Physiological traits for drought phenotyping in cotton

Abstract

ABSTRACT. The objective of this study was to identify physiological traits that could distinguish between cotton genotypes that were tolerant or sensitive to water deficits. The experiment was conducted in a completely randomized design through a factorial combination to analyze four genotypes (BRS 187 8H and ACALA SJ-4 -water deficit tolerant; CNPA 7H and SU-0450/8909 -water deficit sensitive) and two water regimes (watered/always irrigated and stressed/with a water deficit imposed at flowering). Irrigation was suspended for the plants in the water deficit treatment groups when their first flowers appeared. Leaf water potential (ψpd) was monitored until the plants reached -3.0 MPa predawn, at which point leaf samples were collected for analysis. The plants were reirrigated and monitored for a recovery to 50% of leaf water potential. The maximum photochemical efficiency (Fv/Fm), chlorophyll content (SPAD index), relative water content (RWC), disruption of the cell membrane via membrane leakage, carbon isotope composition (δ 13 C), seed cotton yield and fiber quality were evaluated. The trends in membrane leakage and carbon isotope composition were different between the tolerant and sensitive genotypes under a water deficit, which makes these physiological traits suitable for screening for tolerance to water deficits in cotton.Keywords: abiotic stress, Gossypium, water deficit.RESUMO. Traços fisiológicos para fenotipagem de algodoeiro sob seca. Objetivou-se identificar variáveis fisiológicas para distinguir genótipos de algodoeiro tolerantes e sensíveis ao déficit hídrico. O experimento foi conduzido no delineamento inteiramente casualizado em arranjo fatorial, sendo testados quatro genótipos (BRS 187 8H e ACALA SJ-4 -tolerante ao déficit hídrico; CNPA 7H e SU-0450/8909 -sensíveis ao déficit hídrico) e dois regimes hídricos (controle -sempre irrigado e com déficit hídrico imposto na emissão da primeira flor. Na emissão da primeira flor, a irrigação foi suspensa para o grupo a ser submetido ao déficit hídrico. O potencial hídrico foliar foi monitorado na antemanhã até que as plantas dos cultivares em estudo atingissem -3,0 MPa, ponto no qual coletaram-se amostras foliares para análises fisiológicas. Após, irrigou-se as plantas até a obtenção de valor superior a 50% do potencial hídrico foliar (-1,50 MPa). Avaliaram-se a eficiência fotoquímica máxima (Fv/Fm), o conteúdo de clorofila via índice SPAD, o conteúdo relativo de água (CRA), o extravasamento de eletrólitos, a composição isotópica do carbono (δ 13 C), o rendimento de algodão em caroço por planta e a qualidade da fibra. A disruptura de membrana via extravasamento de eletrólitos e a δ 13 C apresentaram-se como potenciais indicadores fisiológicos visando a seleção de genótipos de algodoeiro tolerantes ao déficit hídrico.Palavras-chave: estresse abiótico, Gossypium, déficit hídrico.

Carbon isotope fractionation for cotton genotype selection

“…However, for the selection of plants with high-performing yield components, when plants are grown under unfavorable conditions including water deficiency, the time-consuming mapping of quantitative traits, such as yield and stress tolerance, is difficult because genotypes are never unambiguously inferred from the phenotype. Additionally, estimating WUE relies either on long-term measurements of plant-water consumption or assessments of biomass production; and these large-scale approaches are not feasible in individual plant screening efforts (Blum, 2009;Brito et al, 2011;Tuberosa et al, 2011). As a complementary selection strategy, carbon isotope discrimination (∆) -an indirect indicator for WUE (Farquhar et al, 1989;Brito et al, 2011;Elazab et al, 2012) that correlates closely with water deficit tolerance (Centritto et al, 2009) -can be used as a phenomic facility for plant selection procedures under field condition, saving cost and time-consuming in expensive testing in cotton breeding programs.…”

“…Additionally, estimating WUE relies either on long-term measurements of plant-water consumption or assessments of biomass production; and these large-scale approaches are not feasible in individual plant screening efforts (Blum, 2009;Brito et al, 2011;Tuberosa et al, 2011). As a complementary selection strategy, carbon isotope discrimination (∆) -an indirect indicator for WUE (Farquhar et al, 1989;Brito et al, 2011;Elazab et al, 2012) that correlates closely with water deficit tolerance (Centritto et al, 2009) -can be used as a phenomic facility for plant selection procedures under field condition, saving cost and time-consuming in expensive testing in cotton breeding programs. As it has been extensively established, the link between Δ and WUE is predicated on the concept that both are functionally dependent on intercellular CO 2 concentration (c i ) (Farquhar et al, 1989).…”

1-Methylcyclopropene and Aminoethoxyvinylglycine effects on yield components of field-grown cotton

“…early cotton boll development, during which the plants demand for water is significantly increased. The occurrence of a water deficit, particularly during the reproductive phase, can negatively impact the physiology, growth and yield of the cotton crop (SARANGA et al 2004;ULLAH et al, 2008;BRITO et al, 2011). This report demonstrates that, in general, the ethylene inhibitor applications mitigated the effects of water deficit on the SCY and FY.…”

“…Water deficit is a very important ecological factor resulting in yield reduction and year-to-year variability in cotton productivity (BRITO et al, 2011). The water demand for Santa Helena de Goiás is the accumulation of approximately 400 mm of rainfall from the first square emission until the cut out phase (unpublished data).…”

“…Thus, under field conditions, cotton plants are often exposed to environmental stresses, such as unfavorable temperatures, solar radiation and water availability, particularly during critical stages and during the initial reproductive phase and boll development. During these phases, stress alters the hormone balance and triggers the activation of pathways involved in the stress response, resulting in the abscission of squares and young bolls and the abortion of flowers, causing a reduced seed cotton yield and, consequently, lower fiber yield (STEWART, 2010;BRITO et al, 2011). Additionally, an increase in reproductive structure shedding occurs through an increase in ethylene production (STEWART et al, 2010).…”