Responses of two main Andean crops, quinoa (Chenopodium quinoa Willd) and papa amarga (Solanum juzepczukii Buk.) to drought on the Bolivian Altiplano: Significance of local adaptation

Abstract

The Bolivian altiplano is a vast plateau that lies at an average altitude of 4000 m. It is one of the main agricultural regions of Bolivia. Intense drought and frequent frost have forced peasants to select crops that are resistant to water deficit and low temperature. This study analyses the responses to drought of the main crops on the Altiplano; quinoas (Chenopodium quinoa Willd 'Sajama' and 'Sisa') and papa amarga (bitter potato)(Solanum juzepczukii Buk. 'Luki'). The effects of drought on leaf water potential, stomatal conductance (gs), transpiration (Tr) and photosynthesis (Pn) rate and crop yields were investigated in the field under the natural climatic conditions of an agriculture dry season. The crops suffered severe water; deficit especially during the last two months of the crop cycle. Rainfall was 62 mm and the potential evapotranspiration was 186 min. Drought Caused massive drops in leaf water potential, gs, Tr and Pn in all crops. However, the dynamic of these decreases in quinoas and bitter potato were very different. There was a major, rapid stomatal closure with an associated two-thirds reduction in Tr and Pn and a great decrease in pre-dawn and minimal leaf water potentials in quinoa of the beginning of the drought period. Then, as drought continued, gs, Tr and Pn remained relatively stable while minimal potential reached values below - 4 MPa. Quinoas offset stomatal closure by improved and maintained high leaf water use efficiency (Pn/Tr = 2). The high dry matter yield (around 2500 kg ha-1) indicates the efficiency of these responses. The biter potato had a different response with a stomatal tolerance to water deficit and stable gas exchange during the first four weeks of drought, but gs, Tr and Pn decreased greatly thereafter and Pn/Tr remained relatively low (0.8) compared to quinoa during the whole experiment. Dry matter yield was lower than quinoa but remained relatively-high (1920 kg ha-1). Under the drought conditions. Pre-dawn potential of quinoas and bitter potato was closely correlated with gas-exchange rates; pre-dawn potential appears as a good criterion for water and photosynthesis responses to drought.