First report of Macrophomina phaseolina causing crown and root rot of strawberry in Spain

Abstract

Huelva in southern Spain is a major production area for strawberry (Fragaria × ananassa). At the end of the 2006 season (May-June) collapsed and dying strawberry plants were observed on several cultivars in four fields. Cut crowns of affected plants revealed dark brown necrotic areas on the margins and along the woody vascular ring. Roots of these plants were also shown to be necrotic. Macrophomina-like isolates developed from surface-disinfested affected tissues plated on potato dextrose agar amended with 250 mg L-1 of chloramphenicol. Dark, oblong-shaped sclerotia were observed in affected crown tissue and in culture after 5 to 7 days incubation at 25 ° C. They had an average length of 107 (217 to 62) μ m and width of 71 (110 to 35) μ m. Sequenced rDNA fragments of a single sclerotium isolate CH 724 (Spanish Type Culture Collection, CECT 20715; GenBank Accession No. AM410964) presented a 99% identity with Macrophomina phaseolina. Morphological and molecular results confirmed this species as M. phaseolina (Holliday & Punithalingam, 1970). Six single sclerotium isolates of M. phaseolina from strawberry were used for pathogenicity tests. Each isolate was used to inoculate six strawberry runner plants (cv. Camarosa) growing in pots of coconut fibre substrate for 5 weeks. Plants were inoculated by inserting a fungal colonised toothpick into each crown (Mertely et al ., 2005). An equal number of uninoculated plants treated similarly were left as controls. After 58 days, the incidence of plant death ranged from 67 to 100% depending on isolate. Macrophomina phaseolina was reisolated from all plants showing symptoms. Uninoculated plants remained symptomless.

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].…”

“…In countries where methyl bromide has been eliminated, alternative fumigants are applied, such as chloropicrin with 1,3-dichloropropene, metam sodium or metam potassium. In many cases, the emergence of this disease has been attributed to changes in the chemicals used for pre-transplant fumigation [9,10,11,12,26], a hypothesis that has not yet been demonstrated. In this field several questions remain about the emergence of this disease and the effectiveness of the chemical and non-chemical control available for this and other plant pathogens that inhabit the soil [27,28] Given the need to reduce and eventually eliminate fumigation with chemicals and non-chemicals, the search for resistant cultivars certainly rises as an alternative for efficient disease management.…”

“…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 several studies, the increase of the disease has been attributed to the recent elimination of methyl bromide as a preplant fumigant and its replacement mostly by 1,3-dichloropropene plus chloropicrin for the control of soilborne pathogens and weeds (Avilés et al, 2008).…”