No abstract

RESUMENEl uso indiscriminado de plaguicidas sintéticos en el control de plagas y enfermedades que afectan los cultivos, la salud humana, y el medio ambiente, han conducido a resistencia por parte de insectos y presencia de residuos tóxicos en alimentos. Esto ha propiciado la necesidad de desarrollar enfoques alternativos para el control de especies plaga. En el presente estudio se ha investigado la actividad insecticida del aceite esencial de hojas de Lantana camara sobre el insecto modelo Drosophila melanogaster. Se aisló aceite esencial de las hojas de L. camara utilizando el método de hidrodestilación. El bioensayo se realizó por el método de la OMS para determinación de actividad adulticida contra mosquitos y artrópodos. Diferentes compuestos fueron identificados por análisis de cromatografía de gases -espectrometría de masas. El valor de la CL 50 del aceite fue 0.56 mg cm -2 mientras que el valor de la CL 95 fue 0.96 mg cm -2 sobre Drosophila melanogaster. El rendimiento de aceite esencial de hojas obtenido por hidro-destilación fue 0.022% w/w. El análisis por cromatografía de gases -espectrometría de masas del aceite esencial mostro 66 picos, donde Germacren D (19.29%), B-Cariofileno (14.55%), α-Humuleno (9.51%), Biciclogermacren (8.94%), Germacren B (7.26%) y Terpineno (5.62%) estuvieron presentes en mayores cantidades y contribuyeron con el 56.21% del total de los constituyentes. El aceite esencial de hojas de L. camara mostró actividad adulticida sobre la especie de mosca Drosophila melanogaster y podría ser utilizado para el desarrollo de insecticidas a base de aceite como complementario a los insecticidas sintéticos para el control de moscas causantes de importantes pérdidas económicas. Palabras clave: L. camara, aceite esencial, CG-MS, CL 50-CL95, bioensayo, insecticida. ABSTRACTThe indiscriminate use of synthetic pesticides in the control of pests and diseases affects crops, human health, and the environment, and lead to insect resistance and the presence of toxic residues in food. Previous generated the need to develop alternative approaches to pest species control. In the present study the insecticidal activity of the essential oil of leaves of Lantana camara on the insect model Drosophila melanogaster has been investigated. Essential oil was isolated from L. camara leaves using the hydro-distillation method. The Bioassay test was performed by the WHO method for the determination of adulticidal activity against mosquitoes and arthropods. Different compounds were identified by gas chromatography -mass spectrometry analysis. The LC50 value of the oil was 0.56 mg cm -2 whereas the value of the LC95 was 0.96 mg cm -2 on Drosophila melanogaster. The yield of leaf essential oil obtained by hydro-distillation was 0.022% w/w. Gas chromatography-mass spectrometry analysis of the essential oil showed 66 peaks, where Germacren D (19.29%), B-Caryophyllene (14.55%), α-Humulene (9.51%), Biciclogermacren (8.94%), Germacren B (7.26%) and Terpinene (5.62%) were present in greater amounts and contributed 5...

