Germination response of diverse wild and landrace chile peppers (Capsicum spp.) under drought stress simulated with polyethylene glycol

Authors: Bernau, Vivian; JARDÓN BARBOLLA, LEV - Universidad Nacianal Autonoma De Mexico; MCHALE, LEAH - The Ohio State University; MERCER, KRISTIN - The Ohio State University

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2020
Publication Date: 11/16/2020
Citation: Bernau, V.M., Jardón Barbolla, L., Mchale, L.K., Mercer, K.L. 2020. Germination response of diverse wild and landrace chile peppers (Capsicum spp.) under drought stress simulated with polyethylene glycol. PLoS ONE. 15(11). Article e0236001. https://doi.org/10.1371/journal.pone.0236001.
DOI: https://doi.org/10.1371/journal.pone.0236001

Interpretive Summary: Responses to drought within a single species may vary based on plant development stage, drought severity, and the avoidance or tolerance mechanisms employed by the plant. Early drought stress can restrict plant emergence and seedling growth. Thus, in areas where water is limited, rapid germination leading to early plant establishment may be beneficial. Alternatively, germination without sufficient water to support the seedling may lead to early death so reduced germination under low moisture conditions may also be an adaptive response. We studied the germination response to water stress of diverse chile pepper germplasm collected in southern Mexico from varied climate zones, cultivation systems, and of named varieties. Drought stress was simulated using a polymer solution, polyethylene glycol. Overall, survival time analysis revealed delayed germination at the 20% concentration of PEG across all ecozones. The effect was most pronounced in the genotypes from hotter, drier ecozones. Additionally, germplasm from wetter and cooler ecozones had the fastest rate of germination. Moreover, accessions of the varieties Costeño Rojo and Tusta germinated more slowly and incompletely if sourced from a drier climate than a wetter one, indicating that slower, reduced germination under drought stress may be an adaptive avoidance mechanism. Significant differences were also observed between named varieties with more domesticated types from intensive cultivation systems nearly always germinating faster than small-fruited backyard- or wild-types, perhaps due to less selection effort for the smaller-fruited accessions. Thus, we conclude that there is evidence of local adaptation to both ecozone of origin and source cultivation system in germination characteristics of diverse chile peppers.

Technical Abstract: Responses to drought within a single species may vary based on plant development stage, drought severity, and the avoidance or tolerance mechanisms employed. Early drought stress can restrict emergence and seedling growth. Thus, in areas where water availability is limited, rapid germination leading to early plant establishment may be beneficial. Alternatively, germination without sufficient water to support the seedling may lead to early senescence, so reduced germination under low moisture conditions may be adaptive at the level of the population. We studied the germination response to osmotic stress of diverse chile pepper accessions collected in southern Mexico from varied ecozones, cultivation systems, and of named landraces. Drought stress was simulated using polyethylene glycol solutions. Overall, survival time analysis revealed delayed germination at the 20% concentration of PEG across all ecozones. The effect was most pronounced in the genotypes from hotter, drier ecozones. Additionally, germplasm from wetter and cooler ecozones had the fastest rate of germination. Moreover, accessions of the landraces Costeño Rojo and Tusta germinated more slowly and incompletely if sourced from a drier ecozone than a wetter one, indicating that slower, reduced germination under drought stress may be an adaptive avoidance mechanism. Significant differences were also observed between named landraces, with more domesticated types from intensive cultivation systems nearly always germinating faster than small-fruited backyard- or wild-types, perhaps due to less selection for smaller-fruited accessions. Thus, we conclude that there is evidence of local adaptation to both ecozone of origin and source cultivation system in germination characteristics of diverse chile peppers.