Characterising the interactions between major nematode pathogens and the host coffee plant

Coffee is a hugely significant agricultural crop, produced by millions of growers worldwide. Production is threatened by numerous pests, pathogens, and increasingly unpredictable climactic conditions such as prolonged periods of drought. Nematode pests, distributed on a global scale, damage production by causing reduced coffee bean yield, and can cause plant death. The work described here investigates the interaction between the two major nematode species Meloidogyne incognita and Pratylenchus coffeae and commercially grown coffee cultivars. Various aspects of plant health under infection were measured in order to characterise the tolerance status of each cultivar to the two nematode species. The effect of drought on these cultivars was also investigated. Variable tolerances to infection and drought were observed between cultivars through photosynthetic rate, fresh weight and leaf water content measurements. Robusta cultivars exhibited strong resistance to nematode infection and reproduction in roots. Drought stress was observed to be a greater limiting factor to plant growth than nematode infection. The Robusta cultivar FRT49 and Arabica both showed stable photosynthetic rate measurements under infection and drought treatments, implying good performance in the field under these stresses. Stronger photosynthetic performance at lower soil moisture was seen in FRT79, suggesting that this cultivar may be useful in selective breeding for a drought tolerant rootstock. Reduced P. coffeae populations in FRT65 roots under drought conditions also suggest that this cultivar may have application in limiting the proliferation of this species in the field, although at the cost of coffee bean yield. The observations made here into the early stages of nematode infection and coffee plant development can be used to inform the application of specific cultivars in breeding programs aimed at producing new nematode and drought tolerant rootstock material.