Abstract
Burgeoning population growth, industrial demand, and the predicted global climate change resulting in erratic monsoon rains are expected to severely limit fresh water availability for agriculture both in irrigated and rainfed ecosystems. In order to remain food and nutrient secure, agriculture research needs to focus on devising strategies to save water in irrigated conditions and to develop superior cultivars with improved water productivity to sustain yield under rainfed conditions. Recent opinions accruing in the scientific literature strongly favor the adoption of a “trait based” crop improvement approach for increasing water productivity. Traits associated with maintenance of positive tissue turgor and maintenance of increased carbon assimilation are regarded as most relevant to improve crop growth rates under water limiting conditions and to enhance water productivity. The advent of several water saving agronomic practices notwithstanding, a genetic enhancement strategy of introgressing distinct physiological, morphological, and cellular mechanisms on to a single elite genetic background is essential for achieving a comprehensive improvement in drought adaptation in crop plants. The significant progress made in genomics, though would provide the necessary impetus, a clear understanding of the “traits” to be introgressed is the most essential need of the hour. Water uptake by a better root architecture, water conservation by preventing unproductive transpiration are crucial for maintaining positive tissue water relations. Improved carbon assimilation associated with carboxylation capacity and mesophyll conductance is important in sustaining crop growth rates under water limited conditions. Besides these major traits, we summarize the available information in literature on classifying various drought adaptive traits. We provide evidences that Water-Use Efficiency when introgressed with moderately higher transpiration, would significantly enhance growth rates and water productivity in rice through an improved photosynthetic capacity.
Highlights
Water can be considered as one of the major factors that helped the nomadic hunter-gatherers to settle down in civilized societies
Despite the tremendous progress in genomic approaches leading to the discovery of genes and QTLs, and evolution of robust methodology for transferring these genes and QTL to a recipient background, the progress in genetic enhancement has still remained nominal
Increase in Water-Use Efficiency (WUE) is coupled with the reduction in transpiration, Because of the strong link between transpiration and biomass accumulation, an increase in WUE is often associated with reduced growth rates and yield (Blum, 2009, 2011)
Summary
Water can be considered as one of the major factors that helped the nomadic hunter-gatherers to settle down in civilized societies. Unlike during the green revolution era, agriculture research faces an unprecedented challenge of producing “more” food with “less” resources, especially water In this context, the slogan “more crop per drop” has the greatest relevance. Mulching the soil with plant debris and biodegradable plastic (Prosdocimia et al, 2016) have long been developed and are being practiced These water conservation approaches have significantly contributed to improved productivity in dry land crops like sorghum (Unger and Jones, 1980), groundnut (Ramakrishna et al, 2005), and soyabean (Arora et al, 2011). We discuss the possible physiological and molecular mechanisms that need to be considered for achieving improved drought adaptation Among several traits, those associated with maintenance of leaf turgor and carbon metabolism have the greatest relevance in sustaining growth rates under drought. We make an attempt to evaluate the reasons for the lack of success in improving crop productivity and suggest possible approaches to overcome this lacuna in genetic enhancement
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