Population genetic structure of the African sugarcane stalk borer (Eldana saccharina Walker, Lepidoptera: Pyralidae) in Tanzania

IntroductionThe African sugarcane stalk borer (Eldana saccharina) is a major insect pest of sugarcane in Sub-Saharan Africa. Because its larvae reside inside sugarcane stalks, conventional measures are less effective. Poorly managed infestations can reduce sugar production by up to 18% from damage caused by a single larva. Limited knowledge on the genetic diversity and population structure of E. saccharina, has curtailed insights into developing breeding-based pest management strategies including host resistance.MethodSamples of Eldana saccharina were collected from three altitude-defined agroecological zones in Tanzania. A mitochondrial cytochrome c oxidase subunit I (COI) region was amplified, sequenced, and analyzed to assess genetic diversity, population structure, and phylogenetic relationships among populations.ResultsTwelve unique haplotypes were identified. Observed haplotype diversity was high in the high altitude (Hd=0.64) and medium (Hd=1.00) populations, and moderate in the low-altitude populations (Hd=0.57), although these estimates should be interpreted cautiously due to the small sample size used. Overall genetic differentiation across populations was significant (χ² = 38, P = 0.017). Pairwise comparison showed significant differentiation between high and low altitude populations (FST = 0.35, P = 0.004) and between medium and low altitude populations (FST = 0.21, P = 0.01), whereas differentiation between high and medium altitude populations was low and not significant (FST = 0.1, P = 0.12) A significant positive Tajima’s D value in the low-altitude (2.5, P = 0.01), may indicate possible population contraction or selection, although this inference is provisional due to limited sample size. The presence of geographically structured and zone-specific haplotypes was observed, suggesting preliminary altitude-associated genetic differentiations.DiscussionE. saccharina populations in Tanzania showed substantial mitochondrial genetic diversity and altitude-associated population structure. These findings suggest preliminary basis for considering population variation in the design of locally relevant monitoring, host-resistance breeding, and other targeted pest management strategies.