Characterization and Pathogenicity of Lasiodiplodia theobromae Causing Black Root Rot and Identification of Novel Sources of Resistance in Mulberry Collections

Abstract

Black root rot (BRR) caused by Lasiodiplodia theobromae is an alarming disease of mulberry that causes tremendous economic losses to sericulture farmers in India and China. Successful control of this disease can be attained by screening germplasm and identifying resistant sources. Seventy four diseased root samples were collected from farmer’s fields belonging to four major mulberry growing states of South India. Based on morpho-cultural and scanning electron microscopy studies, 57 fungal isolates were characterized and identified as L. theobromae. Phylogenetic analysis of concatenated internal transcribed spacer and β-tubulin sequences revealed variation of the representative 20 isolates of L. theobromae. Following the root dip method of inoculation, pathogenicity studies on susceptible mulberry genotypes (Victory-1 and Thailand male) recognized the virulent isolate MRR-142. Accordingly, MRR-142 isolate was used to evaluate resistance on a set of 45 diverse mulberry accessions. In the repeated experiments, the mulberry accession ME-0168 which is an Indonesian origin belonging to Morus latifolia was found to be highly resistant consistently against BRR. Eight accessions (G2, ME-0006, ME-0011, ME-0093, MI-0006, MI-0291, MI-0489, and MI-0501) were found to be resistant. These promising resistant resources may be exploited in mulberry breeding for developing BRR resistant varieties and to develop mapping populations which successively helps in the identification of molecular markers associated with BRR.

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“…The results revealed that genotypes Kanva 2, Kokuso 21 and Rokokayaso were resistant against cutting rot disease. Similar results have been reported by Belaghihalli et al, (2022) [4] where in Kanva-2 belonging to Morus indica possessed resistance against Black Root Rot caused by Lasiodiplodia theobromae. Hongthongdaeng (1987) [3] reported that genotypes-Kokuso 21 and Rokokayoso from Morus multicaulis exhibited resistance towards root rot disease.…”

Determining fungal profiles associated at different stages of disease development and confirmation of pathogenicity for deducing aetiology of rough bark disease of cinnamon

“…In inoculation experiments, fungal isolates obtained from plant samples collected from different locations have reported differences in pathogenicity due to species differences, variations in the degree of virulence of the fungal isolates and environmental effects such as temperature and pH (Lu et al, 2018). As reported by Gnanesh et al (2022), out of 20 isolates of Lasiodiplodia theobromae isolated from mulberry plants infected with black root rot disease, 16 were highly virulent and four isolates were less virulent despite being inoculated on susceptible mulberry genotypes.…”

“…In inoculation experiments, fungal isolates obtained from plant samples collected from different locations have reported differences in pathogenicity due to species differences, variations in the degree of virulence of the fungal isolates and environmental effects such as temperature and pH(Lu et al, 2018). As reported byGnanesh et al (2022), out of 20 isolates of Lasiodiplodia theobromae isolated from mulberry plants infected with black root rot disease, 16 were highly virulent and four isolates were less virulent despite being inoculated on susceptible mulberry genotypes.For example, according to Lu et al (2018), 38 isolates of Colletotrichum, isolated from anthracnose-infected tea leaves have reported pathogenicity differences due to the presence of two Colletotrichum spp., temperature range prevailed in the sampling F I G U R E 8 Lesion developed on stems of cinnamon plants inoculated with fungal isolates by cut and paste method, 3 weeks after inoculation (a) and callus-like structure developed 3 months after inoculation (b).TA B L E 2 Details of the fungal isolates and their combinations inoculated by cut and paste method to field-grown plants and the reisolated fungal isolates from the inoculated-stems.…”

Assessment of Molecular Diversity and Population Structure of Pakistani Mulberry Accessions Using Retrotransposon-Based DNA Markers

“…They generally display a high tolerance towards drought, pollution, and poor soil quality. As a result, they are distributed across a wide range of tropical, sub-tropical, and temperate zones in Asia, Europe, North America, South America, and Africa [3,4]. The Morus genus encompasses a total of 24 species within areas with a Mediterranean climate [5].…”