Globodera species (potato cyst nematode; PCN) cause 50-80% losses to UK potato fields. Integrated control of nematodes is widely practised but Britain is heavily dependent on chemical control for PCN. Six successful field trials have been completed with transgenic potato plants expressing a range of nematode defence genes. They provided the first field demonstration of effective transgenic resistance for control of potato-cyst nematodes in UK agriculture. The trials showed that inhibition of a digestive proteinase reduces multiplication of the nematodes on potato. Control of these crop pests was achieved using plant cysteine proteinase inhibitors (cystatins) expressed in rice and sunflower seeds which are already consumed by humans.
Meloidogyne species damage upland rice in both Asia and Africa, with a prevalence of 20% in insular Asia and 50% in continental Asia, they can cause up to 70% yield losses at the field level. Losses of a similar order are likely in Africa. Management is necessary to ensure that cropping sequences do not lead to the build up of nematodes to levels that will damage intolerant crops. Pratylenchus species (particularly P. zeae) are extremely prevalent in Asia (c. 100%) and African upland rice and are very damaging when conditions support high population levels. Meloidogyne graminicola is increasing in importance on irrigated lowland rice in Asia wherever water conservation measures reduce the extent to which flooding controls this pest. Hirschmanniella species are present in over 90% of irrigated fields in Asia where yield losses can reach 40% for continual rice cropping. Attempts to compensate for losses by increasing the number of crops per year exacerbates the problem. Unfortunately cultivar resistance offers only limited nematode control.
Bananas and plantains, of the genus Musa, are the 4th most improtant food crop of sub-Saharan Africa (SSA) and a significant component of food security across the region. Banana cultivars are highly susceptible to a wide range of pest and pathogens, a consequence of the small genetic pool that bananas have to develop resistance to any new threat. One of the most significant pests of all bananas globally are plant parasitic nematodes. The two most significant nematode pests in SSA in terms of damage caused are Radopholus similis and Pratylenchus coffeae. Both are introduced pests, brought in on contaminated planting material from outside the continent. Other nematode pests of banana present in SSA are the native Pratylenchus goodeyi and species of Helicotylenchus, Meloidogyne and Rotylenchulus, though these species are less important economically. Global estimates of losses to nematodes in banana plantations average 20% but reach 70% in SSA where storms topple plants with rotten, nematode-infested root systems.