[3S05Am] 20. Plant Biotechnology

11:20 AM - 11:40 AM JST(2:20 AM - 2:40 AM UTC)

[3Plant-05] Integration of Cry1A-expressing transgenic sugarcane with the sterile insect technique for suppression of Eldana saccharina

○Vanessa Lucinda Lauchande^1,2, Lawrence Nkosikhona Malinga^3,2, Thinandavha Caswell Munyai² (1. Stellenbosch Univ. (South Africa), 2. Univ. KwaZulu-Natal (South Africa), 3. SASRI (South Africa))

Keywords:

GM Crop,Bt Sugarcane,Integrated Pest Management (IPM),Sterile Insect Technique (SIT),Lepidopteran pest

The African sugarcane stalk borer, Eldana saccharina Walker (Lepidoptera: Pyralidae), is a major lepidopteran pest of sugarcane in South Africa. Larval feeding within stalk tissue reduces sucrose yield and assists in fungal infection. Genetic transformation of sugarcane with Bacillus thuringiensis (Bt) Cry toxins offers a targeted approach to larval suppression. However, integration of transgenic crops with complementary biotechnologies aimed at population control remains underexplored. This study evaluated Bt sugarcane expressing Cry1A (GM CRY1A), alone and in combination with the sterile insect technique (SIT), as a proof-of-concept for integrating plant genetic engineering with genetic insect control. Transgenic sugarcane lines were developed from a conventional cultivar (88H0019) through Agrobacterium-mediated transformation with a Cry1A gene construct. Sugarcane lines of both GM CRY1A and 88H0019 controls were established under semi-controlled shade-house conditions at the South African Sugarcane Research Institute. One shade house received regular releases of sterile male E. saccharina (10:1, sterile:non-sterile ratio), while the second acted as a non-sterile release control. Sterile males were produced via gamma irradiation (200 Gy) to induce inherited sterility. Non-sterile moth pairs were introduced in both environments to initiate infestation. At 12 months, stalks were harvested and assessed for percentage stalk bored length (%SBL), percentage internodes bored (%INB), stalk red length (%SRL), and larval infestation per 100 stalks (e/100). The data were analysed using generalized linear and mixed modelling approaches. Overall infestation levels were low (mean 1.2 e/100 stalks), reflecting early crop-stage pest pressure. Despite this, GM CRY1A consistently demonstrated significantly reduced damage and infestation compared to the non-Bt cultivar 88H0019 (p < 0.05). In the SIT release environment, 88H0019 recorded the highest injury (%SBL 0.28; %INB 0.35; %SRL 0.81) and infestation (3.7 e/100), whereas GM CRY1A maintained minimal damage (%SBL 0.02; %INB 0.03; %SRL 0.03) and very low infestation (0.16 e/100). Similar genotype-driven trends were observed in the control environment. While sterile male releases alone did not significantly reduce larval abundance under low-density conditions, the Cry1A transgene produced strong and consistent larval suppression across both environments. These findings confirm the functional efficacy of Cry1A-mediated resistance in sugarcane and demonstrates the feasibility of integrating transgenic crop technology with pest insect control. Although synergistic effects were not detectable under low initial infestation pressure, the complementary modes of action which included, Bt-mediated larval mortality and SIT-driven reproductive suppression provide a conceptual framework for multifaceted biotechnology-based pest management. Future field-scale evaluations under higher pest densities are required to assess additive effects, resistance management potential, and long-term population suppression dynamics. This study illustrates the potential of combining molecular plant biotechnology with population-level genetic control strategies to develop integrated, technology-driven solutions for sustainable crop protection.