Interactive effects of altitude, microclimate and shading system on coffee leaf rust

Shade effects on coffee diseases are ambiguous because they vary depending on the season and environment. Using Coffee Leaf Rust (CLR) as an example, we demonstrate relationships between the environment and shading systems and their effects on disease intensity. We characterized seasonal variations in microclimate and CLR incidence across different altitudes and shading systems, and integrated effects between the environment, shading systems, microclimate and CLR into a piecewise structural equation model. The diurnal temperature range was higher in unshaded systems, but differences decreased with altitude. Humidity related indicators in shaded systems decreased with altitude. At mid and high altitudes, high CLR incidence occurred in the shading system showing a low diurnal temperature range and a high dew point temperature. Our study demonstrates how microclimatic indicators vary as a function of the season, altitude and the coffee shading system, and how this in turn is related to CLR

Characterisation of microclimatic indicators in coffee production systems under varying biophysical contexts and its relation to fungal coffee diseases

The comparison of performance of coffee under shaded and sun-exposed conditions has been explored in numerous studies. The beneficial effects of shading on coffee sustainability through the mitigation of microclimatic extremes have been quantified and are generally wellestablished. It has also been acknowledged that the extent to which shaded systems are advantageous depends on the biophysical context. Particularly in studies on pest and disease dynamics, this variability of shade effects across sites has resulted in contradictory assumptions. In this study, we (i) quantified microclimatic differences between three coffee production systems (coffee shaded by trees, (CT), intercropped with banana (CB), or sun exposed (CO) as a function of different environmental sites. We then (ii) related microclimatic indicators to the intensity of two fungal diseases (Coffee Leaf Rust (CLR), and Coffee Berry Disease, (CBD) of Arabica coffee. Along an altitudinal gradient from 1000 to 2200 m.a.s.l.) and in diverse production systems on the slopes of Mount Elgon, Uganda, we collected hourly data on temperature and relative humidity during the 2015/2016 season in 27 plots. Microclimatic indicators to compare included diurnal temperature range (DTR), the accumulated hours of relative humidity above 95 % (RH>95) during night, and the accumulated hours of temperatures below the dew point (Temp95 and Temp95. Our findings confirm the mitigation property of shading to microclimatic extremes. However, the widely accepted assumption of shade conserving moisture is not applicable considering the spatio-temporal context. (ii) The fact that unshaded systems at high altitudes expose better conditions for dew formation than compared to shaded systems could be a key mechanism explaining the high CBD intensity under unshaded systems and the contradictory CLR responses along the gradient of altitude and shading intensities

Sensory diversity of fonio landraces from West Africa

This study aims to establish if there is some sensory variability among fonio landraces. Fonio, the oldest indigenous and very tasty cereal growing in West Africa, is usually consumed as a couscous. Group interviews of consumers were conducted in Bamako, Mali to identify the main quality criteria of a cooked grain. Fonio grain must be swollen, not sticky with a soft consistency, pale and containing low impurities. Sensory properties of 20 fonio landraces from Mali, Guinea and Burkina Faso were established using a descriptive sensory analysis. Five sensory descriptors were chosen among the quality criteria. Each landrace was tasted and scored in triplicate by a group of 18 trained panellists. Principal component analysis and hierarchical cluster analysis were used. The 20 landraces clustered into four sensory classes. Sensory criteria of variability were first visual characteristics (colour and impurities) and then the consistency of cooked grains. Landraces from Guinea and Mali were variable for both visual and textural characteristics; those from Burkina Faso appeared to be more homo-genous. The sensory variability of fonio offers to processors, who intend to promote this tiny cereal both in the sub-region and beyond, the possibility to choose adapted landraces to develop new products