Inhibitory activities of proteinase inhibitors on developmental characteristics of sugarcane Chilo infuscatellus (Snellen)

A sugarcane wild relative Erianthus arundinaceus was identified as a source of resistance against Chilo infuscatellus, a major devastating pest at the early cropping stage of sugarcane. In the view of earlier studies, inhibitory activities of proteinase inhibitors (PIs) from C. infuscatellus field resistant E. arundinaceus genotypes viz., IK 76 78, IJ 76 400, IK 76 84, IK 76 88, IJ 76 370, FIJI 55, IJ 76 364 and ERI 2798 and a popular variety Co 86032 were done. Although proteinase inhibitors differed significantly among the plant parts of selected genotypes, it was comparatively higher in the apical meristem (70%) followed by leaf sheath (20%) and stalk tissues (11%). The results also showed that E. arundinaceus apical meristem PIs significantly inhibited (> 70%) the midgut proteinase of early shoot borer. Among the genotypes, IJ 76 370 and IJ 76 364 had considerably higher PIs in apical meristem and leaf sheath which showed strong inhibitory activity against gut proteinase of sugarcane shoot borer. Developmental characteristics of the borer showed a significant reduction of larval and pupal survival along with extended larval duration in the genotypes IJ 76 370 and IJ 76 364. Correlation studies indicated negative relationship with shoot borer larval (P < 0.05, r = −0.14) and pupal survival (P < 0.05, r = −0.56**) with apical meristem PIs of E. arundinaceus. Similarly, significant correlations were found between the shoot borer developmental period and apical meristem PIs of E. arundinaceus (P < 0.05, r = 0.52**, P < 0.05, r = 0.24 and P < 0.05, r = 0.56** for larval, pupal and total developmental period of the borer respectively). The study identified two elite genotypes IJ 76 370 and IJ 76 364 which could be used as donors for sugarcane pre-breeding programme for the development of shoot borer resistant varieties. Besides, it could be possible to identify novel insecticidal proteins (PIs) that may be utilized in genetic manipulation work for producing transgenics imparting resistance against sugarcane C. infuscatellus.