Search

The production of cactus prickly pear (Nopalea cochenillifera) as a foraging plant in the Brazilian Northeastern region is limited by diseases for which knowledge of etiology and diversity of pathogens is scarce. In this work Botryosphaeriaceae fungi isolated from cladode spots of cactus prickly pear were characterized based on morphology and phylogeny using on partial nucleotide sequences of ITS-rDNA, EF1-α e β-tub. Four species were identified, of which three caused a brown spot, Lasiodiplodia theobromae, L. jatrophicola and Neofusicoccum batangarum and one, Neoscytalidium hyalinum, caused a squamous spot firstly reported to occur in N. cochenillifera. We report for the first time worldwide L. jatrophicola and N. hyalinum species causing spots on cactus prickly pear.

Six phytotoxins were obtained from the culture filtrates of the ascomycete Neofusicoccum batangarum, the causal agent of the scabby canker of cactus pear (Opuntia ficus-indica L.) in minor Sicily islands. The phytotoxins were identified as (&minus, )-(R)-mellein (1), (&plusmn, )-botryoisocoumarin A (2), (&minus, )-(3R,4R)- and (&minus, )-(3R,4S)-4-hydroxymellein (3 and 4), )-terpestacin (5), and (+)-3,4-dihydro-4,5,8-trihydroxy-3-methylisocoumarin, which we named (+)-neoisocoumarin (6). This identification was done by comparing their spectral and optical data with those already reported in literature. The absolute configuration (3R,4S) to (+)-neoisocoumarin (6) was determined using the advanced Mosher method. All six metabolites were shown to have phytotoxicity on the host (cactus pear) and non-host (tomato) plants, and the most active compounds were (&plusmn, )-botryoisocoumarin A (2), (&minus, )-terpestacin (5), and (+)-neoisocoumarin (6).

Cactus prickly pear (Nopalea cochenilifera) cladodes showing brown spot symptoms were collected of 18 fields of the State of Pernambuco, northeastern Brazil, from March to June 2014. The symptoms were prevalent in 100% of fields surveyed. Small pieces (4 to 5 mm) of necrotic tissues were surface sterilized for 1 min in 1.5% NaOCl, washed twice with sterile distilled water, and plated onto potato dextrose agar (PDA) amended with 0.5 g /liter streptomycin sulfate. Colonies morphologically similar to species of Botryosphaeriaceae were transferred to malt extract agar (MEA); five isolates (CMM 1424, CMM 1425, CMM 1426, CMM 1427, and CMM 1428) presented colonies forming concentric rings, and white mycelium becoming gray to gray-olivaceous after 5 days. Conidial characters were observed after growth on 2% water agar bearing sterilized pine needles for 3 weeks at 25°C under near-UV light. Conidiogenous cells holoblastic, hyaline, smooth, and cylindrical. Conidia were nonseptate, hyaline, smooth, fusoid to ovoid, thin-walled, 15.3 ± 1.4 × 5.4 ± 0.6 µm (n = 50), L/W ratio= 2.8, which are morphological and cultural characteristics typical of Neofusicoccum spp. (Phillips et al. 2013). DNA sequencing of part of the elongation factor 1-alpha (EF1-α) gene and the internal transcribed spacer (ITS1-5.8S-ITS2 rDNA) region were conducted to identify the species as described by (Marques et al. 2013). Sequences of the isolates were 99% similar to those of N. batangarum for EF1-α (GenBank Accession Nos. FJ900653 and FJ900654) and ITS (FJ900607 and FJ900608). Instituto de Patología Vegetal Fil: Conforto, Erica Cinthia. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; Argentina Fil: Bernardi Lima, Nelson. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Fitopatología y Modelización Agrícola (UFyMA); Argentina Fil: Bernardi Lima, Nelson. Universidade Federal Rural de Pernambuco. Departamento de Agronomia; Brasil Fil: Garcete-Gómez, José María. Universidade Federal Rural de Pernambuco. Departamento de Agronomia; Brasil Fil: Câmara, M. P. S. Universidade Federal Rural de Pernambuco. Departamento de Agronomia; Brasil Fil: Michereff, S. J. Universidade Federal Rural de Pernambuco. Departamento de Agronomia; Brasil