Dissecting Quantitative Trait Loci for Spot Blotch Resistance in South Asia Using Two Wheat Recombinant Inbred Line Populations.

Chandan Roy,Arun K Joshi,Vinod K Mishra,Ramesh Chand,Xinyao He,Pawan K Singh,Navin C Gahtyari

doi:10.3389/fpls.2021.641324

Abstract

Spot blotch (SB) disease causes significant yield loss in wheat production in the warm and humid regions of the eastern Gangetic plains (EGP) of South Asia (SA). Most of the cultivated varieties in the eastern part of SA are affected by SB under favorable climatic conditions. To understand the nature of SB resistance and map the underlying resistant loci effective in SA, two bi-parental mapping populations were evaluated for 3 years, i.e., 2013–2015 for the BARTAI × CIANO T79 population (denoted as BC) and 2014–2016 for the CASCABEL × CIANO T79 population (CC), at Varanasi, Uttar Pradesh, India. DArTSeq genotyping-by-sequencing (GBS) platform was used for genotyping of the populations. Distribution of disease reaction of genotypes in both populations was continuous, revealing the quantitative nature of resistance. Significant “genotype,” “year,” and “genotype × year” interactions for SB were observed. Linkage map with the genome coverage of 8,598.3 and 9,024.7 cM in the BC and CC population, respectively, was observed. Two quantitative trait loci (QTLs) were detected on chromosomes 1A and 4D in the BC population with an average contribution of 4.01 and 12.23% of the total phenotypic variation (PV), respectively. Seven stable QTLs were detected on chromosomes 1B, 5A, 5B, 6A, 7A, and 7B in the CC population explaining 2.89–10.32% of PV and collectively 39.91% of the total PV. The QTL detected at the distal end of 5A chromosome contributed 10.32% of the total PV. The QTLs on 6A and 7B in CC could be new, and the one on 5B may represent the Sb2 gene. These QTLs could be used in SB resistance cultivar development for SA.

Highlights

Spot blotch (SB) disease caused by Cochliobolus sativus (Ito and Kuribayashi) Drechsler ex Dastur [anamorph Bipolaris sorokiniana (Sacc.) Shoemaker] is considered a significant disease of wheat (Triticum aestivum L.) in South Asia (SA) (Gupta et al, 2018)
Significant genetic variation was observed for SB among the genotypes in both the BC and CC populations
Twenty-three resistant transgressive segregants were found in the BC population, out of which seven genotypes performed better than the resistant check Chirya 3, whereas in the CC population, 55 genotypes showed higher

Summary

Introduction

Spot blotch (SB) disease caused by Cochliobolus sativus (Ito and Kuribayashi) Drechsler ex Dastur [anamorph Bipolaris sorokiniana (Sacc.) Shoemaker] is considered a significant disease of wheat (Triticum aestivum L.) in South Asia (SA) (Gupta et al, 2018). High temperature and humidity favor the disease development in the warmer wheat growing areas of the eastern Gangetic plains. QTL for Spot Botch Resistance (EGP), in Bangladesh (Siddique et al, 2006), Nepal (Sharma et al, 2007b), and eastern India (Joshi et al, 2007a). The long-established practice of rice–wheat cropping system in the EGP delays the sowing of wheat crop that provides a congenial humid and warm environment for the SB development in the later stages of crop growth. Several attempts have been made including cultural practices and chemical application to control SB, but none of them was completely successful. Integrated disease management using host resistance, chemical control, and cultural practices is considered most effective in managing the disease (Joshi and Chand, 2002)

Methods

Results

Conclusion