Phenotyping from lab to field – tomato lines screened for heat stress using Fv/Fm maintain high fruit yield during thermal stress in the field

Abstract

This study aimed to phenotype young tomato (Solanum lycopersicum L.) plants for heat tolerance by measuring Fv/Fm after short-term heat treatments in climate chambers and selected sensitive (low Fv/Fm) and tolerant (high Fv/Fm) cultivars to investigate their in-field performance. Twenty-eight genotypes were phenotyped at 40:28°C for 2 days in climate chambers. A second screening (four high Fv/Fm and four low Fv/Fm genotypes) was conducted for 4 days at 38:28°C, followed by 5 days’ recovery (26:20°C). The tolerant genotypes maintained high net photosynthesis (PN) and increased stomatal conductance (gs) at 38°C, allowing better leaf cooling. Sensitive genotypes had lower Fv/Fm and PN at 38°C, and gs increased less than in the tolerant group, reducing leaf cooling. Under controlled conditions, all eight genotypes had the same plant size and pollen viability, but after heat stress, plant size and pollen viability reduced dramatically in the sensitive group. Two tolerant and two sensitive genotypes were grown in the field during a heat wave (38:26°C). Tolerant genotypes accumulated more biomass, had a lower heat injury index and higher fruit yield. To our knowledge, this is the first time screening for heat tolerance by Fv/Fm in climate chambers was verified by a field trial under natural heat stress. The differences after heat stress in controlled environments were comparable to those in yield between tolerant and sensitive groups under heat stress in the field. The results suggest that Fv/Fm is effective for early detection of heat tolerance, and screening seedlings for heat sensitivity can speed crop improvement.

Integrated high-resolution phenotyping, chlorophyll fluorescence induction kinetics and photosystem II dynamics under water stress and heat in Wheat (Triticum aestivum)

“…Photosystem II (PSII) photochemistry, light energy absorption, excitation energy trapping, and conversion of excitation energy into electron flow can be targets of stress like water stress and heat and reflect on the overall growth and development of the plant (Poudyal 2019, Sasi et al 2018. Plants also respond to stress stimuli and if the stress is not eliminated in time, a rapid damage of the photosynthetic system occurs.…”

Eco-Physiological Screening of Different Tomato Genotypes in Response to High Temperatures: A Combined Field-to-Laboratory Approach

“…In this framework, it becomes important to perform studies that are able to identify the most promising genotypes able to face heat stress.The relationship between gas exchange and crop yield has been largely studied in tomato, suggesting leaf transpiration as the most reliable indicator for yield prediction under drought [12]. However, beside gas exchange, other photosynthesis related parameters [13] should be taken into account to build a "eco-physiological identity card" for different genotypes.Chlorophyll fluorescence represents a good tool to rapidly and accurately detect plant health status, the occurrence of damage within photosystem II (PSII), and to study heat tolerance in vivo [6,13,14]. The decline of maximum quantum efficiency of PSII (F v /F m ), as well as the increase of non-photochemical quenching (NPQ), are two heat-affected fluorescence parameters [15] related to photoinhibition and photoprotection mechanisms in response to high temperatures [5,10,16].…”

“…The shape of fluorescence curves changes significantly when plants switch from a healthy status to stress, giving precious information on plant capability to overcome the stress [17].Indeed, physiological screening techniques may complement phenotypic measurements and, therefore, increase the efficiency of the selection of tolerant genotypes [18]. Currently, the majority of the experiments on tomato responses to heat stress have been carried out in controlled chambers and only few studies have been performed in the field [11,14,19].On one hand, with the field approach, it is possible to screen a high number of different genotypes. On the other hand, it is not easy to separate the effects of heat stress from other environmental variables, such as light or water depletion, in inducing the plant specific responses being examined [18].…”

“…Chlorophyll fluorescence represents a good tool to rapidly and accurately detect plant health status, the occurrence of damage within photosystem II (PSII), and to study heat tolerance in vivo [6,13,14]. The decline of maximum quantum efficiency of PSII (F v /F m ), as well as the increase of non-photochemical quenching (NPQ), are two heat-affected fluorescence parameters [15] related to photoinhibition and photoprotection mechanisms in response to high temperatures [5,10,16].…”

“…Indeed, physiological screening techniques may complement phenotypic measurements and, therefore, increase the efficiency of the selection of tolerant genotypes [18]. Currently, the majority of the experiments on tomato responses to heat stress have been carried out in controlled chambers and only few studies have been performed in the field [11,14,19].…”