Reconnoitering commercial sugarcane (Saccharum officinarum L.) germplasm’s plant resistance index (PRI) categories in response to the incursion of YSA (Sipha flava) in the sugar industry of Zimbabwe

The study aimed at examining tolerance, antixenosis, and antibiosis expression in seven sugarcane (Saccharum officinarum) (L.) germplasm for Yellow Sugarcane Aphid (YSA) (Sipha flava) resistance. A 7 × 2 factorial design, laid out in a complete randomized block design and replicated four times was used. Variety was the first factor, with seven treatment levels (96-1107, 00-1165, ZN 10, ZN 8, ZN 9, ZN 3 L, and N14). Aphid infestation was a second factor, with two treatments (un-infested (control) and infested). Data was collected on tolerance parameters (chlorophyll loss, net photosynthesis, transpiration and stomatal conductance), antibiosis parameters (total protein content, total soluble sugars, nitrogen, phosphorus, potassium, calcium, and magnesium) and on antixenosis parameters (trichomes and aphid numbers). GenStat 18th edition was used for statistical analysis and Fisher’s Least Significance Difference (p < 0.05) was used for mean treatment separation. Different sugarcane varieties varied significantly (p < 0.05) on resistance mechanisms to YSA. Three levels of PRI (tolerance, antibiosis, and antixenosis) was expressed in 00-1165 sugarcane accession, while varieties; ZN 8, ZN 9 and ZN 3 L showed tolerance and antixenosis. Interaction effects (p < 0.001) between treatments were observed on gas exchange, total soluble sugars, chlorophyll loss, phenol content, and flavonoid content. Variety 00-1165 did not show any differences in chlorophyll loss between the aphid infested and uninfested treatments. Similarly, variety ZN 3 L did not show significant variation in flavonoid concentration between the aphid infested and uninfested treatments. Indeed, the study clearly shows that sugarcane varieties have resistance mechanisms to YSA.