Nacobbus aberrans ranks among the “top ten” plant-parasitic nematodes of phytosanitary importance. It causes significant losses in commercial interest crops in America and is a potential risk in the European Union. The nematicidal and phytotoxic activities of seven plant extracts against N. aberrans and Solanum lycopersicum were evaluated in vitro, respectively. The chemical nature of three nematicidal extracts (EC50,48h ≤ 113 µg mL−1) was studied through NMR analysis. Plant extracts showed nematicidal activity on second-stage juveniles (J2): (≥87%) at 1000 µg mL−1 after 72 h, and their EC50 values were 71.4–468.1 and 31.5–299.8 µg mL−1 after 24 and 48 h, respectively. Extracts with the best nematicidal potential (EC50,48h < 113 µg mL−1) were those from Adenophyllum aurantium, Alloispermum integrifolium, and Tournefortia densiflora, which inhibited L. esculentum seed growth by 100% at 20 µg mL−1. Stigmasterol (1), β-sitosterol (2), and α-terthienyl (3) were identified from A. aurantium, while 1, 2, lutein (4), centaurin (5), patuletin-7-β-O-glucoside (6), pendulin (7), and penduletin (8) were identified from A. integrifolium. From T. densiflora extract, allantoin (9), 9-O-angeloyl-retronecine (10), and its N-oxide (11) were identified. The present research is the first to report the effect of T. densiflora, A. integrifolium, and A. aurantium against N. aberrans and chemically characterized nematicidal extracts that may provide alternative sources of botanical nematicides.
Population densities, population fluctuations, yield loss and disease incidence caused by Nacobbus aberrans on tomato (Lycopersicon esculentum) were studied, using an epidemiological approach, in a field experiment that included three different control regimes: an integrated control (IC) scheme, which included fertilisation, nematicide (ethoprop) and chicken manure; a technical control (TC) scheme, based on the best local practices of fertilisation and use of carbofuran for nematode control; and a check treatment (AC), with no application of fertilisers or nematicide. At least three generations of N. aberrans occurred through the cropping season and the numbers of galls/plant and females/g of root through the crop season were used to define the area under a disease progress curve (AUDPC). The variables b −1 (Weibull's apparent infection rate), AUDPC and Y f (final disease incidence) indicated less crop damage under the IC scheme than under the other two schemes (TC and AC). The IC scheme resulted in increased plant height (41-49%), foliage dry weight (37-53%) and stem diameter (31-41%) compared with the TC and AC schemes. Tomato yields in IC surpassed those from TC and AC by 34 and 83%, respectively, while TC exceeded AC by 73%. The yield loss attributed to N. aberrans was 12, 29 and 83% in IC, TC and AC, respectively. The IC scheme improved commercial production by 20 and 81% in comparison to the TC and AC schemes. This was largely due to effective control of the initial inoculum density, which affects the first generation of the nematode population; control of this generation is essential for avoidance of yield loss. The first generation is completed during the period 0-60 dat (days after transplanting), i.e., during the critical stages of flowering, fruit initiation and fruit set (40, 50 and 60 dat). Data on plant performance taken every 10 days were used to derive a multiple point model for calculation of production loss.
Three new species of Trischistoma and two new species of Tripylina (Trischistomatidae) are described. Trischistoma ripariana n. sp. was collected in the surface organic material and upper rhizosphere soil on a stream bank in Oakville, California, USA. It is characterized by a short, thin body, the vulva at 79-83%, a small index c (17-29) and a short tail, 34-57 µm. Trischistoma corticulensis n. sp. was found in moss on tree bark in a tropical forest at the La Mancha Ecological Institute, Veracruz State, México. The vulva is at 67-73% and the tail is elongate conoid (51-84 µm). Trischistoma helicoformis n. sp. was collected on lichen growing on tree bark near the Carretera Interamericana in Costa Rica. It is characterized by its spiral shape after fixation, the tail length (76-101 µm), a very small index c (10-14.5) and very small sclerotised pieces around the vagina. Tripylina rorkabanarum n. sp. was collected from moss on tree bark in a tropical forest at the La Mancha Ecological Institute. It is characterized by the presence of two cervical setae, the position of the subventral teeth posterior to the dorsal tooth, the absence of sclerotized pieces around the vagina and the distance of the dorsal tooth from the anterior, 10-15 μm. Tripylina iandrassyi n. sp. was collected from soil around a banana tree at the La Mancha Ecological Institute. It is characterized by the presence of a post-uterine sac, well-developed buccal lips, subventral teeth located posterior to the dorsal tooth, one cervical seta in females and two in males, and by spicules not completely surrounded by a muscular sheath.
BACKGROUND: While searching for novel small molecules for new organic pesticide agents against plant-parasitic nematodes, we found that the hexane extract from the roots of Senecio sinuatos and its main secondary metabolite, 3⊎-angeloyloxy-6⊎hydroxyfuranoeremophil-1(10)-ene (1), possess nematicidal activity against the second stage juvenile (J2) of Meloidogyne incognita and Nacobbus aberrans. Both species reduce yield of various vegetable crops. These results encouraged us to synthesize esters 3-9 formed by diol 2, obtained by alkaline hydrolysis of 1 and acetic anhydride, benzoic acid, 2-nitrobenzoic acid, 2-bromobenzoic acid, 4-nitrobenzoic acid, 4-bromobenzoic acid, and 4-methoxybenzoic acid, respectively. The nematicidal activity of these esters was evaluated and compared with that of the free benzoic acids.RESULTS: Natural product 1 and derivatives 2-9 were obtained and characterized by their physical and spectroscopic properties, including one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) experiments; X-ray diffraction analysis established their absolute configuration. The nematicidal activity of compounds 1-9 was assessed in vitro against M. incognita and N. aberrans J2 and was compared to activity shown by benzoic acid, 2-nitrobenzoic acid, 2-bromobenzoic acid, 4-nitrobenzoic acid, 4-bromobenzoic acid, and 4-methoxybenzoic acid. The esters suppressed nematodes more than free benzoic acid. Nacobbus aberrans J2 were suppressed, with compounds 5, 6, and 8 being the most active.CONCLUSION: Esters formed by 3⊎,6⊎-dihydroxyfuranoeremophil-1(10)-ene and orthoor para-substituted benzoic acids containing electron acceptor groups had nematicidal activity against N. aberrans. These compound can potentially serve as a model for the development of new organic nematicidal agents.
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