Spatiotemporal Survey of Multiple Rice Diseases in Irrigated Areas Compared to Rainfed Lowlands in the Western Burkina Faso

Abstract

Multiple constraints affect rice yields and global production in West Africa. Among these constraints are viral, bacterial and fungal pathogens. We aimed to describe the spatiotemporal patterns of occurrence and incidence of multiple rice diseases in farmers’ fields in contrasting rice growing systems in western Burkina Faso. For this purpose, we selected a set of three pairs of sites, each comprising an irrigated area and a neighboring rainfed lowland, and studied them over four consecutive years. We first performed interviews with the rice farmers to better characterize the management practices at the different sites. This study revealed that the transplanting of rice and the possibility of growing rice twice a year are restricted to irrigated areas, while other practices, such as the use of registered rice cultivars, fertilization and pesticides, are not specific but differ between the two rice growing systems. Then, we performed symptom observations at these study sites to monitor the following four diseases: yellow mottle disease, Bacterial Leaf Streak (BLS), rice leaf blast and brown spot. The infection rates were found to be higher in irrigated areas than in rainfed lowlands, both when analyzing all observed symptoms together (any of the four diseases) and when specifically considering each of the two diseases: BLS and rice leaf blast. Brown spot was particularly prevalent in all six study sites, while yellow mottle disease was particularly structured geographically. Various diseases were frequently found together in the same field (co-occurrence) or even on the same plant (coinfection), especially in irrigated areas.

Genetic Structure and Diversity of Rice From Certified Cultivars and Farmer’s Fields in Burkina Faso

“…Highest between site genetic differentiation was between Tengrela rainfed lowland and Banzon irrigated perimeter (F ST = 0.328 [0.311-0.347]). Such a speci city of this site of Tengrela, compared to others study sites, was also evidenced in a previous study on agricultural practices, showing that rice was mostly grown by women, for self-consumption only, with low frequency of chemical fertilization but often manure from household waste (Barro et al 2021).…”

“…In addition, we took advantage of a sampling previously performed in six sites in western Burkina Faso (Barro et al 2021). These six sites are located in three geographical zones (Bama, Banzon and Kar guela), each zone comprising one irrigated area and a neighboring rainfed lowland (Fig.…”

“…In 40 out of these 50 elds (80%), we interviewed the farmer and asked for the rice cultivars grown. We also performed farmer's interviews in the same sites in the two previous years (2016-2017) and subsequent year (2019) (Barro et al 2021). A synthesis of obtained responses (annual frequencies of cultivars grown over the four-year period) are reported in Fig.…”

“…Tengrela was also the only site among the six where only landraces were grown (no use of certi ed cultivars, Fig. 1b, Barro et al 2021) and where a sample was attributed to Aus group (Fig. 2, Fig.…”

Assessment of Genetic Diversity of Rice in Registered Cultivars and Farmers’ Fields in Burkina Faso

“…In addition, we took advantage of a sampling previously performed in six sites located in western Burkina Faso [23]. These six sites are located in three geographical zones (Bama, Banzon and Karfiguela, see Figure 1a), each zone comprising one irrigated area and a neighboring rainfed lowland.…”