Histopathological Changes in Banana Roots Caused by Pratylenchus coffeae, Meloidogyne incognita and Radopholus similis, and Identification of RAPD Markers Associated with P. coffeae Resistance

Worldwide, nematodes are amongst the most important pests of banana. By damaging the root system, nematodes adversely affect the uptake of water and nutrients, the basic needs for plant growth and fruit production. Although phenolics in banana roots are formed in response to infection by various pathogens including nematodes, information on the nature of such compounds and their potential role in defence is scarce. 59 banana genotypes (10 diploids and 49 triploids) were infected with the root-lesion nematode Pratylenchus coffeae, the root-knot nematode Meloidogyne incognita and the burrowing nematode Radopholus similis in glasshouse experiments. The production of phenolic compounds in healthy and nematode-infected banana roots was investigated histochemically, and RAPD markers associated with nematode resistance were identified. Root histological studies revealed higher numbers of cells with phenols and lignified cells in resistant accessions 'Karthobiumtham' (ABB) and 'Bhimkol' (BB) compared to susceptible accessions 'Therahaw-1164' (ABB) and 'Jahaji' (AAA). RAPD analysis using arbitrary oligonucleotide primers differentiated resistant and susceptible banana genotypes. The marker bands found in the resistant accessions could be used to study the molecular basis for resistance to nematodes. Sequencing of these bands could help to establish the mechanism responsible for nematode resistance.