Commercially available sorghum cultivars were tested for resistance to Meloidogyne incognita in order to select cultivars that combine fodder production with M. incognita population management. Initially in a pot test with 12 sorghum cultivars, ‘Kyushuko 3 go’, a sorghum hybrid, supported very low M. incognita reproduction approximately 40 days after inoculation (dai) with 500 second-stage juveniles (J2) pot−1, similar to the resistant green manure ‘Tsuchitaro’. Further tests for development of M. incognita in roots (20 dai with 150 J2 (root system)−1) indicated that the resistance of ‘Kyushuko 3 go’ acts after nematode root penetration. In field tests in 2015 and 2016, ‘Kyushuko 3 go’ suppressed M. incognita population densities, although some variations in field conditions may influence reproduction of M. incognita on ‘Kyushuko 3 go’. These findings demonstrated M. incognita-resistant fodder sorghum cultivars could be a useful alternative to susceptible cultivars for root-knot nematode management.
We surveyed the distribution of nematodes in 56 cones of Pinus thunbergii collected from both live branches and on the forest floor in three coastal and inland habitats and in 11 cones of P. taeda collected at different heights. We identified 47 nematodes to family or genera by analysis of an 18S small subunit rRNA gene sequence. The frequencies of occurrence of free-living cone nematodes were 97% in coastal P. thunbergii, 92% in inland P. thunbergii, and 82% in P. taeda. Phylogenetic analysis assigned the nematodes to four clades with high bootstrap values. Nine sequences that were found only in cones on live branches were clustered with Panagrobelus stammeri and an unknown Panagrobelus sp. Our results imply that nematodes are commonly associated with cones in pine forest ecosystems and that a capacity for anhydrobiosis may be a key to surviving above-ground.
This paper deals with the general morphology of the dorylaimid genus Aporcelinus as a basis for updating its taxonomy. This taxon is morphologically rather homogeneous and characterised by a peculiar combination of apomorphic states of several features, which are described, illustrated and discussed, particularly those concerning lip region, odontostyle, pharyngo-intestinal junction, female genital tract, and caudal region. A revised generic diagnosis is presented and the separation of the genus from its relatives analysed. The updated inventory of Aporcelinus includes 29 valid species with their synonyms and two species inquirendae. A key to identification of species is also given, and a compendium of their morphometrics is provided for comparative purposes.
The hatching and emergence of juveniles from cysts of Heterodera schachtii in response to various stimuli are well understood. These responses relate to means of optimising the chances of successful reproduction and survival of populations. However, the effect of different cultivars of host species is not so well understood. To gain a further understanding of any differences between cultivars of host species, we conducted a number of experiments using root leachates obtained from a range of cultivars of sugar beet (Beta vulgaris), radish (Raphanus sativus) and white mustard (Sinapis alba). Heterodera schachtii cysts were exposed to root leachate solutions in in vitro laboratory assays during which emergence of second-stage juveniles (J2) from cysts was monitored weekly. Significant differences in the stimulation of hatch of J2 were found in response to different sugar beet cultivars and these differences may be driven by differing growth habits of such varieties. However, results obtained from experiments using brassica varieties showed contrasting responses. In one experiment, root leachates appeared to inhibit hatch of J2. However, two experiments did show a stimulation of hatch of J2 and also significant differences in hatch responses due to the age of the plant. These findings may help develop future screening procedures for brassica trap crops and help identify those that show the greatest potential for H. schachtii control.
The root-lesion nematode, Pratylenchus thornei, attacks a wide range of crops and causes significant reductions in global grain production. Breeding programmes are currently restricted to using parents with moderate resistance to P. thornei as cereal cultivars with complete resistance are yet to be identified. This study evaluated 484 of CIMMYT’s spring wheat accessions for resistance to P. thornei of which 56 lines were pre-identified as resistant under controlled growth room conditions. These lines were further evaluated for their resistance and tolerance reactions under field conditions, where 14 accessions maintained their resistance and 16 were moderately resistant against P. thornei. Four lines gave excellent resistant and tolerance reactions to P. thornei. The relationship between the nematode reproduction factor (Pf/Pi) and wheat grain yield in field experiments fits a linear regression model. These findings could be useful for improving P. thornei resistance in wheat.
We analysed the effect of the invasive perennial plant Heracleum sosnowskyi on soil nematode communities and diversity, and plant species composition, by comparing invaded and non-invaded (control) areas in natural conditions. Invasion of H. sosnowskyi caused significant shifts in plant species composition, which subsequently modified nematode assemblages. Stress-sensitive omnivores, fungivores and root-biomass-dependent obligate plant parasites best reflected changes in soil nematode communities under the influence of H. sosnowskyi invasion. The negative effect of H. sosnowskyi was most evident on Aphelenchus, Tylencholaimus, Geocenamus, Helicotylenchus, Pratylenchus, Tylenchorhynchus and Aporcelaimellus. Our results indicate that significant changes in the herbaceous layer after H. sosnowskyi invasion in ecosystems where H. sosnowskyi eventually became dominant impacted soil nematode communities but did not affect nematode diversity. This was in contrast to the habitats where a solitary plant of H. sosnowskyi grew and no significant changes in nematode communities were observed.
This paper presents studies on the life cycle of Heterodera sacchari under in vitro conditions. Pluronic gel was used as a medium for growth of H. sacchari. The life cycle was completed in 7-9 weeks on rice (Oryza sativa, ‘Nipponbare’). After infection, juveniles developed and reached the reproducing adult female stage at 25 days post inoculation (dpi). At 35 dpi, all females produced eggs in various numbers. Some females were translucent and eggs inside could be counted. At 49 dpi females started to tan and developed into dark brown cysts. Hatching of H. sacchari juveniles from cysts could be stimulated by 3 mM ZnCl2 but not by rice root exudates. The in vitro culture of H. sacchari on Pluronic gel can be used efficiently to collect post-infective nematode/host samples at different time points for various studies and to screen different rice cultivars for resistance/susceptibility.