Bacteria-inducing legume nodules involved in the improvement of plant growth, health and nutrition

Bacteria-inducing legume nodules are known as rhizobia and belong to the class Alphaproteobacteria and Betaproteobacteria. They promote the growth and nutrition of their respective legume hosts through atmospheric nitrogen fixation which takes place in the nodules induced in their roots or stems. In addition, rhizobia have other plant growth-promoting mechanisms, mainly solubilization of phosphate and production of indoleacetic acid, ACC deaminase and siderophores. Some of these mechanisms have been reported for strains of rhizobia which are also able to promote the growth of several nonlegumes, such as cereals, oilseeds and vegetables. Less studied are the mechanisms that have the rhizobia to promote the plant health; however, these bacteria are able to exert biocontrol of some phytopathogens and to induce the plant resistance. In this chapter, we revised the available data about the ability of the legume nodule-inducing bacteria for improving the plant growth, health and nutrition of both legumes and nonlegumes. These data showed that rhizobia meet all the requirements of sustainable agriculture to be used as bio-inoculants allowing the total or partial replacement of chemicals used for fertilization or protection of crops

Modern Genomic Tools for Pigeonpea Improvement: Status and Prospects

Pigeonpea owing to its ability to sustain harsh environment and limited input/water requirement remains an excellent remunerative crop in the face of increasing climatic adversities. With nearly 70% share in global pigeonpea production, India is the leading pigeonpea producing country. Since the mid-1900s, constant research efforts directed to improve yield and resistance levels of pigeonpea have resulted in the development and deployment of several commercially accepted cultivars in India, accommodating into diverse agro-climatic zones. However, the crop productivity needs incremental improvements in order to meet the growing nutritional demands, especially in developing countries like India where pigeonpea forms a dominant part of vegetarian diet. Empowering crop improvement strategies with genomic tool kit is imperative to attain the project gains in crop yield. In the context, adoption of next-generation sequencing (NGS) technology has helped establish a wide range of genomic resources to support pigeonpea breeding, and the existing molecular tool kit includes genome-wide genetic markers, transcriptome/genome assemblies, and candidate genes/QTLs for target traits. Similarly, availability of whole mitochondrial genome sequence and derived DNA markers is immensely relevant in order to furthering the understanding of cytoplasmic male sterility (CMS) system and hybrid breeding. This chapter covers the progress of developing modern genomic resources in pigeonpea and highlights their vital role in designing future crop breeding schemes

Molecular Mapping of Genes and QTLs in Pigeonpea

Pigeonpea is one of the most important grain legume crops grown in arid and semiarid regions of the world. There is an increasing demand for the development of new cultivars with high yield potential and better adaptability to adverse environmental conditions. Recent advances in genomics tools and techniques have helped to develop large repertoire of molecular markers and genotypic platforms. The availability of molecular markers facilitated the development of high-density genetic maps that have been used in discovery of important/major QTLs for targeted traits in pigeonpea. In addition, the availability of high-throughput genotypic platforms helped to generate whole genome genotypic data in high-throughput manner necessary for whole genome scanning/genome-wide association mapping of economically important traits. The advances in comparative genomics, transcriptomics, and whole genome sequencing have uncovered thousands of useful genes including some genes unique to pigeonpea crop. The availability of wealth of genomics resources/information will facilitate molecular breeding aimed at improving production and productivity of pigeonpea in extreme environments of arid and semiarid regions of the world

Genomic interventions to improve resilience of pigeonpea in changing climate

Pigeonpea is an important food legume crop for rainfed agriculture in developing countries, particularly in India. Productivity gains in pigeonpea have remained static, and the challenge of improving pigeonpea yield is further aggravated by increasingly uncertain climatic conditions. Improved pigeonpea cultivars with favourable traits, allowing them to cope with climatic adversities, are urgently required. Modern genomic technologies have the potential to rapidly improve breeding traits that confer resistance to biotic and abiotic stresses. Recent advances in pigeonpea genomics have led to the development of large-scale genomic tools to accelerate breeding programs. Availability of high-density genotyping assays and high-throughput phenotyping platforms motivate researchers to adopt new breeding techniques like genomic selection (GS) for improving complex traits. Accurate GS predictions inferred from multilocation and multiyear data sets also open new avenues for ‘remote breeding’ which is very much required to achieve genotype selection for future climates. Speed breeding pigeonpea with deployment of rapid generation advancement (RGA) technologies will improve our capacity to breed cultivars endowed with resilient traits. Once such climate-resilient cultivars are in place, their rapid dissemination to farmer’s fields will be required to witness the real impact. Equally important will be the acceleration of varietal turnover to keep pace with the unpredictably changing climatic conditions so that cultivars are constantly optimized for the climatic conditions at any given time