New insights into colchicine-mediated tetraploidy in Actinidia chinensis ‘Donghong’

Red-fleshed kiwifruit exhibits favorable nutritional characteristics and is renowned for its sweet flavor. However, the majority of red-fleshed kiwifruit species are diploids, producing diminutive fruit sizes and limited resistance to abiotic stress. To cultivate new cultivars with superior traits, we employed colchicine treatment to induce tetraploidy from the diploid Actinidia chinensis cv. ‘Donghong’. In this study, a 20% induction rate was achieved by immersing the apical meristem in 0.2% colchicine solution for 48 hours. The induced tetraploids demonstrated larger stomatal size, lower stomatal density, higher chlorophyll content, and a lower chlorophyll a/b ratio compared to diploids; however, no significant difference in photosynthetic conversion efficiency was observed. Furthermore, the tetraploid red-fleshed kiwifruit grafted on the same tree exhibited superior fruit shape, quality, and weight compared to their diploid parent ‘Donghong’. The vitamin C content in tetraploid fruits increased by 62.6% compared to that in diploids. Also, the tetraploid ‘Donghong’ showed delayed phenology compared to the diploid from leaf buds to fruit ripening. This research not only generated a novel germplasm of tetraploid kiwifruit for future breeding, but also contributes to understanding the mechanism of polyploidy-induced trait variation in kiwifruit.