic constraint in pearl millet production. On the other hand, basidiomycetes are known to produce a large number of antimicrobial metabolites, providing a good source of anti-oomycete agrochemicals. Here, we report the discovery and efficacy of a compound, named Gapp7, purified from Ganoderma applanatum on inhibition of growth and development of S. graminicola, as well as the effects of seed treatment with Gapp7 on protection of pearl millet from downy mildew. Gapp7 consistently demonstrated remarkable effects against S. graminicola by recording significant inhibition of sporangium formation (41.4), zoospore release (77.5) and zoospore motility (91). Analyses of Gapp7 compound using two-dimensional nuclear magnetic resonance spectroscopy and liquid chromatography-mass spectrometry revealed its close resemblance to metominostrobin, a derivative of strobilurin group of fungicides. Furthermore, the Gapp7 was shown to stably maintain the inhibitory effects at different temperatures between 25 and 80 °C. In addition, the anti-oomycete activity of Gapp7 was fairly stable for a period of at least 12 months at 4 °C and was only completely lost after being autoclaved. Seed treatment with Gapp7 resulted in a significant increase in disease protection (63) under greenhouse conditions compared with water control. The identification and isolation of this novel and functional anti-oomycete compound from G. applanatum provide a considerable agrochemical importance for plant protection against downy mildew in an environmentally safe and economical manner