Plant Parasitic Nematodes Associated With Cabbage In Different Agro-Ecological Zones In Nyandarua And Embu Counties, Kenya

ABSTRACT

Cabbage (Brassica oleracea L. Var. capitata) is an important vegetable crop in

Kenya. It is widely used as human food and animal feed. Owing to findings

that cabbage is a poor host to root knot nematode (RKN), this crop has been

incorporated in plant parasitic nematode (PPN) management as a rotation crop.

As a result very little has been done to study nematodes associated with this

crop, yet there are reports of nematodes infecting it. A survey was therefore

conducted in Nyandarua and Embu Agro-ecological Zones (AEZs), of Kenya

to determine the types, abundance and frequency of occurrence of PPNs

associated with cabbage. A total of 60 soil and root samples were collected

from six AEZs. Nematodes were extracted from 100 g of soil per sample using

the modified Baermann extraction tray technique while nematodes within the

roots were extracted using modified maceration and filtration technique. Roots

were rated for galling index using a scale of 0-5, then stained for egg masses

and presence of endoparasitic nematodes. Extracted nematodes were

enumerated and identified to genera level. A total of nineteen (19) genera of

PPNs belonging to ten (10) families of the Order Tylenchida, Dorylaimida and

Triplonchida were identified from both soil and roots. Lesion nematodes

(Pratylenchus spp.) were detected in 58% of the root samples, followed by

Helicotylenchus spp. (27%) and root-knot nematode (RKN) Meloidogyne spp.

(23%). The RKN galling index ranged from 1 to 2 on a scale of 1-5. The lesion

nematodes had the highest frequency of occurrence (A/F) in soil (87%)

followed by Helicotylenchus spp. (82%) and Tylenchorhynchus spp. (67%).

Other PPNs genera were identified at varying absolute frequencies. The

population densities of nematodes differed significantly (P