Response of a Diverse European Soybean Collection to “Short Duration” and “Long Duration” Drought Stress

Abstract

Drought causes significant damage to a high value crop of soybean. Europe has an increasing demand for soybean and its own production is insufficient. Selection and breeding of cultivars adapted to European growth conditions is therefore urgently needed. These new cultivars must have a shorter growing cycle (specifically for adaptation to North-West Europe), high yield potential under European growing conditions, and sufficient drought resistance. We have evaluated the performance of a diverse collection of 359 soybean accessions under drought stress using rain-out shelters for 2 years. The contrasting weather conditions between years and correspondingly the varying plant responses demonstrated that the consequences of drought for an individual accession can vary strongly depending on the characteristics (e.g., duration and intensity) of the drought period. Short duration drought stress, for a period of four to 7 weeks, caused an average reduction of 11% in maximum canopy height (CH), a reduction of 17% in seed number per plant (SN) and a reduction of 16% in seed weight per plant (SW). Long duration drought stress caused an average reduction of 29% in CH, a reduction of 38% in SN and a reduction of 43% in SW. Drought accelerated plant development and caused an earlier cessation of flowering and pod formation. This seemed to help some accessions to better protect the seed yield, under short duration drought stress. Drought resistance for yield-related traits was associated with the maintenance of growth under long duration drought stress. The collection displayed a broad range of variation for canopy wilting and leaf senescence but a very narrow range of variation for crop water stress index (CWSI; derived from canopy temperature data). To the best of our knowledge this is the first study reporting a detailed investigation of the response to drought within a diverse soybean collection relevant for breeding in Europe.

Genetic control of resistance to drought stress in soybean

“…Slow or delayed wilting is known to be a complex trait, that can be the result of several underlying mechanisms in soybean: (i . We have shown a large level of variation for drought index for canopy height (CH-Yr) and number of pods per main stem (PPS-Yr) in the EUCLEG soybean collection [23]. Some accessions were able to maintain high CH and displayed no reduction in the number of pods per plant (NPP), but the relationship between these traits and CW was not clear.…”

“…Responses and traits of relevance for adaptation to drought, and their interactions, were identi ed. Furthermore, we demonstrated a differential response of the accessions to short duration and long duration drought stress [23]. The EUCLEG collection displayed a wide range of phenotypic variation in drought response for maximum absolute growth rate (AGRmax), maximum canopy height (CH), leaf senescence (LSEN) and canopy wilting (CW).…”

“…Here we build further on these two studies [23,60] and report on a GWAS analysis on drought resistance in the EUCLEG soybean collection. Our main goal is to understand the genetic control of drought resistance in this collection of early maturing types.…”

“…Our knowledge of drought resistance in crops is fragmentary, but it is known that multiple plant characteristics and genomic loci in uence the ability of plants to withstand drought stress [10,[18][19][20]. Furthermore, the timing, duration and intensity of the drought stress situation can strongly in uence the plant responses [21][22][23][24]. Therefore, understanding the genetic basis of drought resistance is crucial to get a better insight in resistance mechanisms and for harnessing the genomic regions involved for crop improvement [25][26][27].…”

“…In previous work [23] we investigated the response to drought at the reproductive stage of a collection of early maturing soybean accessions (MG000-II) of relevance for breeding in Europe (the EUCLEG collection). Responses and traits of relevance for adaptation to drought, and their interactions, were identi ed.…”