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Ditylenchus dipsaciis an economically important plant-parasitic nematode affecting European sugar beets. To date, no sugar beet cultivars carrying resistance against D. dipsaciare available to farmers. To find potentially resistant sugar beet lines restricting reproduction and penetration of D. dipsaci, three consecutive in vivobioassays were carried out. The first experiment determined the penetration rate of D. dipsaciin 79 breeding lines and 14 pre-breeding populations. Based on these results, D. dipsacipenetration and reproduction resistance of eight genotypes was intensively investigated. It could be demonstrated that none of the genotypes showed resistance towards D. dipsaci. However, a high variation of the penetration rate by D. dipsaciwas observed among the genotypes. The breeding line ‘DIT_119’ effectively reduced D. dipsacipenetration (34.4 ± 8.8 nematodes/plant at 22 days post-planting) compared to the susceptible control (109.0 ± 16.9) while ensuring a yield comparable to non-inoculated plants. However, the breeding line ‘DIT_119’ did not reduce D. dipsacireproduction. The paternal line of the cultivar BERETTA KWS, demonstrating a high tolerance to D. dipsacicrown rot symptoms, did not reduce penetration and reproduction. Thus, no correlation can be established between reduced penetration rates, reproduction, and tolerance to D. dipsaci. This study provides an essential basis for the development of resistant sugar beet cultivars to D. dipsaci. The variations observed among genotypes now need to be confirmed with larger-scale screenings.

Fluopyram, a succinate dehydrogenase inhibitor fungicide, has shown potential in controlling Meloidogyne incognitaand Rotylenchus reniformisin tomato. The effectiveness of this compound for the control of Ditylenchus dipsaciin sugar beet was evaluated. In this study, laboratory, growth chamber, glasshouse, and field experiments were conducted. In a motility bioassay, the EC50value was determined with 3.00 μg/ml a.i. after 72 h exposure to fluopyram. The growth chamber experiment did not show any effects on D. dipsacipenetration rate; however, field experiments revealed a positive effect of fluopyram applied at planting in reducing D. dipsaciinfectivity. The glasshouse experiment confirmed a limited effect of fluopyram on D. dipsacipopulation development. Under field conditions, despite a reduction of D. dipsacipenetration rates in spring, fluopyram was not effective in reducing the population development until harvest. Consequently, D. dipsacidensities in plant tissue and soil were high at harvest and not different among treatments. However, root-rot symptoms were significantly reduced at harvest. Fluopyram applied at planting showed good potential to reduce root-rot symptoms caused by D. dipsaciin sugar beet. However, for the long-term reduction of nematode populations in soil, further integrated control measures are needed to reduce the risks of substantial yield losses by D. dipsaci.

The potato cyst nematodes (PCN), Globodera rostochiensis(Woll.) and G. pallida(Stone), are important pests of potato globally. Due to their extensive damage potential and the challenge of managing them, these nematodes are under strict regulations in many countries; however, despite these regulations, PCN continue to spread into new areas and countries. In Kenya, G. rostochiensiswas first reported in 2015 and G. pallidawas reported three years later, both in Nyandarua County. Research was conducted to characterize the biology, pathotype, and virulence of G. rostochiensispopulations from Kenya in glasshouse and laboratory studies. The development of G. rostochiensiswas assessed in roots of susceptible potato ‘Désirée’ and resistant ‘Laura’ carrying the H1 resistance gene. The ‘HAR1’ population from Kenya and ‘Ecosse’ from Germany were not able to produce females in the roots of the resistant potato ‘Laura’. The rate of root penetration by G. rostochiensisjuveniles did not differ (p> 0.05) between populations and cultivars. However, in the resistant cultivar, juveniles developed into males only. A total of 736 cumulative degree-days at 6°C base temperature (DD6) were required by ‘HAR1’ to complete the life cycle on ‘Désirée’, whereas ‘Ecosse’ completed the life cycle within 645 DD6. The Kenyan populations lacked obligatory diapause and high numbers of juveniles hatched immediately after maturity. Consequently, the Kenyan populations had the potential to complete up to three reproduction cycles in less than a year. On selected potato cultivars, the populations from Kenya failed to reproduce on 10 out of 13 commercial cultivars tested. The 10 cultivars carried the H1 resistance gene, which suggests that the G. rostochiensispopulations tested belong to the Ro1/4 pathotype group. The virulence of the G. rostochiensispopulations from Kenya did not differ from that of the standard reference population ‘Ecosse’ and therefore can be effectively managed with the commercially available potato cultivars carrying the H1 resistance gene.

Root-knot nematodes (Meloidogynespp.) cause extensive damage to tomato and cucurbit crops in protected cultivation systems. An environmentally benign solution for nematode control is the use of plant resistance that mitigates yield losses and reduces the Meloidogynepopulation in the soil. A collection of three tomato and six cucumber rootstocks was tested for resistance against eight Meloidogyne incognitapopulations (with different levels of virulence) in comparison with the susceptible variety Moneymaker and the resistant varieties Phantasia or Oskar. In addition, M. enterolobiiwas included in these experiments to evaluate the response of the tomato and cucumber plant genotypes. Tests were both conducted in a greenhouse or growth chamber and evaluated after completion of one reproduction cycle. The correlation of plant responses to Meloidogynepopulations from the different experiments showed significant relationships for 13 and 20 out of 36 combinations for the parameters gall index and number of egg masses per root system, respectively. In particular, two a-virulent reference populations showed significant positive relationships for both parameters, resulting in the same ranking of tested plant genotypes across test systems. Conversely, plant genotypes showed different responses when inoculated with virulent populations of M. incognitaor M. enterolobii. Some of the plant genotypes tested showed potential for use in Meloidogynespp. management strategies. However, cucumber plant genotypes seemed more suitable than tomato genotypes. Furthermore, some of the tested cucumber rootstocks were less sensitive when challenged with M. enterolobiiin pot experiments.