Compatibility between entomopathogenic fungi and biorational insecticides in toxicity against Ronderosia bergi under laboratory conditions

Our aim was to evaluate the efficacy of combinations between two biorational insecticides (luphenuron, methoxyfenozide), a new synthetic chemical pesticide (rynaxypyr), and three entomopathogenic fungi strains (Beauveria bassianaLPSc 1067, LPSc1082), and Metarhizium anisopliae (LPSc 907) in the biocontrol of the pest grasshopper Ronderosia bergi (Stål) under laboratory conditions. The insecticides were tested at three concentrations: the average concentration recommended for application in the field (100%) and 50% and finally 25% of that level. The fungal strains used were adjusted to 1×108, 1×106, and 1×104conidia ml-1. The combinations of those insecticides with B. bassiana (LPSc 1067, LPSc 1082) and M. anisopliae (LPSc 907) caused higher mortality to R. bergi nymphs than any of the individual agents used alone. The three insecticides tested did not affect the isolates of the two species of entomopathogenic fungi employed. In conclusion, the use of these biorational insecticides in an IPM program aimed at control of the grasshopper R. bergicould be of value

Pathogenic ability and saline stress tolerance of two Fusarium isolates from Odontesthes bonariensis eggs

Background Several fungal species represent a potential risk to embryos ofOdontesthes bonariensis(Cuvier and Valenciennes, 1835), a euryhaline freshwater fish that lives in the Pampean inland waters and has potential economic relevance. Aims To identify two fungi isolated fromO. bonariensiseggs exposed to saline conditions and to characterize their pathogenicity and tolerance to sodium chloride solutions. Methods The isolates were identified by morphological features, and a preliminar phylogenetic analysis using sequences of translation elongation factor 1-alpha (EF-1α) and calmodulin (CAM) was performed. Koch's postulates were tested to identify the causative agent of fungal infection. The influence of NaCl on the fungal growth was evaluated in in vitro assays. Results The isolates LPSC 1001 and 1002 were identified as representatives of the genusFusarium, and belonging to theFusarium incarnatum-Fusarium equisetispecies complex (FIESC) and theFusarium solanispecies complex (FSSC), respectively. Histological observations on eggs exposed in vitro to both isolates in infectivity assays confirmed the ability of the fungal isolates to penetrate to egg's chorionic membrane, leading to the death of embryos. Increasing NaCl concentration in the culture medium reduced the growth of the isolates LPSC 1001 and 1002, being completely inhibited at 160 and 120g/l NaCl respectively. Conclusions The isolates LPSC 1001 (FIESC) and 1002 (FSSC) were identified as fungal pathogens toO. bonariensiseggs. The use of NaCl solutions as antifungal treatment was not effective to control the infection with these strains.Antecedentes Diversas especies de hongos pueden representar un riesgo importante para los embriones deOdontesthes bonariensis(Cuvier & Valenciennes 1835), un pez de agua dulce eurihalino que vive en las aguas interiores pampeanas y tiene una relevancia económica potencial. Objetivos Identificar dos especies de hongos de huevos deO. bonariensisexpuestos a condiciones salinas y caracterizar su patogenicidad y tolerancia a las soluciones de cloruro de sodio. Métodos Se identificaron los aislamientos por sus características morfológicas, y se realizó un análisis filogenético preliminar utilizando secuencias de traslación del factor 1 alfa elongación (EF- 1α) y calmodulina (CAM). Se llevaron a cabo los postulados de Koch para identificar el agente causante de la infección fúngica. La influencia de NaCl sobre el crecimiento fúngico se evaluó en ensayos in vitro. Resultados Se identificaron los aislamientos LPSC 1001 y 1002 como representantes del géneroFusarium, y pertenecientes al complejo de especiesFusarium incarnatum-Fusarium equiseti(FIESC) y al complejo de especies deFusarium solani(FSSC), respectivamente. Las observaciones histológicas en los huevos expuestos in vitro a ambos aislamientos en los ensayos de infectividad confirmaron la capacidad de estos para penetrar en la membrana coriónica, lo que condujo a la muerte de los embriones. El aumento de la concentración de NaCl en el medio de cultivo redujo el crecimiento de los aislamientos LPSC 1001 y 1002, quedando completamente inhibidos a 160 y 120g/l de NaCl, respectivamente. Conclusiones Se identificaron los aislamientos LPSC 1001 (FIESC) y 1002 (FSSC) como hongos patógenos para los huevos deO. bonariensis; el uso de soluciones de NaCl como tratamiento antifúngico no resultó eficaz para el control de la infección con estas cepas.dia y mes probable de publicaió

