Coffee Cultivars Research Articles

Effects of Time based Different Integrated Organic and Mineral Fertilizer Rate Application on Improved Coffee Cultivar Yield in South Ethiopia

Coffee Production plays a significant role in Ethiopian economy, even though the productivity at farm level is among the lowest as compared to other coffee producing country. Soil degradation is one of the most challenging problems in coffee growing areas of Ethiopia. Declining of soil fertility is a fundamental problem to agricultural growth and a major reason for slow growth of food production. Therefore, this activity was designed to determine optimum application time of integrated organic and inorganic fertilizers under coffee growing areas and to assess the effects of temporal application effects of integrated organic and inorganic fertilizers on coffee yield and yield stability performance of coffee cultivar. The experiment was conducted with RCBD design with four replication and ten treatments settled from integrated organic and inorganic inputs at Awada Agricultural research sub-center starting from 2013-2023 for the last 10 consecutive years. The result demonstrated that, application of 200kgha-1N, 77kgha-1P and 12.5tonha-1 integrated nutrient application at each cropping season resulted statically significant higher yield result as compared to the other nutrient applications. The plot treated with the recommended NP + recommended decomposed coffee husk application per year (200kgha-1N, 77kgha-1P and 12.5ton ha-1) indicated over all yield advantage over the other plots by 22.07% or 345kg/ha of clean coffee yield over the recommended (200kgha-1N, 77kgha-1P) applied alone per year and 33.39% or 522kg/ha of clean coffee yield over the plots treated with recommended decomposed coffee husk (12.5ton ha-1) alone application per each cropping season.

Plant Morphological and Leaf Anatomical Traits in Coffea arabica L. Cultivars Cropped in Gorongosa Mountain, Mozambique

Studies on the genetic diversity of coffee trees are important, considering their role in the maximization of productivity and quality. However, the success of a breeding program depends on the existence of genetic variability in the population under study. Our study aimed to evaluate the genetic diversity of the morpho-agronomic and anatomical leaf traits of different cultivars of Coffea arabica grown in the Gorongosa mountain region, in the area of Gorongosa National Park, Mozambique. The experiment assessed nine coffee cultivars based on their morpho-agronomic and anatomical traits. The plagiotropic branch diameter, leaf dry mass, leaf mass per area, number of epidermal cells + stomata, and stomatal form indicated differences among the studied cultivars. Among the nine C. arabica cultivars grown in the mountainous region of Gorongosa National Park, Mozambique, low genetic variability in morpho-agronomic traits was detected, while the genetic variability in leaf anatomical traits was higher. The nine cultivars were segregated into two groups, one consisting of Catucaí Amarelo 2SL and Catuaí Vermelho IAC 81, and the second consisting of Catuaí Amarelo IAC 39, Catucaí Vermelho 19/8, Acauã, Catucaí 785-15, Costa Rica, Catimor 128, and Catuaí Vermelho IAC 44. The cultivar segregation into the two groups indicated that the morpho-anatomical traits can be considered during the selection stages in breeding programs.

Machine learning models for classifying coffee fruits detachment force

AbstractThe maturation process of coffee (Coffea arabica) trees exhibits inherent variability, producing fruits at various physiological maturity stages. This variability affects the resistance between the fruit and its peduncle, posing a challenge in mechanized harvesting: non‐selective harvesting. A precise classification of coffee fruit detachment force is essential to address this challenge, ensuring coffee's quality and producer's profitability. This study assesses the efficacy of machine learning (ML) models in determining the detachment force across various coffee cultivars under drip‐irrigated and rainfed conditions. The dataset included detachment force measurements from 24 cultivars—13 drip‐irrigated and 11 rainfed—yielding 1152 data points. Variance analysis compared irrigation methods and three maturity stages: green, cherry, and dry. Detachment force was categorized into four classes based on the dataset's quartile distribution. The ML models utilized were random forest (RF), support vector machine (SVM), K‐nearest neighbors, and artificial neural networks. The SVM model was notably effective in classifying detachment force for rainfed cultivars, with a Matthews correlation coefficient (MCC) of 0.78. In contrast, the RF model was particularly adept for drip‐irrigated cultivars, with an MCC of 0.75. The highest classification accuracies were recorded for the extreme force classes I and IV, with precision values of 0.93 and 0.8, respectively, while classes II and III had lower precision at 0.57 and 0.69. Implementing these ML models for detachment force classification has been beneficial, improving decision‐making in mechanized harvesting systems.

