Browsing by Author "Onchari, N. M."

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    MANAGEMENT OF PARASITIC ROOTKNOT NEMATODES IN SWEETPOTATO: REVIEW
    (Chuka University, 2021) Onchari, N. M.; Githae.E. W.; Franklin N.; Muraya M. M.
    Agriculture is the mainstay in Kenyan economy, it currently contributes to 29% in gross domestic product (GDP) and creates employment of over 80% in the rural population. There are four major sub sectors in the agricultural sector which are food crops, industrial crops, livestock, fisheries and horticulture. Sweet potatoes are based under horticultural crops production which are now constrained by many biotic factors including root knot nematodes (RKN).Root knot nematodes pose a significant threat to a wide range of agricultural crops. The effect of RKNs in sweet potatoes are seen through the formation of galls, which reduce water and nutrient uptake, stunted vines and discoloured cracks in root tubers. These effects cause poor quality of tubers hence yield loss and high costs of production leading to poor income. Root knot nematodes diversity depends on ecological conditions and change of environmental conditions with time. Management strategies to control RKN have been practiced over time; cultural methods including fallowing of fields, intercropping and crop rotation have been used however root knot nematodes have ability to infect a wide host range; use of resistant varieties against RKN were adopted however some resistant genes tend to be silent in soil temperatures above 30ᵒC rendering the crop susceptible; use of synthetic nematocides were then found effective against RKN species however they leave residues on plants which are harmful to human consumption and are environmentally unfriendly hence they were banned. With these challenges scientists are focusing on discovery of nematocides from medicinal plants. The use of medicinal plants especially Canavalia ensiformis has shown 87% mortality rate on juveniles at stage two. Due to limited exploration of medicinal plants, more studies are encouraged on the same for RKN management and increase food security
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    Prevalence and distribution of plant parasitic nematodes associated with sweet potato: A case study of Kirinyaga County in Kenya
    (African Scholars Publishing / journal editorial platform based in Africa (Kenya)., 2023-05) Onchari, N. M.; Githae, E. W.; Muraya, M. M.; Nyabuga, F.
    A survey of plant parasitic nematodes (PPNs) associated with sweet potato (Ipomoea batatas) was carried out in three agro-ecological zones of Kirinyaga County in Kenya. Samples of rhizosphere soil and sweet potato tubers were collected for PPN extraction and morphometric characterization. Seven genera were morphologically identified (Meloidogyne, Pratylenchus, Helicotylenchulus, Scutellonema, Rotylenchulus, Heterodera and Aporcelaimellus). There were differences in the shapes and sizes of the mature PPN females and the diameter ranged from 204.3 μm to 437.3 μm. Meloidogyne had the highest prevalence (25%) and distribution (0.161), followed by Pratylenchus with a prevalence and distribution of 23% and 0.151, respectively. Farmers’ perceptions were captured using a semi-structured questionnaire. Overall, sweet potato farming was mainly practiced under mixed cropping (70.11%), small-scale (60.11%) and subsistence (55.17%). A higher proportion of the respondents (49.43%) sourced sweet potato vines from their own farms. The main control strategies applied for PPN were insecticides (55.59%), nematicides (11.49%) and concoctions (5.75%). Of all the respondents, 29.89% could not recognize symptoms of nematode infection. The distribution was significantly (p < 0.05) different among agro-ecological zones, with UM3 (upper midlands) showing the highest prevalence of 31. In conclusion, the differences in shapes and sizes of the mature females extracted from PPNs reveal a high level of morphological diversity. However, morphological characterization should be integrated with molecular methods for proper identification of PPNs. Awareness-raising among farmers about the best practices for proper management of PPN is necessary.