Abstract:
Secondary metabolites serve a variety of ecological purposes, including defense against biotic and abiotic stressors. The
aim of this study was to quantify the total phenol and flavonoid contents in sugarcane leaves that mediate resistance to
yellow sugarcane aphids (YSA) (Sipha flava). A 7 × 2 factorial experiment was conducted in a complete randomized block
design (CRBD). Seven sugarcane varieties namely 00-1165, 96-1107, ZN 8, ZN 9, ZN 10, ZN 3 L, and N14 under two
aphid treatments [(uninfested (control) and infested] were used. 00-1165 showed medium resistance, as shown by its aphid
quantity ratio (AQR), which fell between 0.30 and 0.60. Moreover, ZN 10 is regarded a high sensitive variety because
its AQR was more than 1.50. Highly significant (p < 0.001) differences were recorded in both uninfested and infested
treatments on total phenol and flavonoid content. In the YSA infested plots, 96-1107 recorded the highest phenol content
of 50.31 µg/g, while ZN 3 L had the lowest (25.92 µg/g). Furthermore, N14 recorded the highest flavonoid content of
6.47 µg/g, whereas ZN 3 L produced the lowest (1.60 µg/g) in YSA infested plots. Notably, there was a significant positive
correlation between the percentage change in phenol concentration and aphid number (p = 0.002, r = 0.58), and between
the percentage change in flavonoid concentration and aphid number (p < 0.001, r = 0.70). Moreover, the regression results
showed a significant positive correlation (p < 0.001, r = 0.70) between the percentage change in flavonoid concentration
and the number of aphids. Feeding by YSA increased phenol and flavonoid induced resistance. There is a need to incor
porate sugarcane varieties with high phenol and flavonoid content into the existing YSA management strategies.