Gene pyramiding for achieving enhanced disease and insect multiple resistance in Coffea arabica

AbstractDeveloping a new coffee cultivar can take up to 25 years using traditional approaches. The implementation of molecular tools into the coffee breeding pipeline can speed up the development of high‐yielding varieties with multiple resistance to pests and diseases. This study aimed to verify the presence of gene pyramiding for resistance to coffee berry disease (CBD) and coffee leaf rust and access the breeding potential of a breeding population of coffee (Coffea arabica L.) that presents partial phenotypic resistance to coffee leaf miner. A progeny of 128 individuals was evaluated in 2019 during the coffee maturation stage for 11 agronomic traits. The individuals were genotyped for four loci related to rust and CBD resistance. Gene pyramiding was verified based on the presence of markers linked with the resistance alleles. Genetic parameters were estimated, and a selection index was used to rank the individuals based on the phenotypic evaluation. Gene pyramiding for rust and CBD was detected in ∼82% of the individuals. Moreover, the phenotypic evaluation of rust indicated high levels of resistance, confirmed by the presence of the resistance alleles. Ninety‐five percent of the 38 top‐ranked individuals presented resistance alleles and could be used in an interpopulation recurrent selection scheme with marker‐assisted selection. The studied coffee population has the potential to be used in coffee breeding programs since it presents vigorous individuals with low levels of coffee leaf miner incidence (CLMI) and gene pyramiding for CBD and rust resistance, the main pest and diseases of this crop.

Mycena citricolor isolates from diverse hosts in Costa Rica: Colony aspect, growth dynamics, reproduction in vitro and aggressiveness on Coffea arabica

AbstractThe basidiomycete fungus Mycena citricolor hosts on about 80 plant families. The asexual morph causes the disease known as American leaf spot of coffee (Coffea arabica). We isolated and characterized 15 isolates of M. citricolor collected from coffee plants, shade trees and weeds. Cultures on potato‐dextrose‐agar + yeast extract (PDAY) medium were kept for a week in complete darkness. The cultures were then exposed to light for 7 weeks and co‐cultivated with coffee foliar discs, to stimulate the production of gemmifers. We evaluated the speed of growth, appearance, colour of the mycelium and gemmifers production capacity. All isolates conformed to the typical cultural characteristics of M. citricolor, with beige/white thin and slightly aerial mycelium. The whitest isolate was from Persea americana, which had the slowest growth rate in vitro (6.4 mm/day), while the isolate from weed Kalanchoe pinnata was the fastest, with a speed of 9 mm/day. The most gemmifer‐producing isolates were those isolated from the coffee cultivar Catimor‐Costa Rica 95, Citharexylum donnell‐smithii and Cissus verticillata, with over 200 gemmifers per Petri dish. Isolates from Erythrina and Ipomoea nil produced <50 gemmifers on average. The Composite Aggressiveness Index (CAI) was determined on 2‐year‐old detached coffee branches of the Caturra variety foliage. The least aggressive isolate was from Erythrina poeppigiana (CAI = 0) and the most aggressive was from Kalanchoe pinnata (CAI = 18.87). The isolate from the coffee cultivar Catimor‐Costa Rica 95 was more aggressive than that from the cultivar Caturra (CAI = 9.94 vs. CAI = 3.66). Moreover, successful infection occurred only when the apex of gemmae made direct contact with the coffee leaf when using the inoculum derived from C. verticillata and Anredera cordifolia. These results show the variability in the population of the pathogen. This is the first study that characterizes the growth, morphology, reproduction and aggressiveness of M. citricolor obtained from hosts other than coffee. In addition, it is the first to report the use of coffee foliar discs to induce gemmifer production in vitro and to assess and quantify the effect of gemma position when inoculating coffee leaves.

