Physiological and transcriptomic analyses of healthy and blossom-end-rot (BER)-defected fruit of chili pepper (Capsicum annuum. L.)

Abstract

Calcium (Ca2+) deficiency leads to disease symptoms such as blossom-end-rot (BER), resulting in the cessation of apical growth, curling, shoot and flower tip necrosis, and fruit chlorosis in hot peppers (Capsicum annuum L.). Previous reports have stated that an excessive supply of cations like potassium (K+) and magnesium (Mg2+) affects the incidence of BER in plants of the Solanaceae family, such as tomato. In this study, we aimed to investigate the correlation between the contents of three cations and BER symptoms in pepper fruits. We assessed the distribution of three cations (Ca2+, K+, and Mg2+) in three distinct sections (pedicel, proximal half, and distal half) of the pepper fruit in both healthy and BER-defective peppers. We found that the overall amount of Ca2+ was not correlated with BER symptoms in pepper fruits. Instead, a high Ca2+/ K+ ratio in the pedicel of pepper fruit has a correlative impact on BER symptoms in the chili pepper fruit. Therefore, the manifestation of BER symptoms could be associated with the Ca2+/ K(+ )value and the relative percentage of the calcium-to-potassium ratio in the pedicel of the pepper fruit. Furthermore, we performed a transcriptomic analysis on both BER-resistant and BER-sensitive pepper fruits to gain a more profound understanding of the molecular mechanisms driving BER symptoms in chili peppers. BER-resistant pepper cultivar was shown to deploy defense programs against calcium-deficient stress conditions. We believe that our study provides helpful insights into the importance of the Ca2+/ K+ ratio in preventing physiological diseases, such as BER, in chili pepper cultivation.