Plant-parasitic nematodes associated with cabbage in Nyandarua and Embu Districts Kenya
Kariuki, G. M.
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A survey was conducted to determine the occurrence of plant parasitic nematodes (PPN) associated with cabbage (Brassica oleracea L. var capitata) in Nyandarua and Embu districts of Kenya. A total of 60 soil and roots samples were collected from six agro-ecological zones (AEZs). Nematodes were extracted from 100 g of soil per sample using a modified Baermann extraction tray technique while nematodes inside the roots were extracted using modified maceration and filtration technique. Roots were rated for galling index using a scale of 0-5, then stained in phloxine B and in NaOCl-acid fuchsin for egg masses and presence of endoparasitic nematodes. A total of eighteen (18) genera of PPN belonging to ten (10) families of the order Tylenchida and Dorylaimida were identified from both soil and roots. The populations of various PPN differed significantly (p<0.05). Lesion nematodes (Pratylenchus spp.) were detected in 58% of the root samples, followed by spiral nematodes (27%) while Meloidogyne spp., were third with 23%. The root galling ranged from 1 to 2 on the galling index signifying some level of resistance. Lesion nematodes were also present in the soil at a high absolute frequency of occurrence of 87%; Helicotylenchus spp. had 82% and Meloidogyne spp. 42%. Other nematodes of economic importance included stunt nematode Tylenchorhynchus spp., stubby nematode Paratrichodorus spp. and Trichodorus spp. with 67, 57and 78% absolute frequency of occurrence respectively. Xiphinema spp. and Longidorus spp. were present in relatively lower frequency (28% and 20% respectively) in soil and only 8% and 5% in the roots. Filenchus spp., Coslenchus spp. and Tylenchus spp. were present at a high frequency. This study therefore concludes that cabbage is a potential host to PPN and particularly Pratylenchus spp. and its use as a rotation crop should be evaluated