Comparative genetic assessment of somatic embryo– and seed-derived plants of two arabica hybrid coffee cultivars using SRAP and SCoT molecular markers and organellar and nuclear genes sequencing

Comparative genetic assessment of somatic embryo– and seed-derived plants of two arabica hybrid coffee cultivars using SRAP and SCoT molecular markers and organellar and nuclear genes sequencing

The genome and population genomics of allopolyploid Coffea arabica reveal the diversification history of modern coffee cultivars

Coffea arabica, an allotetraploid hybrid of Coffea eugenioides and Coffea canephora, is the source of approximately 60% of coffee products worldwide, and its cultivated accessions have undergone several population bottlenecks. We present chromosome-level assemblies of a di-haploid C. arabica accession and modern representatives of its diploid progenitors, C. eugenioides and C. canephora. The three species exhibit largely conserved genome structures between diploid parents and descendant subgenomes, with no obvious global subgenome dominance. We find evidence for a founding polyploidy event 350,000–610,000 years ago, followed by several pre-domestication bottlenecks, resulting in narrow genetic variation. A split between wild accessions and cultivar progenitors occurred ~30.5 thousand years ago, followed by a period of migration between the two populations. Analysis of modern varieties, including lines historically introgressed with C. canephora, highlights their breeding histories and loci that may contribute to pathogen resistance, laying the groundwork for future genomics-based breeding of C. arabica.

Biochemical composition of the beans of local coffee cultivars from southwestern Saudi Arabia

Coffee (Coffea arabica L.) is an economically and culturally important crop for the communities of the southwest mountain regions of Saudi Arabia. The objective of the study was to characterize the biochemical composition of the dry green beans of the coffee cultivars grown there. The analysis of variance revealed significant differences among the 66 accessions studied for all eight biochemical compounds analyzed especially, caffeine, trigonelline and chlorogenic acid. Remarkably, caffeine concentrations varied from 0.75 g 100 g−1 in accession KSA-38–1.51 g 100 g−1 in KSA-47 and trigonelline concentrations varied from 0.81 g 100 g−1 in KSA-69–1.64 g 100 g−1 in KSA-6R. However, 55% and 64% of the accessions had low to moderate caffeine and trigonelline concentrations, respectively. Chlorogenic acid concentration varied from 2.35 g 100 g−1 in KSA-3R to 4.33 g 100 g−1 in KSA-32. Because these compounds are the most important bitterness attributes contributing to coffee quality, significant differences in beverage quality are expected between the accessions. Furthermore, the results of the multivariate analysis indicated the presence of considerable diversity among the 66 accessions. The hierarchical cluster analysis grouped the genotypes into fourteen clusters. The observed divergence suggests that genetic gains for biochemical features are possible. Therefore, we recommend accessions KSA-1, KSA-9R, KSA-10, KSA-29, KSA34, KSA37, KSA-38, KSA-39 and KSA-60 for further evaluation.

Responsiveness of Arabica coffee cultivars to skeleton pruning in a low‐altitude region

AbstractSkeleton pruning is a type of pruning that, by cutting lateral branches (plagiotropic), allows the reinvigoration of coffee plants through the renewal of productive branches. The crop response to this management may be affected by several factors, such as the trees age, crop practices, and, mainly, the genotype. This study aimed to identify the Arabica coffee cultivars with greatest responsiveness to skeleton pruning and desirable productive and qualitative characteristics in a low‐altitude region. The experiment was conducted in northeastern São Paulo state, Brazil, at an altitude of 565 m. The experimental design was randomized blocks with four replicates, and the treatments consisted of 17 short‐stature Arabica coffee cultivars. On average, the responsiveness of the cultivars to pruning was 32% in the first year and 14% in the second year. The cultivars IAC Catuaí SH3, IAC Ouro Verde, IAC Obatã 4739, Tupi IAC 1669‐33, Catiguá MG1, Oeiras MG 6851, Pau‐Brasil MG1, Sacramento MG1, IPR 99, IPR 103, and Sabiá Tardio were responsive to skeleton pruning. Among these, Catiguá, Oeiras, Sacramento, and Sabiá stood out with pruning responsiveness above 45%. The cultivars Obatã IAC 4739, Tupi IAC 1669‐33, and Catuaí SH3 stood out in terms of yield, with an average between 40 and 50 bags ha−1. In addition to high yields, the cultivar Obatã IAC 4739 obtained grains with higher weight and sieve 17. Skeleton pruning was found to be genotype dependent and emerged as a viable alternative for revitalizing Arabica coffee cultivars in low‐altitude regions.

