Chaninun Pornsuriya

Corynespora cassiicola causes leaf spot disease on lettuce (Lactuca sativa) cultivated in hydroponic systems in Thailand

Lettuce (Lactuca sativa) is an annual vegetable that is widely cultivated in hydroponic systems in Thailand. In 2016, a leaf spot disease was commonly found on hydroponically-grown lettuce plants in glasshouses in Songkhla province, southern Thailand. The morphology of the fungus that was consistently isolated from the leaf spots was identical to that described for Corynespora cassiicola. The identity of the fungus was confirmed by sequencing the ITS and LSU gene regions. Koch’s postulates were satisfied, proving that C. cassiicola was the causal agent of the recent outbreaks of leaf spot in hydroponically-grown lettuce in Thailand. This paper is the first report of the disease in this country.

Disease Note: Identification of Curvularia oryzae as cause of leaf spot disease on oil palm seedlings in nurseries of Thailand

The causal agent of leaf spot disease of oil palm (Elaeis guineensis) seedling nurseries in Thailand was identified as Curvularia oryzae. The fungus was isolated from leaves with disease symptoms, characterized by morphological properties, and pathogenicity tested. The identity of the phytopathogenic fungus was confirmed through polymerase chain reaction analysis using internal transcribed spacer (ITS) primers, which amplified about a 1 kb product. Sequencing this DNA product confirmed this pathogen was C. oryzae. Furthermore, the pathogenicity test showed that C. oryzae could infect oil palm seedlings.

First report of leaf spot on lettuce caused by Curvularia aeria

In 2017, leaf spots were found on lettuce growing in fields in Songkhla Province, southern Thailand. The fungus isolated from the spot lesions on the leaves was identified as Curvularia aeria (Bat., J.A.Lima and C.T.Vasconc.) Tsuda based on morphological characteristics and DNA sequences of the ITS region of the rRNA gene. After a conidial suspension of the isolate was sprayed on lettuce seedlings, the leaf spots developed on lettuce seedlings, and the fungus was reisolated; leaves of plants inoculated with water did not develop spots. This is the first report of C. aeria causing leaf spot on lettuce.

Choanephora rot caused by Choanephora cucurbitarum on Brassica chinensis in Thailand

In July 2016, wet rot was observed on leaves of Brassica chinensis in a private greenhouse in Hatyai city, Songkhla province, Thailand. The fungal pathogen infected young and expanded leaves. The fungus was identified by morphological characterization and molecular analysis as Choanephora cucurbitarum. Pathogenicity test revealed that C. cucurbitarum could infect B. chinensis.

A new sudden decline disease of bullet wood in Thailand is associated with Ceratocystis manginecans

In Thailand, since 2013, sudden decline of bullet wood (Mimusops elengi) has been noted. The causal agent of this disease was identified based on both morphological and molecular properties as Ceratocystis manginecans. A portion of its ITS, β-tubulin and TEF1-α genes were amplified by PCR with the universal primer pairs PN3/PN16, βt1a/βt1b and EF1-728F/EF1-986R, respectively. Sequencing of the PCR product confirmed this pathogen was C. manginecans. This is the first report on the new sudden decline disease of bullet wood in Thailand associated with C. manginecans.