First Report of Powdery Mildew (Podosphaera pannosa) of Roses in Sinaloa, Mexico

Abstract

Rose (Rosa spp.) is the most important ornamental plant cultivated in greenhouse and open fields in Mexico but its quality has been limited by powdery mildew (PM). High incidence and disease damage is common during winter in Sinaloa, Mexico (temperature range 18 to 25°C and prolonged episodes of relative humidity ≥90%). The fungus attacks leaves and flowers and grows abundantly on the pedicels, sepals, and receptacles, especially when the flower bud is unopened (2). Field advisors in Mexico have referred to Sphaerotheca pannosa (Wallr. ex Fr.) Lév. as a causal agent of the disease. However, there has not been solid scientific evidence to support this statement. Morphometric and molecular analysis were conducted to elucidate the identity of the fungal isolates collected from 2012 through 2013 in northern Sinaloa. PM specimens included eight different rose varieties. Conidiophores and conidia were observed under a compound microscope. The mycelium had a mean diameter of 4.7 to 6.0 μm; conidiophores (Euoidium type) 2 to 5 celled, occasionally 6 celled emerged from the superficial mycelium; conidiophores were unbranched with conidia produced in chains from the apex. The average length of the conidiophores was 54.9 to 98.0 μm; the foot cell of the conidiophores was straight and was 24.9 to 53.6 μm long with a diameter from 8.2 to 9.8 μm across its medium part. Conidia originated from unswollen conidiogenous cells, with fibrosin bodies, formed in long chains, and were cylindrical to ovoid, 25.8 to 30.4 μm long and 13.9 to 17.3 μm wide. The outline of the conidial chains was crenate. Conidia exhibited a slight constriction at one end. The germ tubes emerged from a shoulder of the conidia. The outer wall of partially collapsed conidia showed longitudinal and transversal wrinkling and slight constrictions at the ends; the terminal end of the conidia was concentrically ridged. For molecular characterization, the ITS region of the specimens was amplified with primers ITS1F and ITS4. Phylogenetic analysis was performed with MEGA 6.0 (bootstrap = 1,000) using Kimura 2 parameter (K2P) substitution model. The resulting phylogeny grouped our specimens (GenBank KM001665 to 69) within a clade of Podosphaera pannosa (Wall.: Fr.) de Bary (formerly known as Sphaerotheca pannosa) sequences (e.g., AB525938; bootstrap (1,000) = 98). Phylogenetic and morphometric data are in agreement with descriptions of the anamorphic P. pannosa (1,3). Morphological studies indicate that P. macularis (previously known as S. humuli) and P. pannosa are not indistinctly different (2). Phylogenetic analysis showed relationship to P. pannosa, but not to P. macularis. Typical symptoms caused by P. pannosa were observed. Morphological studies (4) reported the anamorph of P. pannosa on Rosa spp. in central Mexico. To date, no report exists on the molecular identification of P. pannosa associated to roses in northern Sinaloa, Mexico. Future research directions should focus on finding the teleomorph of the fungus to support its identity, and to explore disease management tools such as effective fungicides and developing resistant rose cultivars. References: (1) U. Braun et al. Page 13 in: The Powdery Mildews: A Comprehensive Treatise. APS Press, St. Paul, MN, 2002. (2) R. K. Horst. Compendium of Rose Diseases. APS Press, St. Paul, MN, 1983. (3) L. Leus et al. J. Phytopathol. 154:23, 2006. (4) Yañez-Morales et al. Some new reports and new species of powdery mildew from Mexico. Schlechtendalia 19:46, 2009.

Identificación y alternativas de manejo de la cenicilla del rosal

“…de Bary was identified as the causing agent of the powdery mildew in roses; the morphometric characteristics were similar to those reported by Braun and Cook (2012). However, the number of basal cells observed in this study were 1-2 short cells, which is different to reports by Havrylenko (1995) and Félix-Gastélum et al (2014). These differences may be due to diverse factors such as temperature Volumen 34, Número 1, 2016…”

“…Las diferencias pueden deberse a diversos factores incluyendo la temperatura y humedad, el hospedero (variedad), edad de las hojas y el periodo de muestreo (Salmon, 1900). Los primers ITS1F e ITS4 amplificaron un producto de 574 pb que corresponde a P. pannosa; de manera similar, Félix-Gastélum et al (2014) y Romberg et al (2014) utilizaron los mismos primers para la identificación y detección de P. pannosa en el cultivo de Rosa spp. y Catharanthus roseus (L) G. Don, respectivamente.…”

“…Su efecto se debe a que es un fungicida sistémico con absorción acropétala que actúa inhibiendo la síntesis del ergosterol y la and humidity, the host (variety), age of the leaves, and the sampling period (Salmon, 1900). Primers ITS1F and ITS4 amplified a product of 574 pb, corresponding to P. pannosa; similarly, Félix-Gastélum et al (2014) and Romberg et al (2014) used the same primers to identify and detect P. pannosa in the Rosa spp. crop and Catharanthus roseus (L) G. Don crops, respectively.…”

“…The comparison of the nucleotide sequence obtained (KP902716), with thse deposited in the GenBank showed an identity of 99 to 100 % with P. pannosa accessions presents in Rosa sp. in Mexico, Belgium, the United States, Japan and Switzerland (Saenz and Taylor, 1999;Mori et al, 2000;Cunnington et al, 2003;Leus et al, 2006;Félix-Gastélum et al, 2014), in Rosa maltiflora Thunberg ex Murray from Japan, Rosa rubiginosa L. from Argentina (Takamatsu et al, 2010), and in Rosa rugosa Thunb. from Korea (Lee et al, 2011).…”

Las cenicillas en cultivos agrícolas de Sinaloa: Situación actual sobre su identificación y líneas futuras de investigación

“…Se (=Euoidium) leucoconium with Bary Podosphaera pannosa (Wallr.) as a teleomorph (Félix-Gastélum et al, 2014). Although the teleomorph has not been observed in Sinaloa, it has been confirmed in Korea (Shin, 1999;Lee et al, 2011) and Yugoslavia (Ranković and Čomić, 1997).…”