OBJECTIVE: Plant breeders are increasingly turning to crop wild relatives (CWRs) to ensure food security in a rapidly changing environment. However, CWR populations are confronted with various human-induced threats, including hybridization with their nearby cultivated crops. This might be a particular problem for wild coffee species, which often occur near coffee cultivation areas. Here, we briefly review the evidence for wild Coffea arabica (cultivated as Arabica coffee) and Coffea canephora (cultivated as Robusta coffee) and then focused on C. canephora in the Yangambi region in the Democratic Republic of the Congo. There, we examined the geographical distribution of cultivated C. canephora and the incidence of hybridization between cultivated and wild individuals within the rainforest.
METHODS: We collected 71 C. canephora individuals from home gardens and 12 C. canephora individuals from the tropical rainforest in the Yangambi region and genotyped them using genotyping-by-sequencing (GBS). We compared the fingerprints with existing GBS data from 388 C. canephora individuals from natural tropical rainforests and the INERA Coffee Collection, a Robusta coffee field gene bank and the most probable source of cultivated genotypes in the area. We then established robust diagnostic fingerprints that genetically differentiate cultivated from wild coffee, identified cultivated-wild hybrids and mapped their geographical position in the rainforest.
RESULTS: We identified cultivated genotypes and cultivated-wild hybrids in zones with clear anthropogenic activity, and where cultivated C. canephora in home gardens may serve as a source for crop-to-wild gene flow. We found relatively few hybrids and backcrosses in the rainforests.
CONCLUSIONS: The cultivation of C. canephora in close proximity to its wild gene pool has led to cultivated genotypes and cultivated-wild hybrids appearing within the natural habitats of C. canephora. Yet, given the high genetic similarity between the cultivated and wild gene pool, together with the relatively low incidence of hybridization, our results indicate that the overall impact in terms of risk of introgression remains limited so far.

Uganda is a major global coffee exporter and home to key indigenous (wild) coffee resources. A comprehensive survey of Uganda\'s wild coffee species was undertaken more than 80 years ago (in 1938) and thus a contemporary evaluation is required, which is provided here. We enumerate four indigenous coffee species for Uganda: Coffea canephora, C. eugenioides, C. liberica (var. dewevrei) and C. neoleroyi. Based on ground point data from various sources, survey of natural forests, and literature reviews we summarise taxonomy, geographical distribution, ecology, conservation, and basic climate characteristics, for each species. Using literature review and farm survey we also provide information on the prior and exiting uses of Uganda\'s wild coffee resources for coffee production. Three of the indigenous species (excluding C. neoleroyi) represent useful genetic resources for coffee crop development (e.g. via breeding, or selection), including: adaptation to a changing climate, pest and disease resistance, improved agronomic performance, and market differentiation. Indigenous C. canephora has already been pivotal in the establishment and sustainability of the robusta coffee sector in Uganda and worldwide, and has further potential for the development of this crop species. Coffea liberica var. dewevrei (excelsa coffee) is emerging as a commercially viable coffee crop plant in its own right, and may offer substantial potential for lowland coffee farmers, i.e. in robusta coffee growing areas. It may also provide useful stock material for the grafting of robusta and Arabica coffee, and possibly other species. Preliminary conservation assessments indicate that C. liberica var. dewevrei and C. neoleroyi are at risk of extinction at the country-level (Uganda). Adequate protection of Uganda\'s humid forests, and thus its coffee natural capital, is identified as a conservation priority for Uganda and the coffee sector in general.

Emerging processing methods have been applied in coffee bean processing for improved sensory quality. The processes focus on optimizing the fermentation process of the coffee cherries and beans. This involves various pathways, including the formation of volatiles, flavor precursors and organic acids and the reduction in the concentrations of bioactive compounds. Comprehensive information regarding the effect of these emerging processes on the chemical, biological and sensory properties of the coffee beans is summarized. Emerging processes affected the coffee bean to various degrees depending on the raw material and the method used. The emerging methods promoted the reduction of bioactives such as caffeine and phenolics in coffee beans. Substantial improvement of these processes is needed to obtain coffee beans with improved biological activities. Effort to simplify the methods and optimize the post-fermentation process is crucial for the methods to be easily accessible by the producers and to produce defect-free coffee beans.

