Comparative heat stress responses of three hot pepper (Capsicum annuum L.) genotypes differing temperature sensitivity

Abstract

As global temperatures have steadily increased over past decades, studying of the impacts of heat stress on morpho-physiological traits and economic yields of horticultural crops have been increasingly gained attentions by many scientists and farmers. Hot pepper (Capsicum annuum L.) is an important vegetable crop mostly grown in open-fields in South Korea. In this study, the impacts of prolonged heat stress on three hot pepper genotypes differing by levels of stress susceptibility were evaluated. The study was conducted in two different temperature-controlled greenhouses for 75 days. 48 days old plants were grown in control and heat-treated greenhouses where the temperatures had been set at 30 °C and 35 °C during the day for 75 days, respectively. Morphological, physiological, and nutrient characteristics of three accessions were measured. All hot pepper accessions were enabled to recover from prolonged heat stress exposures within approximately a month. The phenomenon of recovery was observed in some significant morphological and physiological characteristics. For example, the plant growth rate and photosynthesis rate significantly increased after 40th days of heat treatment. The heat stress sensitivity varied between genotypes. The plants that produced more fruits over biomass at early stage of heat treatment had relatively slow recovery, resulting in the largest yield loss. This key morphological characteristic can be used for future breeding program to adapt the prolonged heat stress.

Figure 1

The effects of prolonged heat stress on plant growth of three hot pepper accessions, including PHR5, PHR18, and PHR23 for 34 and 75 days of heat treatments. Blue bars: 20 cm.

Figure 2

Plant heights and stem thickness of three hot pepper (Capsicum annuum L.) accessions, including PHR5, PHR18, and PHR23, treated by heat stress for 75 days. The blue line indicates hot pepper grown under control condition, while the red line indicates the accession grown in heat stress condition. The black bars indicate standard error.

Figure 3

Effects of heat stress on leaf electrolyte leakage rate of three hot pepper accessions, including PHR5, PHR18, and PHR23, for prolonged period in heat stress treatment and control greenhouses. The black bars indicate standard error.

Figure 4

Effects of prolonged heat treatment on the net photosynthesis rate (A) and PSII efficiency (Qy, Fv/Fm) of hot pepper accessions, including PHR5, PHR18, and PHR23, grown in heat-treated and control greenhouses for 75 days. The black bars indicate standard error.