Sink Strength Maintenance Underlies Drought Tolerance in Common Bean

Abstract

Drought is a major limiter of yield in common bean, decreasing food security for those who rely on it as an important source of protein. While drought can have large impacts on yield by reducing photosynthesis and therefore resources availability, source strength is not a reliable indicator of yield. One reason resource availability does not always translate to yield in common bean is because of a trait inherited from wild ancestors. Wild common bean halts growth and seed filling under drought and awaits better conditions to resume its developmental program. This trait has been carried into domesticated lines, where it can result in strong losses of yield in plants already producing pods and seeds, especially since many domesticated lines were bred to have a determinate growth habit. This limits the plants ability to produce another flush of flowers, even if the first set is aborted. However, some bred lines are able to maintain higher yields under drought through maintaining growth and seed filling rates even under water limitations, unlike their wild predecessors. We believe that maintenance of sink strength underlies this ability, since plants which fill seeds under drought maintain growth of sinks generally, and growth of sinks correlates strongly with yield. Sink strength is determined by a tissue’s ability to acquire resources, which in turn relies on resource uptake and metabolism in that tissue. Lines which achieve higher yields maintain higher resource uptake rates into seeds and overall higher partitioning efficiencies of total biomass to yield. Drought limits metabolism and resource uptake through the signaling molecule abscisic acid (ABA) and its downstream affects. Perhaps lines which maintain higher sink strength and therefore higher yields do so through decreased sensitivity to or production of ABA.

In situpod growth rate reveals contrasting diurnal sensitivity to water deficit inPhaseolus vulgaris

“…Recent reviews have emphasized improving rates of photosynthesis as a means to increase yield ( Long et al , 2006 ; Hogy et al , 2010 ; Zhu et al , 2010 ). More recently, the need to consider other factors that contribute to the development of sink and reproductive structures has been highlighted ( Braun et al , 2014 ; Körner, 2015 ; White et al , 2016 ; Chang et al , 2017 ; Smith et al , 2018 ; Hageman et al , 2020 ; Hageman and Van Volkenburgh, 2021 ). Whilst yield development is undoubtedly under multigenic control and influenced by a range of factors, numerous investigations have sought to characterize pre-determinates of yield for use in monitoring and selection programmes (e.g.…”

Water Shortage Affects Vegetative and Reproductive Stages of Common Bean (Phaseolus vulgaris) Chilean Landraces, Differentially Impacting Grain Yield Components

“…Abiotic stresses such as high temperature and drought in early reproductive stages often result in failure of fertilization or abortion of seeds [ 52 , 53 , 54 , 55 ] and consequently a reduced yield. Additionally, stress causes reduced photosynthesis that negatively impacts the source strength for the fixation of carbohydrates, which is an additive to the transport limitation of photosynthates to sink organs [ 29 , 31 ].…”

“…However, the RLAE appears to be a key factor in grain yield, where Bayote was highly delayed during RW compared with OW, in contrast to Coyunda. Evidence from other researchers has demonstrated that a conservative leaflet growth strategy mediated by water availability during early plant development has a lower effect on yield [ 29 , 58 ]. This suggests that in contrast to the effect observed under the vegetative state, during the reproductive phase, sink strength is increased for indeterminate landraces (new leaves, flowers, and pods).…”

“…Both parameters consistently present significant correlations with yield under water stress [ 27 ]. Recently, it was reported that sink strength plays a key role in the drought tolerance of common bean [ 28 , 29 ]. Sink strength is determined by the ability of a tissue to acquire resources, which relies on resource uptake and metabolism in that tissue.…”

“…Sink strength is determined by the ability of a tissue to acquire resources, which relies on resource uptake and metabolism in that tissue. It has been observed that plants that are able to fill seeds under drought maintain the growth of sinks, which correlates strongly with grain yield [ 28 , 29 ].…”