Preventive and Curative Effects of Salicylic and Methyl Salicylic Acid Having Antifungal Potential against Monilinia laxa and the Development of Phenolic Response in Apple Peel.

The effects of salicylic acid (SA) and one of its better-known derivatives-methyl salicylic acid (MeSA)-on the infection of apple fruits with the fungus Monilinia laxa, which causes brown rot, were investigated. Since research to date has focused on preventive effects, we also focused on the curative use of SA and MeSA. Curative use of SA and MeSA slowed the progression of the infection. In contrast, preventive use was generally unsuccessful. HPLC-MS was used to analyze the content of phenolic compounds in apple peels in healthy and boundary peel tissues around lesions. The boundary tissue around the lesions of untreated infected apple peel had up to 2.2-times higher content of total analyzed phenolics (TAPs) than that in the control. Flavanols, hydroxycinnamic acids and dihydrochalcones were also higher in the boundary tissue. During the curative treatment with salicylates, the ratio of TAP content between healthy and boundary tissue was lower (SA up to 1.2-times higher and MeSA up to 1.3-times higher content of TAPs in boundary compared to those in healthy tissue) at the expense of also increasing the content in healthy tissues. The results confirm that salicylates and infection with the fungus M. laxa cause an increased content of phenolic compounds. Curative use of salicylates has a greater potential than preventive use in infection control.

Alteration of the content of primary and secondary metabolites in strawberry fruit by Colletotrichum nymphaeae infection.

The effects of infection with Colletotrichum nymphaeae , the causative agent of strawberry black spot, were studied on two strawberry cultivars: susceptible 'Elsanta' and tolerant 'Honeoye' cultivars. Four treatments were established: (1) artificial inoculation; (2) spray application of pyraclostrobin + boscalid (Signum); (3) foliar spraying with calcium (Stopit); and (4) control (spraying with water). Primary metabolites (sugars and organic acids) and secondary metabolites (phenolic compounds) were determined in strawberry fruit with the use of HPLC-MS(n). Infected fruit accumulated large amounts of total sugars and low levels of organic acids. The sugar/acid ratio was higher in the infected and in Ca-treated strawberries. The contents of ellagic acid derivatives, flavonols, oligomeric procyanidins, flavan-3-ols, and total phenolics were highest in inoculated strawberry fruit. Results indicated that fungicide and calcium sprayings did not alter polyphenolic levels in plant tissue.

Cylindrocarpon pauciseptatum sp. nov., with notes on Cylindrocarpon species with wide, predominantly 3-septate macroconidia.

A Cylindrocarpon species with up to 10 microm wide, straight and predominantly 3-septate macroconidia, subglobose to ovoidal microconidia and chlamydospores, is described as Cyl. pauciseptatum. It is most similar to Cyl. austrodestructans but no chlamydospores and microconidia are formed in the latter. Similar macroconidia also occur in Cyl. theobromicola, which forms oval to ellipsoidal microconidia at least sparsely and has slightly curved macroconidia, and Cyl. destructans var. crassum, which forms abundant 1-celled microconidia. DNA sequence data of the internal transcribed spacer regions 1 and 2 plus the 5.8S rDNA and the partial beta-tubulin gene were used for phylogenetic inferences. Cylindrocarpon pauciseptatum and Cyl. macrodidymum are monophyletic and are closely related to other species of Cylindrocarpon sensu stricto including members of the Cyl. destructans (teleomorph, Neonectria radicicola) species complex, which accommodates Cyl. liriodendri (teleomorph, Neon. liriodendri), Cyl. destructans var. crassum and Cyl. austrodestructans (teleomorph, Neonectria austroradicicola comb. nov.). Cylindrocarpon theobromicola is distantly related to species of Cylindrocarpon sensu stricto or Neonectria sensu stricto. It clustered among cylindrocarpon-like species with curved macroconidia, of which some belong to the Neon. mammoidea group. Relatively voluminous cells in sporodochial conidiophores of Cyl. theobromicola resembled those described for Campylocarpon, which is closely related to members of the Neon. mammoidea group including Cyl. theobromicola. Cylindrocarpon pauciseptatum has been isolated from roots of Vitis spp. in South-eastern Europe (Slovenia) as well as New Zealand, where it also occurs on roots of Erica melanthera.

AFLP Analysis of Intraspecific Variation Between Monilinia laxa Isolates from Different Hosts.

We analyzed with an amplified fragment length polymorphism (AFLP) marker system the genetic diversity and relationships among 67 Monilinia laxa isolates obtained from different host plants. From a total of 1,089 amplified bands scored using 20 primer combinations with two selective nucleotides, 354 were polymorphic and further used in genetic diversity analysis. Genetic relationships among isolates were assessed with different phenetic approaches, including unweighted pair group method with arithmetic mean clustering and principal coordinate analysis; the population's differentiation estimate was analyzed by molecular variance; and model-based clustering was employed to infer population structure. All four analyses clearly showed significant differences between isolates from apple trees and isolates from other host plants. No further grouping according to any other host plant was observed. The results indicate host specialization of apple isolates and support the taxonomic grouping of apple isolates.