Distributions, conservation status, and abiotic stress tolerance potential of wild cucurbits (Cucurbita L.)

Abstract

Crop wild relatives-wild species closely related to cultivated plants-are valuable genetic resources for crop improvement, but gaps in knowledge constrain their conservation and limit their further use. We develop new information on the distributions, potential breeding value, and conservation status of the 16 known wild relatives of cultivated pumpkins, squashes, zucchini, and gourds (Cucurbita L.). The taxa occur from the central USA to Central America, plus two South American species, with the greatest richness in central Mexico and the western borderlands between Mexico and the USA. We determine the majority of species are of medium priority for conservation, both with regard to collecting for ex situ maintenance, and for enhanced habitat protection. Summary• Crop wild relatives are valuable genetic resources for crop improvement.Knowledge gaps, including with regard to taxonomy, distributions, and characterization for traits of interest constrain their use in plant breeding. These deficiencies also affect conservation planning, both with regard to in situ habitat protection, and further collection of novel diversity for ex situ maintenance.• Here we model the potential ranges of all 16 known wild cucurbit taxa (Cucurbita L.), use ecogeographic information to infer their potential adaptations to abiotic stresses, and assess their ex situ and in situ conservation status.• The taxa occur from the central USA to Central America, plus two South American species. Predicted taxon richness was highest in central Mexico and in the western borderlands between Mexico and the USA. We find substantial ecogeographic variation both across taxa and among populations within taxa, with regard to low temperatures, high and low precipitation, and other adaptations of potential interest for crop breeding.• We categorize 13 of the taxa medium priority for further conservation as a combination of the ex situ and in situ assessments, two low priority, and one sufficiently

Modelled distributions and conservation priorities of wild sorghums (Sorghum Moench)

“…(2020) and Khoury, Carver, Kates, et al. (2020), with four scores calculated for both ex situ and in situ schemes. All scores had a scale of 0–100, with 0 representing extremely poor conservation, and 100 representing complete conservation.…”

Main Challenges and Actions Needed to Improve Conservation and Sustainable Use of Our Crop Wild Relatives

“…When looking at the primary genepool, 242 of the 1667 CWR taxa included in the Harlan and de Wet CWRs inventory were found to be under-represented in ex situ collections and the countries identified as the highest priority for further germplasm collecting are China, Mexico, and Brazil [29]. Khoury et al [77] used gap analysis to assess the degree of representation of Cucurbita CWR taxa in conservation in situ, as well as ex situ in genebanks and botanic gardens. For the Cucurbita genus, including 16 CWR and six cultivated species, the authors established detailed taxon-related ex situ, as well as in situ (i.e., protected areas) conservation priorities and suggested further in situ protected areas that would cover the greatest amount of populations of the largest number of taxa.…”

“…For the Cucurbita genus, including 16 CWR and six cultivated species, the authors established detailed taxon-related ex situ, as well as in situ (i.e., protected areas) conservation priorities and suggested further in situ protected areas that would cover the greatest amount of populations of the largest number of taxa. Khoury et al [77] concluded that 68.8% of wild Cucurbita taxa were assessed as high or medium priority for further collecting for ex situ conservation and 81.3% had a high or medium priority for further protection in situ, including all of the progenitors of the cultivated species. Furthermore, four taxa were listed as having very few accessions and, thus, very limited diversity is available for crop breeding.…”

“…Furthermore, four taxa were listed as having very few accessions and, thus, very limited diversity is available for crop breeding. Khoury et al [77] suggested that these figures might be considered as 'typical' for the CWRs at large.…”

The Potential of Payment for Ecosystem Services for Crop Wild Relative Conservation

“…It is important to note that CWR occur not only in wild ecosystems but also in disturbed and in human managed environments including in and around agricultural fields. While these may be considered as locally useful resources by farmers, wild-harvesters and others, they also may be regarded as agricultural nuisances, for example in wild pumpkins ( Cucurbita L.), where populations close to agricultural fields in the United States and Mexico may be purposely extirpated because the gene flow can introduce bitterness into the fruit of cucurbit crops [ 45 ].…”