Identification of QTLs for Resistance to Sclerotinia Stem Rot and BnaC.IGMT5.a as a Candidate Gene of the Major Resistant QTL SRC6 in Brassica napus

Abstract

Stem rot caused by Sclerotinia sclerotiorum in many important dicotyledonous crops, including oilseed rape (Brassica napus), is one of the most devastating fungal diseases and imposes huge yield loss each year worldwide. Currently, breeding for Sclerotinia resistance in B. napus, as in other crops, can only rely on germplasms with quantitative resistance genes. Thus, the identification of quantitative trait locus (QTL) for S. sclerotiorum resistance/tolerance in this crop holds immediate promise for the genetic improvement of the disease resistance. In this study, ten QTLs for stem resistance (SR) at the mature plant stage and three QTLs for leaf resistance (LR) at the seedling stage in multiple environments were mapped on nine linkage groups (LGs) of a whole genome map for B. napus constructed with SSR markers. Two major QTLs, LRA9 on LG A9 and SRC6 on LG C6, were repeatedly detected across all environments and explained 8.54–15.86% and 29.01%–32.61% of the phenotypic variations, respectively. Genotypes containing resistant SRC6 or LRA9 allele showed a significant reduction in disease lesion after pathogen infection. Comparative mapping with Arabidopsis and data mining from previous gene profiling experiments identified that the Arabidopsis homologous gene of IGMT5 (At1g76790) was related to the SRC6 locus. Four copies of the IGMT5 gene in B. napus were isolated through homologous cloning, among which, only BnaC.IGMT5.a showed a polymorphism between parental lines and can be associated with the SRC6. Furthermore, two parental lines exhibited a differential expression pattern of the BnaC.IGMT5.a gene in responding to pathogen inoculation. Thus, our data suggested that BnaC.IGMT5.a was very likely a candidate gene of this major resistance QTL.

Detecting the Hormonal Pathways in Oilseed Rape behind Induced Systemic Resistance by Trichoderma harzianum TH12 to Sclerotinia sclerotiorum

“…In the field, two inoculation procedures of leaves and stems were carried out on both genotypes (90 days old) as described in detail previously [5], with some minor modifications to assess the resistance to the pathogen. The lesion length along the leaves was measured at 1, 2, 4, 6, 8 and 10 dpi, and the lesion length along the stems of both genotypes was measured at 1, 2, 4, 6, 8, 10 and 30 dpi.…”

“…SSR is reported from most of the oilseed-producing areas of the world, including China, India, Iran, USA, Brazil, Canada, Germany, Italy, Sweden, France, Finland, England and Denmark [1–4]. Sclerotinia sclerotiorum causes 0–20% of yield loss every year in Brassica napus crops and can reach up to 80% in severely infected fields in China [5]. …”

The control of sclerotinia stem rot on oilseed rape (Brassica napus): current practices and future opportunities

“… Based on comparative analysis by Li et al . (2015a), the independently discovered QTLs Sll16 (Zhao et al ., ) and SRC6 (Wu et al ., ) overlap, as do the independently discovered QTLs LRA9, SRA9 (Wu et al ., ) and qSR11‐1 (Wei et al ., ). …”

“…For many of the mapping studies, resistance was assayed at multiple B. napus life stages. Studies that assayed both seedling and mature plant life stages often found QTLs that were specific to each life stage (Zhao & Meng, ; Wu et al ., ). Notably, Wu et al .…”

Three Inoculation Methods for Evaluating Sclerotinia Blight Resistance in Peanut

“…Detached leaf assays have been used to identify quantitative trait loci for resistance to S. sclerotiorum in soybean (Arahana et al, 2001) and Brassica napus (Wu et al, 2013). In peanut, Hollowell et al (2003) developed an excised leaflet assay after obtaining inconsistent results using detached stems.…”