First Report of Crown Rot of Strawberry Caused by Macrophomina phaseolina in Chile

Abstract

In recent years, an increase of collapsed and dead strawberry plants has been observed in several fields in central Chile, specifically in San Pedro, Melipilla, an important area for strawberry cultivation in the country. To determine the causal agent of the disease and the extent of the problem, 25 sample sites of 1 ha each, distributed in different San Pedro zones, were surveyed at the end of the 2011 season (from December 2010 to February 2011). Cross sections of the crowns of symptomatic strawberry plants showed necrotic tissue and brown-red to dark brown areas on the vascular ring. Samples of the affected crowns were superficially disinfested and plated on potato dextrose agar with 200 μg/ml of streptomycin sulfate. Dark gray colonies were observed after 7 days of incubation at 24°C. Pure cultures of the pathogen showed aerial mycelium and abundant dark oblong sclerotia. Fifty sclerotia were measured, averaging 120 × 74 μm. Twenty-one isolates were identified molecularly utilizing the species specific primers MpKFI and MpKRI (2) that yielded a 350-bp fragment. The amplified DNA fragments were sequenced and BLAST analysis showed a 99% nucleotide sequence identity with Macrophomina phaseolina (GeneBank Accession No JX535007.1). Both morphological and molecular analyses confirmed that the isolated species corresponded to M. phaseolina, causal agent of crown and root rot in strawberry. Four representative isolates were selected to conduct pathogenicity tests. Inoculum was prepared by incubating the pathogen for 28 days at 20°C in sterilized oat seeds. Pots of 1.5 liters were filled with a mixed substrate of peat and perlite (2:1), amended with inoculated oats at 9 g per liter of substrate. ‘Camarosa’ strawberry plants were planted and grown in a glasshouse for 1 month. Six replicated plants per isolate and six plants growing on non-inoculated substrate were left as controls. Ninety-five percent of the inoculated plants showed wilt and collapse symptoms 22 days after transplant, whereas no symptoms were observed in the control plants. M. phaseolina was reisolated from the crowns of symptomatic plants, fulfilling Koch's postulates. The pathogen was isolated from symptomatic strawberry plants in 14 of the 25 sampled sites. Although M. phaseolina was described previously on other crops in Chile, to our knowledge, this is the first report of M. phaseolina causing crown rot of strawberry. The disease has been recently reported in Spain, the United States, and Argentina (1,3,4). References: (1) M. Avilés et al. Plant Pathol. 57:382, 2008. (2) B. Babu et al. Mycologia 99:797, 2007. (3) O. Baino et al. Plant Dis. 95:1477, 2011. (4) S. Koike. Plant Dis. 92:1253, 2008.

Susceptibility of strawberry cultivars to root and crown rot caused by Macrophomina phaseolina

“…The disease was reported in strawberry in Illinois in 1958 [8], and after that in France in 1993 [7]. In recent years there have been multiple reports in major growing regions: in 2005 in Florida, United States, and Israel [9,10]; in 2008 an increase in the incidence of the disease was reported in California, United States [11]; in the same year it was pointed out as an emerging disease in Huelva, Spain [12]; during 2011 the pathogen was identified in Tucumán, Argentina [13], in Iran it was reported in 2012 [14]; and in Australia and Chile it was reported as causing serious damage to the strawberry crop in 2013 [15,16].…”

“…Usually these symptoms first appear after the plants have been established in the field, at the beginning of harvest, or when subjected to stress, resulting in complete collapse or death. The affected plants show necrotic lesions in the inner crown tissue, vascular and cortical, with cracks and orange-brown discoloration [12,16,20] The pathogen forms sclerotia in infected tissues, which allows it to survive in plant debris or in the soil for long time, constituting the initial inoculum of the disease [21]. Pathogens are usually found in the top 20 cm of soil [22].…”

Genetic and biological characterization of Macrophomina phaseolina (Tassi) Goid. causing crown and root rot of strawberry

“…In strawberry (Fragaria ×ananassa Duchesne ex Rozier), an increased incidence of root and crown rot caused by M. phaseolina has been detected in recent decade, seriously damaging strawberry fields in different countries, including Spain (Avilés et al, 2008), Argentina (Baino et al, 2011), Iran (Sharifi and Mahdavi, 2012), Australia (Hutton et al, 2013), and Chile (Sánchez et al, 2013).…”

“…In this region, the growers are small producers, and in contrast to the main producing countries, most of them do not apply pre-transplant chemical fumigants. Curiously, an explosive increase in the crown and root rot of strawberry caused by M. phaseolina has been detected (Sánchez et al, 2013).…”

Caracterización morfológica y molecular de aislados de Macrophomina phaseolina asociados a caña de azúcar en México

“…De acuerdo con Babu et al 2 , las secuencias de ADN obtenidas con los iniciadores específicos MpKFI y MpKRI pueden ser utilizadas para identificar de manera rápida, selectiva y específica el hongo M. phaseolina. De manera similar, Zhang et al 15 y Sánchez et al 12 usaron los iniciadores específicos MpKFI y MpKRI para la identificación y detección de aislados de M. phaseolina en el cultivo de fresa y frijol mungo (Vigna radiata L.), respectivamente.…”