Determining morphological and biochemical indices to select for smut-resistant sugarcane varieties

Abstract

ABSTRACT In Sri Lanka, smut in sugarcane (Saccharum spp. hybrid) is caused by Sporisorium scitamineum and results in significant crop yield and economic losses. Current field evaluation methods to identify smut resistance in sugarcane are time consuming and do not show an association between disease resistance and the resistance mechanisms. This research was conducted to identify morphological and biochemical characters as selection indices of smut-resistant varieties to strengthen the existing varietal selection program. Fifty accessions were selected from the sugarcane germplasm collection and tested for their resistance to S. scitamineum by the standard inoculation method. The disease incidence and Area Under Disease Progress Curve (AUDPC) were assessed in the first two crop cycles. Pearson correlation coefficients were used to identify relationships of AUDPC with evaluated nine morphological and biochemical characteristics. Principal component analysis (PCA) was used to identify the indices associated with smut resistance and select the superior sugarcane varieties. Significant negative correlations (P < 0.05) were detected between AUDPC and total phenols in the leaves, bud hardness, foliage inclination angle (FIA) and number of scale leaves in the buds. The tested nine morphological and biochemical indices formed four major clusters by PCA with a cumulative contribution rate of 66%. The findings revealed that total phenols in the leaf, bud hardness, FIA and the number of scale leaves in the bud are useful, simple and non-laborious indices to determine sugarcane smut resistance in varietal selection.