Flowering synchrony and cultivar compatibility as key factors for optimising sweet cherry pollination and production

Abstract

Effective pollination management is essential for optimised yields in animal-pollinated crops. Sweet cherry (Prunus avium) is a crop with 82% of its production associated with animal pollination. Therefore, factors impacting pollination play a key role in sweet cherry production. These factors are often accounted for in pollinator management and orchard design; however, flower phenology, cultivar compatibility, and their impacts on yield are poorly understood and often not considered. We investigated how flowering overlap among cultivars and cultivar inter- and self-compatibility impact sweet cherry cultivars' suitability as pollen donors and recipients in Beira Interior, a key production region in Portugal. For this, we performed floral biology experiments in the field and under controlled greenhouse conditions. We compared the pollination success of compatible cultivars sharing one S-allele or none. We also assessed pollinator dependence and pollen limitation levels of the studied cultivars, as well as natural pollen deposition and fruit set levels. We observed that, although often overlooked, flower phenology is very important for determining suitable cultivar pairings, and flowering overlaps differ greatly from the existing literature, likely reflecting regional responses. Controlled hand pollination experiments revealed that pollen tube growth, a more straightforward and feasible pollination metric than fruit set in a mass-flowering crop with naturally low fruit set, can be effectively used to assess compatibility levels. Crossings between cultivars without common S-alleles and between cultivars sharing one S-allele resulted in similar pollen tube numbers and fruit set levels, indicating that both pairing types are suitable. Additionally, we detected pollination deficits in the studied cultivars, likely resulting from inadequate pollination services or poor pollen donor availability in the orchard. Altogether, we estimated the cultivar suitability of 81 different pairs of sweet cherry for the Beira Interior region. Our study highlights the importance of considering plant-related factors, namely flower phenology and cultivar compatibility, to develop targeted and effective management guidelines for sweet cherry producers, emphasising the significant impact these factors can have on production and the necessity of including them in orchard management and design.