Exploiting Phenylpropanoid Derivatives to Enhance the Nutraceutical Values of Cereals and Legumes.

Phenylpropanoids are a diverse chemical class with immense health benefits that are biosynthesized from the aromatic amino acid L-phenylalanine. This article reviews the progress for accessing variation in phenylpropanoids in germplasm collections, the genetic and molecular basis of phenylpropanoid biosynthesis, and the development of cultivars dense in seed-phenylpropanoids. Progress is also reviewed on high-throughput assays, factors that influence phenylpropanoids, the site of phenylpropanoids accumulation in seed, Genotype × Environment interactions, and on consumer attitudes for the acceptance of staple foods rich in phenylpropanoids. A paradigm shift was noted in barley, maize, rice, sorghum, soybean, and wheat, wherein cultivars rich in phenylpropanoids are grown in Europe and North and Central America. Studies have highlighted some biological constraints that need to be addressed for development of high-yielding cultivars that are rich in phenylpropanoids. Genomics-assisted breeding is expected to facilitate rapid introgression into improved genetic backgrounds by minimizing linkage drag. More research is needed to systematically characterize germplasm pools for assessing variation to support crop genetic enhancement, and assess consumer attitudes to foods rich in phenylpropanoids.

Suppression of soil nitrification by plants.

Nitrification, the biological oxidation of ammonium to nitrate, weakens the soil's ability to retain N and facilitates N-losses from production agriculture through nitrate-leaching and denitrification. This process has a profound influence on what form of mineral-N is absorbed, used by plants, and retained in the soil, or lost to the environment, which in turn affects N-cycling, N-use efficiency (NUE) and ecosystem health and services. As reactive-N is often the most limiting in natural ecosystems, plants have acquired a range of mechanisms that suppress soil-nitrifier activity to limit N-losses via N-leaching and denitrification. Plants' ability to produce and release nitrification inhibitors from roots and suppress soil-nitrifier activity is termed 'biological nitrification inhibition' (BNI). With recent developments in methodology for in-situ measurement of nitrification inhibition, it is now possible to characterize BNI function in plants. This review assesses the current status of our understanding of the production and release of biological nitrification inhibitors (BNIs) and their potential in improving NUE in agriculture. A suite of genetic, soil and environmental factors regulate BNI activity in plants. BNI-function can be genetically exploited to improve the BNI-capacity of major food- and feed-crops to develop next-generation production systems with reduced nitrification and N2O emission rates to benefit both agriculture and the environment. The feasibility of such an approach is discussed based on the progresses made.

Genetics- and genomics-based interventions for nutritional enhancement of grain legume crops: status and outlook.

Meeting the food demands and ensuring nutritional security of the ever increasing global population in the face of degrading natural resource base and impending climate change is the biggest challenge of the twenty first century. The consequences of mineral/micronutrient deficiencies or the hidden hunger in the developing world are indeed alarming and need urgent attention. In addressing the problems associated with mineral/micronutrient deficiency, grain legumes as an integral component of the farming systems in the developing world have to play a crucial role. For resource-poor populations, a strategy based on selecting and/or developing grain legume cultivars with grains denser in micronutrients, by biofortification, seems the most appropriate and attractive approach to address the problem. This is evident from the on-going global research efforts on biofortification to provide nutrient-dense grains for use by the poorest of the poor in the developing countries. Towards this end, rapidly growing genomics technologies hold promise to hasten the progress of breeding nutritious legume crops. In conjunction with the myriad of expansions in genomics, advances in other 'omics' technologies particularly plant ionomics or ionome profiling open up novel opportunities to comprehensively examine the elemental composition and mineral networks of an organism in a rapid and cost-effective manner. These emerging technologies would effectively guide the scientific community to enrich the edible parts of grain legumes with bio-available minerals and enhancers/promoters. We believe that the application of these new-generation tools in turn would provide crop-based solutions to hidden hunger worldwide for achieving global nutritional security.

Grain iron and zinc density in pearl millet: combining ability, heterosis and association with grain yield and grain size.

