Physiological Basis of Salt Stress Tolerance in a Landrace and a Commercial Variety of Sweet Pepper (Capsicum annuum L.)

Abstract

Salt stress is one of the most impactful abiotic stresses that plants must cope with. Plants’ ability to tolerate salt stress relies on multiple mechanisms, which are associated with biomass and yield reductions. Sweet pepper is a salt-sensitive crop that in Mediterranean regions can be exposed to salt build-up in the root zone due to irrigation. Understanding the physiological mechanisms that plants activate to adapt to soil salinization is essential to develop breeding programs and agricultural practices that counteract this phenomenon and ultimately minimize yield reductions. With this aim, the physiological and productive performances of Quadrato D’Asti, a common commercial sweet pepper cultivar in Italy, and Cazzone Giallo, a landrace of the Campania region (Italy), were compared under different salt stress treatments. Quadrato D’Asti had higher tolerance to salt stress when compared to Cazzone Giallo in terms of yield, which was associated with higher leaf biomass vs. fruit ratio in the former. Ion accumulation and profiling between the two genoptypes revealed that Quadrato D’Asti was more efficient at excluding chloride from green tissues, allowing the maintenance of photosystem functionality under stress. In contrast, Cazzone Giallo seemed to compartmentalize most sodium in the stem. While sodium accumulation in the stems has been shown to protect shoots from sodium toxicity, in pepper and/or in the specific experimental conditions imposed, this strategy was less efficient than chloride exclusion for salt stress tolerance.

Polyphasic OKJIP Chlorophyll a Fluorescence Transient in a Landrace and a Commercial Cultivar of Sweet Pepper (Capsicum annuum, L.) under Long-Term Salt Stress

“…The leaf model pipelines indicated that after long-term salinity conditions, ETo/CS M in S120 was halved in QA and reduced to 30% in CG as compared to S0 (Figure 6), so it was the potential capacity of CO 2 fixation. These data corroborate the reduction in yield under high salinity of 49% in the commercial cultivar and 82% in the landrace reported in a previous paper for the same experiment [40].…”

“…More precisely, the less the thermal dissipation, the more the photodamage [ 54 ]. Under sustained stress conditions, as it was for S120 treatment that showed low CO 2 assimilation since DAT 102 [ 40 ], these mechanisms may result insufficient. Further investigations are required to quantify NPQ mechanisms to confirm this assertion in the two pepper genotypes under our experimental conditions.…”

“…The authors reported that impaired photosynthetic capacity was associated with chlorophyll degradation not caused by Na+, disrupting chloride homeostasis in the chloroplasts. We observed a significant stress effect on the chlorophyll content index (CCI) measured on DAT 85 [ 40 ]. CCI in the control plants was 13% statistically significantly higher in CG than QA.…”

“…CCI in the control plants was 13% statistically significantly higher in CG than QA. However, CCI in S120 decreased by 31% in CG as compared to the control, while no stress effect occurred in QA [ 40 ]. The green deepness of the leaf model in Figure 6 also shows that long-term salt stress caused a higher reduction in chlorophyll content of CG than QA.…”

“…This species shows some salt tolerance differences among cultivars [ 37 , 38 , 39 ]. In a long-term salt-stress experiment, [ 40 ] Giorio et al (2020) tested the hypothesis of higher salt stress tolerance of a traditional landrace than a widely spread high-yield commercial cultivar. Nevertheless, the commercial cultivar showed better salt tolerance than the landrace in terms of yield reduction.…”