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SummaryThere is a demand for novel products for the control of plant-parasitic nematodes, so we characterised the effectiveness of some plant essential oils against Meloidogyne incognita and verified the efficiency of the major component from the most toxic oils and their analogues using in vitro and in vivo assays. In this study, the essential oils from Piptadenia viridiflora, Hyptis suaveolens and Astronium graveolens against M. incognita were evaluated, but only P. viridiflora oil showed toxicity toward M. incognita. Benzaldehyde was its main component according to GC-MS analysis. In in vitro assays, benzaldehyde (100 and 200 μg ml−1) and its oxime (400 μg ml−1) caused a higher rate of M. incognita second-stage juvenile (J2) mortality than the nematicide carbofuran (170 μg ml−1). Reductions of more than 90% in the number of galls and eggs, even greater than that observed with carbofuran, were observed in the assay where the J2 were placed in solutions of benzaldehyde and its oxime 48 h prior to tomato plant inoculation. Application of benzaldehyde together with M. incognita J2 to the substrate resulted only in a reduction in the number of eggs (42-65%); however, its oxime reduced both the number of galls (43-84%) and eggs (23-89%). Therefore, the P. viridiflora oil, its major component benzaldehyde, and the analogue benzaldehyde oxime are toxic to M. incognita. In two different in vivo assays, benzaldehyde oxime was confirmed as toxic to M. incognita with a greater efficacy than benzaldehyde.

RESUMO-O objetivo do trabalho foi avaliar a reação de genótipos de maracujazeiro a Meloidogyne spp.. O experimento foi conduzido em casa de vegetação em DBC, com seis repetições, em esquema fatorial 9x2 (Passiflora giberti, P. nitida, P. setacea, P. mucronata, P. cincinnata, P. ligularis, P.alata REACTION OF PASSION FRUIT GENOTYPES TO Meloidogyne incognita race 3 AND Meloidogyne javanicaABSTRACT -The aim of this study was to evaluate the reaction of genotypes of passion fruit to Meloidogyne spp.. The experiment was carried out in a greenhouse in RBD with six replications in 9 x 2 factorial designs (Passiflora giberti, P. nitida, P. setacea, P. mucronata, P. cincinnata, P. ligularis, P. alata, BRS Sol do Cerrado cultivar and selection M19-UFV x Meloidogyne javanica and M. incognita race 3). According to Oostenbrink criteria, and Moura and Régis, the BRS Sol do Cerrado, and selection M-19-UFV and P. alata behaved as immune to M. incognita. In addition to these, P. cincinnata and P. setacea were immune to M. javanica. Passiflora cincinnata and P.giberti behaved as resistant to M. incognita and M. javanica, respectively. According to Taylor and Sasser, the genotypes classified as immune by the other criteria were classified as resistant to nematodes. All the nematological variables evaluated in P. giberti, P. ligularis, P. mucronata and P. nitida were superior in plants infected by M. incognita. Regardless of the nematode, P mucronata presented larger number of root galls, egg masses, eggs, J2 and RF, as compared to the other genotypes. The root fresh matter weight of P. ligularis and P. mucronata was smaller in the presence of M. incognita as compared to M. javanica.

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In this study, the full genome sequence of Bacillus velezensis strain UFLA258, a biological control agent of plant pathogens was obtained, assembled, and annotated. With a comparative genomics approach, in silico analyses of all complete genomes of B. velezensis and closely related species available in the database were performed. The genome of B. velezensis UFLA258 consisted of a single circular chromosome of 3.95 Mb in length, with a mean GC content of 46.69%. It contained 3,949 genes encoding proteins and 27 RNA genes. Analyses based on Average Nucleotide Identity and Digital DNA–DNA Hybridization and a phylogeny with complete sequences of the rpoB gene confirmed that 19 strains deposited in the database as Bacillus amyloliquefaciens were in fact B. velezensis. In total, 115 genomes were analyzed and taxonomically classified as follows: 105 were B. velezensis, 9 were B. amyloliquefaciens, and 1 was Bacillus siamensis. Although these species are phylogenetically close, the combined analyses of several genomic characteristics, such as the presence of biosynthetic genes encoding secondary metabolites, CRISPr/Cas arrays, Average Nucleotide Identity and Digital DNA–DNA Hybridization, and other information on the strains, including isolation source, allowed their unequivocal classification. This genomic analysis expands our knowledge about the closely related species, B. velezensis, B. amyloliquefaciens, and B. siamensis, with emphasis on their taxonomical status.

