Morphological variation of male A. arguta plants affects their flowering potential and pollen efficiency

Actinidia arguta (Siebold et Zucc.) Planch. ex Miq. is functionally a cryptic dioecious plant and successful pollination is crucial for achieving high quality fruit. The extent and bases of morphological variability in female genotypes have been well studied, but here we focus on the males. Mature plants of seven male A. arguta genotypes were studied in 2016 and 2017 during which a suite of phenological and morphological features was measured on ten randomly chosen one-year-old canes on each plant. This analysis was complemented by two other, specialized measures potentially related to pollination efficiency, namely pollen quality, and quantity. The time of bud break was similar each year across all genotypes and the pollen quality was uniformly very high (viability - 95.0-99.9% and germination - 89.0-97.3%). However, the ten genotypes exhibited high variability in both the number of flowers per inflorescence and pollen quantity, indicating marked differences in their flowering potential and efficiency as pollinizers. The male kiwiberry indicators developed in this study - flowering potential and pollen efficiency, appear to be effective tools for the comparative evaluation of male A. arguta genotypes.