Starch profiles and their biothysnthetic markers in selected east African highland cooking bananas

Abstract

The East African Highland Cooking bananas (EAHCBs), a staple food and a key source of carbohydrates for millions in the Great Lakes region, are primarily consumed as cooked products. Despite their nutritional and economic significance, limited scientific attention has been given to understanding the diversity of starch properties in these cultivars and their underlying genetic basis. This study aimed to profile the starch physicochemical characteristics and identify associated genetic markers in selected EAHB cultivars to support value-added utilization of this banana and its targeted breeding for commercial industrial applications. A total of 11 banana cultivar starches were analyzed for starch content, amylose-to-amylopectin ratio, granule morphology, solubility indices and swelling power, pasting properties and molecular structure and chemical composition using standard biochemical and AOAC analysis techniques. Concurrently, molecular profiling was conducted using real time PCR for differential expression levels and Sanger sequencing to identify genetic markers linked to observed starch traits. Results revealed significant variability in the physicochemical and functional characteristics among the cultivars in key starch parameters, with certain varieties showing traits desirable for industrial or nutritional applications when compared to common commercial starches (native and modified). Marker-trait association studies identified specific gene potentially controlling starch quality attributes. PLSR analysis revealed that GBSS1, MaSSIII-1, and SDE each play distinct but complementary roles in regulating starch properties in East African Highland Cooking Bananas (EAHCB). It further pinpointed specific starch biosynthesis genes that influence specific starch parameters. For example, GBSS1 was strongly associated with viscosity-related traits, particularly pasting temperature. MaSSIII-1, by contrast, with starch yield, starch content, Particle size and mechanical strength consistent with its role in synthesizing branched amylopectin chains that form semi- crystalline regions crucial for thermal stability and gelatinization behavior. SDE while has a less dominant but still relevant role in starch functionality. It showed moderate influence on swelling power and solubility significantly affected amylose content, amylose–amylopectin ratios, and suggesting a regulatory role in fine-tuning starch granule structure and organization through the activity of debranching enzymes. These results underscore the multi-gene control of starch functionality in bananas, where GBSS1 governs quantity and structure, MaSSIII-1 modulates thermal properties, and SDE influences granule architecture thereby providing important insights for improving starch quality through targeted breeding. These findings provide foundational knowledge for the development of improved EAHCB cultivars tailored for both food and non- food applications through marker-assisted selection. The study contributes to bridging the gap between traditional crop use and modern genetic improvement approaches, enhancing the value chain of cooking bananas in the region. Future work should validate the identified markers in larger populations and explore their role in starch biosynthesis pathways.