Diplodia mutila causing seedling mortality of the palm Iriartea deltoidea

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.

Light Converts Endosymbiotic Fungus to Pathogen, Influencing Seedling Survival and Niche-Space Filling of a Common Tropical Tree, Iriartea deltoidea

“…An additional experiment showed that pathogenicity of D. mutila increased with light availability. We inoculated 22 healthy 6-month old I. deltoidea seedlings (no foliar spots or insect marks) with D. mutila , following inoculation procedures from previous studies [25]. Foliar spots produced by D. mutila had a higher growth rate and mortality was greater and faster at higher light availability ( F 1,22  = 93.26, P  = 0.0001, r 2  = 0.816) (Fig.…”

“…Diplodia mutila is frequently an asymptomatic endophyte in seeds, fruits, leaves of healthy juvenile and mature plants of I. deltoidea (88.4% infection of adult plants [29]) but can also act as a pathogen, causing mortality in young I. deltoidea seedlings after 5 to 16 days of infection and producing foliar spots in adult plants [25] (Fig. 5A–D).…”

“…Diplodia mutila is an endophytic/pathogenic fungus infecting I. deltoidea [25], with approximately 88.4% of the adult palms being infected, 45.1% of newborn seedlings, and 63.2% of 1-year old seedlings [29]. Diplodia mutila and related species have been reported as endophytes or latent pathogens for several plant species worldwide [27], [28], [29].…”

Phaeoacremonium spp. and Botryosphaeriaceae spp. Associated with Date Palm (Phoenix dactylifera L.) Decline in Iran

“…) and reported as the causal agent of seedling mortality of Iriartea deltoidea palm trees in Peru (Alvarez‐loayza et al. ). According to the pathogenicity test, Pm.…”

Rare species advantage? Richness of damage types due to natural enemies increases with species abundance in a wet tropical forest

“…Some studies suggest that damage decreases at high irradiance levels (Augspurger ), while other studies found that an increase in irradiance can increase damage by natural enemies (Alvarez‐Loayza et al . ). The effect of abiotic factors may vary with traits of the host species; for example, drought may increase vulnerability to natural enemies in drought‐intolerant, but not drought‐tolerant species (Fine, Mesones & Coley ).…”