Relationship between biochemical constituents of sweet potato cultivars and resistance to weevil (Cylas formicarius Fab.) damage

The relationship between biochemical constituents of vines and tubers of 11 sweet potato cultivars, viz., C-43, S-30, H-268, OP-217, Cross-4, X-5, Kalmegh, C-71, K-24, OP-5 and V-35, and tolerance/resistance to damage due to sweet potato weevil, Cylas formicarius was investigated. Any significant impact of percentage moisture content of vines (65.81–77.9)/tubers (67.06–77.13) was not observed. In the case of dry matter content of various cultivars, it was positively correlated with weevil infestation of vines, while with tubers it was negatively correlated. Variety Cross-4 showed the highest dry matter content (34.19%) in vines and also revealed the maximum infestation (41.28%) but the tubers possessed the lowest dry matter content (24.32%). Irrespective of the cultivar, the silica content was always higher in the vines (2.1 to 2.9%) as compared to tubers (1.3 to 2.6%). The weevil incidence was negatively correlated with silica content of all the cultivars in the case of both vines and tubers. Nitrogen and protein contents were higher in vines than the tubers in each of the cultivars. These constituents showed positive correlation with the weevil incidence and gave significant response in the case of vines as compared to tubers. The coefficient of correlation (r = 0.857) showed that significant negative correlation existed between the per cent potash content in vines and weevil incidence. The vines and tubers of cultivars OP-217 and OP-5 possessed the highest amount of potash, i.e., 0.9 and 0.37%; and 0.97 and 0.36% respectively and exhibited the lowest weevil incidence (11.85 and 12.05%). Also, the phosphorus content was negatively correlated with the weevil incidence both in the case of vines (r = 0.774) and tubers (r = -0.451). The cultivar OP-217 having the highest percentage of phosphorus both in the vines and tubers, i.e., 0.175 and 0.15%, supported the lowest weevil incidence, i.e., 11.85 and 12.05%, respectively.