Resumen. El género Fusarium es un patógeno asociado al marchitamiento del chile y con reducción del rendimiento del cultivo. Las rizobacterias son una alternativa para mejorar la producción agrícola y protección contra fitopatógenos. En el presente estudio se evaluó el antagonismo in vitro de diez cepas de Bacillus contra Fusarium equiseti ITCF1 y F. solani ITCF2, todas la cepas bacterianas inhibieron el crecimiento micelial entre 21.28 y 71.70 %, adicionalmente las cepas CBMT2 y CBMT51 presentaron halos de inhibición contra F. equiseti con halos de 3.76 y 6.37 mm.

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A total of 20 plants belonging to different genera (Acalypha, (3), and Vitex) were selected from native flora of the Yucatan peninsula. All plants selected were collected and separated in to leaves, stems and roots. These were then extracted with ethanol and their crude extracts (54) were evaluated against Alternaria tagetica, Colletotrichum gloeosporioides, Fusarium oxysporum and Rhizopus sp. using the filter paper disc diffusion assay. Results lead to the selection of 33 crude extracts active against at least one of the target strains, which were assessed to determine their ability to inhibit the mycelial growth of the pathogenic fungi in a second antifungal assay. The results of this assay indicated that extracts from the roots of Croton chichenensis were the most promising, with a wide activity spectrum against all pathogens tested in both assays with inhibition percentages of greater than 60%. Furthermore, extracts from leaves of Ambrosia hispida, Trichilia minutiflora, and roots of Acalypha gaumeri were able to cause growth inhibition against two or three pathogen strains (C50%). Studies of these active extracts should be continued at different levels. In general, results revealed a good bioactive potential of the flora from the Yucatan peninsula to produce metabolites with potential applications as botanical pesticides in the near future.

The Trichoderma species act as plant symbionts, decomposers of organic material, and as antagonists of root phytoparasites. To estimate the potential of four native strains of Trichoderma as growth promoters of Capsicum annuum L. and as biocontrol against root knot nematode Meloidogyne incognita (Kofoid and White) Chitwood, two bioassays in greenhouse were established. In one, the capacity of Trichoderma to promote initial growth of seedlings (36 d after planting, dap) was evaluated. In the other, the biocontrol of Trichoderma against M. incognita at 96 dap was also evaluated. The Trichoderma strains and the chemical fertilization treatment significantly promoted seedling growth at 36 dap (P ≤ 0.01). With respect to the control, T. atroviride promoted greater height in the seedlings, while T. atroviride, T. virens and T. harzianum-C2 increased fresh weight in roots (60.14%) and both T. atroviride and T. harzianum-C2 produced up to 82.30% more dry root biomass. In biocontrol, the control plants registered the highest damage with galling indexes of 85.50% (P ≤ 0.01). The lowest galling indexes were estimated with all the Trichoderma strains (21.60% to 35%). Trichoderma atroviride reduced egg production by 63% and the production of females by 14.36%, with respect to the oxamyl nematicide. Biocontrol of the nematode through the application of the Trichoderma strains favored growth of the plants in general. The fungal species studied show potential as growth promoting agents and as biocontrol agents M. incognita in C. annuum.

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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.

Habanero pepper (Capsicum chinense Jacq.) does not have a specific fertilization. Therefore, the aim of this study was to evaluate growth, photosynthesis and accumulation of macro and micronutrients of habanero pepper plants. Plants were established in nutrient film technique (NFT) hydroponic systems. Two universal balanced solutions (Steiner and Hoagland) were compared versus a conventional solution (control: Soria solution). The concentration of macro and micronutrients in roots, stems, and leaves, photosynthetic activity of plants, total nitrate, amino acid and protein contents, and growth parameters were evaluated. According to the results, concentrations of K, Mg, Ca, Cu and Zn in plant tissues were higher in the Steiner and Hoagland treatments than control. In addition, the Steiner and Hoagland treatments increased the maximum photosynthetic rate (Amax) (81% and 80% respectively), light-saturated CO2 assimilation rate (Asat) (3.8-fold and 3-fold, respectively) and maximum catalytic activities of Rubisco (Vcmax) (51% and 30% respectively) with respect to the control. Hoagland treatment increased total nitrate content (3.66 mg g-1 FW), but Steiner treatment increased amino acids in leaves (169.97 mg g-1 FW) and control increased total proteins (1.49 mg g-1 FW). Steiner and Hoagland solutions significantly increased plant height (59% and 41% respectively), leaf area (1.26-fold and 1.02-fold, respectively), and total dry mass (80% and 69% respectively) with respect to the control solution. The results suggest that Steiner and Hoagland nutrient solutions provided nutrients that improve growth and photosynthetic activity. Moreover, total nitrate, amino acid and protein accumulation depend on the N source employed in nutrient solutions.

Eugenia winzerlingii (Myrtaceae) is an endemic plant from the Yucatan peninsula. Its organic extracts and fractions from leaves have been tested on two phloem-feeding insects, Bemisia tabaci and Myzus persicae, on two plant parasitic nematodes, Meloidogyne incognita and Meloidogyne javanica, and phytotoxicity on Lolium perenne and Solanum lycopersicum. Results showed that both the hexane extract and the ethyl acetate extract, as well as the fractions, have strong antifeedant and nematicidal effects. Gas chromatography-mass spectrometry analyses of methylated active fractions revealed the presence of a mixture of fatty acids. Authentic standards of detected fatty acids and methyl and ethyl derivatives were tested on target organisms. The most active compounds were decanoic, undecanoic, and dodecanoic acids. Methyl and ethyl ester derivatives had lower effects in comparison with free fatty acids. Dose-response experiments showed that undecanoic acid was the most potent compound with EC50 values of 21 and 6 nmol/cm2 for M. persicae and B. tabaci, respectively, and 192 and 64 nmol for M. incognita and M. javanica, respectively. In a phytotoxicity assay, medium-chain fatty acids caused a decrease of 38–52% in root length and 50–60% in leaf length of L. perenne, but no effects were observed on S. lycopersicum. This study highlights the importance of the genus Eugenia as a source of bioactive metabolites for plant pest management.