Combinatorial impacts of elevated CO2 and temperature affect growth, development, and fruit yield in Capsicum chinense Jacq

Hot chilli ('Bhut Jolokia') (Capsicum chinense Jacq.) is the hottest chilli widely grown in the North-Eastern region of India for its high pungency. However, little information is available on its physiology, growth and developmental parameters including yield. Therefore, the present research was undertaken to study the physiological responses of Bhut Jolokia under elevated CO2 (eCO(2)) and temperature. Two germplasms from two different agro-climatic zones (Assam and Manipur) within the North-East region of India were collected based on the pungency. The present study explored the interactive effect of eCO(2) [at 380, 550, 750 ppm (parts per million)] and temperature (at ambient, > 2 degrees C above ambient, and > 4 degrees C above ambient) on various physiological processes, and expression of some photosynthesis and capsaicin related genes in both the germplasms. Results revealed an increase (> 1-2 fold) in the net photosynthetic rate (P-n), carbohydrate content, and C: N ratio in 'Bhut Jolokia' under eCO(2) and elevated temperature regimes compared to ambient conditions within the germplasms. Gene expression studies revealed an up-regulation of photosynthesis-related genes such as CsRuBPC2 (Ribulose biphosphate carboxylase 2) and CsSPS (Sucrose phosphate synthase) which, explained the higher P-n under eCO(2) and temperature conditions. Both the germplasm showed better performance under CTGT-II (Carbon dioxide Temperature Gradient Tunnel having 550 ppm CO2 and temperature of 2 degrees C above ambient) in terms of various physiological parameters and up-regulation of key photosynthesis-related genes. An up-regulation of the Cs capsaicin synthase gene was also evident in the study, which could be due to the metabolite readjustment in 'Bhut Jolokia'. In addition, the cultivar from Manipur (cv. 1) had less fruit drop compared to the cultivar from Assam (cv. 2) in CTGT II. The data indicated that 550 ppm of eCO(2) and temperature elevation of > 2 degrees C above the ambient with CTGT-II favored the growth and development of 'Bhut Jolokia'. Thus, results suggest that Bhut Jolokia grown under the elevation of CO2 up to 550 ppm and temperature above 2 degrees C than ambient may support the growth, development, and yield.