Screening Ornamental Pepper Cultivars for Temperature Tolerance Using Pollen and Physiological Parameters

Abstract

<jats:p>Temperature affects reproductive potential, aesthetic, and commercial value of ornamental peppers (<jats:italic>Capsicum annuum</jats:italic> L.). Limited information is available on cultivar tolerance to temperature stress. An experiment was conducted using pollen and physiological parameters to assess high and low temperature tolerance in ornamental peppers. In vitro pollen germination (PG) and pollen tube length (PTL) of 12 morphologically diverse ornamental pepper cultivars were measured at a range of temperatures, 10 to 45 °C with 5 °C increments. Cell membrane thermostability (CMT), chlorophyll stability index (CSI), canopy temperature depression (CTD), and pollen viability (PV) were measured during flowering. From the modified bilinear temperature–PG and PTL response functions, cardinal temperatures (T<jats:sub>min</jats:sub>, T<jats:sub>opt</jats:sub>, and T<jats:sub>max</jats:sub>) for PG and PTL and maximum PG (PG<jats:sub>max</jats:sub>) and PTL (PTL<jats:sub>max</jats:sub>) were estimated. Cultivars varied significantly for PG, PTL, cardinal temperatures for PG and PTL, and all three physiological parameters. Cumulative temperature response index (CTRI) of each cultivar, calculated as the sum of 12 individual temperature responses derived from PV, PG<jats:sub>max</jats:sub>, PTL<jats:sub>max</jats:sub>, T<jats:sub>min</jats:sub>, T<jats:sub>opt</jats:sub>, and T<jats:sub>max</jats:sub> for PG and PTL, CMT, CTD, and CSI were used to distinguish differences among the cultivars and classify for high (heat) and low (cold) temperature tolerance. Based on CTRI–heat, cultivars were classified as heat-sensitive (‘Black Pearl’, ‘Red Missile’, and ‘Salsa Yellow’), intermediate (‘Calico’, ‘Purple Flash’, ‘Sangria’, and ‘Variegata’), and heat-tolerant (‘Chilly Chili’, ‘Medusa’, ‘Thai Hot’, ‘Explosive Ember’, and ‘Treasures Red’). Similarly, cultivars were classified for cold tolerance as cold-sensitive, moderately cold-sensitive, moderately cold-tolerant, and cold-tolerant based on CTRI–cold. ‘Red Missile’ and ‘Salsa Yellow’ were classified as cold-tolerant. Cultivar screening using pollen parameters will be ideal for reproductive temperature tolerance, whereas physiological parameters will be suitable for screening vegetative temperature tolerance. The identified heat- and cold-tolerant cultivars are potential candidates in breeding programs to develop new ornamental and vegetable pepper genotypes for high and low temperature tolerance.</jats:p>

Expression of Target Gene Hsp70 and Membrane Stability Determine Heat Tolerance in Chili Pepper

“…CELL MEMBRANE THERMOSTABILITY. Electrical conductivity has been used as an index of membrane stability to identify heat-tolerant genotypes in chili (Gajanayake et al, 2011) and for screening heat-tolerant genotypes in different crops (Wahid et al, 2007). A highly significant (P < 0.05) difference was observed among the genotypes for CMT (Fig.…”

“…The autoclaved tubes were cooled to room temperature, the contents were mixed thoroughly, and a final conductance (CEC 2 and TEC 2) reading was taken. The CMT was calculated using the following equation, where TEC and CEC are a measure of conductance in the treated and control test tubes, respectively, for the initial (CEC 1 and TEC 1) and final (CEC 2 and TEC 2) conductance measurements (Gajanayake et al, 2011).…”

Modelled distributions and conservation status of the wild relatives of chile peppers (CapsicumL.)

“…Unlike tomato ( Solanum lycopersicum L.; Lin et al, ) and potato ( Solanum tuberosum L.) (Hirsch et al, ), other important crops in the Solanaceae, the genetic diversity contained in wild relatives of chile peppers has not been well studied (van Zonneveld et al, ) or widely utilized (Mongkolporn & Taylor, ), aside from a few reports of disease resistance (Kenyon, Kumar, Tsai, & Hughes, ). Tolerance of wild Capsicum to abiotic stresses such as salinity, drought, flooding and heat, all recognized challenges in the production of the crop taxa (Aloni, Peet, Pharr, & Karni, ; De Pascale, Ruggiero, Barbieri, & Maggio, ; Gajanayake, Trader, Reddy, & Harkess, ; Han, Li, Wang, & Miao, ; Maas & Hoffman, ; Rao & Li, ), has not been investigated.…”

Impact of moderate and extreme climate change scenarios on growth, morphological features, photosynthesis, and fruit production of hot pepper

“…Also, pollination and fertilization of hot pepper are significantly decreased at >30°C air temperature conditions (Erickson & Markhart, ; Khah & Passam, ; Pagamas & Nawata, ). Also, at <35°C night air temperature condition, the pollen viability and pollen tube behavior are reduced (Gajanayake, Trader, Reddy, & Harkess, ; Usman, Mamat, Mohd, Aishah, & Annuar, ). Thus, the control and RCP 4.5 treatments had normal shaped hot pepper fruits, while the RCP 8.5 treatment showed abnormal development (Figure b).…”