Genetics of micronutrients and their relationships with grain yield and other traits have a direct bearing on devising effective strategies for breeding biofortified crop cultivars. A line × tester study of 196 hybrids and their 28 parental lines of pearl millet (Pennisetum glaucum (L.) R.Br.) showed large genetic variability for Fe and Zn densities with predominantly additive gene action and no better-parent heterosis. Hybrids with high levels of Fe and Zn densities, involved both parental lines having significant positive general combining ability (GCA), and there were highly significant and high positive correlations between performance per se of parental lines and their GCAs. There was highly significant and high positive correlation between the Fe and Zn densities, both for performance per se and GCA. Fe and Zn densities had highly significant and negative, albeit weak, correlations with grain yield and highly significant and moderate positive correlation with grain weight in hybrids. These correlations, however, were non-significant in the parental lines. Thus, to breed hybrids with high Fe and Zn densities would require incorporating these micronutrients in both parental lines. Also, simultaneous selection for Fe and Zn densities based on performance per se would be highly effective in selecting for GCA. Breeding for high Fe and Zn densities with large grain size will be highly effective. However, combining high levels of these micronutrients with high grain yield would require growing larger breeding populations and progenies than breeding for grain yield alone, to make effective selection for desirable recombinants.

Fertilizer induced nitrous oxide emissions from Vertisols and Alfisols during sweet sorghum cultivation in the Indian semi-arid tropics.

Nitrous oxide (N(2)O) emissions from Vertisols and Alfisols during sweet sorghum cultivation in the Indian semi-arid tropics were determined using a closed chamber technique during the rainy season (June-October) of 2010. The study included two treatments, nitrogen (N) at a rate of 90 kg/ha and a control without N fertilizer application. The N(2)O emissions strongly coincided with N fertilization and rainfall events. The cumulative N(2)O-N emission from Alfisols was 1.81 N(2)O-N kg/ha for 90 N treatment and 0.15 N(2)O-N kg/ha for the 0 N treatment. Similarly, the N(2)O-N emission from Vertisols was 0.70 N(2)O-N kg/ha for 90 N treatment and 0.09 N(2)O-N kg/ha for the 0 N treatment. The mean N(2)O-N emission factor for fertilizer induced emissions from the Alfisols was 0.90% as compared to 0.32% for Vertisols. Our results suggest that the N(2)O emissions are dependent on the soil properties. Therefore, the monitoring of N(2)O emissions from different agro-ecological regions, having different soil types, rainfall characteristics, cropping systems and crop management practices are necessary to develop comprehensive and accurate green house gas inventories.

Plant prebiotics and human health: Biotechnology to breed prebiotic-rich nutritious food crops

Microbiota in the gut play essential roles in human health. Prebiotics are non-digestible complex carbohydrates that are fermented in the colon, yielding energy and short chain fatty acids, and selectively promote the growth of Bifidobacteria and Lactobacillae in the gastro-intestinal tract. Fructans and inulin are the best-characterized plant prebiotics. Many vegetable, root and tuber crops as well as some fruit crops are the best-known sources of prebiotic carbohydrates, while the prebiotic-rich grain crops include barley, chickpea, lentil, lupin, and wheat. Some prebiotic-rich crop germplasm have been reported in barley, chickpea, lentil, wheat, yacon, and Jerusalem artichoke. A few major quantitative trait loci and gene-based markers associated with high fructan are known in wheat. More targeted search in genebanks using reduced subsets (representing diversity in germplasm) is needed to identify accessions with prebiotic carbohydrates. Transgenic maize, potato and sugarcane with high fructan, with no adverse effects on plant development, have been bred, which suggests that it is feasible to introduce fructan biosynthesis pathways in crops to produce health-imparting prebiotics. Developing prebiotic-rich and super nutritious crops will alleviate the widespread malnutrition and promote human health. A paradigm shift in breeding program is needed to achieve this goal and to ensure that newly-bred crop cultivars are nutritious, safe and health promoting.