Genomic Markers Linked to Meloidogyne Chitwoodi Resistance Introgressed From Solanum Bulbocastanum to Cultivated Potato and Their Utilility in Marker-assisted Selection

Meloidogyne chitwoodi is a major threat to potato production in the Pacific Northwest region of United States. Infected tubers are rendered unmarketable, hence growers’ profitability is adversely affected. Breeding for nematode resistance is a long-term process and phenotyping the segregating populations for nematode resistance is the most time-consuming and laborious part of the process. Using DNA-based markers closely linked to the nematode resistance trait for marker-assisted selection (MAS) could enhance breeding efficiency and accuracy. In the present study, a pool of phenotyped progenies segregating for nematode resistance and susceptibility were fingerprinted using a 21K single nucleotide polymorphism (SNP) array. Eight candidate SNPs located on potato Chromosome 11, segregating with the nematode resistance trait were identified and used as landmarks for discovery of other marker types such as, simple sequence repeat (SSR) and insertion-deletion (INDEL) markers. Subsequently, a total of eight SNPs, 30 SSRs and four INDELS located on scaffold 11 of Solanum. bulbocastanum were used to design primers; markers were validated on a panel of resistant and susceptible clones. Two SNPs (SB_MC1Chr11-PotVar0066518 and SB_MC1Chr11-PotVar0064140), five SSRs (SB_MC1Chr11-SSR04, SB_MC1Chr11-SSR08, SB_MC1Chr11-SSR10, SB_MC1Chr11-SSR13 and SB_MC1Chr11-SSR20) and one INDEL (SB_MC1Chr11-INDEL4) markers differentated between the resistant and susceptible clones in the test panel as well as other segregating progenies using simple PCR technique and high resolution melting curve analysis. These markers are robust, highly reproducible and easy to use for MAS of nematode resistant potato clones to enhance the breeding program.

Nematode Genome Announcement: Draft genome of Meloidogyne chitwoodi, an economically important pest of potato in the Pacific Northwest

Meloidogyne chitwoodi is one of the most devastating pests of potato in the U.S. Pacific Northwest (PNW). Nematode-infected tubers develop external as well as internal defects, making the potatoes unmarketable, and resulting in economic losses. Draft genome assemblies of three M. chitwoodi genotypes, Mc1, Mc2 and Mc1Roza, were generated using Illumina and PacBio Sequel RS II sequencing. The final assemblies consist of 30, 39 and 38 polished contigs for Mc1, Mc2 and Mc1Roza, respectively, with average N50 of 2.37 Mb and average assembled genome size of ~47.41 Mb. An average of 10,508 genes were annotated for each genome. BUSCO analysis indicated that 69.80% of the BUSCOs were complete whereas 68.80%, 0.93% and 12.67% were single copy, duplicated and fragmented, respectively. These highly contiguous genomes will enrich resources to study potato-nematode interactions and enhance breeding efforts to develop nematode resistant potato varieties for PNW.

Solanum linnaeanum and Solanum sisymbriifolium as a sustainable strategy for the management of Meloidogyne chitwoodi

Root-knot nematodes (RKN), Meloidogyne spp., are important crop pests that cause severe losses in crop production worldwide, reducing both productivity and crop quality. Meloidogyne chitwoodi Golden, O'Bannon, Santo & Finley, 1980 is considered a quarantine organism by the European and Mediterranean Plant Protection Organization (EPPO) causing damage in tomato and potato crops. The development of nonchemical and sustainable management strategies to reduce nematode damage is crucial. The resistance of Solanum linnaeanum Hepper & P.-M.L. Jaeger and S. sisymbriifolium Lamarck cv. Sis 6001 to M. chitwoodi was evaluated based on gall index (GI), the Bridge & Page (1980) rating chart and reproduction factor (RF). Both plant species were resistant to M. chitwoodi. Solanum linnaeanum had an average of 519 small root swellings/plant, with 45% adult nematodes inside the roots, all males. Solanum sisymbriifolium had GI ≤ 2 and RF ≤ 1 with a high percentage (69%) of nematodes inside the roots that did not develop beyond the sexually undifferentiated second-stage. The use of S. linnaeanum as a new source of resistance is a good alternative for the control of RKN in the quest to develop nonchemical and sustainable management strategies to protect crops.

Integrated management of Meloidogyne chitwoodi and M. fallax in potato: a complicated agronomical puzzle in the Netherlands and Belgium.

Meloidogyne chitwoodi and M. fallax have been important nematode problems in arable farming in the Netherlands and Belgium ever since their detection in the 1980s. Their quarantine status and the damage inflicted on product quality in important cash crops such as potato, carrots, black salsify and gladiolus has increased drastically the need for integrated nematode management strategies that prevent yield losses and further spreading. This chapter elaborates on the economic importance, host range, distribution, symptoms of damage, biology and life cycle, interactions with other nematodes and pathogens, recommended integrated nematode management (prevention, inventory, crop rotation and supporting measures), and management optimization of M. chitwoodi and M. fallax. Future research requirements are also mentioned.

Lowering quality damage in open-field vegetables caused by Meloidogyne chitwoodi and M. fallax in the low countries.

The Low Countries (the Netherlands and Belgium) provide some of the best agricultural soils in the world for open-field vegetable production rendering high yields per hectare. Since the 1990s, pre-harvest quality control of carrots (Daucus carota) and black salsify (Scorzonera hispanica) showed an increase in tap root damage with severe galling and rough surface rendering the infected vegetables unprocessable. This quality damage was caused by the polyphagous root-knot nematodes Meloidogyne chitwoodi and M. fallax. This chapter discusses the geographical distribution, damage symptoms, economic impact, recommended integrated management, and management optimization of M. chitwoodi and M. fallax. Future research requirements and future developments are also mentioned.

Correction to: Transcriptome profiling of resistance response to Meloidogyne chitwoodi introgressed from wild species Solanum bulbocastanum into cultivated potato

Following the publication of this article [1], the authors noted an error in Figure 11.