**1. Introduction**

Legumes are well known for their nutritional and health benefits, as well as their contribution to agricultural system sustainability. They are the most important single source of vegetable protein in human diets and cattle feed (forages) [1]. Legumes are frequently used as an intercrop (e.g., paired with cereals) or in crop rotation in farming systems, resulting in a reduction in pests, diseases, and weed populations while increasing overall farm production and income for smallholder farmers. Other than


#### **Table 1.**

*List of genetic resources of pigeonpea.*

commercial and economic importance, legumes have gotten less attention than cereals in terms of increasing agricultural production. A variety of abiotic stresses are threatening the legume crops [2]. Studies on stress tolerance processes have led to the identification of characters related with tolerance in plants, as well as the molecular regulation of stress-responsive genes. Some of these researches have paved the way for new opportunities to investigate the molecular basis of plant stress responses and find novel features and associated genes for agricultural plant genetic improvement (**Table 1**) [15].

*Cajanus cajan* also named as Pigeonpea, arhar, tur, red gram, is a major pulse crop of the world's semi-arid regions and India's second most important pulse crop after chickpea. It is high in protein (21–28%), carbohydrates, vitamins, fats, and minerals [4]. Pigeonpea has become an important crop in India throughout time, with attempts being undertaken to produce high yielding varieties by conventional breeding and biotechnology approaches [16]. Plants have evolved complex signaling pathways that include receptors, secondary messengers, phytohormones, and signal transducers to detect different stresses and adapt to changing environmental conditions. These inherent processes promote stress signal transduction and the activation of stressresponsive gene expression in order to maintain plant growth and productivity [17].

Pigeonpea breeding has been more difficult than in other dietary legumes due to crop specific features and a very sensitive nature [18]. For more than five decades, low productivity and lack of stability have been major production challenges in this crop. This scenario is caused by abiotic stressors, in addition to genetic and agronomic factors. This dilemma can now be turned around by simultaneously reducing crop losses and increasing crop yielding capabilities [19]. This hardy crop is subjected to a variety of abiotic stresses, including moisture (waterlogging/drought), temperature, photoperiod, and mineral (salinity/acidity) stress (**Table 2**) [25]. Drought and heat stress, two important abiotic stress elements affecting crop loss and yield, are notable effects of climate change. Drought disrupts the pigeonpeas' symbiotic association, reducing growth and finally leading to lower crop production [26]. The tension exerted on the

*Perspective Chapter: An Insight into Abiotic Stresses in Pigeonpea – Effects and Tolerance DOI: http://dx.doi.org/10.5772/intechopen.110368*


#### **Table 2.**

*Different pigeonpea genotypes tolerant to abiotic stress and their mechanism [18].*

northern and north-eastern areas of India where temperature extremes (too low/too high) during the reproductive stage affect the production rate [27].

Other than temperature and drought, aluminum toxicity in acidic soil is also a constraint for production. Some regions of Haryana and Punjab, where the pigeonpea is affected by waterlogging, soil erosion and salinity pressures [28]. All these factors have a significant impact on productivity, yet few changes have been made in genotypes which are resistant to these abiotic stresses. Hence, the purpose of the present study is to examine the available information on abiotic stresses and discuss approaches to improve pigeonpea resistance to these constraints.
