Table_3_Farmer and Field Survey in Cassava-Growing Districts of Rwanda Reveals Key Factors Associated With Cassava Brown Streak Disease Incidence and Cassava Productivity.docx

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.

木薯（Manihot esculenta Crantz）在卢旺达是一项至关重要的作物，其消费量位列第三大主食。然而，由于多种限制因素，包括重要的病毒性疾病，如木薯褐条病（CBSD），木薯的产量仍远低于其潜力。鉴于可通过多种因素减轻病毒性疾病的影响，识别木薯农业系统中从种子系统到农民实践及认知环节的病毒污染途径至关重要。本研究旨在（1）评估当前木薯种子系统和农民的实践及其对影响木薯生产的生物限制的认知，（2）确定CBSD的现状及其通过种子系统渠道传播的关联关键因素，以及（3）确定影响卢旺达木薯产量的因素。2019年5月至9月，在卢旺达13个地区开展了横断面研究。共访问了130位农民和木薯田，评估了CBSD的发生率和严重程度。CBSD在所有木薯生产区均有发现，其中尼亚萨地区记录的最高田间发病率达到62%（95% CI = 56–67%），其次是布格塞拉地区，其严重度评分为3.0 ± 0.6，达到60%（95% CI = 54–65%）。RT-PCR检测显示CBSD的检出率为35.3%，乌干达木薯褐条病毒占主导地位（21.5%），木薯褐条病毒占4%，混合感染占10%。非正式的木薯种子系统在个体农民中占主导地位，而大多数合作社使用优质种子。研究发现，肥料的使用、土地规模、耕作系统、木薯病毒病以及种植的木薯品种类型（p < 0.001）对木薯生产有显著影响。仅有半数参与者实施了疾病管理措施。与CBSD感染显著相关的因素（p < 0.05）包括扦插来源、与边界的邻近程度、木薯的年龄以及CBSD传播和管理的认知。