Farmers’ Perceptions, Distribution and Molecular Characterization of Groundnut Rosette Disease in Western Kenya

Abstract

Groundnut rosette disease (GRD) is the most important viral disease of groundnuts in sub-Saharan Africa. In Kenya, GRD attack especially before flowering results in 100% loss in pod yield. Surveys were conducted between 2015 and 2017 to determine farmers’ knowledge and perceptions of GRD and its management as well as its distribution in five major groundnut growing Counties of western Kenya. In addition, the molecular diversity of the viruses causing GRD was determined. A structured questionnaire was used to assess GRD incidence and severity as well as farmers’ knowledge and management of GRD. Reverse transcription (RT)-polymerase chain reaction (PCR) was used for the detection of groundnut rosette assistor virus (GRAV), groundnut rosette virus (GRV) and satellite RNA (SatRNA), the causal agents of GRD in symptomatic and asymptomatic samples collected during the survey. The amplified RT-PCR products from the isolates of GRAV, GRV and Sat-RNA from infected groundnut plants were sequenced using the Sanger sequencing method. The sequences were edited, aligned and compared with other published sequences from GenBank using a Basic Local Alignment Search Tool (BLAST) and phylogenetic analysis. A total of 76 purposively selected farmers with groundnut fields were interviewed, and results indicated that pests and diseases are the main production constraints as indicated by 77% of the farmers. Awareness of GRD varied significantly (P < 0.001) among the farmers across the five counties as well as their knowledge on causes and management of GRD (P < 0.001The study findings revealed that 18.4% of groundnuts farmers in western Kenya had some knowledge about GRD. For the management of GRD, more than forty percent (43.58%) of respondents removed infected plants from the fields, 12.34% sprayed plants showing disease symptoms with chemical insecticides, 12.58% carried out crop rotations in their fields while 27.76% did not apply any management strategy on the diseased plants. It was also observed that GRD was prevalent in all the fields surveyed in the five Counties. The highest (35.7%) mean disease incidence was in Busia County while the lowest (23.1%) incidence was in Siaya. The most conspicuous symptoms observed in all the fields inspected were yellow/chlorotic and green rosette. The highest (3.1) mean disease severity was observed in farmers’ fields in Busia County, while the lowest (2.8) was observed in Siaya. Both GRAV and GRV were detected in all symptomatic and asymptomatic samples of groundnut leaves collected from the surveyed region. There was high degree of nucleotide identity among the Kenyan GRAV isolates from the five Counties in western Kenya. In conclusion, groundnut farmers in the sampled regions have limited awareness, knowledge and management of GRD. It is therefore important to build capacity of the farmers on detection, identification of the disease and its management. GRD is widely distributed in all groundnut fields in western Kenya and hence the need to use certified seeds. The disease is caused by presence of GRAV and GRV. It’s therefore important for plant breeders to develop groundnut varieties that are resistance to both GRAV and GRV with farmers’ preferred traits and high yielding. Researchers to perform Next Generation Sequencing to identify other unknown viruses infecting groundnuts in western Kenya