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“Can bean yield losses caused by drought, heat stress and climate change be ameliorated by enhancing pod-specific stomatal conductance?”

Periodic Reporting for period 2 - Pod Yield (“Can bean yield losses caused by drought, heat stress and climate change be ameliorated by enhancing pod-specific stomatal conductance?”)

Période du rapport: 2019-06-12 au 2020-06-11

Droughts in Mexico reduce agricultural production and cause major damage to livelihoods, costing £billions to the economy. Mexico’s reliance on rain-fed agriculture, and its arid zones, makes it vulnerable to drought, yield loss, and soil degradation. Mexico’s geography, population, and urbanisation with habitat loss, make it exposed to the effects of overexploitation of resources, droughts, and climate change. Common bean is the most important grain legume in human diets, and a major source of nutrition. Mexico is a centre of origin, domestication, and diversity for beans, and they are central to Mexican culture and Latin American and African food security. Drought stress is a major concern because most bean agriculture is rain-fed, not irrigated. The development of novel bean varieties and production of beans with greater climate change resilience will impact positively on the poorest communities reliant on timely rains, as well as global Food Security. The overall objectives are to identify mechanisms of drought tolerance from the related desert species, tepary bean, and translate these into common beans to improve water deficit resistance. Characterising drought responses through developmental, physiological, and transcriptomic analyses will help us understand divergent approaches to stress resilience. Stomata are microscopic valves on leaf and pod surfaces that control water loss and CO2 uptake for photosynthesis. By altering stomatal traits such as size and density, we can improve water use efficiency. In this project we compared stomatal traits across beans and used this information to enhance drought resilience to begin creating ‘Climate Smart’ bean crops for Latin American agriculture. By improving water use of bean crops, we can promote more resilient systems of production under climate change, improve economic securities for farmers and maintaining sustainable sources of healthy food.
This project combined comparative physiological and genetic analyses of drought responses in common bean with the arid zone tepary bean and incorporated observations from these responses into novel soybean transformations to test proof-of-concept methodologies for legume water use improvement. By combining transcriptomics with legume transformation and functional genomics we have identified genes involved in common bean and soybean stomatal development and epidermal patterning. These genes will allow us to modify gas exchange properties of the legumes to improve water use efficiency and drought tolerance. Our results based on tepary terminal drought experiments, suggest that reducing stomatal numbers to prolong water supply to the pod under drought is a modus of tepary. I took the same approach as I have taken successfully in rice, harnessing a universal control mechanism to modulate stomatal patterning, involving Epidermal Patterning Factors to enhance water use and drought tolerance in bean. Aided by a joint Master’s Student with Prof. Covarrubias, Brianda de la Sancha, we tested functional orthology of bean EPFs by over-expression and complementation and these data directed our decision-making. We chose to address the question using an alternative legume species, soybean and in the Return Phase we had the opportunity to test several transgenic events to observe the impact of increased EPF production in soybean leaves, consequential reduced stomatal densities, and changes in gas exchange properties. With Masters student and now-technician, Miles Bate-Weldon, we have shown that several lines have reduced pod densities and no apparent yield or seed quality penalties despite the lower stomatal densities.

During the final period, COVID-19 forced the closure of both host institutes and prevented full completion of many experimental plans, but provided time to undertake further detailed analyses, write-ups, and article submissions and publications. All on-going and new collaborative projects with IBT-UNAM were largely put on hold as UNAM was shut-down to the same degree as the University of Sheffield. Nevertheless, I was able to participate online in international stakeholder workshops, conferences, and these experiments formed the basis of new collaborations and will continue provide new results over the coming year or more.
This MSCA IF GF has set the foundation for UK-Mexico research in bean drought improvement. We have obtained transcriptomic analyses of drought tolerant bean water deficit strategies to identify new candidate genes for bean crop improvement. We have tested mutant and transgenic beans and their stomatal traits with the aim of adapting them for drought resilience under climate change. Long term positive impacts will include fewer crop losses, greater yields to improve farmer profits and community wealth and health, to improve socio-economic issues and enhanced resilience and sustainable intensification of legume agriculture. Testament to the project’s successes, we were awarded the Newton Prize Mexico 2018, as well as GCRF and Mobility Grants to continue new lines of investigation into bean crop climate resilience. Now that the MSCA IF GF is concluded, I will continue these fruitful collaborations between UNAM and Sheffield in my new role as a Research Leader in the Royal Botanic Gardens, Kew, where I will help increase the societal impacts to benefit European, Latin American, and global Food Security for years to come.
Bean flower and pod infrared thermal imaging of transpiration