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.
Highlights
Celina/QTee® (‘Colorée de Juillet’ x ‘Williams’), one of the most promising pear cultivars developed by the Norwegian breeding program Graminor, was released in 2010 [1]
Identical analyses on the five other pear cultivars included in this study revealed that all of them, with the exception of ‘Anna’, are only semi-compatible with ‘Celina’, while ‘Anna’ is the only fully cross-compatible cultivar used as a pollinizer in the examined orchards
Meteorological data obtained within this study indicate weather patterns uncharacteristic for this region, such as warm and dry conditions during bloom and high post bloom temperatures
Summary
Celina/QTee® (‘Colorée de Juillet’ x ‘Williams’), one of the most promising pear cultivars developed by the Norwegian breeding program Graminor, was released in 2010 [1]. In Norwegian orchards, this cultivar flowers medium to late, usually in mid-May and produces attractive fruits with red blush and good fruit quality, storability and shelf life, which ripen in the beginning of September. Adverse weather conditions and a low attractiveness of pear flowers to insect pollinators [3] often strongly hamper cross-pollination [4] and the fertilization of pear ovules. Adequate fertilization represents a prerequisite for seed development, which is in turn essential for growth and development of high-quality fruits. It is considered most favorable for the production of high-quality fruit that majority of ovules of the flowers are fertilized [5]. In case only a sub-fraction of the ovules is fertilized, resulting fruits can be small [6,7]
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