Resistance to Spot Blotch in Two Mapping Populations of Common Wheat Is Controlled by Multiple QTL of Minor Effects.

Pawan Singh,Philomin Juliana,Ravi Singh,Etienne Duveiller,Arun Joshi,Xinyao He,Carolina Sansaloni,Uttam Kumar,Susanne Dreisigacker

doi:10.3390/ijms19124054

Abstract

Spot blotch (SB) is an important fungal disease of wheat in South Asia and South America. Host resistance is regarded as an economical and environmentally friendly approach of controlling SB, and the inheritance of resistance is mostly quantitative. In order to gain a better understanding on the SB resistance mechanism in CIMMYT germplasm, two bi-parental mapping populations were generated, both comprising 232 F2:7 progenies. Elite CIMMYT breeding lines, BARTAI and WUYA, were used as resistant parents, whereas CIANO T79 was used as susceptible parent in both populations. The two populations were evaluated for field SB resistance at CIMMYT’s Agua Fria station for three consecutive years, from the 2012–2013 to 2014–2015 cropping seasons. Phenological traits like plant height (PH) and days to heading (DH) were also determined. Genotyping was performed using the DArTSeq genotyping-by-sequencing (GBS) platform, and a few D-genome specific SNPs and those for phenological traits were integrated for analysis. The most prominent quantitative trait locus (QTL) in both populations was found on chromosome 5AL at the Vrn-A1 locus, explaining phenotypic variations of 7–27%. Minor QTL were found on chromosomes 1B, 3A, 3B, 4B, 4D, 5B and 6D in BARTAI and on chromosomes 1B, 2A, 2D and 4B in WUYA, whereas minor QTL contributed by CIANO T79 were identified on chromosome 1B, 1D, 3A, 4B and 7A. In summary, resistance to SB in the two mapping populations was controlled by multiple minor QTL, with strong influence from Vrn-A1.

Highlights

Spot blotch (SB) is an important fungal disease in wheat with global importance, mostly prevailing in humid tropical regions of South Asia and South America and Zambia [1]
In a mapping population derived from the cross Avocet × Saar, Lillemo et al [11] demonstrated the major effect of pleiotropic multi-fungal resistance gene Lr34 located on chromosome 7DL and the minor effect of gene Lr46 located on chromosome 1BL on SB resistance, the former gene being named as Sb1
This study unraveled the underlying mechanism for the phenotypic association between SB resistance and leaf tip necrosis (LTN) earlier reported by Joshi et al [12], since both Lr34 and Lr46 are associated with LTN

Summary

Introduction

Spot blotch (SB) is an important fungal disease in wheat with global importance, mostly prevailing in humid tropical regions of South Asia and South America (such as eastern India, Bangladesh, Nepal, Brazil, Paraguay and Bolivia) and Zambia [1]. It is the anamorph that causes severe foliar blotch in field conditions, whereas the teleomorph (the sexual stage) has only been found under natural environments in Zambia [4]. The major QTL on chromosome 5BL was reported by Kumar et al [9,10] and was recently designated as Sb2 [14]. Singh et al [16] reported two major QTL on chromosomes 7BL and 7DL in a Brazilian SB resistant cultivar “BH 1146”, and Adhikari et al [17] and Gurung et al [18] identified multiple QTL on various chromosomes using association mapping

Methods

Results

Conclusion