Field resistance and molecular detection of the orange rust resistance gene linked to G1 marker in Brazilian cultivars of sugarcane

Abstract

<jats:p>ABSTRACT Sugarcane (Saccharum spp.), an important crop for tropical and subtropical countries, is used in the production of sugar and biofuel. Orange rust, a disease caused by the fungus Puccinia kuehnii, can reduce the yield and harm the sugarcane industry. Molecular markers linked to resistance genes can help breeding programs confirm introgression of favorable alleles, find new resistance sources and release new cultivars that have durable resistance. In the current study, the aims were (i) to evaluate in the field the resistance to orange rust of 24 Brazilian commercial cultivars; (ii) to assess the frequency of the allele at G1 marker locus in the set of cultivars, and (iii) to study the usefulness of G1 marker to predict the resistant phenotype and its potential for marker assisted selection. A diagrammatic scale, which ranged from 1 (plants without symptoms) to 9 (highly susceptible plants), was used to determine the disease severity. Considering resistant cultivars those with mean severity up to 3, G1 marker efficiency in predicting the resistant phenotype was 71.43%. In addition, there was a reduction of 35% in the overall mean severity when G1 marker was present. G1 marker is an important molecular tool that can be used by breeding programs in the search for sugarcane cultivars resistant to orange rust.</jats:p>

Experimental evaluation of genomic selection prediction for rust resistance in sugarcane

“…Similarly, the degree of resistance of BR was associated with the increase of copies of brown resistance allele Bru1 in the parental clones of Canal Point sugarcane breeding nursery (McCord, 2016). Several studies reported several different QTL having both large and minor effects associated with BR and OR resistance in sugarcane (Balsalobre et al, 2016;Daugrois et al, 1996;Fier et al, 2020;Yang et al, 2018;Yang et al, 2017), which indicates that that the BR and OR resistance must be regarded as complex traits that are mainly governed by both large-and small-effect QTL. Therefore, it is very hard to detect and capture all the QTL through MAS during selection.…”

“…To the best of our knowledge, only one polymerase chain reaction-based diagnostic marker (G1) linked with a major QTL associated with OR resistance has been reported (Yang et al, 2018). This marker is currently being used in multiple breeding programs for selecting OR resistance germplasm with an approximately 71% selection accuracy compared with phenotype data (Fier et al, 2020). Thus, another 29% accessions in the breeding program remain unknown or misidentified for the disease reaction, although those accessions may have other potential.…”

Research Article Resistance to orange rust associated with the G1 molecular marker in parents of Brazilian RB sugarcane varieties

“…Parents were classified as resistant (rAUDPC ≤ 0.02), intermediate (0.02 < rAUDPC > 1.87) and susceptible (rAUDPC ≥ 1.87). For classification, the rAUDPC value obtained in the present work was used for the SP79-2233 and RB867515 varieties, considered susceptible to orange rust and resistant to orange rust, respectively (Garcés et al 2014;Klosowski et al, 2015;Chapola et al, 2016;Fier et al, 2020).…”

“…Molecular markers associated with resistance alleles can be extremely useful in identifying resistant genotypes in the early stages of breeding programs and can be used in the process of marker-assisted selection (MAS) (Alzate-Marin et al, 2005). In addition, it can be used to indicate potential parents for future crosses and establish resistance alleles (Fier et al, 2020). Genotype classification by molecular techniques in sugarcane has been used for resistance to brown rust (Puccinia melanocephala) (Barreto et al, 2017).…”

“…The G1 molecular marker was the first marker to be published associated with the resistance of sugarcane to orange rust and showed an efficiency of 65.8% in the prediction of resistant phenotypes in mapping studies of a F1 segregating population obtained from the cross between clones CP95-1039 (resistant) and CP88-1762 (susceptible) (Yang et al, 2018). Fier et al (2020) reported an evaluation efficiency in predicting resistance to orange rust of 71.43% using the molecular marker G1 when evaluating Brazilian commercial cultivars, whereas Hoepers et al (2020) observed an efficiency in predicting the resistant phenotype of 22.86% using clones in the selection phase and commercial cultivars.…”