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Legumes are an integral part of the ecosystem that contributes to sustainable agricultural development across the globe and ensures nutritional security, particularly among the poor segment of the society. Among several legumes cultivated in the world, common bean, chickpea, cowpea, groundnut, lentil, pigeonpea, and soybean are the major seven legumes highly preferred across the globe. The combined production of these major legumes has followed an increasing trend with the global production increase by 548.6% between triennium ending 1961–1963 and 2014–2016 owing to a combined effect of area expansion by 152.6% (128.37 m ha) and productivity enhancement by 85.9% during the same period. The global annual growth rates (AGRs) of total area, production, and yield of these major legumes during the 1961–2016 period are 1.7%, 3.5%, and 1.2%, respectively. The highest AGR for production was observed in the case of soybean (4.5%) followed by cowpea (4.1%), lentil (3.5%), groundnut (2.2%), pigeonpea (1.8%), common bean (1.5%), and chickpea (1.1%), while the highest AGR for productivity was observed in the case of groundnut (1.5%) followed by soybean (1.4%), cowpea (1.4%), lentil (1.4%), common bean (1.1%), chickpea (0.9%), and pigeonpea (0.4%). The global future demand and supply projections of these legumes clearly highlight the importance of developing countries in legume production. The country-wise demand and supply gaps and the changes in pattern of their utilization over time will drive the future research focus on legumes in those countries.

Farming communities, around the world, who earn their livelihoods through their hard work with limited resources and many times under unfriendly and risky agricultural environments are the main providers of plant proteins to masses by cultivating legumes. Besides proteins, legumes also contain valuable vitamins, mineral and fibre necessary for nutritional security. Globally, over a dozen legume species are cultivated in different agro-ecologies and cropping systems, but seven of them, namely, soybean (Glycine max), groundnut (Arachis hypogaea), cowpea (Vigna unguiculata), common bean (Phaseolus vulgaris), chickpea (Cicer arietinum), lentil (Lens culinaris) and pigeonpea (Cajanus cajan), hold promise with respect to their adaptation, productivity, international trade and consumer preferences. Legumes as a group, unfortunately, carry a tag of low productivity, and in spite of reasonable research efforts in general, their yield enhancement goals still remain unfulfilled. For this bottleneck various factors such as lack of high yielding cultivars, low research priority, inadequate inputs, relegation of the crops to second-grade lands, disease and insect losses and use of the age-old research tools and technologies can be held responsible. It seems that legume researchers have already lost valuable time and opportunities to provide farmers with high yielding cultivars with wide adaptation and incurring least damage due to biotic and abiotic stresses. Presently, the adverse effects of climate changes are also looming large, and hence, there is compelling need to re-emphasize the research priorities on a global basis. To highlight the importance of legumes to the human race and to make the legumes (including pulses) affordable to the poor, the 68th session of the UN General Assembly declared 2016 as the “International Year of Pulses”. It seems now the time is ripe to revisit the production trends and key constraints facing legumes and develop smart R&D plans, keeping in view the recent developments in the fields of genomics, genetic engineering/editing, crop breeding, agronomy and technology transfer. Therefore, there was a need to document these advances that can help the research community to develop a road map. In view of this, we have brought the experts working in different areas of legumes together to document their experiences and provide a road map through this book.

Protein-rich food legumes are usually cultivated as rain-dependent crops under subsistence agriculture. Besides this, most farmers are deprived of improved seeds due to lack of interest in both public and private seed industries. These factors lead to unacceptably poor yields at the farm level. In a number of field crops, the cultivation of hybrids has resulted in quantum jump in their productivity, but by contrast in legumes, only inbred cultivars are in cultivation with poor harvests. In the last few decades, breeders are attempting to develop hybrid breeding technology in two legumes, faba bean and pigeonpea, where natural out-crossing is sufficient to support their large-scale hybrid seed production. Besides these, attempts are also being made to develop a hybrid technology in soybean, where male sterility systems have been bred, and attempts are being made to enhance the level of cross-pollination to facilitate the production of cross-pollinated seed. Of the three crops, the success has been achieved only in pigeonpea [Cajanus cajan (L.) Millsp.] where three commercial hybrids have been bred. In farmers’ fields, these hybrids produce 30–50% more yield over the local control. This review deals with breeders’ efforts towards developing hybrid technology in the three legume crops along with the major accomplishments in hybrid pigeonpea breeding.

Pigeonpea [Cajanus cajan (L.) Millsp.] is traditionally cultivated as an annual crop in semi-arid regions of the world. It has a number of characteristics such as diverse maturity time, drought tolerance and natural out-crossing which makes it unique among legumes. These traits not only allow its cultivation in diverse environments and cropping systems, but also permit implementation of different breeding methods. Pigeonpea is a crop of sustainable agriculture and poor crop management, exposure to diseases and pests coupled with unpredictable rains hinder crop improvement activities. However, recently partial out-crossing has been exploited to develop cytoplasmic male-sterility (CMS) based hybrid breeding technology. Thus far, three hybrids have been released for cultivation with yield advantages of 30–50% over standard varieties. Pigeonpea R&D now also enjoys a wealth of genomics resources such as a draft genome sequence, resequencing data, candidate genes and markers associated with key traits. Genomics and breeding efforts are underway to make pigeonpea a more sustainable crop and to unlock the genetic diversity present in germplasm to develop new cultivars rapidly.

Complexity of yield formation is well understood by all, and there is no specific formula for breeding high-yielding cultivars. Breeders, however for a long time, have relied on selecting various individual traits, which, they thought, will contribute to yield formation directly or indirectly, and in these ways, successes have been achieved in almost all the crops. In pigeonpea, the most important individual plant traits, known to be linked to seed yield are number of pods, primary and secondary branches, and pod-bearing bunches. All these traits are quantitative in nature and have low heritability. In this paper, an attempt has been made to identify various qualitative and quantitative traits related to seed yield, quality, and those preferred for marketing and milling. A brief description about their inheritance and association with yield has also been provided to help breeders in decision-making.