Biochar: A Valid Additive to Enhance Kiwifruit In Vitro Proliferation

Biochar, a by-product of agri-food waste, has shown benefits in plant growth and soil health. However, its use in vitro remains underexplored. This study investigates the impact of biochar supplementation in the culture medium, alone or in combination, with 6-benzylaminopurine (BAP), on kiwifruit (Actinidia chinensis var. deliciosa), cv. Tomuri proliferation. Kiwifruit explants were cultured on media enriched with 0, 4, or 6 g/L biochar, without or with BAP (0.2 mg/L), over two subcultures (SUB1 and SUB2). Parameters such as shoot and root number and length, fresh and dry weight, as well as plantlets’ total phenolic content and antioxidant activity, were measured and analyzed. Biochar enhanced plantlets proliferation, particularly with BAP. In SUB1, at 4 g/L, biochar promoted shoot production (2.00 vs. 1.63) and their length (1.50 cm vs. 0.98), independently of the presence of BAP. The presence of biochar in the BAP-free media, favored rhizogenesis; particularly in SUB2, where on average, 5.58 roots per plantlets were recorded. Biochar increased the plantlets’ total phenolic content and antioxidant activity, especially in BAP-free media. The addition of biochar as an additive to the culture medium during the kiwifruit in vitro proliferation phase could be a breakthrough outcome for the nursery sector.