A Survey Of Causal Agents Associated With Sugarcane Yellowing In Northeast Brazil

The etiological agents of the yellow leaf syndrome (YLS) are the Sugarcane yellow leaf virus (ScYLV), and phytoplasmas of different groups. Due to a lack of knowledge on the occurrence of YLS and the importance of sugarcane to Brazil, the aims of this study were to assess the occurrence and distribution of the pathogens associated with YLS in sugarcane cultivation areas in three states of Northeast Brazil. For this purpose, 101 sugarcane samples with symptoms of YLS were collected in 2018 crop cycle. ScYLV and a new phytoplasma were detected by RT-PCR and nested PCR, respectively. The identity of virus- and phytoplasma-positive samples was confirmed by Sanger sequencing, and these sequences were used in subsequent phylogenetic studies. Both pathogens were present in all sampled regions. ScYLV and the phytoplasma were detected in 40.4% and 62.2% of the samples, respectively. Mixed infections were found in 33.5% of the samples. Phylogenetic analysis showed that the ScYLV isolates identified were most closely related to ScYLV genotypes REU, PER, HAW, CHN2 and BRA. The phytoplasma 16S rDNA gene nucleotide sequences shared 99.0% identity with sequences of the 16SrVII phytoplasmas from Argentina and Brazil. This is the first report of the presence of a member of the 16SrVII phytoplasma group in association with sugarcane leaf yellowing in the world. These findings are important to raise awareness among sugarcane producers on the impact of pathogens causing YLS in Northeast Brazil.