Question

biotic stress resistance in increasing productivity of plant

Answer 1

Introduction

Abiotic stresses, notably extremes in temperature along with supply of water and inorganic solutes, frequently limit growth and productivity of major crop species. They reduce the average yield for major crop plants by more than 50% (Bray et al. 2000Bray EA, Bailey-Serres J, Weretilnyk E. 2000. Responses to abiotic stresses. In: Buchanan BB, Gruissem W, and Jones ; Araus et al. 2002Araus JL, Slafer GA, Reynolds MP, Royo C. 2002. Plant breeding and drought in C3 cereals: what should we breed for? Ann Botany. 89:925–940. doi: 10.1093/aob/mcf049[Crossref], [PubMed], [Web of Science ®], [Google Scholar]). Water stress in its broadest sense includes both drought and salinity stress. Drought and salinity that are becoming increasingly significant in limiting plant growth are believed to cause serious salinization of more than 50% of all /s00425-003-1105-5[Crossref], [PubMed], [Web of Science ®], [Google Scholar]). One abiotic stress decreases the ability of plant to resist a second stress. For example, low water supply makes plants more susceptible to damage from high irradiance due to reduction in its ability to reoxidize NADPH, involved in dissipating energy delivered to photosynthetic light-harvesting reaction centers.

Abiotic stresses such as drought, salt and low temperature, which adversely affect plant growth and productivity, lead to a series of morphological, physiological, biochemical and molecular changes in plants in order to adapt and as such survive under stress conditions (Wang et al. 2003Wang W, Vinocur B, Altman A. 2003. Plant responses to drought, salinity and extreme temperatures: towards genetic engineering for stress tolerance. Planta. 218:1–14. doi: 10.1007/s00425-003-1105-5[Crossref], [PubMed], [Web of Science ®], [Google Scholar]). Plant abiotic stresses and response of plants to these stresses have been extensively studied. Improvement of crop plants with traits that confer tolerance to these stresses was practiced using traditional and modern breeding methods. Classical plant breeding methods involving inter-specific or inter-generic hybridization and in vitro-induced variation have been applied to improve the abiotic stress tolerance of various crop plants but have so far met with limited success. Conventional breeding strategies are limited by the complexity of quantitative traits, low genetic variance of yield components under stress conditions and lack of efficient selection criteria (Tester & Bacic 2005Tester M, Bacic A. 2005. Abiotic stress tolerance in grasses. From model plants to crop plants. Plant Physiol. 137:791–793. doi: 10.1104/pp.104.900138[Crossref], [PubMed], [Web of Science ®], [Google Scholar]; Varshney et al. 2011Varshney RV, Bansal KC, Aggarwal PK, Datta SK, Craufurd PQ. 2011. Agricultural biotechnology for crop improvement in a variable climate: Hope or hype? Trends Plant Sci. 16:363–371. doi: 10.1016/j.tplants.2011.03.004[Crossref], [PubMed], [Web of Science ®], [Google Scholar]). It is important, therefore, to look for alternative strategies to develop stress-tolerant crops. Genetic engineering that allows us to mobilize genes from virtually any source has given a strong landmark over plant breeding. Starting with 1.7 million hectares in 1996, a total of 134 million hectares of land was brought into cultivation of transgenic crops in 2009 (James 2009James C. 2009. ISAAA 41: global status of commercialized biotech/GM crops: 2009. The first fourteen years, 1996 to 2009. Ithaca, NY: International Service for the Acquisition of Agri-biotech growth rate of approximately 80-fold between 1996 and 2009, transgenic technology represents the fastest adopted technology for the production of crops. This ability to manipulate genes could lead to rational and deliberate attempts to alter the crops for improvement of their agronomic performance. Molecular breeding together with genetic engineering contributed substantially to our understanding of the complexity of stress response. In order to understand the basis of stress tolerance, the diversity of the stress response and its utility for the survival of plants are needed to be investigated. This review focuses on recent advances in basic research of abiotic stress tolerance at the molecular level, with the main emphasis on genetic engineering approaches that are generally used to create economically important stress-resistant transgenic plants.

Abiotic stress and plant productivity

Plant productivity is severely affected by abiotic stresses. Abiotic stresses negatively influence survival, biomass production, accumulation and grain yield of most crops (Grover et al. 2001Grover A, Kapoor A, Lakshmi OS, Agarwal S, Sahi C, Agarwal K, Agarwal M, Dubey H. 2001.