N.K. Pandey

Comparative transcriptomic analysis of roots of contrasting Gossypium herbaceum genotypes revealing adaptation to drought

BackgroundRoot length and its architecture govern the adaptability of plants to various stress conditions, including drought stress. Genetic variations in root growth, length, and architecture are genotypes dependent. In this study, we compared the drought-induced transcriptome of four genotypes of Gossypium herbaceum that differed in their drought tolerance adaptability. Three different methodologies, namely, microarray, pyrosequencing, and qRT–PCR, were used for transcriptome analysis and validation.ResultsThe variations in root length and growth were found among four genotypes of G.herbaceum when exposed to mannitol-induced osmotic stress. Under osmotic stress, the drought tolerant genotypes Vagad and GujCot-21 showed a longer root length than did by drought sensitive RAHS-14 and RAHS-IPS-187. Further, the gene expression patterns in the root tissue of all genotypes were analyzed. We obtained a total of 794 differentially expressed genes by microarray and 104928 high-quality reads representing 53195 unigenes from the root transcriptome. The Vagad and GujCot-21 respond to water stress by inducing various genes and pathways such as response to stresses, response to water deprivation, and flavonoid pathways. Some key regulatory genes involved in abiotic stress such as AP2 EREBP, MYB, WRKY, ERF, ERD9, and LEA were highly expressed in Vagad and GujCot-21. The genes RHD3, NAP1, LBD, and transcription factor WRKY75, known for root development under various stress conditions, were expressed specifically in Vagad and GujCot-21. The genes related to peroxidases, transporters, cell wall-modifying enzymes, and compatible solutes (amino acids, amino sugars, betaine, sugars, or sugar alcohols) were also highly expressed in Vagad and Gujcot-21.ConclusionOur analysis highlights changes in the expression pattern of genes and depicts a small but highly specific set of drought responsive genes induced in response to drought stress. Some of these genes were very likely to be involved in drought stress signaling and adaptation, such as transmembrane nitrate transporter, alcohol dehydrogenase, pyruvate decarboxylase, sucrose synthase, and LEA. These results might serve as the basis for an in-depth genomics study of Gossypium herbaceum, including a comparative transcriptome analysis and the selection of genes for root traits and drought tolerance.

Physiological performance and differential expression profiling of genes associated with drought tolerance in contrasting varieties of two Gossypium species

Cotton is mostly cultivated under rain-fed conditions in India, thus faces frequent drought conditions during its life cycle. Drought being a major stress factor responsible for yield penalty, there has always been a high priority to generate knowledge on adaptation and tolerance of cotton. In the present study, four cotton varieties, JKC-770 and KC-2 (Gossypium hirsutum), and JKC-717 and RAHS-187(Gossypium herbaceum), were imposed to drought. Under drought condition, differential changes in physiological characters like net photosynthesis, transpiration, stomatal conductance, chlorophyll fluorescence, relative water content (RWC), and predawn water potential (ψ 0) showed a change. While proline, malondialdehyde (MDA), and glutathione-S-transferase (GST) content increased along with a concomitant change in the expression of their associated genes. Under moderate stress, tolerant varieties maintain lower ψ 0 probably due to higher proline content as compared to sensitive varieties. Cyclic electron flow (CEF) also plays an important role in tolerance under mild water stress in G. hirsutum varieties. CEF not only activates at high light but also initiates at a very low light intensity. Expression analysis of genes reveals that drought-tolerant varieties showed enhanced detoxifying mechanism by up-regulation of asparagine synthase (AS), glutathione-S-transferase (GST), and methyl glyoxalase (GlyI) genes under drought stress. Up-regulation of Δ1-pyrroline-5-carboxylase synthase (Δ1P5CS) enhanced accumulation of proline, an osmolyte, under drought in tolerant varieties. While the drought-sensitive varieties showed up-regulation of ethylene responsive factor (ERF) and down-regulation of WRKY70 responsible for senescence of the leaf which correlated well with the high rate of leaf fall in sensitive varieties under water stress.

Physiological performance and differential expression profiling of genes associated with drought tolerance in root tissue of four contrasting varieties of two Gossypium species

Root growth in drying soil is generally limited by a combination of mechanical impedance and water stress. As the major function of root tissue is water and nutrient uptake, so it imparts an important role in plant growth and stress management. Previously, we have studied physiological performance and expression profiling of gene associated with drought tolerance in leaf tissue of four cotton varieties. Here, we have further continued our studies with the root tissue of these varieties. The Gossypium hirsutum species JKC-770 is drought-tolerant and KC-2 is drought-sensitive, while Gossypium herbaceum species JKC-717 is drought-tolerant and RAHS-187 is drought-sensitive. JKC-770 and JKC-717 the drought-tolerant varieties showed a comparatively high glutathione-S-transferase, superoxide dismutase, proline along with their gene expression, and low malondialdehyde content indicating low membrane damage and better antioxidative defense under drought condition. The expression levels of cellulose synthase, xyloglucan:xyloglucosyl transferase, and glycosyl hydrolases suggest modulation in cell wall structure and partitioning of sugars towards osmoprotectants instead of cell wall biosynthesis in tolerant varieties. Heat shock proteins and serine/threonine protein phosphotases show upregulation under drought condition, which are responsible for temperature tolerance and protein phosphorylation, respectively. These effects many metabolic processes and may be playing a key role in drought tolerance and adaptability of JKC-770 towards drought tolerance. The long-term water use efficiency (WUE) estimated in terms of carbon isotope discrimination (∆13C) in the root tissues showed maximum depletion in the ∆13C values in JKC-770 variety, while minimum in RAHS-187 under drought stress with reference to their respective control, suggesting a high WUE in JKC-770 variety.

An assessment of contract farming system for potato seed production in Punjab-A case study

The study was conducted to assess the contract farming system of potato seed production in Punjab with a sample of 30 contract and 30 non-contract farmers from Jalandhar district of Punjab. The major motivating factors identified for participating in the contract farming were assured price, diversification, access to assured market, extension services etc. There was no participation of marginal and small farmers in contract farming. The average net income of contract farmers was about 12 per cent higher than non-contract farmers. The major constraints in potato seed contract farming were pest and disease attacks, non-availability of labor during peak period, difficulty in meeting quality requirement etc. The study suggests that government, non-governmental organizations and other related agencies should play an active role in the contractual arrangement.

Market Arrival and Price behaviour of Potato in Agra district of uttar Pradesh

Potato is the major vegetable of India. Variation in output of potato over the years leads to wide fluctuation in its price exposing the growers to a high risk situation. To cope with this, information on potential market and quantum of arrivals and prices of potato in different months of year is necessary for farmers. The current study attempted to analyze the variation in arrivals and prices of potato in highest potato producing district of Uttar Pradesh i.e. Agra. Time series data for last 10 years on area and production as well as market arrivals and prices of potato was collected from various government organizations. The findings indicated that the annual growth rates in area and production of potato during last ten years were significant and positive. However in case of productivity, it was insignificant and negative. The annual compound growth rates of arrivals were comparatively higher than that of market price. Inter-year variations in market arrivals and prices of potato were observed. The monthly arrival of potato was highest in the month of January and lowest in the month of October. Accordingly, the market price was highest during October-November and lowest in the month of February. The seasonal index of arrival showed that the arrivals were low during June to November and higher during December to May. The results confirmed that there were both negative and positive relationships across months between market arrivals and prices in terms of correlation coefficients.