Effect of Drought Stress on Capsaicin and Antioxidant Contents in Pepper Genotypes at Reproductive Stage.

Muhammad Azam Khan,Gabrielle Sousa Mafra,Xiukang Wang,Ferdinando Branca,Asma Gulzar,Tahir Mahmood,Rashid Mehmood Rana,Sunny Ahmar,Freddy Mora-Poblete,Fahad Masoud Wattoo,Saima Saeed,Xionming Du

doi:10.3390/plants10071286

Abstract

Pepper is one of the most important vegetables and spices in the world. Principal pungency is contributed by secondary metabolites called capsaicinoids, mainly synthesized in the placenta of pepper fruit. Various factors, including drought, limit pepper production. Flowering is one of the most sensitive stages affected by drought stress. The current study was conducted to determine the effect of drought on different pepper genotypes at the flowering and pod formation stages. Hot pepper (Pusajuala and Ghotki) and Bell pepper (Green Wonder and PPE-311) genotypes were subjected to drought (35% field capacity) at two different stages (flowering (DF) and pod formation (DP) stage). In comparison, control plants were maintained at 65% field capacity. The data regarding flowering survival rates, antioxidant protein activity, and proline content, were collected. Results indicated that parameters like flower survival percentage, number of fruits per plant, and fruit weight had significant differences among the genotypes in both treatments. A high proline level was observed in Green Wonder at the pod formation stage compared to other genotypes. Capsaicin contents of hot pepper genotypes were affected at the pod formation stage. Antioxidants like GPX were highly active (190 units) in Ghotki at pod formation. Bell pepper genotypes had a high APX activity, highly observed (100 units) in PPE-311 at pod formation, and significantly differ from hot pepper genotypes. In the catalase case, all the genotypes had the highest values in DP compared to control and DF, but Pusajuala (91 units) and Green Wonder (83 units) performed best compared to other genotypes. Overall, the results indicate that drought stress decreased reproductive growth parameters and pungency of pepper fruit as most of the plant energy was consumed in defense molecules (antioxidants). Therefore, water availability at the flowering and pod formation stage is critical to ensure good yield and pepper quality.

Highlights

Pepper (Capsicum spp.) is one of the important vegetables and spices of the world
The pepper genotypes are grouped into three major clusters under three different treatments, including control, D(F), and D(P), which showed the significant effects of treatment application
The measured traits, including antioxidants and production traits, are divided into two major groups. This indicates the unique response of hot pepper and bell pepper to the drought stress at different reproductive stages

Summary

Introduction

Pepper (Capsicum spp.) is one of the important vegetables and spices of the world. It contains a wide range of phytochemicals, such as neutral and acidic phenolic compounds, which are important nutritional antioxidants that may reduce the risk of degenerative, mutagenic, and chronic diseases [1,2]. The phytochemicals in pepper have been reported to possess many biochemical and pharmacological properties, such as antioxidant, antiinflammatory, anti-allergic, and anti-carcinogenic activities [3]. Ripened pepper is naturally rich in ascorbic acid (vitamin C) and provitamin A [4], which neutralizes free radicals in the human body and reduces the risk of diseases such as arthritis, cardiovascular disease, cancer and the aging process [5,6,7]. Several studies have proved the antimicrobial activity of peppers [9,10]

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