Search

Introduction: Although drought resistance of a plant may be achieved through morphological, structural, physiological, cellular, and molecular adaptations, most studies remain limited to quantifying the effect of drought on biomass., Methods: Using a highthroughput phenotypic imaging system, we evaluated the drought resistance of 151 bean accessions (Phaseolinae; Fabaceae) in an explorative approach, by quantifying five different traits simultaneously: biomass, water use efficiency (WUE), relative water content (RWC), chlorophyll content (NDVI), and root/shoot ratio. Since crop wild relatives are important resources for breeding programs, we analyzed both wild and cultivated accessions, most of which have never been evaluated for drought resistance before., Results: We demonstrate that the five traits are affected very differently by drought in the studied accessions, with significant correlations existing only between the biomass and WUE indicators (r=0.39), and between the RWC and NDVI indicators (r=0.40). When grouping accessions by subgenus or by species, large intraspecific and withinsubgenus variation was found. For this reason, we performed a cluster analysis, which grouped the accessions into five distinct clusters with similar response profiles. We also correlated the drought resistance for each accession to local climate variables at their original collection sites. The biomass, WUE, and RWC indicators were significantly correlated to annual precipitation (r=0.40, r=0.20, r=0.22, respectively), confirming that accessions from arid environments are generally more drought resistant., Discussion: Our results demonstrate that the drought resistance of Phaseolinae beans is a multifaceted characteristic and cannot be simply quantified through biomass. Furthermore, the broader knowledge of the drought resistance of the accessions studied here may prove an invaluable resource for future crop production., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Verheyen, Dhondt, Abbeloos, Eeckhout, Janssens, Leyns, Scheldeman, Storme and Vandelook.)

Peach palm (Bactris gasipaes Kunth) has had a central place in the livelihoods of people in the Americas since pre-Columbian times, notably for its edible fruits and multi-purpose wood. The botanical taxon includes both domesticated and wild varieties. Domesticated var gasipaes is believed to derive from one or more of the three wild types of var. chichagui identified today, although the exact dynamics and location of the domestication are still uncertain. Drawing on a combination of molecular and phenotypic diversity data, modeling of past climate suitability and existing literature, we present an integrated hypothesis about peach palm's domestication. We support a single initial domestication event in south western Amazonia, giving rise to var. chichagui type 3, the putative incipient domesticate. We argue that subsequent dispersal by humans across western Amazonia, and possibly into Central America allowed for secondary domestication events through hybridization with resident wild populations, and differential human selection pressures, resulting in the diversity of present-day landraces. The high phenotypic diversity in the Ecuadorian and northern Peruvian Amazon suggest that human selection of different traits was particularly intense there. While acknowledging the need for further data collection, we believe that our results contribute new insights and tools to understand domestication and dispersal patterns of this important native staple, as well as to plan for its conservation.

For most crops, like Capsicum, their diversity remains under-researched for traits of interest for food, nutrition and other purposes. A small investment in screening this diversity for a wide range of traits is likely to reveal many traditional varieties with distinguished values. One objective of this study was to demonstrate, with Capsicum as model crop, the application of indicators of phenotypic and geographic diversity as effective criteria for selecting promising genebank accessions for multiple uses from crop centers of diversity. A second objective was to evaluate the expression of biochemical and agromorphological properties of the selected Capsicum accessions in different conditions. Four steps were involved: 1) Develop the necessary diversity by expanding genebank collections in Bolivia and Peru; 2) Establish representative subsets of ~100 accessions for biochemical screening of Capsicum fruits; 3) Select promising accessions for different uses after screening; and 4) Examine how these promising accessions express biochemical and agromorphological properties when grown in different environmental conditions. The Peruvian Capsicum collection now contains 712 accessions encompassing all five domesticated species (C. annuum, C. chinense, C. frutescens, C. baccatum, and C. pubescens). The collection in Bolivia now contains 487 accessions, representing all five domesticates plus four wild taxa (C. baccatum var. baccatum, C. caballeroi, C. cardenasii, and C. eximium). Following the biochemical screening, 44 Bolivian and 39 Peruvian accessions were selected as promising, representing wide variation in levels of antioxidant capacity, capsaicinoids, fat, flavonoids, polyphenols, quercetins, tocopherols, and color. In Peru, 23 promising accessions performed well in different environments, while each of the promising Bolivian accessions only performed well in a certain environment. Differences in Capsicum diversity and local contexts led to distinct outcomes in each country. In Peru, mild landraces with high values in health-related attributes were of interest to entrepreneurs. In Bolivia, wild Capsicum have high commercial demand.

