Storage of nematode-infected soil, roots and nematode suspensions is important in nematological research. The available storage methods are based on potato cyst nematodes, where cysts with viable eggs can be stored for long periods at 4 degrees C. When dealing with other nematode species, understanding the effect of storage temperature is crucial. This study was designed to investigate the decline rate and survival of four root-knot and a lesion nematode of both temperate and tropical origin, when stored at 4 degrees C in three substrates: water, soil and roots. The starting density (P-i ) for each substrate was determined at t = 0 and survival of all nematode species was estimated at 10-day intervals for 100 days. During storage, population densities of all species declined in all substrates exponentially. A slower decline rate (r(d) = 0.988-0.999) was observed for juveniles of Meloidogyne fallax in water, soil and roots compared to juveniles of M. hapla and Pratylenchus penetrans. Meloidogyne incognita was seriously affected by cold storage with the highest decline rate (r(d) = 0.919-0.977) observed in all substrates. Only data on the root substrate were obtained for M. javanica with a decline rate of (r(d) = 0.977) predicting zero survival at t > 100 days. Notable is the higher fraction of surviving P. penetrans (P-i = 0.238-0.545) in all substrates during the storage period, compared with all other species. Based on the results, it is recommended to process nematode samples in the three substrates as quickly as possible, as underestimation of the actual population densities is likely. Consequences of cold storage in handling and processing of samples from different substrates are discussed.

The root-knot nematode (Meloidogyne spp.) is an obligate plant parasite and is one of the largest threats to the Australian sweetpotato industry, causing crop losses of up to 57% of marketable yield. In this study, two potential fungal biocontrol agents were encapsulated in alginate granules and their nematophagous activity was assessed in a laboratory-based microcosm experiment. Both species of fungi significantly reduced numbers of root-knot nematodes in red ferrosol soil. A greater reduction was observed in untreated field soil prior to introduction of root-knot nematodes and fungal biocontrol agents compared to soil that had been heat-sterilised. In a ten-week glasshouse experiment, no significant difference in the root-knot nematode populations in sweetpotato roots and soil was found between fungal biocontrol agent and control treatments. There was a trend towards an increase in the sweetpotato storage root weight and reduction in storage root damage in fungal biocontrol agent compared to control treatments, and both yield and damage levels were similar to those achieved from the use of chemical nematicide treatments. These results demonstrate the need for greater understanding of the interactions between soil biological populations and introduced nematophagous fungi if effective biocontrol is to be consistently achieved with these bioagents under field conditions.

The root-knot nematode Meloidogyne javanica is a significant pathogen that causes substantial yield losses in tomato plants. Moroccan farmers generally lack knowledge regarding the density of this pathogen, which can trigger visible and localised symptoms. Additionally, regional studies that establish damage thresholds for this issue are scarce. This study investigated the damage threshold of M. javanica on tomato plants using nine initial population densities (Pi) of second-stage juveniles (J2s): 0, 0.5, 1, 2, 4, 8, 16, 32 and 64 J2s (g dry soil)-1. Aboveground growth (plant height and fresh and dry shoot weight) and belowground growth (root length and diameter) were assessed after 90 days. The plant growth parameters were significantly reduced at higher inoculum densities. The Seinhorst model fitting revealed the highest minimum relative yield (m) for shoot fresh weight (m = 0.761 +/- 0.012) and the lowest for root diameter (m = 0.509 +/- 0.026). The tolerance limit (T) varied, with the highest shoot dry weight (T = 1.657 +/- 0.329 J2s (g soil)-1) and lowest root diameter (T = 0.095 +/- 0.019 J2s (g soil)-1). The production of eggs by M. javanica increased significantly with increasing initial population density, rising from 211 +/- 64 eggs (g roots)-1 at 0.5 J2s (g soil)-1 to 3735 +/- 380 eggs (g roots)-1 at 64 J2s (g soil)-1, representing a 17.7-fold increase. Tomato plants exhibited the maximum galling index at lower nematode densities. Symptoms began at densities as low as 0.095 J2 (g soil)-1, with severity increasing with nematode density. Given the severe damage caused at low densities, Moroccan farmers must adopt early detection and effective management strategies.

Soybean is the main oilseed cultivated worldwide. Even though Brazil is the world's largest producer and exporter of soybean, its production is severely limited by biotic factors. Soil borne diseases are the most damaging biotic stressors since they significantly reduce yield and are challenging to manage. In this context, the present study aimed to evaluate the potential of a bacterial strain (Ag109) as a biocontrol agent for different soil pathogens (nematodes and fungi) of soybean. In addition, the genome of Ag109 was wholly sequenced and genes related to secondary metabolite production and plant growth promotion were mined. Ag109 showed nematode control in soybean and controlled 69 and 45% of the populations of Meloidogyne javanica and Pratylenchus brachyurus, respectively. Regarding antifungal activity, these strains showed activity against Macrophomia phaseolina, Rhizoctonia solani, and Sclerotinia sclerotiorum. For S. sclerotiorum, this strain increased the number of healthy plants and root dry mass compared to the control (with inoculation). Based on the average nucleotide identity and digital DNA-DNA hybridization, this strain was identified as Bacillus velezensis. Diverse clusters of specific genes related to secondary metabolite biosynthesis and root growth promotion were identified, highlighting the potential of this strain to be used as a multifunctional microbial inoculant that acts as a biological control agent while promoting plant growth in soybean.