First characterization of a newly emerging phytopathogen, Sclerotinia sclerotiorum causing white mold in pea

Abstract

Pea (Pisum sativum L.) is of global importance as a food crop for its edible pod and seed. A new disease causing the tan to light brown blighted stems and pods has occurred in pea (P. sativum L.) plants in Chapainawabganj district, Bangladesh. A fungus with white‐appressed mycelia and large sclerotia was consistently isolated from symptomatic tissues. The fungus formed funnel‐shaped apothecia with sac‐like ascus and endogenously formed ascospores. Healthy pea plants inoculated with the fungus produced typical white mold symptoms. The internal transcribed spacer sequences of the fungus were 100% similar to Sclerotinia sclerotiorum, considering the fungus to be the causative agent of white mold disease in pea, which was the first record in Bangladesh. Mycelial growth and sclerotial development of S. sclerotiorum were favored at 20°C and pH 5.0. Glucose was the best carbon source to support hyphal growth and sclerotia formation. Bavistin and Amistar Top inhibited the radial growth of the fungus completely at the lowest concentration. In planta, foliar application of Amistar Top showed the considerable potential to control the disease at 1.0% concentration until 7 days after spraying, while Bavistin prevented infection significantly until 15 days after spraying. A large majority (70.93%) of genotypes, including tested released pea cultivars, were susceptible, while six genotypes (6.98%) appeared resistant to the disease. These results on identification, characterization, host resistance, and fungicidal control of white mold could be valuable to achieve improved management of a new disease problem for pea cultivation.

Cosmos white rot: First characterization, physiology, host range, disease resistance, and chemical control

“…The disease exhibited a range of characteristic symptoms that have common analogies with Sclerotinia disease [9,10,14]. From the infected crop, a single fungus was consistently isolated that showed unique cultural and morphological characteristics similar to those of S. sclerotiorum, for example, fast-growing white aerial thin mycelia, hyaline, branched, and multinucleated hyphae, no conidia or conidiophore, globose to cylindrical sclerotia at the growing margins and production of apothecia, asci, and ascospores [10,14,15]. Sequence comparisons and phylogenetic analyses of ITS regions revealed them the fungal strains of S. sclerotiorum.…”

“…In Bangladesh, S. sclerotiorum appears as an emerging phytopathogen that gradually infects an increasing number of hosts [10,15]. In the present study, the fungus was highly pathogenic to 20 hosts from the Asteraceae (C. officinalisi, C. indicum), Apocynaceae (C. roseus), Solanaceae (S. tuberosum, S. lycopersicum, S. melongena, C. annum), Fabaceae (L. purpureus, P. vulgari, L. culinaris, V. radiata, V. mungo), Apiaceae (D. carota), Brassicaceae (R. sativus, B. juncea), Lythraceae (P. granatum), Amaranthaceae (S. oleracea), Convolvulaceae (I. batatas, I. aquatica), and Elaecarpaceae (E. serratus).…”

“…The pathogen was initially identified based on the emerging colony, and morphological characters and their similarities with the previous reference works in the same laboratory [9,10,14,15]. The pure mycelial isolates were transferred onto PDA plates and cultured at 25 ± 2°C in the dark for a week to study the colony characteristics.…”

“…Surface sterilized sclerotia were placed inside the sand (10 sclerotia/plates) and incubated at 4°C in the dark for 6 weeks. The Petri dishes having germinating sclerotia were transferred to another incubator at 20°C under scattered fluorescent irradiation (260 μmol/m 2 /s) until apothecial discs were developed [15]. The morphological features of apothecia and ascospores were examined under a light microscope (40× and 100×).…”

“…Five days after pathogen inoculation, disease severity was estimated by measuring the percent area diseased on the leaves. Based on disease severity, the level of protection attained by each fungicide was calculated as follows [15]:…”