Ditylenchus dipsaci and Ditylenchus destructor as a threat to potato production

Abstract

Potato (Solanum tuberosum) is an economically important crop worldwide. Plant parasitic nematodes are important potato production constraint. Potato stem nematode Ditylenchus dipsaci and potato tuber rot nematode Ditylenchus destructor are listed as quarantine nematodes. The occurrence of morphologically indistinguishable biological races and populations differing in host preference and occurring at different stages of speciation and reproductive isolation makes identification of D. dipsaci complex.  D. destructor may occur in separate or mixed population, posing a complex threat to potato production in terms of yield losses and limiting trade. To date, comprehensive information on D. dipsaci and D. destructor as potato pest is not fully documented. To date characterization of intraspecific variations of biological races in D. dipsaci species complex, as well as in D. destructor based on ribosomal intergenic spacer region (IGS) has not been documented. Additionally, climate change has impact on the life cycle of nematodes. This is known to influence population growth and consequently yield losses. Potato varieties have not been tested for their tolerance and sensitivity to both D. dipsaci and D. destructor. Such knowledge is vital for development and breeding of resistant varieties. Varying population densities are known to have variant yield loss impact. This has not been documented for D. destructor and potato plant. Alternative crops used by farmers for rotation cultivation are also potential hosts for both D. dipsaci and D. destructor. It’s the objective of this PhD research to characterize D. dipsaci and D. destructor using polyphasic approach. Also to evaluate the effect of temperature to on life cycle of D. destructor, determine the sensitivity and tolerance of various potato cultivars to D. destructor and assess the host range and population increase on selected alternative crops to potato.