Genetic Variability and Aggressiveness of Tilletia indica Isolates Causing Karnal Bunt in Wheat

Abstract

Karnal bunt caused by Tilletia indica is a quarantine disease of wheat causing huge economic losses due to the ban on the import of bunted grains. This study was designed to characterize pathogenicity, aggressiveness and genetic diversity of 68 Tilletia indica isolates collected from different geographic regions of Pakistan. Forty-six isolates were tested for their pathogenicity on eight wheat varieties, out of which three were non-aggressive. The coefficient of infection (CI) ranged from 15.73% (PB-25) to 10% (PB-68, PB-60, and PB-43). The isolates collected from central Punjab showed higher infestation compared to other isolates. Among the wheat varieties used for the aggressiveness study, WL-711 showed susceptible reaction with 10.88% CI, while NIFA-Barsat, HD-29, Janbaz, Bakhtawar-92, Tatara, and AARI 2011 showed resistance to the highly resistant response. These isolates were amplified using 31 random amplified polymorphic DNA (RAPD) markers and 32 inter-simple sequence repeat (ISSR) markers for diversity analysis. The principal component analysis (PCA) and analysis of molecular variance (AMOVA) showed greater divergence among isolates collected from Punjab and Khyber Pakhtunkhwa (KPK), with a moderate level of admixture. The isolates from Faisalabad (Punjab) were more aggressive compared to isolates from KPK and were clearly separated based on PCA, indicating the significant genetic distance in the populations. Our findings will assist breeders and pathologists in better understanding the pathogenic variability in Tilletia indica and in subsequent disease management.

Comparative analysis of nine Tilletia indica genomes for the development of novel microsatellite markers for genetic diversity and population structure analysis

“…Additionally, the occurrence of highly aggressive isolates of T. indica in Haryana, Rajasthan, Punjab, Uttar Pradesh, Uttarakhand, Jammu, and Himachal Pradesh also supported the movement of fungus from one region to another through seed or air. Similar results pertaining to the absence of region-specific virulence variability were also reported by Aasma et al (2022) .…”

“…In this connection, current research attempts to make a comparative analysis of nine T. indica genomes available in the public domain for the development of novel and neutral microsatellite markers to dissect the genetic diversity and structure of the field population of T. indica . Earlier researchers have used a series of molecular markers or typing methods to analyze the genetic variability of T. indica ( Avinash et al, 2000 ; Seneviratne et al, 2009 ; Aggarwal et al, 2010 ; Parveen et al, 2015 ; Aasma et al, 2022 ). Unfortunately, these methods are dominant types and are unable to establish analogous reproducibility of markers across populations at the genetic level, thereby being of limited significance, especially for comparative genotyping studies ( Agarwal et al, 2008 ; Rao et al, 2018 ).…”

“…These markers reveal the presence of a significant level of variation (94%) among the collected isolates at the genetic level. Although a flood of information pertaining to the assessment of the reaction of wheat germplasm to natural infection with KB is available ( Kaur and Kaur, 2005 ; Riccioni et al, 2008 ; Aasma et al, 2022 ), limited research efforts were made to determine the variability of the large pool of T. indica isolates in terms of aggressiveness. Therefore, in the current study, a research plan was executed with the aim of capturing the real situation regarding the aggressivity of T. indica isolate prevalence in different wheat growing sites in the northern part of India.…”

“…Earlier researchers have used a series of molecular markers or typing methods to analyze the genetic variability of T. indica (Avinash et al, 2000;Seneviratne et al, 2009;Aggarwal et al, 2010;Parveen et al, 2015;Aasma et al, 2022). Unfortunately, these methods are dominant types and are unable to establish analogous reproducibility of markers across populations at the genetic level, thereby being of limited significance, especially for comparative genotyping studies (Agarwal et al, 2008;Rao et al, 2018).…”

“…There are a flood of research reports that illustrate the potential of nucleic acid-derived markers for unzipping the variation among fungal pathogens at the genome level ( Kumar et al, 2013 ; Kashyap et al, 2015 , 2019b ; Goswami et al, 2017 ; Choudhary et al, 2018 ; Jiménez-Becerril et al, 2018 ; Prasad et al, 2018 ). For instance, genetic markers such as inter simple sequence repeats (ISSR) and random amplified polymorphic DNA (RAPD) have been extensively utilized to understand the genetic diversity of T. indica isolates ( Avinash et al, 2000 ; Seneviratne et al, 2009 ; Aggarwal et al, 2010 ; Parveen et al, 2015 ; Aasma et al, 2022 ). Unfortunately, the aforementioned markers are dominant and unable to determine analogous reproducibility across populations, thereby being of little significance, especially for comparative genotyping studies ( Agarwal et al, 2008 ; Rao et al, 2018 ).…”