Drought responses in Coffea arabica as affected by genotype and phenophase. II – photosynthesis at leaf and plant scales

Summary The aim of this work was to compare gas exchanges from leaf to whole plant scales, in two Ethiopian accessions (‘E083’ and ‘E027’), and two bred cultivars (Iapar 59 and Catuaí 99) of Arabica coffee (Coffea arabica L.) cultivated under irrigated and rainfed conditions. Variations in gas exchanges were evaluated over four phenophases (leaf expansion – BE1 and BE2, and berry harvesting – BH1 and BH2), covering the first two production years in the coffee life cycle. We addressed the following questions: Are gas exchanges modified by water availability at leaf and/or plant scales? Do bred cultivars and wild accessions differ in their physiological responses to water availability and phenophases? Photosynthesis (A), stomatal conductance (gs), and transpiration (E) were measured on the recently fully expanded leaves at the upper canopy stratum. The functional-structural plant modelling (FSPM) was used to integrate A at whole plant photosynthesis (A”p), based on 3D virtual trees constructed under VPlants modelling platform. Despite high A values of ‘E083’ overall phenophases, a strong decline in A”p under rainfed condition was observed due to lower plant leaf area as compared to irrigated condition. Catuaí 99 and ‘E083’ were more sensitive to drought than Iapar 59 and ‘E027’, considering photosynthesis at leaf and plant scales. At the last BH2 phenophase, A, gs, E, and carboxylation efficiency were similar between irrigated and rainfed conditions for all genotypes, suggesting some acclimation of leaf gas exchange to the environment. However, A”p benefited by water management in all phenophases as plant leaf area increased. These findings revealed the need to develop methodologies for structural and functional analyses at plant scale, an important step towards the realistic responses of plants and orchards to the surrounding environment.

Drought responses in Coffea arabica as affected by genotype and phenophase. I – leaf distribution and branching

Summary In Coffea arabica, there is a small genetic distance between wild and bred genotypes. However, coffee genotypes express differential acclimation to multiple drought cycles, allowing them to successfully deal with water-limiting conditions. We hypothesized that bred coffee cultivars have a plant structure less sensitive to drought than wild genotypes. Plant and leaf architecture were analyzed over the coffee strata of two cultivars (Iapar 59 and Catuaí 99) and two wild Ethiopia accessions (‘E083’ and ‘E027’) grown under rainfed conditions and irrigation. During two consecutive productive years, evaluations were taken at leaf and berry expansion (BE1 and BE2) and harvest (BH1 and BH2) phenophases. The plant canopy was divided into up to four strata of 40 cm of thickness. Topological and geometric coding of coffee trees was performed in three botanical scales – metamers, branches, and plants in multiscale tree graphs (MTGs), following the VPlants modeling platform. Leaf and branch area per plant increased with tree structure development, being always significantly higher in irrigated than in rainfed plants over all phenophases. The individual leaf area was the least sensitive to water regime in Catuaí 99, while the 2nd order axis elevation – angle in relation to horizontal plane, ranging from 0° to 90° – of bred cultivars was less sensitive to drought than in ‘E083’. This finding partially corroborated our hypothesis that orchestrated reprograming of leaf/branch responses over the vertical plant profile were less sensitive to water availability in cultivars than in wild accessions. Leaves of 2nd to 4th-order branching were roughly plagiophile, while the 1st-order leaves were classified as extremophiles. When the coffee leaves were planophile, irrespective of genotype, this pattern was found at the lowest, 1st plant stratum, and the newest developed 4th stratum. Such responses were not obligatorily related to water regime, similar to branch elevation – with exception of ‘E083’, very sensitive to drought. Taken together, our data suggest that the leaf and branch elevations in C. arabica were more influenced by light distribution through the canopy profile – i.e., self-shading – than by water availability.

