First report of a new pathogenic variant of Cercospora canescens on mungbean (Vigna radiata) from India

Abstract

Atypical symptoms were observed on the recently released mungbean (Vigna radiata)cv. Meha that were attributed to the pathogen Cercospora canescens during the sampling of Cercospora leaf spot disease. The disease severity caused by the putative new strain of C. canescens (isolate NFCCI-2370) varied from 60 to 80% at the farm of the Indian Institute of Pulses Research Kanpur, India. Similar atypical symptoms were also observed at neighbouring research stations where seed multiplication of cv. Meha is performed. Yield losses from the new strain varied from 50-70% at these sites that was significantly higher than with the previously identified typical strain. Symptoms of the new strain were dry necrotic, grey irregular sporulating spots without chlorotic margins. The pathogen was isolated from infected leaves using the method of Goode & Brown (1970) and purified by single spore isolation in the laboratory.Isolates of the pathogen were confirmed as C. canescens by productionofcercosporin (Daub, 1982) and typical conidia and conidiophores (Ellis & Martin, 1882). Inoculation on to plants of cvs. Meha, Kopergaon and Malvia Joyoti with a monoconidial culture of the new strain produced the atypical symptoms described (Fig. 1a), whereas inoculation with the typical C. canescens isolates (MTCC-10835) produced several small, angular, necrotic water-soaked grey sporulating lesions surrounded by chlorotic margins (Fig. 1b). A morphological comparison of the new strain (NFCCI-2370) with the typical strain (MTCC-10835) was done using mycelium from infected leaves. The new strain was distinguished from the typical strain by 1-2 scars on the conidiophores, whereas the number of scars was 2-7 in the typical strain. The conidiophores (90.09 µm x 9.64 µm) and conidia (128.94 µm x 5.49 µm) were also shorter in the new strain (Table 1). The new strain bears a single conidium at the tip of conidiophores with a prominent scar (Fig. 2). The radial growth, colony morphology and pigment production of the new strain (NFCCI-2370) on PDA at 25°C (Ferrater et al., 2004) was faster, i.e.3.82 mm/day and colony colour was creamy without production of cercosporin or spores (Fig. 3).The identity of the new strain (NFCCI-2370) together with the other isolate (MTCC-10835) was further confirmed by comparison of ITS (Internal Transcribed Spacer) sequence data with reference isolates. BLASTn analysis of the sequence obtained showed 98-99% homology with reference isolatesof C. canescens. The ITS region of rDNA was amplified with primers ITS1/ ITS4 and sequences of these isolates have been deposited in GenBank (Accession Nos. JF747032 and JF747033). Isolate NFCCI-2370 has been deposited with the National Facility for

Delineating Genotype × Environment interactions towards durable resistance in mungbean against Cercospora leaf spot (Cercospora canescens) using GGE biplot

“…CLS is a severe fungal disease in mungbean, and no highly resistant sources are reported till date. Identification of CLS resistant mungbean genotypes becomes more complicated due to pathogenic variability (Chand et al, ) and wider host range (Iqbal, Zubair, & Haqqani, ; Singh, Kumar, Mishra, Pandey, & Arya, ). Identification of mungbean genotypes with less CLS severity along with stable performance across diverse locations is pertinent for accommodating these resistant sources in future breeding programme and integrated disease management.…”

“…Fungicidal management to control the disease is neither economical nor an environment friendly strategy. Presence of host and pathogenic variability (Chand, Singh, Chhattarpal, & Kumar, ) seeks immediate attention of identification of durable resistance sources against CLS in mungbean followed by utilization of these sources as donors in resistance breeding pogramme for managing the issue in comprehensive manner. Unfortunately, progress in breeding CLS resistant cultivar has been limited due to complicacy in screening process, wider host range and intricacy due to species complexity of the genus Cercospora (Barbetti, ; Chand et al, ; Chankaew et al, ).…”

Biotic and Abiotic Constraints in Mungbean Production—Progress in Genetic Improvement

“…Reports of yield losses of 33–44% due to Rhizoctonia root rot (Singh et al, 2013a) and 30–70% due to anthracnose (Kulkarni, 2009; Shukla et al, 2014) from India were estimated. Yield losses due to CLS were 97% in Pakistan and different states of India (Iqbal et al, 1995; Chand et al, 2012; Bhat et al, 2014), and 40% due to powdery mildew (Khajudparn et al, 2007). Among the minor fungal diseases, 20% yield loss was reported due to Fusarium wilt (Anderson, 1985) and 10% due to Alternaria leaf spot (Maheshwari and Krishna, 2013).…”

Perspectives and Challenges for Sustainable Management of Fungal Diseases of Mungbean [Vigna radiata (L.) R. Wilczek var. radiata]: A Review

“…A wide range of yield losses (23-96%) due to Cercospora leaf spot was reported from field trials conducted at different states of India (Kaur, 2007;Chand et al, 2012;Bhat et al, 2014) and up to 61% from Pakistan (Iqbal et al, 1995). The impact of powdery mildew on mungbean also was reported from different countries.…”