Powdery mildew [Leveillula taurica (L ev.) Arn] is a fungus causing epidemics on chile peppers (Capsicum sp.) worldwide. It was first observed in New Mexico in the late 1990s and has been a reoccurring issue. During the 2017 growing season, environmental conditions were highly favorable for powdery mildew development and severe infection was observed. This provided a unique opportunity to identify novel sources of resistance in Capsicum to powdery mildew. In the present study, the incidence and severity of powdery mildew was evaluated for 152 chile pepper accessions comprising different cultivars and species. Major differences in disease severity and incidence were observed among the accessions. Of the 152 accessions, 53 were resistant, i.e., received a disease index (DI) score of £1. When examining across Capsicum species, 16 Capsicum annuum accessions, all 8 Capsicum baccatum, all 21 Capsicum chinense, 5 of 6 Capsicum frutescens, the Capsicum chacoense accession, and the Capsicum rhomboideum accession were resistant. These results provide several accessions with resistance that can be used in breeding programs. Especially important are the C. annuum resistant accessions, as this resistance can be more quickly incorporated into commercially important C. annuum cultivars as compared with interspecific hybridizations.
Global climate change is having a significant effect on agriculture by causing greater precipitation variability and an increased risk of drought. To mitigate these effects, it is important to identify specific traits, adaptations, and germplasm that improve tolerance to soil water deficit. Local varieties, known as landraces, have undergone generations of farmer-mediated selection and can serve as sources of variation, specifically for tolerance to abiotic stress. Landraces can possess local adaptations, where accessions adapted to a particular environment will outperform others grown under the same conditions. We explore adaptations to water deficit in chile pepper landraces from across an environmental gradient in Mexico, a center of crop domestication and diversity, as well in improved varieties bred for the US. In the present study, we evaluated 25 US and Mexico accessions in a greenhouse experiment under well-watered and water deficit conditions and measured morphological, physiological, and agronomic traits. Accession and irrigation regime influenced plant biomass and height, while branching, CO2 assimilation, and fruit weight were all influenced by an interaction between accession and irrigation. A priori group contrasts revealed possible adaptations to water deficit for branching, CO2 assimilation, and plant height associated with geographic origin, domestication level, and pepper species. Additionally, within the Mexican landraces, the number of primary branches had a strong relationship with precipitation from the environment of origin. This work provides insight into chile pepper response to water deficit and adaptation to drought and identifies possibly tolerant germplasm.
Global climate change is having a significant effect on agriculture by causing greater precipitation variability and an increased risk of drought. To mitigate these effects, it is important to identify specific traits, adaptations, and germplasm that improve tolerance to soil water deficit. Local varieties, known as landraces, have undergone generations of farmer-mediated selection and can serve as sources of variation, specifically for tolerance to abiotic stress. Landraces can possess local adaptations, where accessions adapted to a particular environment will outperform others grown under the same conditions. We explore adaptations to water deficit in chile pepper landraces from across an environmental gradient in Mexico, a center of crop domestication and diversity, as well in improved varieties bred for the US. In the present study, we evaluated 25 US and Mexico accessions in a greenhouse experiment under well-watered and water deficit conditions and measured morphological, physiological, and agronomic traits. Accession and irrigation regime influenced biomass and height, while branching, CO2 assimilation, and fruit weight were all influenced by an interaction between accession and irrigation. A priori group contrasts revealed possible adaptations to water deficit for primary branching, CO2 assimilation, and plant height associated with geographic origin, domestication level, and pepper species. Additionally, within the Mexican landraces, the number of primary branches had a strong relationship with precipitation from the environment of origin. This work provides insight into chile pepper response to water deficit and adaptation to drought and identifies possibly tolerant germplasm.
Background Peppers, bell and chile, are a culturally and economically important worldwide. Domesticated Capsicum spp. are distributed globally and represent a complex of valuable genetic resources. Objectives Explore population structure and diversity in a collection of 467 peppers representing eight species, spanning the spectrum from highly domesticated to wild using 22,916 SNP markers distributed across the twelve chromosomes of pepper. Results These species contained varied levels of genetic diversity, which also varied across chromosomes; the species also differ in the size of genetic bottlenecks they have experienced. We found that levels of diversity negatively correlate to levels of domestication, with the more diverse being the least domesticated.
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