Identifying successful combinations by fertility index in old garden roses and hybrid tea roses crosses

Abstract

The success of rose breeding programs is low due to poor seed sets and germination rates. Determining fertile parents and cross combinations that show high compatibility could increase the effectiveness of breeding programs. In this study, three rose varieties belonging to Rosa × hybrida (Jumilia, First Red and Magnum), and two old garden rose species (Black Rose and Cabbage Rose) with known ploidy levels were reciprocally crossbred under controlled conditions to determine the successful crosses by checking fertility. The pollen germination rate (PG), crossability rate (CR), seed number per fruit (SNpF), seed production efficiency (SPE), seed germination rate (SGR), fruit weight (FW), seed weight (SW) and stigma number (SiN), etc. were recorded. Comprehensive fertility index value was calculated. Principal component analysis (PCA), correlation matrix, and hierarchical heat map were used to evaluate the data. The findings showed that old garden roses had more viable pollen than hybrid tea roses. The crossing success improved as pollen fertility increased. Also, female parent fertility improved crossing success just as much as pollen fertility. Although the pollen fertility and stigma numbers were low, some combinations had higher CR and SPE. The maximum SPE (from 8.67% to 19.46%) was determined in combinations where Black Rose was the female parent despite the lower stigma number and low pollen fertility. The highest CR was recorded in Black Rose × First Red (94.36%). All combinations in which Black Rose was used as the female parent had a more stable CR. The SNpF of combinations where hybrid rose varieties were female parents and old garden roses were pollen parents was higher than other combinations where hybrid rose varieties were both female and pollen parents. The SPE in intraspecific crosses was lower than that obtained from interspecific crosses. Moreover, the SGR decreased in combinations that produced heavier seeds. The results suggested that SPE is a more accurate parameter than SNpF in demonstrating combination success in breeding programs. Black Rose × First Red, Black Rose × Jumilia, Black Rose × Magnum and Black Rose × Cabbage Rose combinations can be used successfully as the PCA and heat map showed. Black Rose showed better performance as both seed and pollen parents according to the comprehensive fertility index. From the correlation matrix, it is understood that the number of stigmas cannot be an important criterion in parent selection. Old garden roses can be used as parents to increase the success of breeding programs. However, it is necessary to reveal how successful they are in transferring desired characteristics such as scent, petal number, and color.

Crossability of miniature rose and quantitative and qualitative traits in hybrids

“…Considering that miniature roses with small flower diameters may have less stigma, they had lower seed formation than other modern roses. It has been reported that fruit formation, the number of seeds per fruit, and seed formation are lower in interspecies crosses than that in intraspecies crosses ( Kılıç, 2023 ). Successful results were obtained in fruit formation, the number of seeds per fruit, and seed formation by crossbreeding between species in miniature roses with limited fertility.…”

Transmission of Flower Traits and Fertility in Black Rose x Hybrid Tea Rose Cross Combination

“…All parents were obtained as one-year-old plants from a company in Şanlıurfa. The planting of plants, greenhouse growing conditions, and cultural practices such as irrigation, fertilization, and pest control were carried out following the procedures described by Kılıç (2023).…”

“…Some modern and old garden roses were found to have at least 3.4 times more stigma than the Black rose (Doğan et al, 2020;Kılıç, 2023). Therefore, in crossbreeding studies involving genotypes with fewer stigmas, the number of seeds is expected to be lower compared with genotypes with more stigmas.…”

“…Parent selection is the most crucial stage in increasing the success of rose breeding programs, where the success rate of developing new varieties decreases to 0.002% due to the challenges in sexual reproduction (Chaanin, 2003;Kılıç, 2023). Genotypes to be used as pollen parents are expected to have high pollen quality, whereas genotypes to be used as seed parents require more fruit and seed sets and a high seed germination rate.…”