Screening for Barley Waterlogging Tolerance in Nordic Barley Cultivars (Hordeum vulgare L.) Using Chlorophyll Fluorescence on Hydroponically-Grown Plants

Abstract

Waterlogging can reduce crop yield by 20%-50% or more, and lack of efficient selection methods is an obstacle in plant breeding. The methods currently used are mainly indices based on germination ability in Petri dishes and leaf chlorosis in plants grown in waterlogged soils. Cultivation in oxygen-depleted nutrient solution is the ultimate waterlogging system. Therefore methods based on root growth inhibition and on fluorescence in plant material hydroponically grown in oxygen-depleted solution were evaluated against data on biomass accumulation in waterlogged soils. Both traits were correlated with waterlogging tolerance in soil, but since it was easier to measure fluorescence, this method was further evaluated. A selection of F 2 plants with high and low fluorescence revealed a small but significant screening effect in F 3 plants. A test of 175 Nordic cultivars showed large variations in chlorophyll fluorescence in leaves from oxygen-stressed seedlings, indicating that adaptation to waterlogging has gradually improved over the past 40-50 years with the introduction of new cultivars onto the market. However, precipitation also increased during the period and new cultivars may have inadvertently been adapted to this while breeding barley for grain yield. The results suggest that the hydroponic method can be used for screening barley populations, breeding lines or phenotyping of populations in developing markers for quantitative trait loci.

QTL for chlorophyll fluorescence of barley plants grown at low oxygen concentration in hydroponics to simulate waterlogging

“…Residual biomass was strongly correlated with QY in the study by Bertholdsson (2013), suggesting a direct relationship QY could thus be used instead of the more labour-demanding residual biomass. The hydroponic cultivation method in combination with leaf fluorescence measurements was therefore used in the present study for phenotyping a double-haploid (DH) population where the parents segregated both for waterlogging in soil and QY.…”

“…Chlorophyll fluorescence is widely accepted as an indicator of the activity of PSII, which is involved in electron transport in plant photosynthesis and is particularly sensitive to stresses (Fracheboud et al 2004;Guo et al 2008;Gu et al 2012). Various fluorescence parameters have been found to be closely correlated with carbon assimilation under different stresses in rice (Guo et al 2008), lucerne (Smethurst and Shabala 2003), soybean (Yin et al 2010), wheat ) and maize (Fracheboud et al 2004), as well as grain yield in barley (Bertholdsson 2013) and, under optimal conditions intriticale (Hura et al 2009). Fluorescence parameters has also been used for mapping QTL in relation to drought stress in wheat (Czyczyło-Mysza et al 2011), rice (Gu et al 2012) and barley (Guo et al 2008;Wójcik-Jagla et al 2013), salt tolerance in barley (Aminfar et al 2011) and biomass and yield in wheat (Czyczylo-Mysza et al 2013).…”

“…Differences in waterlogging tolerance (WLT) are among the factors determining grain yield. Breeding for grain yield in barley has therefore led indirectly, to improved WLT in the last 50 years (Bertholdsson 2013). However, direct screening should probably be more efficient.…”

“…Fluorescence parameters has also been used for mapping QTL in relation to drought stress in wheat (Czyczyło-Mysza et al 2011), rice (Gu et al 2012) and barley (Guo et al 2008;Wójcik-Jagla et al 2013), salt tolerance in barley (Aminfar et al 2011) and biomass and yield in wheat (Czyczylo-Mysza et al 2013). However, to our knowledge there have been no previous efforts to associate chlorophyll fluorescence with WLT, besides research by Pang et al (2004) and Bertholdsson (2013), who used it to characterise WLT of barley cultivars.…”

“…The latter method was used by Zhou (2011) to obtain more accurate phenotyping. Bertholdsson (2013) developed a hydroponic method with cultivation of plantlets in O 2 -depleted nutrient solution, which allows many plants to be tested in a limited space under fully controlled growth conditions. In his study, the growth reduction under hypoxia stress was correlated with results obtained in soil studies, and also with the chlorophyll fluorescence parameter quantum yield (QY) of electron transport for photosystem (PS) II (Genty et al 1989).…”