Abstract
Cassava (Manihot esculenta Crantz) is a vital crop in Rwanda where it ranks as the third most consumed staple. However, cassava productivity remains below its yield potential due to several constraints, including important viral diseases, such as cassava brown streak disease (CBSD). Because various factors can be addressed to mitigate the impact of viral diseases, it is essential to identify routes of virus contamination in the cassava agrosystems from the seed system to farmer's practices and knowledge. The present study aimed at (1) assessing the current cassava seed system and farmers' practices and their knowledge of the biotic constraints to cassava production, (2) determining the status of CBSD as well as critical factors associated with its spread through the seed system channels, and (3) determining factors that influence cassava productivity in Rwanda. A cross-sectional study was carried out from May to September 2019 in 13 districts of Rwanda. A total of 130 farmers and cassava fields were visited, and the incidence and severity of CBSD were evaluated. CBSD was detected in all cassava-producing districts. The highest field incidence of CBSD was recorded in the Nyanza district (62%; 95% CI = 56–67%) followed by the Bugesera district (60%; 95% CI = 54–65%), which recorded the highest severity score of 3.0 ± 0.6. RT-PCR revealed the presence of CBSD at the rate of 35.3%. Ugandan cassava brown streak virus was predominant (21.5%) although cassava brown streak virus was 4% and mixed infection was 10%. An informal cassava seed system was dominant among individual farmers, whereas most cooperatives used quality seeds. Cassava production was found to be significantly influenced by the use of fertilizer, size of the land, farming system, cassava viral disease, and type of cassava varieties grown (p < 0.001). Disease management measures were practiced by a half of participants only. Factors found to be significantly associated with CBSD infection (p < 0.05) were the source of cuttings, proximity to borders, age of cassava, and knowledge of CBSD transmission and management.
Highlights
Cassava (Manihot esculenta Cranzt) ranks as the sixth most important food crop worldwide and the fourth after rice, maize, and wheat among developing and emerging countries (Otekunrin and Sawicka, 2019; Saranraj et al, 2019)
Cassava plays an important role as a food security crop in sub-Saharan Africa, it is used as a cash crop in various cassava-growing regions (Spencer and Ezedinma, 2017; Munganyinka et al, 2018)
The yield potential of cassava under optimum conditions is about 90 tons of fresh roots per hectare, which is equivalent to 30 tons of cassava dry matter per hectare (El-Sharkawy, 2004)
Summary
Cassava (Manihot esculenta Cranzt) ranks as the sixth most important food crop worldwide and the fourth after rice, maize, and wheat among developing and emerging countries (Otekunrin and Sawicka, 2019; Saranraj et al, 2019). Despite its resilience under adverse environmental conditions, the production of cassava remains constrained by several abiotic and biotic factors The former includes postharvest deterioration, infertile soils, planting unimproved traditional varieties, and inadequate farming practices, whereas the latter includes green mites, mealy bug, cassava bacterial blight, and viral diseases (Bull et al, 2011; Kombate et al, 2017). Plant pathologists and extension services recognize the importance of establishing a disease-free seed system to mitigate the spread of CBSD (Mbanzibwa et al, 2009; Patil et al, 2015; Maruthi et al, 2017). Despite the emergence of CBSD in cassava fields in Rwanda, there has been limited information about the CBSD distribution and factors associated with its transmission as well as factors that affect cassava productivity in the country. The present study aimed at assessing the impact of farmers’ practices and their knowledge of the biotic constraints on cassava production as well as determining the status of CBSD and the critical factors associated with its spread through the seed system channels
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