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POSTERS: Cultural control

Effect of thermotherapy for ratoon stunt on leaf scald control.
Caroline Andreato - UFSCAR. Rodrigo Gazaffi- UFSCAR, Alfredo Seiiti Urashima- UFSCAR

New sugarcane fields covered 1.2 million hectares in Brazil in 2018. These fields were formed by vegetative propagation, which is also the major inoculum for both ratoon stunt (RSD) and leaf scald (LS), two systemic diseases. RSD is caused by Leifsonia xyli subsp. xyli, a fastidious bacterium with no characteristic symptom, whereas LS caused by Xanthomonas albilineans (Xa) has a latent infection, a symptomless stage of the disease. Once the dissemination of these diseases into new fields is an invisible process, the use of hot water treatment (HWT) of seedpieces is a major strategy of disease control. Numerous studies are available on thermotherapy for RSD control, the most recommended in Brazil are 50°C for 2h and 52°C for 30min. The prescribed HWT for LS is 50°C for 3h. There is no information on LS control by the thermotherapy used for RSD. Therefore, the present work examined the effect of the HWT for RSD on the LS suppression. Two cultivars LS-contaminated with different titers of Xa were submitted to 50°C/2 h and 52°C/30min and compared to untreated control. DNA was extracted from vascular bundles of 194, 215, 230 days old canes and PCR test carried out employing primers PGBL1/PGBL2. Our data showed that the use of HWT had a beneficial effect to control Xa. Also, the combination 50°C/2h were more effective for controlling the disease if compared with 52°C/30min, suggesting that HWT employed for RSD is also effective for LS, which was not documented previously.

1Master student at PPGPVBA - UFSCar