Genetic diversity and virulence of Iranian Bipolaris
sorokiniana isolates causing common root rot disease
Zainab Zolfaghary, Mehdi Nasr Esfahan, Khoshnood Nourollahi & Hamid Akbarzadeh
Sydowia 74: 107-119
Published online on August 30th, 2021
Wheat, Triticum aestivum L., is an important and strategic crop worldwide. In recent times, wheat crops in Iran are seriously affected by common root and crown rot disease (CRCR), caused by Bipolaris sorokiniana. A survey was conducted during the 2016–2017 growing seasons in 50 wheat fields. A total of 48 B. sorokiniana isolates were collected from infected root and crown tissues, a month before maturity of the wheat plants. The isolates were subjected to virulence assays, and morphological, phylogenetic and genetic diversity analyses. The virulence of ten random isolates was confirmed on wheat cv. ‘Parsi’ under greenhouse conditions. For phylogenetic studies, the nucleus ITS region was sequenced in three random isolates, B4 (Zarin shahr), P1 and P5 (Baraan-e-Jonubi). To evaluate the genetic diversity of B. sorokiniana isolates, after DNA extraction, ten pairs of simple sequence repeat (SSR) primer were used. The results of the virulence assays showed that all the isolates are pathogenic in various degrees, causing 41–100 % disease severity, which were not directly correlated with geographic region. Morphological and phylogenic studies of the isolates confirmed B. sorokiniana as the causal agent of the root and crown rot disease. In total, the ten SSR primer pairs produced 16 distinct polymorphic bands. The mean polymorphic information content (PIC) was 0.716, marker index (MI) 3.467, and Shannon index (I) 0.497. BS096 and BS070 primers indicated the best efficiency in showing genetic diversity between different B. sorokiniana isolates. A cluster analysis with NTSYS software was developed using UPGMA method and Jaccard’s similarity matrix formation, with a coefficient of 89 %. Cluster analysis based on amplification patterns showed that the classified groups were not correlated with geographical regions. The results of this study showed that SSR markers, with the polymorphism percent of the primers varying from 50–100 %, at an average of 73.33 %, are a reliable marker system for detecting a high level of polymorphism to study the genetic variation of B. sorokiniana isolates and are meaningful for developing strategies to prevent and control wheat root rot.
Keywords: ITS region, phylogeny, SSR, Triticum aestivum, UPGMA.
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