**2. Major stresses influencing** *C. cajan* **productivity**

#### **2.1 Waterlogging**

Waterlogging is a major abiotic stress affecting pigeonpea production where annual rainfall is 600–1500 mm [29]. The primary biological consequence of waterlogging is a lack (hypoxia) or full lack (anoxia) of oxygen in the soil, which creates anaerobic conditions and limits plant growth and development, thus seed yield. Oxygen shortage causes electrolyte leakage, exposing the cell to the outside environment, which can lead to lipid and nucleic acid peroxidation and, eventually, death [30]. Previous studies found that proline accumulation, starch content, and effective H2O2 detoxification are among the significant biochemical alterations that play a major role in waterlogging resistance in pigeonpea genotypes. During monsoon, this plant is susceptible to phytophthora blight disease due to waterlogging and hence causes yield losses [31].

Another study identified that high nitrogen uptake and development of aerenchyma in ICPL-84023 enabled it to sustain growth under waterlogging [32]. Total reducing sugars, superoxide dismutase, membrane stability index, number of pods per plant, pod dry weight, and seed yield, are some biochemical changes that can be affected by waterlogging [33]. Crossings between tolerant and sensitive lines revealed greater genetic variety than crosses between tolerant lines, implying the possibility of genetic improvement for this crop. Lines derived from crosses involving *C. acutifolius*

have the unique property of enhancing tolerance under water logging circumstances for resource poor farming communities [29]. It is estimated that agriculture would be impacted globally by these forecasted climate changes. A better understanding of this legume crop resource and their characterization in terms of desirable traits for climate change adaptation are essential for the use of adapted *C. cajan* genetic resources in strengthening the resilience of future production systems [34].
