The Role of Leaf Pubescence in Resistance to Yellow Sugarcane Aphids (YSA), Sipha flava, in Selected Sugarcane, Saccharum officinarum Varieties

Abstract

Screening for leaf pubescence in sugarcane (Saccharum officinarum L.) varieties against yellow sugarcane aphid (YSA) (Sipha flava) remains unexplored in the sugar industry of Zimbabwe. Field trials were undertaken to investigate the interaction between leaf pubescence and YSA. A 7*2*3 factorial complete randomized block design (CRBD) replicated four times was used, under two aphid treatments (Alice pesticide sprayed (control) and YSA infested). The first factor was varieties (96-1107, 00-1165, ZN 10, ZN 8, ZN 9, ZN 3L, and N14), aphid treatment was the second factor at two levels (sprayed and infested), and leaf position was the third factor (leaf position-1, leaf position-2 and leaf position-3). Quantitative data on trichome density (mm²) was measured using a light microscope, and aphids were physically counted to determine their number. The trichome density (mm²) and aphid number in the control varied greatly (p<0.001), showing prominent variation depending on the leaf position (p<0.001), and the variety (p<0.001). In aphid-infested plots, ZN 10 had the lowest trichome density (30.9; 41.27; 56.72/mm²) for leaf-1, leaf-2, and leaf-3, respectively, whereas the sugarcane variety 00-1165 had the highest trichome density for all three leaf positions (105.7, 115.7 and 131/mm²), respectively. Linear regression analysis confirmed a significant (p<0.001) negative correlation between the number of aphids for different varieties and trichome density. Resistance to YSA feeding on different sugarcane varieties is mediated by leaf pubescence, or dense trichomes. Farmers in the sugar industry should integrate pubescent (high-density trichome) sugarcane varieties into their existing YSA management strategies.

Keywords:

Leaf pubescence, trichomes, leaf position, sugarcane, Sipha flava.