Identifying physiological and genetic determinants of faba bean transpiration response to evaporative demand

Mandour, Hend and Khazaei, Hamid and Stoddard, Frederick L and Dodd, Ian C (2023) Identifying physiological and genetic determinants of faba bean transpiration response to evaporative demand. Annals of Botany. ISSN 0305-7364

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Background and aims Limiting maximum transpiration rate (TR) under high vapor pressure deficit (VPD) works as a water conservation strategy. While some breeding programs have incorporated this trait into some crops to boost yields in water-limited environments, its underlying physiological mechanisms and genetic regulation remain unknown for faba bean (Vicia faba). Thus we aimed to identify genetic variation in TR response to VPD in a faba bean recombinant inbred lines (RILs) population derived from two parental lines with contrasting water use (Mélodie/2 and ILB 938/2). Methods Plants were grown in well-watered soil in a climate-controlled glasshouse with diurnally fluctuating VPD and light conditions. Whole plant transpiration was measured in a gas exchange chamber that tightly regulated VPD around the shoot under constant light, while whole-plant hydraulic conductance and its components (root and stem hydraulic conductance) were calculated from dividing TR by water potential gradients measured with a pressure chamber. Key results Although TR of Mélodie/2 increased linearly with VPD, ILB 938/2 limited its TR after 2.0 kPa. Nevertheless, Mélodie/2 had a higher leaf water potential than ILB 938/2 at both low (1.0 kPa) and high (3.2 kPa) VPD. Almost 90% of the RILs limited their TR at high VPD with a break-point (BP) range of 1.5<BP<3.0 kPa and about 10% had a linear TR response to VPD. Thirteen genomic regions contributing to minimum and maximum transpiration, and whole-plant and root hydraulic conductance, were identified on chromosomes 1 and 3, while one locus associated with BP transpiration was identified on chromosome 5. Conclusions This study provides insight into the physiological and genetic control of transpiration in faba bean and opportunities for marker-assisted selection to improve its performance in water-limited environments.

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Journal Article
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Annals of Botany
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16 Feb 2023 17:00
Last Modified:
31 Mar 2023 12:10