Abstract
Karnal bunt of wheat is an internationally quarantined disease affecting trade, quality, and production of wheat. During 2015–2016, a severe outbreak of Karnal bunt disease occurred in north-western plain zone of India. The present study was undertaken to decipher genetic variations in Indian isolates of Tilletia indica collected from different locations. Seven multilocus sequence fragments were selected to differentiate and characterize these T. indica isolates. A phylogenetic tree constructed based on pooled sequences of actin-related protein 2 (ARP2), β-tubulin (TUB), eukaryotic translation initiation factor 3 subunit A (EIF3A), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), histone 2B (H2B), phosphoglycerate kinase (PGK), and serine/threonine-protein kinase (STPK) showed that isolate KB-11 (Kaithal, Haryana) was highly conserved as it was located in cluster 1 and has the maximum sequence similarity with the reference strain. Other isolates in cluster 1 included KB-16 and KB-17, both from Uttar Pradesh, and KB-19 from Haryana. Isolates KB-07 (Jind, Haryana) and KB-18 (Mujaffar Nagar, Uttar Pradesh) were the most diverse and grouped in a subgroup of cluster 2. Maximum numbers of single nucleotide polymorphisms (SNPs) (675) were in the PGK gene across the T. indica isolates. The minimum numbers of SNPs (67) were in KB-11 (Kaithal, Haryana), while the maximum number of SNPs (165) was identified in KB-18, followed by 164 SNPs in KB-14. KB-18 isolate was found to be the most diverse amongst all T. indica isolates. This first study on multilocus sequence typing (MLST) revealed that the population of T. indica was highly diverse.
Highlights
Tilletia indica Mitra is a floret infecting fungal pathogen which causes Karnal bunt disease of wheat
A phylogenetic tree was constructed based on the pooled amplified gene sequences, namely actin-related protein 2 (ARP2), TUB eukaryotic translation initiation factor 3 subunit A (EIF3A), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), histone 2 B (H2B), phosphoglycerate kinase (PGK) and serine/threonine-protein kinase (STPK), and with the reference gene sequence
The present study revealed that the population of T. indica in the north-western plain zone of India was highly diverse
Summary
Tilletia indica Mitra is a floret infecting fungal pathogen which causes Karnal bunt disease of wheat. It is a re-emerging disease in India. Several countries have had restrictions on importing wheat from countries where the disease has been reported [3]. Teliospores survive in the soil for many years in a dormant state, which is the main source of primary inoculum for the disease [8]. These teliospores are liberated during harvesting/threshing to the soil surface, and the disease cycle begins again. The erratic occurrence of Karnal bunt disease is climatedependent and requires certain conditions, further making it a complex phytopathogen
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