Browsing by Author "Njeri, Editah"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Plant parasitic nematode assemblages associated with sweet potato in Kenya and their relationship with environmental variables
    (Springer, 2016-11) Karuri, Hannah W.; Olago, Daniel; Neilson, Roy; Njeri, Editah; Opere, Alfred; Ndegwa, Paul
    Sweet potato is one of the most important staple food crops consumed in Kenya and throughout Africa but yields are greatly reduced by plant parasitic nematodes (PPN). The aim of this study was to determine the prevalence of PPN in Kenyan sweet potato fields and their relationship with soil and climatic variables. Soil samples were collected from sweet potato fields in Busia, Teso, Kisii, Embu and Makueni counties. Thirteen nematode genera were identified across the five counties with Meloidogyne, Pratylenchus and Rotylenchus being the most prevalent. There was a significant (P <0.05) relationship between PPN abundance and sodium, calcium and iron. Canonical correspondence analysis of climatic variables revealed that the relationship between rainfall and nematode genera was significant (P <0.05) while maximum and minimum temperatures were not significant. This description of PPN assemblages associated with sweet potato in Kenya and their relationship with environmental variables provides a starting point from which appropriate nematode management strategies can be implemented.
  • Thumbnail Image
    Item
    Response of Selected Kenyan Rice Cultivars to Infection by Root Knot Nematode (Meloidogyne incognita)
    (Springer, 2019-03-22) Nyaga, Justine M.; Namu, John; Alakonya, Amos; Karuri, Hannah; Masanga, Joel; Njeri, Editah
    Meloidogyne incognita causes huge yield losses in rice which is the third most important cereal crop in Kenya. The aim of this study was to identify M. incognita-resistant rice cultivars from Kenya and relate the responses to known resistance pathways with OsPR1a, OsPAL1, and OsJAMYB as marker genes in rice. Five rice cultivars BW 196, Basmati 217 (Pishori), Sindano, IR 2793-80-1 (grown in lowland irrigated fields), and NERICA 4 (grown in upland rainfed fields) were evaluated for resistance to M. incognita under greenhouse conditions in two separate trials. The number of nematode eggs, reproduction factor (RF), and the level of galling were determined. The RF was used to select resistant cultivars. There was a significant difference (P < 0.001) in the number of eggs, galling index, and RF among the cultivars. NERICA 4, BW 196, and Sindano were classified as resistant with an RF <1. There was differential expression of the three marker genes between susceptible and resistant cultivars. OsJAMYB gene was up-regulated in leaves of all rice cultivars after 1 and 3 days post inoculation (dpi). OsPAL1 was up-regulated in leaves of all varieties at 3 dpi while OsPR1a was down-regulated in leaves of resistant plants at 1 dpi and 3 dpi. These results provide an insight on sources of M. incognita resistance in Kenyan rice and it also forms an interesting starting point for further studies on defense responses of common rice varieties to root knot nematode infection.v
  • Thumbnail Image
    Item
    Response of Selected Kenyan Rice Cultivars to Infection by Root Knot Nematode (Meloidogyne incognita)
    (2019-03) Namu, John; Alakonya, Amos; Karuri, Hannah W.; Nyaga, Justin; Masanga, Joel; Njeri, Editah
    Meloidogyne incognita causes huge yield losses in rice which is the third most important cereal crop in Kenya. The aim of this study was to identify M. incognita-resistant rice cultivars from Kenya and relate the responses to known resistance pathways with OsPR1a, OsPAL1, and OsJAMYB as marker genes in rice. Five rice cultivars BW 196, Basmati 217 (Pishori), Sindano, IR 2793-80-1 (grown in lowland irrigated fields), and NERICA 4 (grown in upland rainfed fields) were evaluated for resistance to M. incognita under greenhouse conditions in two separate trials. The number of nematode eggs, reproduction factor (RF), and the level of galling were determined. The RF was used to select resistant cultivars. There was a significant difference (P < 0.001) in the number of eggs, galling index, and RF among the cultivars. NERICA 4, BW 196, and Sindano were classified as resistant with an RF <1. There was differential expression of the three marker genes between susceptible and resistant cultivars. OsJAMYB gene was up-regulated in leaves of all rice cultivars after 1 and 3 days post inoculation (dpi). OsPAL1 was up-regulated in leaves of all varieties at 3 dpi while OsPR1a was down-regulated in leaves of resistant plants at 1 dpi and 3 dpi. These results provide an insight on sources of M. incognita resistance in Kenyan rice and it also forms an interesting starting point for further studies on defense responses of common rice varieties to root knot nematode infection.