Identification of QTLs for Spot Blotch Resistance in Two Bi-Parental Mapping Populations of Wheat.

Navin C Gahtyari,Xinyao He,Paritosh K Malaker,Krishna K Roy,Md A Hakim,Chandan Roy,Arun K Joshi,Mohamed M A Reza,Pawan K Singh

doi:10.3390/plants10050973

Abstract

Spot blotch (SB) disease caused by the hemibiotrophic pathogen Bipolaris sorokiniana inflicting major losses to the wheat grown in warm and highly humid areas of the Indian subcontinent, including Bangladesh, necessitates identification of QTLs stably expressing in Indian subcontinent conditions. Thus, two RIL mapping populations, i.e., WC (WUYA × CIANO T79) and KC (KATH × CIANO T79), were phenotyped at Dinajpur, Bangladesh for three consecutive years (2013-2015) and genotyped on a DArTseq genotyping by sequencing (GBS) platform at CIMMYT, Mexico. In both populations, quantitative inheritance along with transgressive segregation for SB resistance was identified. The identified QTLs were mostly minor and were detected on 10 chromosomes, i.e., 1A, 1B, 2A, 2B, 2D, 4B, 4D, 5A, 5D, and 7B. The phenotypic variation explained by the identified QTLs ranged from 2.3–15.0%, whereby QTLs on 4B (13.7%) and 5D (15.0%) were the largest in effect. The identified QTLs upon stacking showed an additive effect in lowering the SB score in both populations. The probable presence of newly identified Sb4 and durable resistance gene Lr46 in the identified QTL regions indicates the importance of these genes in breeding for SB resistance in Bangladesh and the whole of South Asia.

Highlights

Wheat (Triticum aestivum L.) grown in the warm and humid regions of the world, in particular South Asia, is vulnerable to many biotic stresses, among which spot blotch (SB)caused by Cochliobolus sativus
Wheat crops are vulnerable to SB in Bangladesh and other parts of the Eastern Gangetic Plains (EGP) in South Asia, they become much more vulnerable when sown late, which coincides with warmer temperatures and rain during the grain filling stages [35,36]
It is important to note that the identified QTLs act in an additive fashion and stacking of the QTLs, in the upcoming era of genomic selection, can be an effective breeding strategy

Summary

Introduction

Wheat (Triticum aestivum L.) grown in the warm and humid regions of the world, in particular South Asia, is vulnerable to many biotic stresses, among which spot blotch (SB)caused by Cochliobolus sativus The disease is estimated to cause 15–20% average yield loss in South Asia [3], under favourable conditions, more than 85% losses during the summer season in Zambia [4] and on susceptible wheat cultivars [5] were observed. The grains in the infected spikes become shrivelled with a characteristic black point towards the embryo end [8]. This pathogen is known to cause multiple diseases in wheat such as seedling blight, seedling rot, common root rot and seed rot [9]. To fight the SB menace, a special initiative by CIMMYT was undertaken in 2009 especially for disease-prone

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