Abstract
Crop wild relatives of sweetpotato [Ipomoea series Batatas (Choisy) D. F. Austin] are a group of species with potential for use in crop improvement programs seeking to breed for drought tolerance. Stress memory in this group could enhance these species’ physiological response to drought, though no studies have yet been conducted in this area. In this pot experiment, drought tolerance, determined using secondary traits, was tested in 59 sweetpotato crop wild relative accessions using potential short-term memory induction. For this purpose, accessions were subjected to two treatments, i) non-priming: full irrigation (up to field capacity, 0.32 w/w) from transplanting to harvest and ii) priming: full irrigation from transplanting to flowering onset (FO) followed by a priming process from FO to harvest. The priming process consisted of three water restriction periods of increasing length (8, 11, and 14 days) followed each by a recovery period of 14 days with full irrigation. Potential stress memory induction was calculated for each accession based on ecophysiological indicators such as senescence, foliar area, leaf-minus-air temperature, and leaf 13C discrimination. Based on total biomass production, resilience and production capacity were calculated per accession to evaluate drought tolerance. Increase in foliar area, efficient leaf thermoregulation, improvement of leaf photosynthetic performance, and delayed senescence were identified in 23.7, 28.8, 50.8, and 81.4% of the total number of accessions, respectively. It was observed that under a severe drought scenario, a resilient response included more long-lived green leaf area while a productive response was related to optimized leaf thermoregulation and gas exchange. Our preliminary results suggest that I. triloba and I. trifida have the potential to improve sweetpotato resilience in dry environments and should be included in introgression breeding programs of this crop. Furthermore, I. splendor-sylvae, I. ramosissima, I. tiliacea, and wild I. batatas were the most productive species studied but given the genetic barriers to interspecific hybridization between these species and sweetpotato, we suggest that further genetic and metabolic studies be conducted on them. Finally, this study proposes a promising method for improving drought tolerance based on potential stress-memory induction, which is applicable both for wild species and crops.
Highlights
In 2018, sweetpotato [Ipomoea batatas (L.) Lam.] was the root crop with the second highest global production after cassava [Manihot esculenta Crantz] (FAO, 2020)
Effects of the water treatment for ChlSPAD, foliar area (FA), and dT were significant (p < 0.05) for 33.9, 81.4, and 81.4% of the total accessions and the effect of time was significant in all accessions for ChlSPAD, FA, and dT
Primed accessions in this study showed physiological mechanisms that enable plants to cope with severe drought conditions
Summary
In 2018, sweetpotato [Ipomoea batatas (L.) Lam.] was the root crop with the second highest global production after cassava [Manihot esculenta Crantz] (FAO, 2020). Sweetpotato is known for its ability to grow in droughtprone soils with low external input (fertilizer and pesticide) requirements, while thanks to a short growing cycle, it is recognized as an excellent crop for post-crisis (hurricane, flooding, refugee settlement, etc.) situations (Bradbury and Holloway, 1987; Mwanga and Ssemakula, 2011; Mekonnen et al, 2015). Climate change’s negative effect on sweetpotato productivity is of rising concern in regions affected by increasing global temperatures, such as tropical and subtropical areas of Sub-Saharan Africa (Low et al, 2009; Schulze, 2011; Knox et al, 2012). Resilient sweetpotato varieties could play an extremely important food and nutrition security role in the developing world, one that will increase in importance as the availability of good cropping areas becomes more limited
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