Seed cotton yield in Northern Cameroon has been declining since the 80s despite breeding efforts. In order to evaluate the impact of genetic improvement on this decline, we conducted field experiments in two locations with 10 widely grown cotton cultivars released in Cameroon between 1950 and 2009. The rate of genetic gain (GG) was estimated with a linear regression of the cultivar mean on its year of release (YR). Contrasts between rates of GG observed with different planting dates were estimated and tested. Our results revealed a rate of GG on fibre yield of 3.3 kg ha−1 year−1 due to increased ginning out-turn (3.9% and 6.2% in 60 years in Garoua and Maroua, respectively). There was no GG on leaf area index (LAI), radiation use efficiency (RUE), aerial biomass, harvest index and on seed cotton yield. We concluded that cotton breeding efforts in Cameroon have successfully improved cotton fibre yield but there is still some room for seed cotton yield improvement.

Cotton, a high-value crop of primary financial importance for Greece, is directly affected by a wide range of environmental parameters, and water scarcity threatens the sustainability of irrigated cotton production in many regions around the world. Reducing inputs with an appropriate cultivar may not decrease cotton production and fiber quality while improving sustainability. To investigate cotton varietal responses to water stress and lack of nutrients, in the climate of north Greece, a three-year experiment was conducted in Thessaloniki, Greece. Four cotton cultivars (three of Greek origin and one from Africa) were cultivated under four irrigation (normal and reduced by 75%, 50%, and 25%) and two fertilization levels (normal and 50%). The effect of these treatments on productivity and quality were estimated, with the final objective being the reduction of inputs and more sustainable cotton production. Cotton producers are dealing with a cost price squeeze and the present study demonstrates that reducing the fertilization inputs even by half and the reduction of irrigation by 25% has no significant effect neither on yield nor on the main technological characteristics. This highlights the fact that a more sustainable use of inputs, contrary to common management, will have almost the same yield and even increase the farmer’s income.

Description du sujet. L’impact du changement climatique remet en cause la stratégie de diffusion variétale de la Société de Développement et des Fibres Textiles au Sénégal (SODEFITEX), basée sur la distinction de deux variétés : l’une adaptée aux conditions humides et l’autre aux risques de sècheresse. À partir de données recueillies en station expérimentale et en parcelles d’agriculteurs de 2004 à 2011, l’étude évalue la pertinence de cette stratégie. Objectifs. L’objectif de l’étude est d’évaluer la méthode de sélection variétale et la performance des variétés cultivées et à l’essai, soumises à des environnements hydriques contrastés du fait de la variabilité spatiale et temporelle de la pluviosité et des pratiques culturales. Méthode. La méthodologie développée permet d’identifier l’occurrence d’un stress hydrique sévère durant les phases critiques de floraison et de développement des capsules vis-à-vis du rendement en coton-graine et la qualité de la fibre. L’indicateur de vécu hydrique produit est ensuite introduit dans l’analyse statistique en tant que co-variable descriptive de l’environnement. Résultats. L’indicateur produit permet de discriminer les rendements en coton-graine en station expérimentale et chez les producteurs. Bien qu’un effet variétal soit constaté sur le rendement égrenage et les caractéristiques technologiques des fibres, aucune variété ne se distingue des autres vis-à-vis du vécu hydrique. Conclusions. À défaut de variété adaptée aux stress hydriques, les résultats militent en faveur de l’adoption d’une seule variété sur le bassin de production. La stratégie de diffusion des variétés mériterait toutefois d’être renouvelée pour mieux rendre compte des conditions de culture en milieu réel et permettre l’évaluation des variétés par les producteurs.

Late planting due to erratic onset of the rainy season is becoming more frequent in the Sahelo-Sudanian climate where cotton is grown, causing seed cotton yield (SCY) loss and higher risk of drought at the end of the crop cycle. Therefore, cultivars should be adapted to late (from July 10) planting date (PD) in Senegal. The aim of this study was to analyse the interaction between genotypes and PD on SCY in Senegal under rainfed conditions. Field experiments were conducted in 2018 and 2019 using a split-plot design (two PDs, eight cultivars) at three experimental stations. Robust analysis of SCY was used to moderate the effect of potential outliers. The average SCY was 1404 kg/ha under early planting, and 714 kg/ha under late planting. The best SCY was obtained under early planting conditions, in environments with good rainfall. The loss due to late planting was significantly affected by cultivar choice. None of the cultivars performed best under both early and late PD. Under early PD, cultivar CS 50 gave the best SCY, while under late PD it was cultivar IRMA Q302. The best performing cultivar on average depended on the proportion of early plantings. A model was developed to identify the best overall cultivar based on the expected proportion of early planting, as a decision support tool for the cotton development company, if only one cultivar is released. The benefit of releasing a second cultivar for late-planted fields is considered.