First Report of the Soybean Cyst Nematode, Heterodera glycines, on Soybean in Zhejiang, Eastern China

Evaluation Soybean Cultivars for Reaction to Heterodera glycines Populations HG Types 7 and 1.3.4.7 in Northeast China

Soybean cyst nematode Heterodera glycines (SCN) is a major threat to global soybean production. Effective management of this disease is dependent on the development of resistant cultivars. Two SCN HG Types, 7 and 1.3.4.7. were previously identified as prevalent H. glycines populations in Northeast China. In order to evaluate soybean cultivars resistant to local SCN populations, 110 domestic commercial soybeans from different regions of Northeast China were assessed in the greenhouse to determine their potential as novel sources of resistance. The results suggested that cultivars responded differently to the two HG types. Of the 110 soybean cultivars evaluated, 24 accessions were classified as resistant or moderately resistant to HG Type 7, and five cultivars were classified as resistant or moderately resistant to HG Type 1.3.4.7. Among the tested cultivars, Kangxian 12 and Qingdou 13 had resistance response to both HG types 7 and 1.3.4.7. Thus, these broad-based SCN cultivars will be the valuable materials in the SCN resistance breeding program.

The Spatial Distribution and Genetic Diversity of the Soybean Cyst Nematode, Heterodera glycines, in China: It Is Time to Take Measures to Control Soybean Cyst Nematode

The continuous evolution and spread of virulent forms of the soybean cyst nematode (SCN) driven by the environment and anthropogenic intervention is a serious threat to the soybean production worldwide, including China. Especially in China, the implemented measures to control SCN are insufficient for sustainable agricultural development yet. We summarized our knowledge about the spread and spatial distribution of SCN in China and the virulence diversity in the main soybean growing areas. To reveal the genetic relatedness and diversity of SCN populations, we re-sequenced 53 SCN genomes from the Huang-Huai Valleys, one of the two main soybean growing areas in China. We identified spreading patterns linked to the local agroecosystems and topographies. Moreover, we disclosed the first evidence for the selection of complex virulence in the field even under low selection pressure in an example from North Shanxi. SCN is present in all soybean growing areas in China but SCN susceptible cultivars are still largely grown indicating that SCN-related damage and financial loss have not received the attention they deserve yet. To prevent increasing yield losses and to improve the acceptance of resistant cultivars by the growers, we emphasized that it is time to accelerate SCN resistance breeding, planting resistant cultivars to a larger extent, and to support farmers to implement a wider crop rotation for sustainable development of the soybean production in China.

FMRFamide-Like Peptide 22 Influences the Head Movement, Host Finding, and Infection of Heterodera glycines

The FMRFamide-like peptides (FLPs) represent the largest family of nematode neuropeptides and are involved in multiple parasitic activities. The immunoreactivity to FMRFamide within the nervous system of Heterodera glycines, the most economically damaging parasite of soybean [Glycine max L. (Merr)], has been reported in previous research. However, the family of genes encoding FLPs of H. glycines were not identified and functionally characterized. In this study, an FLP encoding gene Hg-flp-22 was cloned from H. glycines, and its functional characterization was uncovered by using in vitro RNA interference and application of synthetic peptides. Bioinformatics analysis showed that flp-22 is widely expressed in multiple nematode species, where they encode the highly conserved KWMRFamide motifs. Quantitative real-time (qRT)-PCR results revealed that Hg-flp-22 was highly expressed in the infective second-stage juveniles (J2s) and adult males. Silencing of Hg-flp-22 resulted in the reduced movement of J2s to the host root and reduced penetration ability, as well as a reduction in their subsequent number of females. Behavior and infection assays demonstrated that application of synthetic peptides Hg-FLP-22b (TPQGKWMRFa) and Hg-FLP-22c (KMAIEGGKWVRFa) significantly increased the head movement frequency and host invasion abilities in H. glycines but not in Meloidogyne incognita. In addition, the number of H. glycines females on the host roots was found to be significantly higher in Hg-FLP-22b treated nematodes than the ddH₂O-treated control J2s. These results presented in this study elucidated that Hg-flp-22 plays a role in regulating locomotion and infection of H. glycines. This suggests the potential of FLP signaling as putative control targets for H. glycines in soybean production.

The Heterodera glycines effector Hg16B09 is required for nematode parasitism and suppresses plant defense response

Soybean cyst nematode (Heterodera glycines Ichinohe) is a sedentary root endoparasite that causes serious yield losses on soybean (Glycine max) worldwide. H. glycines secrets effector proteins into host cells to facilitate the success of parasitism. Nowadays, a large number of candidate effectors were identified from the genome sequence of H. glycines. However, the precise functions of these effectors in the nematode-host plant interaction are unknown. Here, an effector gene of dorsal gland protein Hg16B09 from H. glycines was cloned and functionally characterized through generating the transgenic soybean hairy roots. In situ hybridization assay and qRT-PCR analysis indicated Hg16B09 is exclusively expressed in the dorsal esophageal cells and up-regulated in the parasitic-stage juveniles. The constitutive expression of Hg16B09 in soybean hairy roots caused an enhanced susceptibility to H. glycines. In contrast, in planta silencing of Hg16B09 exhibited that nematode reproduction in hairy roots was decreased compared to the empty vector control. In addition, Hg16B09 also suppressed the expression of soybean defense-related genes induced by the pathogen-associated molecular pattern flg22. These data indicate that the effector Hg16B09 might aid H. glycines parasitism through suppressing plant basal defenses in the early parasitic stages.

Genetic structure analysis of populations of the soybean cyst nematode, Heterodera glycines, from north China

To elucidate the genetic differentiation of the host populations ofHeterodera glycines, 348 individuals from 13 populations of three host plants (Nicotiana tabacum,Glycine maxandRehmannia glutinosa) in north China were genotyped using eight microsatellite loci. A significant departure from Hardy-Weinberg equilibrium (Fis) was found in all populations. BOTTLENECK results showed that only three populations (ZT, CR, and MR) may have experienced a genetic bottleneck. The pairwiseFSTvalues among the three host populations ranged from 0.0503 to 0.2867. There was no significant relationship between the genetic distance and geographical distance. STRUCTURE analyses suggest thatR. glutinosamight have important influence on the genetic differentiation ofH. glycinesin north China. Our study demonstrates thatH. glycinesis an inbred species that is highly genetic differentiated.