Productivity of coffee plantations is threatened by both climate change and decreasing revenues of coffee growers. Using shade trees might protect against temperature variability, erosion and excessive radiation but there may be trade-offs in productivity and quality. While impacts of shade trees on arabica (Coffea arabica) have been reviewed, a global synthesis on robusta (Coffea canephora) coffee is lacking. We assessed how shade affects robusta growth and productivity, and what are the interactions and trade-offs. We conducted a systematic literature search in Web of Science and CAB Abstracts on 16 December 2019. Thirty papers fulfilled our inclusion criteria of being experimental studies on the impact of overstory trees with approximately half being from Brazil or India. Shade improved robusta tree growth and yield with some contrasting effects on physicochemical and biochemical properties. Shade (> 30%) was associated with reduced beverage quality. Significant interactions between shade and location, rainfall level and robusta clone were found. Among the clones tested, 06V, C153, LB1, GG229 and JM2 showed a higher productivity and growth (from + 17 to + 280%) under moderate shade (41–65%). This is the first meta-analysis of the effects of shade on robusta coffee. By synthesizing data from different studies, we highlight for the first time that the effect of shade on robusta coffee depends on tree age. Shade had positive impacts on older robusta trees (mean of 16 years), while the impact of shade on younger trees was either insignificant or negative. We highlight the importance of both clone type and tree ages. Research gaps included a lack of knowledge on the effects of shade with respect to coffee and shade tree age as well as interactive effects. More in-depth studies are needed to understand the mechanisms of how shade trees affect robusta coffee.

Societal Impact Statement “Fine flavor” cocoa, known for its superior flavor and aroma, commands a higher price for farmers than “bulk” cocoa produced for market. These fine flavor cocoa varieties make an important contribution to the agricultural sector in Ecuador. However, cocoa diversity is threatened by deforestation. The effective preservation, characterization, and use of cocoa tree diversity are therefore essential to the future development of this market. We carried out participatory collection surveys with local communities in the Ecuadorian Amazon Forest, to evaluate the genetic diversity of native cocoa trees and protect trees as a resource for local communities. Accessing this wealth of diversity will aid farmers to safeguard cocoa against climate change and develop new varieties for market. Summary The aromatic Nacional variety of Theobroma cacao, emblematic of Ecuador, is highly sought after by the chocolate industry. The modern Nacional is a hybrid population resulting from genetic admixture that has lost the specificity of the ancestral variety. In the context of progressive forest disappearance, the objective of our study was to collect, safeguard, and evaluate native aromatic cocoa trees from Ecuadorian Amazon areas previously identified as areas of origin of the Nacional variety, as well as those that extend toward the northern Amazon. Four collection expeditions were organized in the Ecuadorian Amazon provinces of Zamora‐Chinchipe, Morona‐Santiago, and Pastaza in close collaboration with local communities. A total of 283 native accessions were collected and safeguarded at experimental stations and in local communities. The genetic diversity of the cocoa trees was analyzed by comparison to known genetic groups with a set of 48 simple sequence repeat (SSR) markers. This new collection clearly enriches the currently known diversity and improves knowledge of the global genetic structure of cocoa trees. Our results clarify the geographic origin of the Nacional variety in the vicinity of an archeological site that housed a Maya Chinchipe population that consumed cacao 5,000 years ago. In addition, our analyses revealed clues to the origin of Criollo, another ancient variety with a fine flavor. These new genetic resources will be used in breeding programs for the varietal improvement of new aromatic cocoa varieties and more globally for the selection of new varieties adapted to environmental changes.

Coffee agroforestry systems could reconcile agricultural and environmental objectives. While pests and diseases can reduce yield, their interactions with shade and nutrition have been rarely researched, and are particularly lacking in perennial systems. We hypothesized that intermediate shade levels could reduce coffee pests while excess shade could favor fungal diseases. We hypothesized that organic rather than mineral fertilization would better synchronize with nutrient uptake and higher nutrient inputs would be associated with reduced pest and disease damage due to higher plant vigor, yet effects would be less obvious in shaded plots as coffee growth would be light-limited. Using three-year-old trees of Coffea canephora var. Robusta (robusta coffee) in the Ecuadorian Amazon, we compared a full-sun system with four shading methods creating different shade levels: (1) Myroxylon balsamum; (2) Inga edulis; (3) Erythrina spp.; or, (4) Erythrina spp. plus Myroxylon balsamum. Conventional farming at either (1) moderate or (2) intensified input and organic farming at (3) low or (4) intensified input were compared in a split-plot design with shade as the main plot factor and farming practice as the sub-plot factor. The infestation of the following pests and disease incidences were evaluated monthly during the dry season: brown twig beetle (Xylosandrus morigerus), coffee leaf miner (Leucoptera coffeella), coffee berry borer (Hypothenemus hampei), anthracnose disease (Colletotrichum spp.), thread blight (Pellicularia koleroga), and cercospora leaf spot (Cercospora coffeicola). Coffee berry borer and brown twig beetle infestation were both reduced by 7% in intensified organic treatments compared to intensified conventional treatments. Colonization of coffee berry borer holes in coffee berries by the entomopathogenic fungus Beauveria bassiana was also assessed. Brown twig beetle infestation was significantly higher under full sun than under Inga edulis, yet no other shade effects were detected. We demonstrate for the first time how intensified input use might promote pest populations and thus ultimately lead to robusta coffee yield losses.

Recent surveys conducted on Amazonian cocoa trees in their home range are a unique opportunity to assess the aromas, diversity and potential of the Ecuadorian Amazon to create new aromatic cocoa varieties. Our results reveal informations about the diversity and genesis of aromas in Ecuadorian fine cocoa. The great aromatic diversity could enrich cocoa flavour selection programmes and provide Amazonian populations with new income linked to aromatic varieties, which could lead to a 'grand cru' chocolate. Until now, breeding programmes have been mainly focused on

Resistant cultivars offer a pathway to sustainable intensification by maintaining yields and reducing inputs in the face of disease pressure. Past studies of economic returns to crop breeding research for disease resistance measured farm-level benefits, by comparing yields for improved resistant varieties (RVs) to susceptible traditional varieties. This approach will poorly approximate actual research benefits if non-RV pest management options exist, because it does not account for farmer pest control behavior. We propose a unit cost model that controls for farm-level yields and pesticide inputs. The model estimates the difference in unit variable costs (UVC), with and without disease pressure for RV adopters and non-adopters, while holding pest control inputs, farm characteristics, and other factors fixed. We apply the model to data from 136 bean farmer households in northern Ecuador, where RV research is ongoing and fungicide use is widespread. We find no difference in UVC, with and without disease pressure for non-adopters. For adopters, UVC is 24% lower with disease pressure than without. This translates to an ex-post net present value (NPV) of USD 698,828 and an internal rate of return (IRR) of 17%, compared to an NPV of USD 887,391 and IRR of 29%, when accounting for yield differences only. The results oblige impact assessments to account for changes in yields and input costs when pest management is an option.