S-Genotyping and Seed Paternity Testing of the Pear Cultivar ‘Celina’

Abstract

The diploid Celina/QTee® (‘Colorée de Juillet’ × ‘Williams’), one of the most promising pear cultivars developed by the Norwegian breeding program Graminor, was launched in 2010. In Norway, the flowering is medium to late, while the fruits ripen in the beginning of September. The fruits are attractive with an intense red blush (50%) on a green background. Although, ‘Celina’ is cultivated in the most climatically suitable regions for fruit cultivation, present in Norway, unfavorable environmental conditions for pear pollination can have a very negative effect on fruit set and consequent yield. The aim of this study was to determine the S-alleles of ‘Celina’, as well as its frequently used pollinizers, and, through paternity testing of ‘Celina’ seeds, give a recommendation regarding the most important pollinizers of this pear cultivar. In order to accomplish this, ‘Celina’ and its potential pollinizers were all S-genotyped. After harvest, seeds collected from ‘Celina’ fruit in 2017 and 2018 were genotyped using eleven microsatellite markers. Genomic DNA was also extracted from leaf material collected from ‘Celina’, as well as from five pear cultivars used as pollinizers in the three examined orchards, and analyzed using the same marker set. Subsequently a simple sequence repeat (SSR) database was constructed and used for gene assignment analyses with the aim of quantifying pollen donor contribution from individual pollinizers. The obtained results indicate that ‘Anna’, the only examined pollinizer that was fully cross-compatible with ‘Celina’, together with ‘Fritjof’, the genotype which had the highest flowering overlap with ‘Celina’, proved to be the most successful pollinizers across all seasons and orchards. Although both cultivars were ubiquitous in the examined orchards, either as planted trees or as branches introduced during the flowering period, they were the most abundant pollinizers in only one orchard each. It is therefore possible to conclude that pollinizer abundance has a secondary significance in pollinizer success within investigated ‘Celina’ orchards.

Determining Pollinizer Success Rates among Several Apple (Malus domestica L.) Cultivars Using Microsatellite Markers

“…However, this marker system is also highly efficient in parent identification [26], parent-offspring analyses [27], as well as multi-generational pedigree network reconstruction [28]. More recently, microsatellite markers have been used to identify the pollen donors of the pear and plum seeds collected in commercial orchards in Norway in order to determine the success rate of individual pollinizers [29][30][31]. Regarding similar molecular studies on apples, allozyme and isoenzyme profiles of apple seeds have been employed to conduct paternity analyses and thus to gain insight into the pollen dispersal and pollination in apple orchards [22,32].…”

Functionality of Embryo Sacs in Pear Cultivars ‘Ingeborg’ and ‘Celina’ as Related to Fruit Set under Nordic Climate

“…Depending on the year, unfavorable environmental conditions during flowering can have a very negative effect on fruit set and yield quantity in Norwegian pear orchards. Therefore, it is important to secure good pollination by planting suitable pollinizer genotypes together with the main cultivars [5,6].…”

“…For determination of the most efficient pollinizers for the pear cultivars 'Ingeborg' and 'Celina', the following methods have been applied so far: fluorescent analysis of progamic phase of fertilization [5,35], examination using microsatellite markers [6,36,37], and study of flowering performance and phenology [38]. So, as a follow up from the previous manuscript where pollen tube growth in different crossing combinations of 'Ingeborg' and 'Celina' was described [5], the aim of this work was to investigate the functionality of the embryo sacs, from developing, through viability, and up to the fertilization success and fruit set of the diploid ('Celina') and the triploid ('Ingeborg') pear cultivars, that can affect irregular yields of these cultivars.…”

Phenotypic assessment of pear varieties in mutual pollination

“…Under favorable flowering conditions, the degree of pollen fertility increases, the conditions for pollination and fertilization conditions improve, which leads to good fruit setting, especially in the variants of cross and free pollination [4][5][6]. There are a large number of cultivars that require a pollinator, but there are also self-fertile cultivars [7][8][9]. Self-fertility is a valuable biological and economic trait.…”