Quinoa at high temperatures and saline environments. Current knowledge and insights from wild vs. domesticated quinoa temperature response comparisons

EDMUNDO PLOSCHUK ; FRANCISCO RODILLO ; DANIEL BERTERO ; RAMIRO CURTI

Laayoune

Conferencia; First International Forum on Biosaline Agriculture; 2019

Foundation Phosboucraaa e International Center for Biosaline Agriculture

Crop production in saline environments requires coping with several simultaneous stresses, of which salinity is just one of the list of problems to deal with. I requires a combination of agronomic practices and adequate selection of species and genotypes within them adressing not only current challenges but those to come. Quinoa (Chenopodium quinoa) is an halophyte plant traditionally cultivated in the Andean Region and the lowlands of Chile in South America. Because of its high salinity tolerance it is used as a model plant for physiological studies and has been introduced in several countries of the Middle East and North Africa as an alternative crop for marginal environments. Quinoa is not only a salinity tolerant crop, it is able to produce highly nutritious seeds under combinations of low precipitations, poor soils, low temperatures and high radiation, many of these limitations being found in the above mentioned countries. As part of these adaptation studies, quinoa genotypes from a range of origins were evaluated as winter crops in desert or semi-arid environments looking for high productivity and stability, productivity under saline environments or saline irrigation water, and high temperatures. In paralell to that, research conducted in several countries looked for the mechanisms behind stress tolerance in quinoa, particularly those to salinity, water deficits and low temperatures. Interactions between stresses have been much less explored, and high temperature responses are much less understood. In this conference I will review the current state of knowledge about factors related to early crop stablishment under low temperatures in mediterranean type environments (germination), grow under salinity, and high temperature responses. In a second part, I will show results of ongoing research being conducted by my team evaluating quinoa wild ancestor (Chenopodium hircinum) as a source of tolerance to stresses not found in the cultivated species. C. hircinum is a wild plant found in many environments of Argentina where stresses like high temperatures, water deficit, low temperatures and waterlogging are frequently experienced. Our current research is focused on high temperature responses, and it is hypothesized that wild quinoas originating in hot environments will exhibit better performance than quinoa under high temperatures linked to traits that could be transferred to the cultivated species. The capacity to sustain higher leaf conductances and transpiration in hot environments, leading to cooler plants, is proposed as a mechanisms explaining that performance. A pot experiment was conducted under two temperatures in glasshouses in the Faculty of Agronomy of the University of Buenos Aires, comparing 17 wild populations with 5 domesticated genotypes. These last five were not strictly quinoa but the results of crosses of several quinoa lines with Chenopodium berlandieri (another wild quinoa from North America) originating from hot environments in the United States. Temperatures remainded well above outside averages for the whole experiment (late summer to early autumm) with average, máximum and mínimum average temperatures of 23, 31.7 and 16.8 °C for the cooler glasshouse and 25, 33.3 and 19.9 °C for the hotter one. Plants were evaluated for duration of development, leaf size, chlorophyll content, specific leaf area and several photosynthetic parameters, including maximum photosynthetic rate (Pmax), leaf conductance, transpiration and instantaneous water use efficiency (P max transpiration -1). Comparison between temperatures and species showed that development was delayed by higher temperatures in most plants, but the change was mostly non significant with a máximum of 15 % and no difference between species. Chlorophyll content was systematically higher at high temperatures and in C. hircinum compared to quinoa. This temperature effect was not associated to smaller leaves, as leaf size exhibited a complex response to temperature, with some populations or genotypes showing evidence of acclimation of leaf size to higher temperatures. Specific leaf area (SLA, cm2 mg -1 leaf) variation was related more to species than temperature differences and was higher in quinoa. SLA was negatively related to chlorophyll content, but changes in neither of both variables was related to that in photosynthetic rate. Photosynthetic rates were sytematically higher in C hircinum (Pmax 29 vs 23 µ Mol cm 2 seg-1) and were negatively affected by temperature, with the exception of two quinoa genotypes, which had up to 25 % higher values under higher temperatures. Higher Pmax and transpiration rates were related to higher leaf conductances. Interesting, and in agreement with our hypothesis, some of the highest conductance values were observed in wild populations from hot environments in North West Argentina. Transpiration rate was higher at high temperatures in spite of lower conductances, and differences between temperatures were related to those in vapour pressure differences (VPD). Water use efficiencies (corrected by VPD) were negatively related to both leaf conductance and transpiration rate and not associated to Pmax. These responses need to be integrated with those at higher hierarchycal levels to value its contribution to temperature tolerance and as screening tools for large genotype collections.