Short communication: Presence of Fusarium graminearum sensu stricto associated with triticale (× Triticosecale Wittmack) in Argentina

Aim of study: To report the occurrence of Fusarium graminearum sensu stricto (s.s.) on triticale grains from field samples in Argentina and the potential mycotoxin production for these isolates.Area of study: Buenos Aires province, ArgentinaMaterial and methods: A total of 40 samples from different crops (barley, rye, triticale, and wheat) showing Fusarium head blight symptoms were taken during 2017/2018 harvest season. Colonies with colour and mycelium similar to Fusarium were taken and were morphologically and molecularly identified. The potential to produce deoxynivalenol, 15-acetyl deoxynivalenol and zearalenones was determined. Also, the Koch´s postulates were used to evaluate the pathogenic capacity of the F. graminearum s.s. isolates in triticale.Main results: Two Fusarium isolates were identified morphologically as F. graminearum, which were confirmed molecularly by PCR using the specific Fg16 F/R primers pair and by sequencing red and tri101 genes. The sequences obtained were compared with those available in the NCBI database using BLAST tools, showing 99-100% homology with those belonging to F. graminearum s.s. The results demonstrated that F. graminearum s.s. isolates were pathogenic when triticale spikes were inoculated by spraying under greenhouse conditions.Research highlights: To our knowledge, this is the first time that the presence of F. graminearum s.s. is reported associated with triticale in Argentina

Occurrence and distribution of soil Fusarium species under wheat crop in zero tillage

The presence of Fusarium species in cultivated soils is commonly associated with plant debris and plant roots. Fusarium species are also soil saprophytes. The aim of this study was to examine the occurrence and distribution of soil Fusarium spp. at different soil depths in a zero tillage system after the wheat was harvested. Soil samples were obtained at three depths (0-5 cm, 5-10 cm and 10-20 cm) from five crop rotations: I, conservationist agriculture (wheatsorghum- soybean); II, mixed agriculture/livestock with pastures, without using winter or summer forages (wheatsorghum- soybean-canola-pastures); III, winter agriculture in depth limited soils (wheat-canola-barley-late soybean); IV, mixed with annual forage (wheat-oat/Vicia-sunflower); V, intensive agriculture (wheat-barley-canola, with alternation of soybean or late soybean). One hundred twenty two isolates of Fusarium were obtained and identified as F. equiseti, F. merismoides, F. oxysporum, F. scirpi and F. solani. The most prevalent species was F. oxysporum, which was observed in all sequences and depths. The Tukey�fs test showed that the relative frequency of F. oxysporum under intensive agricultural management was higher than in mixed traditional ones. The first 5 cm of soil showed statistically significant differences (p = 0.05) with respect to 5-10 cm and 10-20 cm depths. The ANOVA test for the relative frequency of the other species as F. equiseti, F. merismoides, F. scirpi and F. solani, did not show statistically significant differences (p . 0.05). We did not find significant differences (p . 0.05) in the effect of crop rotations and depth on Shannon, Simpson indexes and species richness. Therefore we conclude that the different sequences and the sampling depth did not affect the alpha diversity of Fusarium community in this system

Virulence and enzymatic activity of three new isolates of Beauveria bassiana (Ascomycota: Hypocreales) from the South American locust Schistocerca cancellata (Orthoptera: Acrididae)

Schistocerca cancellata is a large-sized acridid, which has historically represented the greatest agricultural problem in southern South America, causing serious economic losses. Since 2015 S. cancellata entered in a state of outbreak condition of historical proportions, producing frequent and large swarms of up to 25 km² in the north and central region of Argentina and areas of neigh boring Bolivia and Paraguay. At present, chemical insecticides are still the only means available for the control of S. cancellata. We analyzed under laboratory conditions the effectiveness of three fungal strains of Beauveria bassiana isolated from S. cancellata and also determined the relationship between chitinase, protease, and lipase levels at different temperatures of these fungi and their insecticidal activities. The pathogenicity assays were carried out by the sprayed method with concentrations of 1 × 10⁴, 1 × 10⁶ and 1 × 10⁸ conidia/ml. We observed that isolate LPSc 1227 caused the highest mortality at each dose studied, ranging from 100% at a dose of 1 × 10⁸ conidia/ml to 33.3 ± 3.2% at the lowest dose of 1 × 10⁴ conidia/ml. Moreover, in this isolate the highest values of chitinolytic and proteolytic activity were recorded (2.31 ± 0.31 and 1.78 ± 0.04), respectively

