Methodologies for Scoring <i>Pseudomonas syringae</i> pv. <i>Actinidiae</i> Floral Bud Rot and the Impact on Yield Potential in <i>Actinidia chinensis</i> var. <i>deliciosa</i>

Flower production is a key determinant of yield in many fruit crops, including kiwifruit ( Actinidia chinensis var. deliciosa ). Floral development is influenced by both genetic and environmental factors, with biotic stressors such as pathogens also playing a role in reproductive success. In kiwifruit, the bacterial pathogen Pseudomonas syringae pv. actinidiae (Psa) has been linked to floral bud rot (FBR), a phenomenon that may affect flower opening and overall yield. However, the effects of Psa on flower development and fruit set have not yet been thoroughly investigated. We examined the development of Psa‐induced FBR on yield potential within an A. chinensis var. deliciosa seedling population. Two novel methods were employed to determine the severity of FBR symptoms in a kiwifruit seedling population. The first method involved detailed daily measurements of FBR on individual flower buds, recorded over a flowering season. The final fate of each flower bud (successful or unsuccessful fruit set) and the shape of the resulting fruit (normal or deformed) were recorded. The second, more efficient method used less detailed scoring of the FBR symptoms. Results showed that the development of FBR symptoms was not correlated with the severity of the final FBR expression, with an average of 11 days from the symptom onset to the final FBR expression. Flower buds with over 50% of the sepals affected by FBR have a lower chance of successful pollination and, if pollination does occur, there is a higher chance that a deformed fruit will form. Both detailed and simplified methodologies effectively scored FBR symptoms within an A. chinensis var . deliciosa seedling population, with the simplified four‐category scoring system being the more efficient.