Common bean (Phaseolus vulgaris L.) is an important grain legume cultivated worldwide as food for humans and livestock (Schwartz et al., 2005). Common beans in central Chile reach up to 3,893 ha from which 1,069 ha are located in the Maule region. Common bean is produced by small farmers who have limited access to fertilization, technical irrigation, and crop protection. In spring 2018, bean plants initially showed a slight yellowing and premature senescence 50 days after sowing (das) until showing wilting symptoms (70 -100 das) in Curepto fields (35 05'S; 72 01'W), Maule region. The basal part of affected plants displayed internal reddish-brown discoloration of the vascular tissues. Based on the plant external symptoms, we estimated an incidence between 15% and 45% in bean fields. Nine symptomatic plants were collected, and surface washed with sterile water and disinfested with 75% ethanol (v/v). Then small fragments (5-mm) from damage vascular tissue from each plant were cut and placed on Petri dishes containing PDA acidified with 0.5 ml/l of 92% lactic acid (APDA, 2%). The isolations were incubated for seven days at 25°C. Nine Fusarium-like isolates from single-spore on APDA (2%) became pale vinaceous, floccose with abundant aerial mycelium and dark vinaceous reverse colony, with a growing rate of 10.8 to 11.6 mm/d at 25°C (Lombard et al., 2019). Phialides were short, singular growing laterally on the mycelium. Macroconidia were hyaline, fusiform with basal foot cells shaped to pointed and apical cells tapered, 2-5 septate, and 28.6 to 47.6 (av. 38.1) μm long x 2.2 to 3.6 (av. 3.1) μm wide. Microconidia were hyaline, oval to ellipsoid, one-celled, and 4.5 to 10.9 (av. 6.1) μm long and 2.2 to 3.3 (av. 2.7) μm wide (n=50 spore). For molecular identification, three isolates (Curi-3.1, Be-8.1, and Be-11.3) were sequenced using PCR amplification of the partial sequences of beta-tubulin (BT) and translation elongation factor 1-α gene (TEF) (Lombard et al., 2019). NCBI BLAST analysis showed 99 to 100% similarity with sequences (TEF; BT) of strain CPC 25822 of Fusarium oxysporum. The maximum-likelihood phylogenetic analysis placed the Chilean isolates in the F. oxysporum complex clade. Chilean sequences were deposited into GenBank under accession numbers MW419125, MW419126, MW419127 (TEF) and MW419128, MW419129, MW419130 (BT). Pathogenicity tests (isolates Curi-3.1, Be-8.1, and Be-11.3) were conducted under greenhouse (15-28°C, 85%RH) on healthy bean plants (n=30) cv. Blanco Español INIA cultivated in pots (sand/peat moss/soil) at the University of Talca. Plants that are 30 days-old were inoculated using 200 μl of conidial suspension (106 conidia/ml) on wounded roots (crown). Control plants (n=10) were similarly inoculated with sterile distilled water. After 45 days, all inoculated plants with F. oxysporum isolates developed necrotic lesions on vascular tissue, and chlorosis, and wilting while control plants remained healthy. This experiment was conducted twice. The pathogen was reisolated (100%) from diseased plants and molecularly identified as F. oxysporum. To our knowledge, this is the report of a severe outbreak of F. oxysporum causing Fusarium yellows in P. vulgaris in the Maule region, Chile. Previously, F. oxysporum has been reported affecting tomato (Sepúlveda-Chavera et al., 2014) and blueberry in Chile (Moya-Elizondo et al., 2019).

In recent years, the number of apple trees affected by Botryosphaeria cankers and dieback has considerably increased in central Chile. This study aimed to identify the species of Botryosphaeriaceae associated with canker and dieback symptoms, estimate disease incidence and distributions, and study their pathogenicity and virulence on apple and other fruit crops. A field survey of 34 commercial orchards of apple (7-to 30-year-old) was conducted in 16 localities obtaining 270 symptomatic branches and trunks samples in 2017 and 2018 growing seasons. The incidence of Botryosphaeria canker and dieback ranged between 5 and 40%, and a total of 255 isolates of Botryosphaeriaceae spp. were obtained from 238 cankers. Morphological identification along with phylogenetics studies of the internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2) of the rDNA, part of the translation elongation factor 1-α (tef1-α), and part of the beta tubulin (tub2) genes allowed to identify Diplodia mutila (n = 49 isolates), D. seriata (n = 136 isolates), Lasiodiplodia theobromae (n = 16 isolates) and Neofusicoccum arbuti (n= 54 isolates). L. theobromae was isolated mainly of apple dieback from northern localities. All pathogens tested were pathogenic, causing canker and dieback symptoms on lignified twigs of apple, pear, walnut, and green grapevine shoots in the field. Isolates of N. arbuti were the most virulent by reproducing more severe cankers on lignified tissues inoculated. This study reports D. mutila and L. theobromae for the first time associated with Botryosphaeria canker and dieback in Chile, and it is the first description of N. arbuti causing apple dieback worldwide.

The Andes range in Ecuador presents high biodiversity and characteristic altitudinal gradients, which are frequently threatened by deforestation and farming. In particular, forest have developed in the high inter-Andean alley on volcanic soils forming a unique ecoregion. Little is known on the fungal biodiversity of soil in such high Andean gallery forest submitted to strong degradation pressures. Therefore, in this study we evaluated wether the soil mycobiome was associated with altitudinal gradients during the dry season. Three representative locations were selected based on altitude: A (3,309 meters above the sea level, masl), B (3,809 masl) and C (4,409 masl). High performance sequencing (NGS) of the ITS region of ribosomal DNA genes with Illumina technology was used to explore the fungal taxonomic composition in the soil samples. Our results showed changes in the structure of fungal communities in the different locations, related to the relative abundance of Amplicon Sequence Variants (ASV). Higher fungal diversity was related with the altitudinal gradient with average taxa ranging from 675, 626 and 556 ASVs, respectively from location A to C. The results highlight the complexity and diversity of fungal communities in high Andean forest and the need to protect these unique mycobiomes. The findings in this ecosystem of Ecuador will improve our understanding of distribution, diversity, ecology, and biological perspectives for the restoration of terrestrial microbiomes.