Survey of the Bru1 gene for brown rust resistance in Brazilian local and basic sugarcane germplasm

Abstract

Bru1 is currently the major gene conferring brown rust resistance in sugarcane, and diagnostic markers are available. A survey for the presence of this gene was conducted on 391 genotypes including Brazilian cultivars, clones and basic germplasm. The efficiency of these markers for identifying resistant cultivars and artificially inoculated basic germplasm was also evaluated. The Bru1 frequency among cultivars (73.5%) suggests this gene is the prevalent source of brown rust resistance in Brazilian sugarcane breeding programmes. Most of the cultivars known to be resistant were positive for Bru1, although other genes for resistance could be present in lines not having Bru1. Only 17.8% of the basic germplasm accessions were positive for the Bru1 gene, and a low correlation between Bru1 diagnostic markers and brown rust severity was observed for basic germplasm accessions. Overall, Bru1 diagnostic markers proved to be efficient identifying resistant cultivars and clones and have potential to be in screening brown rust resistance in Brazilian breeding programmes.

Genetic diversity and population structure of Saccharum hybrids

“…The low prevalence of the Bru1 gene in the EEAOC´s germplasm was previously reported by Racedo et al [12], whereas, Brazilian accessions showed a high frequency of haplotype I, revealing a genetic fixation effect of Bru1 in this germplasm, mainly for breeding genotypes. Similar results were presented by Neuber et al [14] and Barreto et al [39].…”

“…In a previous study where sugarcane accessions of EEAOC´s bank were evaluated under field infection, only 16.3% of resistant genotypes to brown rust harboured the Bru1 gene [12], proposing the existence of other alternative resistant sources, recently confirmed by Chaves et al [13]. Whereas a high frequency of Bru1 (73.5%) among brazilian cultivars suggested this gene is the prevalent source of brown rust resistance in Brazilian sugarcane breeding programmes [14], reinforcing the importance of germplasm exchange between both programs. Regarding orange rust, another major disease impacting sugarcane production worldwide caused by P. kuehnii, a PCR-based resistance gene-derived maker, G1 was developed and it can be effectively utilized in sugarcane breeding programs to facilitate the selection process [15].…”

Quantitative Trait Loci Mapping and Development of KASP Marker Smut Screening Assay Using High-Density Genetic Map and Bulked Segregant RNA Sequencing in Sugarcane (Saccharum spp.)

“…Association mapping method was also used based on 119 sugarcane genotypes fingerprinted for 944 SSR alleles, and four sugarcane red rot resistance markers were obtained ( Singh et al, 2016 ). However, to date, Bru1 PCR diagnostic markers for identifying brown rust resistant cultivars remains the only example of marker-assisted selection (MAS) in sugarcane ( Costet et al, 2012 ; Glynn et al, 2013 ; Racedo et al, 2013 ; Li et al, 2016 ; Neuber et al, 2017 ). Thus, studies validating sugarcane DNA markers in breeding program or germplasm identification remain very limited.…”

Novel alleles linked to brown rust resistance in sugarcane

“…Bru1 , detected in the cultivar R570, is a major gene with dominant effect (Daugrois et al, 1996). The presence of Bru1 was evaluated in different sugarcane germplasm around the world (Costet et al, 2012; Glynn et al, 2013; Li et al, 2017; Neuber et al, 2017; Parco et al, 2014, 2017; Racedo et al, 2013). Overall, results showed a high presence of Bru1 in modern resistant cultivars, making the durability of the Bru1 resistance gene vulnerable.…”