Arabica coffee beans are sold at twice the price, or more, compared to Robusta beans and consequently are susceptible to economically motivated adulteration by substitution. There is a need for rapid, non-destructive, and efficient analytical techniques for monitoring the authenticity of Arabica coffee beans in the supply chain. In this study, multispectral imaging (MSI) was applied to discriminate roasted Arabica and Robusta coffee beans and perform quantitative prediction of Arabica coffee bean adulteration with Robusta. The Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA) model, built using selected spectral and morphological features from individual coffee beans, achieved 100% correct classification of the two coffee species in the test dataset. The OPLS regression model was able to successfully predict the level of adulteration of Arabica with Robusta. MSI analysis has potential as a rapid screening tool for the detection of fraud issues related to the authenticity of Arabica coffee beans.

Vietnam is the second-largest coffee producer in the world after Brazil. Of the two main coffee production species, namely, Arabica and Robusta, Vietnam is the largest producer of Robusta worldwide [1]. Based on previous reports, the planted coffee area in Vietnam was 695.600 ha and its production was 1.76 million tons in 2020, in which the Central Highlands region accounts for approximately 73% of the planted area and production [2]. Hence, this region is known as the capital of coffee plantations and production in Vietnam. Previous studies have focused on the diversity of rhizospheric bacteria from this plant species cultivated in this region based on cultivation methods [3], [4], [5], [6], [7], [8]. However, no report has been found on the rhizospheric microbial diversity of this important plant in Vietnam. To our knowledge, a dataset of rhizospheric microbial communities of the coffee plant grown in the Central Highlands is still unclear. This report presents a dataset of the rhizosphere microbiome from a representative sample obtained by mixing five rhizospheric soil samples of Coffea canephora L. cultivated in the Central Highlands region using metagenomic next-generation sequencing. This dataset provides information on the rhizospheric microbial diversity of Robusta coffee, particularly its functionality. Therefore, cultivation techniques for sustainable Robusta coffee production in the region could be developed by applying indigenous rhizospheric microbial resources.

UNASSIGNED: Many cultivated coffee varieties descend from Coffea canephora, commonly known as Robusta coffee. The Congo Basin has a century long history of Robusta coffee cultivation and breeding, and is hypothesized to be the region of origin of many of the cultivated Robusta varieties. Since little is known about the genetic composition of C. canephora in this region, we assessed the genetic diversity of wild and cultivated C. canephora shrubs in the Democratic Republic of the Congo.
METHODS: Using 18 microsatellite markers, we studied the genetic composition of wild and backyard-grown C. canephora shrubs in the Tshopo and Ituri provinces, and from the INERA Yangambi Coffee Collection. We assessed genetic clustering patterns, genetic diversity, and genetic differentiation between populations.
RESULTS: Genetic differentiation was relatively strong between wild and cultivated C. canephora shrubs, and both gene pools harbored multiple unique alleles. Strong genetic differentiation was also observed between wild populations. The level of genetic diversity in wild populations was similar to that of the INERA Yangambi Coffee Collection, but local wild genotypes were mostly missing from that collection. Shrubs grown in the backyards were genetically similar to the breeding material from INERA Yangambi.
CONCLUSIONS: Most C. canephora that is grown in local backyards originated from INERA breeding programs, while a few shrubs were obtained directly from surrounding forests. The INERA Yangambi Coffee Collection could benefit from an enrichment with local wild genotypes, to increase the genetic resources available for breeding purposes, as well as to support ex situ conservation. This article is protected by copyright. All rights reserved.

Coffee beans were roasted to medium, dark and very dark degrees, and respective brews were in vitro digested and tested for α-glucosidase inhibition, to explore their antidiabetic potential. Phenolic acids (PA) and Maillard reaction indices (MRI) were quantified before and after digestion. Molecular docking was carried out to investigate α-glucosidase inhibition mechanisms. In vitro digested coffee inhibited α-glucosidase more effectively, compared to undigested samples, but without differences between roasting degrees. The inhibitory effect may be attributed to chlorogenic acids (CGA), which were the most abundant PA in digested coffees. In fact, molecular docking predicted a high affinity of CGA for α-glucosidase. Even though digestion nullified roasting-induced differences in α-glucosidase inhibition, CGA showed a decreasing trend upon digestion. Similarly, MRI did not differ among coffees upon digestion but decreased compared to undigested samples. Overall, the results reported in this study suggest that the presence of different compounds in coffee matrix may contribute to an antidiabetic effect.