The sensory quality and the contents of quality-determining chemical compounds in unfermented and fermented cocoa from 100 cacao trees (individual genotypes) representing groups of nine genotype spectra (GG), grown at smallholder plantings in the municipality of Waslala, Nicaragua, were evaluated for two successive harvest periods. Cocoa samples were fermented using a technique mimicking recommended on-farm practices. The sensory cocoa quality was assessed by experienced tasters, and seven major chemical taste compounds were quantified by near infrared spectrometry (NIRS). The association of the nine, partially admixed, genotype spectra with the analytical and sensory quality parameters was tested. The individual parameters were analyzed as a function of the factors GG and harvest (including the date of fermentation), individual trees within a single GG were used as replications. In fermented cocoa, significant GG-specific differences were observed for methylxanthines, theobromine-to-caffeine (T/C) ratio, total fat, procyanidin B5 and epicatechin, as well as the sensory attributes global score, astringency, and dry fruit aroma, but differences related to harvest were also apparent. The potential cocoa yield was also highly determined by the individual GG, although there was significant tree-to-tree variation within every single GG. Non-fermented samples showed large harvest-to-harvest variation of their chemical composition, while differences between GG were insignificant. These results suggest that selection by the genetic background, represented here by groups of partially admixed genotype spectra, would be a useful strategy toward enhancing quality and yield of cocoa in Nicaragua. Selection by the GG within the local, genetically segregating populations of seed-propagated cacao, followed by clonal propagation of best-performing individuals of the selected GG could be a viable alternative to traditional propagation of cacao by seed from open pollination. Fast and gentle air-drying of the fermented beans and their permanent dry storage were an efficient and comparatively easy precondition for high cocoa quality.

There is a growing call for inventories that evaluate geographic patterns in diversity of plant genetic resources maintained on farm and in species' natural populations in order to enhance their use and conservation. Such evaluations are relevant for useful tropical and subtropical tree species, as many of these species are still undomesticated, or in incipient stages of domestication and local populations can offer yet-unknown traits of high value to further domestication. For many outcrossing species, such as most trees, inbreeding depression can be an issue, and genetic diversity is important to sustain local production. Diversity is also crucial for species to adapt to environmental changes. This paper explores the possibilities of incorporating molecular marker data into Geographic Information Systems (GIS) to allow visualization and better understanding of spatial patterns of genetic diversity as a key input to optimize conservation and use of plant genetic resources, based on a case study of cherimoya (Annona cherimola Mill.), a Neotropical fruit tree species. We present spatial analyses to (1) improve the understanding of spatial distribution of genetic diversity of cherimoya natural stands and cultivated trees in Ecuador, Bolivia and Peru based on microsatellite molecular markers (SSRs); and (2) formulate optimal conservation strategies by revealing priority areas for in situ conservation, and identifying existing diversity gaps in ex situ collections. We found high levels of allelic richness, locally common alleles and expected heterozygosity in cherimoya's putative centre of origin, southern Ecuador and northern Peru, whereas levels of diversity in southern Peru and especially in Bolivia were significantly lower. The application of GIS on a large microsatellite dataset allows a more detailed prioritization of areas for in situ conservation and targeted collection across the Andean distribution range of cherimoya than previous studies could do, i.e. at province and department level in Ecuador and Peru, respectively.

Significant cocoa production in the municipality of Waslala, Nicaragua, began in 1961. Since the 1980s, its economic importance to rural smallholders increased, and the region now contributes more than 50% of national cocoa bean production. This research aimed to assist local farmers to develop production of high-value cocoa based on optimal use of cacao biodiversity. Using microsatellite markers, the allelic composition and genetic structure of cacao was assessed from 44 representative plantings and two unmanaged trees. The population at Waslala consists of only three putative founder genotype spectra (lineages). Two (B and R) were introduced during the past 50 years and occur in >95% of all trees sampled, indicating high rates of outcrossing. Based on intermediate allelic diversity, there was large farm-to-farm multilocus genotypic variation. GIS analysis revealed unequal distribution of the genotype spectra, with R being frequent within a 2 km corridor along roads, and B at more remote sites with lower precipitation. The third lineage, Y, was detected in the two forest trees. For explaining the spatial stratification of the genotype spectra, both human intervention and a combination of management and selection driven by environmental conditions, appear responsible. Genotypes of individual trees were highly diverse across plantings, thus enabling selection for farm-specific qualities. On-farm populations can currently be most clearly recognized by the degree of the contribution of the three genotype spectra. Of two possible strategies for future development of cacao in Waslala, i.e. introducing more unrelated germplasm, or working with existing on-site diversity, the latter seems most appropriate. Superior genotypes could be selected by their specific composite genotype spectra as soon as associations with desired quality traits are established, and clonally multiplied. The two Y trees from the forest share a single multilocus genotype, possibly representing the Mayan, 'ancient Criollo' cacao.

