Background: The more than 4100 species of phytoparasitic nematodes are responsible for an estimated economic loss in the agricultural sector of nearly $125 billion annually. Knowing the main lines of research and concerns about nematodes that affect plants is fundamental. Methods: For this reason, an analysis using bibliometric data has been carried out, with the aim of tracing the state of world research in this field, as well as knowing the main lines of work, their priorities, and their evolution. Results: This will allow us to establish strategic lines for the future development of this research. Conclusions: The analysis has allowed us to detect that the interest in nematodes affecting plants has not stopped growing in the last decades, and that tomato, soybean, and potato crops are the ones that generate the most interest, as well as nematodes of the genus Meloidogyne and Globodera. Likewise, we have detected that the main lines of research in this field are focused on biological control and host–parasite interaction.

Olive growing is a centenarian activity in Andalusia, Southern Spain. Andalusia holds the largest olive tree growing area in the world. In spite of the relevance of olive growing for the Mediterranean economy, the influence of soil biodiversity on olive crops has been seldom studied. We hypothesized that soil diversity must be well preserved because the Andalusian olive groves are low-input and no-till systems. Soil depth should also help to structure soil diversity. We tested the effect of site features and soil management on nematode diversity, soil properties and soil food webs. Site features included use, position, orientation, radiation, slope, altitude and regional scale. Soil management included tillage and herbicide use. Results show that at the large scale, nematode abundance and soil food web structure were reduced under the tree canopy affected by herbicides by 57.9 and 14.2 %, respectively, in comparison to areas not treated with herbicides. Nematode abundance decreased by 47.7 %, taxa richness by 12.4 % and soil food web structure by 23.4 % in areas where herbicides are applied, in comparison to surrounding oak woodlands. The absence of vegetation in bare soils impacted the lower levels of the soil food web, depleting bacterial and fungal-mediated decomposition channels. This depletion spread up in turn to microbivore nematodes and nematodes in the upper level. We also found that nematode abundances decreased with soil depth on average by 73.2 % from the top soil layer (0–2 cm) to the deepest one (10–20 cm), irrespectively of the tillage practice.

With a surface area of 37 000 ha and an annual yield of 3 × 10⁶ t, the south-east of Spain, predominantly the coast of Almeria, is the largest horticultural growing area under protected cultivation in Europe. A survey on perception of the impact of root-knot nematodes on vegetable production was carried out in this area by face-to-face interviews with 120 farm advisors. The survey was designed to evaluate opinions about prevalence and severity of root-knot nematode-induced diseases, percentage of infested area and effectiveness of root-knot nematode control methods. According to the answers, 17.7% of the fields were infested with root-knot nematode and 18.8% of the cultivable area within each site showed root-knot nematode disease symptoms, which came to 2.0% of the total area used to grow vegetables in the region. Average yield loss was estimated at about 30.8% of total vegetable production, and 38.1% of the farm advisors considered that root-knot nematode infections had increased over the last 5 years. Most farm advisors (78.3%) stated that the most commonly used control method was chemical soil fumigation. Non-fumigant nematicides were cited by 59.8% of them, grafting and resistant cultivars by 42.3%, soil solarisation 38.1%, plant extracts 14.4% and biofumigation 6.2%. The majority of farm advisors considered the application of fumigant nematicides combined with soil solarisation, and grafting onto resistant rootstocks as the most effective methods of root-knot nematode control. In addition to the interviews, plant and soil samples were taken from plastic greenhouses throughout the region to determine species of root-knot nematode present. Meloidogyne javanica was the most prevalent species followed by M. incognita and M. arenaria, but species distribution was linked to the predominating crop sequence in each area, since M. javanica occurred less frequently when sweet pepper rather than tomato appeared in the crop sequence.

Soil-borne pathogenic fungi (SBPF) and root-knot nematodes (RKN) co-exist in the rhizosphere and are major pathogens causing root diseases in cucurbits. Current knowledge on soil-borne pathogens of cucurbit crops grown under protected cultivation, their host-pathogen interactions, and mechanisms of resistance has been reviewed. Plant resistance is an effective and sustainable method to control soil-borne diseases and the available resistant cultivars and rootstocks to key soil-borne pathogens are reported. The importance of proper pathogen diagnosis in the right choice of cultivar or rootstock is highlighted because of the specificity in the response of the cucurbit crops to fungal and nematode species and races. Plants protect themselves through common mechanisms of resistance against SBPF and RKN including hardening of their cell walls, pathogenesis-related (PR) proteins, and production of antimicrobial molecules. The activity of some enzymes, such as peroxidases and phenylalanine lyase, is increased after pathogen infection and is higher on SBPF and RKN resistant than susceptible cucurbits. Plant hormones such as salicylic acid, jasmonic acid, and ethylene are involved in the response of cucurbits to SBPF. Most mechanisms of resistance to RKN affect post-infection development of the nematode, which results in a delay or disruption of the life cycle. Traditional and biotechnological tools used for breeding for resistance in cucurbits are described. Grafting is an effective non-host resistance method to control primarily Fusarium wilt but not to control RKN. However, new rootstocks with resistance to both pathogens have been developed recently and their effects on fruit quality and yield stability need additional studies. The impact of grafting on yield in pathogen-infested soils is discussed.