Genetic diversity analysis of commercial Arabica coffee in Nepal using Molecular markers

Coffee is an established plant for its flavor and has high commercial use. In Nepal, the popularity of coffee is increasing for its high economic value. However, its diversity and the status of its genetic mapping have not been studied in Nepal. In the present study, the genetic diversity of 28 coffee accessions was assessed by using twenty-four SSR markers with the aim of studying the variation of coffee in accord with the genetic markers from a molecular approach. With the use of DNA extraction and marker selection for its amplification using PCR tools, a total of 81 loci from SSR were identified. Of all SSR 63.22% showed for mean polymorphism. The mean polymorphic information content of SSR was 0.38, which showed low genetic diversity of SSR markers among Coffea genotypes. On the basis of the SSR marker, the unweighted pair group method with arithmetic mean (UPGMA) dendrogram constructed showed a similar group of distribution among 28 accessions, which was further supported by a principle coordinate analysis scatter plot. The phylogenetic relationships among the accessions were assessed by SSR marker, which also showed low diversity in coffee genotypes. Our study demonstrated the use of SSR markers in diversity analysis as the data were informative and highly reproducible for evaluating relationships among coffee cultivars in Nepal. The use of more markers systems and a high genotype pool would have been beneficial in accessing more accurately. Regardless, the information from the phylogenetic relationship study could be useful for breeding, varietal improvement, and for conservation programs.

Resistance Evaluation of Gurage Coffee Accessions Against Coffee Berry Disease (Colletotrichum Kahawae Waller and Bridge)

Coffee Arabica is an important crop in the national economy of Ethiopia. Coffee berry disease (CBD), coffee wilt disease (CLD) and coffee leaf rust (CLR) are the most important coffee diseases in the country. Development of coffee cultivars for different localities having a character of diseases resistant, high yielding and quality coffee is important. Previous research works have little effort to provide varieties that are suitable for Gurage zone southern parts of Ethiopia. Hence, this study was carried out to evaluate Gurage coffee accessions against CBD. Evaluations of Gurage coffee accessions were conducted under field by Attach Berry Test and laboratory by Detach Berry Test methods in Randomized Complete Block Design and Completely Randomized Design, respectively in 2018. The study result indicated that Gurage coffee accessions Gu-18, Gu-1 and Gu-4 had lower CBD infection level in both field and laboratory experiment, which was 5.4, 8.29 and 11.37 and 32.5, 45.0 and 25.8 %, respectively. Those coffee accessions that showed low level of infection are an opportunity for further breading research work and could be the best alternatives to CBD management particularly for the study area. Future research should focus on evaluating the promising Gurage coffee accessions in seedling inoculation test and in multi-location field trials for several years.

Physiological and morphological responses of Arabica coffee cultivars to soil compaction

ABSTRACT Compaction caused by mechanization affects soil quality and, consequently, the development of crops. This study aimed to evaluate the effect of different degrees of soil compaction on the physiology, morphology, and anatomy of different coffee cultivars in a controlled environment. The experiment was carried out in a greenhouse, with randomized block design in a 5 × 5 factorial arrangement, with five coffee cultivars (Arara, Catuaí Amarelo IAC 62, Catuaí Vermelho 144, MGS Paraíso 2 and Mundo Novo IAC 379-19) and five degrees of compaction (68, 74, 80, 86 and 92 %), with four repetitions, totaling 100 experimental units. The following variables were evaluated in the aboveground biomass: plant height, number of leaves, diameter of the orthotropic branch, fresh mass of leaves and stem, leaf area, gas exchange, and chlorophyll a and b index; in the roots: length, surface area, volume, diameter of fine and coarse roots, fresh and dry mass of roots, as well as anatomical characteristics. Results showed that soil with degrees of compaction above 80 % negatively affected the variables evaluated. Catuaí Vermelho 144 presented the worst performance regardless of the degree of compaction, while Arara and MGS Paraíso 2 showed the best performance under the evaluated compaction degrees. Anatomical structure of the roots was modified with soil compaction, and no differences were observed among cultivars.

