Effect of thermotherapy, Leifsonia xyli subsp. xyli titres, sugarcane genotype and diagnostic techniques on ratoon stunt control in Brazil

Abstract

Aims: To examine the interaction of diagnostic techniques, initial titres of Leifsonia xyli subsp. xyli (Lxx), sugarcane genotype and thermotherapy on ratoon stunt (RSD) control. Methods and Results: Single buds of RB867515, RB92579 and RB966928 were submitted to 50°C/2 h or 52°C/30 min under factorial block design and five replications; results were checked 9 months later by serological (DBI) and molecular (PCR) techniques. A 10,000 bootstrapping simulations were performed to infer the best plot size based on the experimental coefficient of variation. Analysis of variance showed significance only on initial Lxx titres and RSD control. Despite the absence of significance in the overall analysis, minor differences in control success with different methods and cultivars are predicted to have a major epidemiological impact on RSD, considering successive harvests and vegetative increase. According to an epidemiological interpretation, the 50°C/2 h treatment was more effective, cultivar RB966928 was the most susceptible and the PCR-based method was the most sensitive for pathogen detection. The minimum required plants per plot was 15, indicating high precision of our experiment Conclusions: Data interpretation considered both the statistical analysis and the epidemiology aspect of RSD in order to improve RSD management. The Brazilian sugarcane industry will benefit from this approach since it is not using it.Significance and Impact of the Study: This is the first study that examined multiple factors that affect RSD control. Our work pinpointed the importance of the thermotherapy, its best combination as well as the diagnostic test. Also, the effect of the cultivar to respond to management strategies. Because the epidemiological aspect of RSD was taken into consideration, results of our work can have an impact on RSD control in the field.

Changing the diagnostic paradigm for sugarcane: development of a mill-based diagnostic for ratoon stunting disease in crude cane juice

“…The NAA based detection methods currently used by the sugarcane industry rely on complicated and time-consuming qPCR based diagnostic methods only suitable for diagnostic laboratory environments; however it provides absolute quantification of pathogen load and is an indirect measure of the extent of infection within a farm ( Grisham et al., 2007 ; Young et al., 2016 ; Johnson, 2019a ; Johnson, 2019b ; Andreato et al., 2022 ). In contrast, our RSD-LAMP assay is a semi-quantitative method, although we observed a positive correlation with the amount of Lxx DNA in crude juice samples, with early signal detection suggestive of high Lxx titer within a sample.…”

Effect of leaf scald disease on a major Brazilian sugarcane cultivar and cultivar reaction to Xanthomonas albilineans

“…As mentioned, samples for lab-assay were performed only on asymptomatic canes. The molecular diagnostic initiated by extracting total DNA from the most basal internode employing the CTAB method as previously described (23). PCR was run employing primers XAF1 and XAR1 with reaction mixture and ampli cation conditions described previously (24); the presence of X. albilineans was con rmed by visualization of a 600p fragment.…”

“…For this purpose, canes of 11-12 months of age were taken to laboratory, identi ed and sap collected from the most basal internode. Soon after, a dot blot immunoassay was carried out as previously described (23). Shortly, 100µl of vascular uids was extracted from the most basal internode of each plant, applied to the nitrocellulose membrane, heated, blocked with non-fat milk, incubated with polyclonal antibodies and the presence of X. albilineans checked by indirect enzyme-linked immunosorbent assay (ELISA) employing rabbit anti-X.…”