Physiological Efficiency of Sugarcane Clones under Water-Limited Conditions

Highlights`Significant reductions in canopy temperature depression (CTD), chlorophyll fluorescence (Fv/Fm), SPAD index, and leaf rolling index were observed under limited irrigation during the grand growth stage of sugarcane.This study highlights the significance of CTD and Fv/Fm as useful physiological tools for selecting sugarcane clones suitable for production under water-limited conditions.Clones Co 10026, Co 13006, Co 85019, Co 62175, Co 86010, and Co 1148 performed better under limited irrigation, and these clones can reduce the amount of irrigation water required for sugarcane production, ensuring water security.Abstract. Sugarcane is one the most important commercial crops in India and globally. The annual water requirement for sugarcane ranges from about 1000 to 2900 mm, and this variation mainly depends on the agro-ecological conditions, cultivation practices, and crop cycle. In a changing climate, the delay or failure of monsoons will have a direct effect on the water available for irrigation in India. Given these constraints, sustaining sugarcane production is challenging. The ICAR-Sugarcane Breeding Institute (ICAR-SBI) in Coimbatore, India, has developed sugarcane genotypes that are resilient to drought stress. To study the role of physiological traits in identifying sugarcane varieties suitable for water-limited conditions, an experiment was conducted at ICAR-SBI with sugarcane clones in field conditions using irrigation at 100% cumulative pan evaporation (I0) and with 50% reductions in the volume and frequency of irrigation (I2). Physiological traits, including canopy temperature depression (CTD), chlorophyll fluorescence (Fv/Fm), soil plant analysis development (SPAD) index, leaf rolling index (LRI), and cane yield, were recorded for sugarcane clones grown under I0 and I2. Significant reductions of 85.9%, 15.4%, 4.9%, 44.9%, and 56.0%, respectively, in CTD, Fv/Fm, SPAD index, LRI, and cane yield were found for water-limited conditions (I2) compared to I0. Fv/Fm showed a decreasing trend in I2 compared to I0 and also showed a significant positive correlation (r = 0.43) with cane yield. CTD varied significantly between the two treatments and also showed a significant positive correlation with cane yield (r = 0.45). Both Fv/Fm and CTD are adaptive traits for water-limited conditions and are useful for screening sugarcane clones suitable for water-limited conditions. Clones Co 10026, Co 13006, Co 85019, Co 62175, and Co 86010 had superior cane yields under water-limited conditions (I2) and better physiological traits. Water deficit is one of the most critical abiotic stresses that affect sugarcane productivity. By growing clones that are water use efficient (Co 10026, Co 13006, Co 85019, Co 62175, and Co 86010), the irrigation water requirement can be reduced for sugarcane production in India. In addition, new sugarcane clones can be developed for water-limited conditions by using the identified clones in breeding programs for water use efficiency, and water security can be achieved for sugarcane grown tropical and sub-tropical areas of India. Keywords: Canopy temperature, Chlorophyll fluorescence, Global water security, Irrigation, Water productivity