Boron nutrition in horticultural crops for enhancing yield and fruit quality

Boron (B) is an essential micronutrient involved in reproductive development, fruit growth, yield formation, and quality of horticultural crops. It contributes to cell wall integrity, membrane function, carbohydrate transport, pollen germination and pollen tube growth, fruit set, and nutrient translocation. B availability influences reproductive development, yield, and fruit quality, with both deficiency and excess adversely affecting crop performance, while optimal B nutrition can promote fruit development and quality. However, B responses vary considerably with crop species and cultivar, initial B status, application rate and source, and environmental conditions. This review critically examines the physiological and biochemical roles of B and the proposed mechanisms underlying its effects in horticultural crops, with emphasis on reproductive development, yield, fruit quality, and postharvest performance. It evaluates variability and limitations in the available evidence, particularly dose- and crop-dependent responses, and critically assesses the emerging use of nano-boron, including concerns related to phytotoxicity, environmental safety, nanoparticle stability, economic feasibility, and limited field validation. Although nano-boron has shown promising potential, current evidence remains insufficient to establish its consistent superiority over conventional B sources across horticultural crops. Key research gaps and priorities for developing safe, effective, and field-applicable B management strategies are also identified.