Cultivars of Arabica coffee: Characterization and interception of solar radiation

Cultivars of Arabica coffee: Characterization and interception of solar radiation

Influence of maturation and roasting on the quality and chemical composition of new conilon coffee cultivar by chemometrics

Coffee is one of the most consumed beverages worldwide. Espírito Santo is the largest Brazilian producer of conilon coffee, and invested in the creation of new cultivars, such as “Conquista ES8152”, launched in 2019. Therefore, the present study aimed to evaluate the effects of maturation and roasting on the chemical and sensorial composition of the new conilon coffee cultivar “Conquista ES8152”. The coffee was harvested containing 3 different percentages of ripe fruits: 60%, 80%, and 100%, and roasted at 3 different degrees of roasting: light, medium, and dark, to evaluate the moisture and ash content, yield of soluble extract, volatile compound profile, chlorogenic acid and caffeine content, and sensory profile. “Conquista ES8152” coffee has a moisture content between 1.38 and 2.62%; ash between 4.34 and 4.72%; and yield between 30.7 and 35.8%. Sensory scores ranged between 75 and 80 and the majority of volatile compounds belong to the pyrazine, phenol, furan, and pyrrole groups. The content of total chlorogenic acids was drastically reduced by roasting, with values between 2.40 and 9.33%, with 3-caffeoylquinic acid being the majority. Caffeine was not influenced by either maturation or roasting, with values between 2.16 and 2.41%. The volatile compounds furfural, 5-methylfurfural, and 2-ethyl-5-methylpyrazine were positively correlated with the evaluated sensory attributes and 5-methylfurfural was the only one significantly correlated with all attributes. Ethylpyrazine, furfuryl acetate, 1-furfurylpyrrole, 4-ethyl-2-methoxyphenol, and difurfuryl ether were negatively correlated. The stripping did not affect the quality and composition of this new cultivar, however, the roasting caused changes in both the chemical and sensorial profiles, appropriately indicated by the principal component analysis.

Inheritance of Resistance to Bacterial Halo Blight and Bacterial Leaf Spot in Arabica Coffee.

Developing coffee cultivars resistant to multiple diseases by combining resistance genes is a top priority in breeding programs. To create cultivars resistant to diseases and nematodes, we transferred genes for resistance to bacterial infections caused by Pseudomonas coronafaciens pv. garcae, which causes bacterial halo blight (BHB), and P. amygdali pv. tabaci, which causes bacterial leaf spots (BLS), into Arabica coffee. Genetic analyses were conducted on breeding populations to estimate the number and function of genes that confer resistance to BHB and BLS. In total, 2,109 plants in the F2 generation and reciprocal backcrosses were inoculated with P. coronafaciens pv. garcae, while 1,996 plants were inoculated with P. amygdali pv. tabaci. Results showed that resistance to both pathogens had a heritability of 0.99, and the segregations of resistance indicated that each disease was controlled by a single dominant gene. The analyses also revealed that the resistance genes for BHB and BLS were linked, with an average distance of 10.75 cM between them on the same chromosome.