BACKGROUND: Humic acid is a promising natural resource to be utilized as an alternative for increasing soil fertility and crop production. A field experiment was conducted on the loamy sand soil at the Central Coffee Research Institute research farm, Karnataka, India for 2 years to evaluate the influence of humic acid on yield and bean quality of coffee with six treatments. The treatments comprised of recommended dose of fertilizer (RDF), humic acid soil application and foliar spray along with nutrient mixture and growth hormones.
RESULTS: The data of the yield attributes of coffee revealed that the highest total nodes per branch, crop nodes per branch, flower buds, total number of fruits per branch and fruit set percentage of 17.45, 9.4, 208.65, 153.31 and 3.28, respectively, were recorded by T6 , which consists of RDF + humic acid granules at 10 kg acre-1  + nutrient mixture spray (1 kg urea, 1 kg SSP, 0.75 kg MOP, 1 kg ZnSO4  + 75 mL Planofix 200 L-1  + humic acid at 600 mL 200 L-1 as foliar application 25 days after blossom) during the both years of study. Humic acid application significantly improved the yield in both seasons of research. The same trend was observed in coffee bean quality and tree nutrients status. Postharvest nutrient status in the soil did not show any significance.
CONCLUSIONS: The study emphasized that application of humic acid as soil and foliar application improves the yield attributes, yield and quality of coffee apart from the economic profitability. © 2020 Society of Chemical Industry.

N,N-dimethylpiperidinium (mepiquat) is a new process-induced compound formed from natural constituents during the cooking process. Mepiquat was first found in coffee and cereal products, but its formation mechanism in coffee is still unclear. In the current study, Arabica and Robusta coffee beans were roasted at different temperatures (215, 220, and 230 °C) to study the effect of roasting process on mepiquat formation. The highest mepiquat content, 1,020 µg/kg, was found in dark roast (230 °C) Indonesia Wahana, while 430 µg/kg of mepiquat was detected in medium roast (220 °C) Vietnam Robusta. At the same roasting temperature, higher level of mepiquat was observed in Arabica than in Robusta. In both species, substances related to mepiquat formation, including betaine, choline, trigonelline, lysine, carnitine, pipecolic acid (PipAc), pipecolic acid betaine (PipBet), were also detected. The lysine-based Maillard reaction and decarboxylation in Arabica and Robusta promoted mepiquat formation through the degradation of choline and trigonelline, and the formation of intermediate products. Results from both the model system and selected commercial beans showed that choline and trigonelline had a significant correlation (P < 0.01) with mepiquat formation in Arabica. PRACTICAL APPLICATION: Mepiquat is considered as a new process-induced compound resulting from typical roasting conditions, but its formation mechanism in coffee is still unclear. This work demonstrates the formation mechanism of mepiquat by many precursor substances contained in Arabica and Robusta. It is very important to figure out how mepiquat is \'\'naturally\" present in daily diets, especially in those processed at high temperatures.

We obtained data regarding the metabolites from flowers, the skin pulp, green beans and peaberry green beans of the robusta coffee plant (Coffea canephora). The beans were processed using a wet-hulled method. The volatile compounds from the flowers were extracted using a solid-phase microextraction. Secondary metabolites from the skin pulp, green beans, and peaberry green beans were extracted by a maceration method using methanol as a solvent. The separation and identification of metabolites were conducted using gas chromatography-mass spectrometry. The flower\'s volatile compounds were identified by matching the generated spectra with the NIST14 library as a reference, whereas the metabolites in the skin pulp, green beans, and peaberry green beans were identified using the WILLEY09TH library as a reference. The identified volatile compounds in flowers have been listed in Table 1, and the identified skin pulp, green bean, and peaberry green bean metabolite compounds have been listed in Table 2.