The search for natural nematicides that are biodegradable with little or no human toxicity has intensified in recent years. In this context, the use of essential oils has the potential to function as an alternative plant–parasitic nematode control strategy, and their characterization may identify new nematicidal molecules. In this study, the nematicidal activity of Cinnamomum zeylanicum essential oil, its most abundant biochemical component and its analogue were evaluated against Meloidogyne incognita. Mean LC50 and LC95 values for C. zeylanicum oil were 49 µg/ml and 131 µg/ml, respectively. When J2 placed in C. zeylanicum oil at its LC50 concentration were used to inoculate tomato plants, the reduction in numbers of galls and eggs versus samples inoculated using J2 and no C. zeylanicum oil was 98%. C. zeylanicum essential oil reduced levels of M. incognita J2 that hatched 38%–54%, while carbofuran (positive control) did not prevent hatching. C. zeylanicum oil applied at a concentration of 800 µg/ml to a potted substrate containing infested tomato plants significantly reduced numbers of M. incognita galls. The cinnamaldehyde molecule within C. zeylanicum oil had LC50 and LC95 values of 64 and 768 µg/ml, respectively, while LC50 and LC95 values for cinnamaldehyde oxime were 323 and 529 µg/ml, respectively. Both cinnamaldehyde and its oxime inhibited hatching in M. incognita J2. These findings indicate that C. zeylanicum essential oil, its major biochemical component, cinnamaldehyde and cinnamaldehyde oxime (a cinnamaldehyde analogue) can be used to reduce levels of M. incognita.

Several oilseed plants have been researched for biodiesel production in Brazil, and Crambe abyssinica Hochst is one of the most promising species. The effect of the phytonematodes M. incognita race 3 and Meloidogyne javanica on C. abyssinica plants was evaluated in greenhouse experiments. A randomized block design with five nematode inoculum levels (350, 700, 1400, 2800, and 5600 eggs) and ten replications was used. C. abyssinica plants without inoculation were used as controls, and the viability of the nematodes used was tested in tomato plants inoculated with 2000 eggs. The plots consisted of pots containing one plant. The number of root knots (NG), number of egg masses (NEM), and number of eggs + second-stage juveniles (NEJ2) per root system, number of J2 per 200 cm3 of soil (NJ2), and shoot dry weight (SDW) of the inoculated C. abyssinica plants were evaluated at 45 days after inoculation. The reproduction factor (RF) of the nematodes was also evaluated. The resistance of the plants to the phytonematodes was classified using the RF criterion. Crambe abyssinica plants are susceptible to the different inoculum levels of Meloidogyne javanica and M. incognita used, and the data of all nematode variables (NG, NEM, NEJ2, NJ2, and RF) were fitted by linear models.

Meloidogyne is a relevant plant-parasitic nematode that causes enormous damage. It is very challenging to control, and there are not many chemicals available on the market for that. As an alternative method of nematode control, biofumigation is increasingly gaining space. This research aimed to study the reaction of Xanthosoma sagittifolium to Meloidogyne enterolobii, M. incognita, and M. javanica and soil biofumigation with X. sagittifolium leaves for M. enterolobii control. The reaction test was performed in the populations 0 (control), 333, 999, 3,000, 9,000, 27,000 eggs and eventual juveniles. X. sagittifolium did not host the Meloidogyne species studied, even in a high population. X. sagittifolium leaves incorporated in soil at concentrations 0 (control), 0.45, 0.9, 1.8, 3.6 g were also studied to control M. enterolobii, and they were able to reduce galls and eggs. The number of galls and egg masses was reduced to a concentration of 1.8 g. In the maximum concentration, the number of galls was less than 15 galls, and the eggs were also reduced to less than 200 eggs. As these macerates emitted nematicidal volatile organic compounds (VOCs) against M. enterolobii, it reduced the infectivity and reproduction of nematodes.