Efficiency of absorption, translocation, and use of nitrogen by water-stressed coffee

Climate change and the expansion of agricultural lands to low-fertility soils have prompted studies on the effects of water and nutritional stress on nutrient uptake and use. This study aimed to evaluate the efficiency of absorption, translocation, and use of N in coffee cultivars under water stress (WS) and different N doses. The experiment was performed hydroponically and arranged in a 4 × 2 × 4 factorial randomized block design with three replications. These factors consisted of four coffee varieties, two N doses, and four levels of WS. At the end of the experiment, the dry matter production, N concentration, and N accumulation of plants, as well as nutritional efficiency indices were evaluated. The data were subjected to analysis of variance and regression. The results showed that in plants previously well-supplied with N, N stress induces greater allocation of dry matter in roots, mitigating the effects of subsequent water deficits on shoot dry matter production. Young Mundo Novo plants subjected to N stress followed by increasing water stress maintained a high utilization efficiency (UE). Young Acauã plants well-supplied with N, maintained their N utilization efficiency up to -1.6 MPa of water stress; however, when they were N starved, they underwent a drastic reduction in UE at potentials below -0.22 MPa.

Effects of reduced rainfall on coffee quality and volatile composition.

For a significant subset of agricultural products, including coffee, wine, and tea, sensory perceptions of terroir (i.e., characteristic flavors imparted by the growing environment) are tightly linked to the product's value. With increasing climate change, it is critical to understand how shifts in climate, such as changes in precipitation, may interact with management practices (e.g., cultivar selection) to impact sensory quality in terroir-driven crops, and what biochemical compounds may be associated with those impacts. Here, sensory quality and volatile profile composition were assessed for four Arabica coffee (Coffea arabica) cultivars grown in a field experiment where precipitation was reduced by rainout shelters, resulting in 14% lower soil moisture on average. Our results indicate an overall increase in yield coincident with a moderate decrease in sensory quality in response to reduced precipitation. The presence and magnitude of the sensory quality shift varied by cultivar and sensory attribute, though the Acidity attribute was consistently negatively impacted across cultivars, albeit with a high degree of uncertainty. Additionally, 31 volatile compounds were identified across green coffee samples that were variably impacted by reduced precipitation. Hierarchical clustering analysis identified patterns in volatile clustering associated with sensory attributes that suggest reduced precipitation effects on sensory attributes may depend on non-linear combinations of secondary metabolites. Ultimately, our results advance efforts to improve predictions of climate impacts on coffee-growing landscapes and communities and highlight the value of considering indicators of harvest value beyond yield to improve economic forecasts for agroecosystems under climate change. This article is protected by copyright. All rights reserved.

A Method for Selection of Coffee Varieties Resistant to Fusarium stilboides

Fusarium bark disease (FBD) of coffee caused by Fusarium stilboides Steyaert has been associated with yield losses and tree death in coffee-growing countries, including Kenya. Varietal resistance is of utmost importance in managing the disease, and the continued increase in host resistance is considered sufficient to control the disease. Therefore, this study investigated the response of four coffee cultivars to F. stilboides. Fifteen hypocotyls from Coffea arabica (Ruiru 11, Batian and SL 28), plus two other coffee species, Coffea canephora (Robusta coffee) and Coffea liberica (Liberica coffee), were inoculated with various concentrations of three F. stilboides isolates (NRF 930/18, TN002B (I), BS008B (A)) using both the injection and drenching methods. The stem injection method was performed by injecting one microliter of the F. stilboides spore solution into the hypocotyl. In the drenching method, coffee seedlings had their roots cut and transplanted in a transplanting mixture, after which 10 mL of the F. stilboides spore solution was applied to the soil surface in each pot. The inoculated hypocotyls were incubated at 24 ± 2 °C for 105 days. The plants were watered regularly as necessary while the development of symptoms was observed and assessed weekly. Disease severity was evaluated using a modified scale of 0–4, while incidence was scored as a percentage of infected seedlings. Coffee seedlings inoculated with F. stilboides developed symptoms such as wilting, stunted growth and defoliation. In the first season, the coffee cultivars of Ruiru 11 and Liberica inoculated with Fusarium stilboides had pronounced severity compared to other cultivars. In the second season, the coffee cultivars Batian and Ruiru 11 had pronounced severity compared to other cultivars. The isolate TN002B (I) was observed to be highly virulent as compared to other isolates. The variation in response to disease infection exhibited by the four cultivars presents a key input in breeding programs for resistance to F. stilboides.