This study focused on clarifying phylogenetic relationships and evolution within Caricaceae. Our phylogenetic analysis based on nucleotide sequences from the ITS of the ribosomal DNA and three chloroplast fragments (matK, trnL-trnF, and psbA-trnH) included 29 taxa belonging to five genera: the neotropical genera Carica, Vasconcellea, Jarilla, and Jacaratia and the equatorial African genus Cylicomorpha. Having a relatively low mutation rate, matK, and trnL-trnF were used for estimating relationships at the generic level, while intrageneric evolution within Vasconcellea was studied with the more variable ITS and psbA-trnH sequences. Gaps, coded as binary characters, were added to the sequence alignments before performing Maximum Parsimony and Maximum Likelihood analyses. Monophyly of Caricaceae as well as phylogenetic distance between Carica and Vasconcellea species, previously belonging to the same genus, and monophyly of the resurrected genus Vasconcellea were emphasized. Within Vasconcellea, the largest genus of this family, two well-confirmed evolutionary lineages could be discerned: (1) V.xheilbornii, V. weberbaueri, V. stipulata, and V. parviflora and (2) a clade holding all other taxa of the genus. Incongruence between nuclear ITS and chloroplast psbA-trnH datasets, shown to be significantly caused by some taxa of the genus Vasconcellea, indicated that reticulate events in this genus might be more frequent than previously suspected. Moreover, intra-individual ITS sequence heterogeneity provided further evidence for the hybrid or introgressed origin of different taxa and one presumed hybrid belonging to this genus.

The chloroplast and mitochondrial DNA diversity of 61 genotypes belonging to 18 Vasconcellea species, the so-called highland papayas, was studied by PCR-RFLP analysis of two non-coding cpDNA regions ( trnM- rbcL and trnK1- trnK2) and one non-coding mtDNA region ( nad4/1- nad4/2). This sample set was supplemented with six genotypes belonging to three other Caricaceae genera: the monotypic genus Carica, including only the cultivated papaya, and the genera Jacaratia and Cylicomorpha. Moringa ovalifolia was added as an outgroup species. The PCR-amplified cpDNA regions were digested with 18 restriction endonucleases, the mtDNA region with 11. A total of 22 point mutations and four insertion/deletions were scored in the sample. A higher level of interspecific variation was detected in the two cpDNA regions in comparison to the analysis of the mtDNA. Wagner parsimony and Neighbor-Joining analysis resulted in dendrograms with similar topologies. PCR-RFLP analysis supported the monophyly of Caricaceae, but among the 26 mutations scored, an insufficient number of markers discriminated between the different Caricaceae genera included in this study. Hence the inference of the intergeneric relationships within Caricaceae was impossible. However, some conclusions can be noted at a lower taxonomic level. The Caricaceae species were divided into two lineages. One group included only Vasconcellea spp., whereas the second included the remaining Vasconcellea spp., together with the papaya genotypes and those from the other Caricaceae genera. This may indicate a higher level of inter-fertility for the Vasconcellea species from the latter clade in interspecific crossings with papaya. The putative progenitors of the natural sterile hybrid V. x heilbornii, i.e. V. stipulata and V. cundinamarcensis, were only distantly related to V. x heilbornii. This indicates that probably none of these species was involved as the maternal progenitor in the origin of V. x heilbornii. Surprisingly, V. x heilbornii had organellar genome patterns identical with V. weberbaueri, suggesting a possible involvement of this species in the origin of V. x heilbornii. On the basis of discrepancy between morphological traits and the cpDNA profiles of some pairs of Vasconcellea species, we believe that besides V. x heilbornii, some other species have originated through interspecific hybridization. A reticulate evolution for Vasconcellea has therefore been suggested. Finally, intraspecific cpDNA variation was detected in V. microcarpa, thus providing molecular evidence for the high diversity previously indicated by morphological observations.