Antifungal activity and ultrastructural alterations in Pseudocercospora griseola treated with essential oils Atividade antifúngica e alterações ultraestruturais em Pseudocercospora griseola tratado com óleos essenciais

Pseudocercospora griseola, the etiologic agent of angular leaf spot of common bean (Phaseolus vulgaris), is an important disease in all bean-producing regions worldwide and may cause extremely high yield losses. The control of this disease is made more difficult by the pathogen's genetic variability and the inefficiency of fungicides. In this study, of 26 essential oils tested at different concentrations, 25 demonstrated efficiency in affecting the germination of strains 63-31 and 63-63 of the pathogen, reaching inhibition levels of between 80% and 100%. Cymbopogon citratus and Cymbopogon martinii inhibited conidia germination at all concentrations; Eugenia caryophyllata, Cinnamomum sp., Thymus vulgaris, Matricaria recutita, Cordia verbenacea, Origanum vulgare, Cymbopogon nardus, at 0.1 and 0.5%; and Zingiber officinale, Mentha arvensis, Chamaecyparis pisifera, Lavandula officinalis, Ocimum basilicum, Pimpinella anisum, Ocimum selloi, Baccharis dracunculifolia, Laurus nobilis, Citrus sinensis, Melaleuca alternifolia and Eucalyptus globulus, at 0.5%. The main constituents identified were cinnamaldehyde in Cinnamomum sp.; eugenol in E. caryophyllata; trans-&#946;-farnesene in M. recutita; pulegone in C. verbenacea; thymol in T. vulgaris; geranial and neral in C. citratus, and geraniol in C. martini. Through transmission electron microscopy (TEM), it was verified that C. citratus, C. martini and E. caryophyllata presented direct fungitoxic action on P. griseola, causing severe damage to the cellular ultrastructure of the conidia, invalidating germination. These results indicated that essential oils are a promising alternative strategy for the control of angular leaf spot in bean, representing less risk to human health and the environment.<br>Pseudocercospora griseola, agente etiológico da mancha angular do feijoeiro comum (Phaseolus vulgaris), é uma doença importante nas regiões produtoras de feijão em todo o mundo e pode causar perdas de produtividade extremamente elevados. O controle dessa doença é dificultado pela variabilidade genética do patógeno e da ineficiência de fungicidas. Neste estudo, de 26 óleos essenciais testados em concentrações diferentes, 25 demonstraram eficiência em inibir a germinação das linhagens 63-31 e 63-63 do agente patogênico, atingindo níveis de inibição entre 80% e 100%. Cymbopogon citratus e Cymbopogon martini inibiram a germinação de conídios em todas as concentrações; Eugenia caryophyllata, Cinnamomum sp., Thymus vulgaris, Matricaria recutita, Cordia verbenacea, Origanum vulgare, Cymbopogon nardus, em 0,1 e 0,5%, e Zingiber officinale, Mentha arvensis, Chamaecyparis pisifera, Lavandula officinalis, Ocimum basilicum, Pimpinella anisum, Ocimum selloi, Baccharis dracunculifolia, Laurus nobilis, Citrus sinensis, Melaleuca alternifolia e Eucalyptus globulus, em 0,5%. Os principais constituintes identificados foram cinamaldeído em Cinnamomum sp.; Eugenol em E. caryophyllata; trans-&#946;-farneseno em M. recutita; pulegona em C. verbenacea; timol em T. vulgaris; geranial e neral em C. citratus e geraniol em C. martini. Através de microscopia eletrônica de transmissão (TEM), verificou-se que C. citratus, C. martini e E. caryophyllata apresentaram ação antifúngica direta sobre P. griseola, causando graves danos na ultraestrutura celular dos conídios, invalidando a germinação. Esses resultados indicaram que os óleos essenciais são uma estratégia alternativa promissora para o controle da mancha angular do feijoeiro, o que representa menos risco para a saúde humana e ao ambiente