Mechanism of Biochemical Resistance in Sugarcane Varieties Derived from Saccharum and Erianthus Against Borer Pests

The popular sugarcane varieties grown across India were screened for resistance against early shoot borer (ESB), Chilo infuscatellus (Snellen) and internode borer (INB), Chilo sacchariphagus indicus (Kapur) (Lepidoptera: Crambidae) for three consecutive years (2019–2021) at the ICAR-Sugarcane Breeding Institute, Coimbatore, Tamil Nadu, India. Five of the seven varieties (Co 11015, Co 0212, Co 86032, Co 0238, and Co 09004) are commercial sugarcane hybrids (CSH), while the other two (Co 06030, Co 06022) are commercial hybrids derived from an Erianthus base (CSHE). The field screening studies revealed that ESB and INB incidences were significantly lower in the CSHs introgressed Erianthus base than in Saccharum. Furthermore, INB attacked internodes were significantly reduced in their length and girth invariably in all the commercial hybrids. However, INB bored stem tunnelling length was insignificant among the inbred of Saccharum and Erianthus. The varieties Co 06030 and Co 06022 derived from Erianthus showed a detrimental effect on the growth and development of ESB and INB. Similarly, the commercial variety Co 0238, had a significantly lower borer survival rate and a prolonged larval developmental period. A significant increase in secondary metabolites, including phenols, proteinase inhibitors (PIs), polyphenol oxidase (PPO), and silicon content of these varieties, could have a negative impact on the biology of ESB and INB, suggesting an antibiosis mechanism of resistance. Correlation studies confirmed that proteinase inhibitors (PIs), silicon content and total phenols were negatively correlated to ESB and INB incidence as well as their developmental growth parameters, whereas total sugars were positively correlated to ESB and INB incidence. The study identified two sugarcane varieties Co 06030 and Co 06022 with Erianthus base which exhibited a moderate tolerant reaction to sugarcane borers. These varieties could be cultivated in borer endemic areas as well as included in the sugarcane integrated pest management (IPM) programme. Furthermore, these two varieties (Co 06030 and Co 06022) can be employed as donors in the sugarcane breeding programme to develop borer tolerant varieties in the future.