Farmers’ Perceptions, Occurrence and Transmission of Moroccan Watermelon Mosaic Virus Infecting Cucurbits in Selected Counties in Kenya

Abstract

Cucurbits are important food crops worldwide due to their nutritional benefits and also contribution to the national economies. In Kenya, cucurbits are mainly produced by small scale farmers for their leaves, immature and mature fruits and seeds. However, the production in the country is constrained by viral disease infections including Moroccan watermelon mosaic virus (MWMV), a potyvirus in the family potyviridae. The virus is transmitted by several species of aphids in a non-persistent manner and also by mechanical means.The cucurbit crops can be infected by the virus at every stage of growth, with early infection resulting in total yield loss if no management measures are taken.The virus was recently reported in Kenya in two counties infecting pumpkin (Cucurbita pepo L). Since the virus is known to infect several cucurbit species, determination of farmers perceptions, and distribution of MWMV in the major cucurbits growing counties in the country as well as transmission to different host species are important in the development of effective management strategies. A survey was conducted in the year 2024, covering a total of 229 cucurbit fields in seven sub-counties within three counties namely; Machakos County (Matungulu and Kangundo sub-counties) Kirinyaga County (Kirinyaga East, Kirinyaga West, and Mwea East sub-counties) and Embu County (Embu West and Mbeere North sub-counties). To understand farmers’ knowledge, perception and management strategies of the MWMVdisease, a total of 229 farmers’were randomly identified in seven sub-counties and a semi-structured questionnaire was administered through face to face interviews.The disease severity in the farmers’ fields was determined using a scale of 0 to 4. To determine the disease incidence, ten (10) plants per field were visually inspected for symptoms that are associated with MWMV disease. Moroccan watermelon mosaic virus distribution was determined by testing samples collected from the field using polymerase chain reaction (PCR)-based approach. To determine the influence of host plant species on aphid’s transmission efficiency of the virus, a greenhouse trial was carried out at the Jomo Kenyatta University of Agriculture and Technology (JKUAT). Aphids (Myzus persicae) were obtained from the University farm and maintained on common beans (Phaseolus vulgaris) plants established in the pots and placed in cages in an insect freee screenhouse. Two infected and natural host plants; pumpkin and papaya were used as source of MWMV inoculum for subsequent aphid transmissions. The experiment was laid out in a completely randomized design (CRD) with three treatments replicated (3) times. To transmit the virus, aphids were straved for one hour before feeding on the infected plants for 30 seconds to acquire the virus, The viruliferous aphids were then transferred to the healthy plants and allowed to feed for 40 seconds before spraying them with an insecticide. The plants were observed for MWMV disease symptoms development daily after transmission for a period of six weeks. Data for farmers perceptions were subjected to analysis of variance at p < 0.05 using (SPSS) and correlation analysis was done to determine the relationship between knowledge, perception and management of MWMV. Incidence and severity data was analysed through descriptive statistics, percentages and mean values using (SPSS). Influence of host plant efficiency data was analysed by determining the virus presence based on the amplification of the right size of fragment as observed in the agarose gel electrophoresis. The findings indicate that the farmers were aware of MWMV disease symptoms presence in their farms ranging from deformation, dark green blisters, and mosaic. Majority of the respondents 49.5% perceived the symptoms to be caused by weather changes, while 16.1% associated the symptoms with pest infestation while 11.1% did not know the cause of the symptoms in their farms. As a management measure, majority of the famers 85.5% used chemical control.The highest disease severity of 3.8 was recoded in Matungulu sub-county in Machakos county and the lowest 1.6 in Embu West sub-county in Embu county. Kangundo and Kirinyaga East sub-counties recorded the highest disease incidence of 100% while Kirinyaga West reported the lowest disease incidence of 62.5%. The number of positive samples was 12,8,4,and 3obtained from Matungulu, Embu West, Mwea East, and Mbeere North subcounties respectively. All the samples tested positive were from pumpkin crop species. Moroccan watermelon mosaic virus aphid transmission occurred from pumpkin to watermelon, Zucchini, and butter nut and not in papaya. Conversely, the virus was transmitted by aphids from papaya to zucchini crop species and not in the other cucurbit species. Although the virus was earlier reported in two counties, the presence of the virus to these counties under current study indicates that the virus is present in other counties and could probably spread to other parts of the country leading to damage cucurbit crops. Further, pumpkin crop species could be playing an important role in the epidemiology of the disease. Limited knowledge and management of MWMVsuggest farmers’ training is necessary for improved disease diagnostics and management. Futher, a detailed survey across the country is recommended to determine the extent of the virus spread.