نوع مقاله : مقاله پژوهشی
نویسنده
استادیار، پژوهشکده میوه های معتدله و سردسیری، موسسه تحقیقات علوم باغبانی، سازمان تحقیقات، آموزش و ترویج کشاورزی، کرج، ایران.
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسنده [English]
Apricot (Prunus armeniaca L.) is a temperate fruit crop of high horticultural and economic value, exhibiting high adaptability to different climatic conditions across Iran. To develop new self-compatible genotypes, seven promising hybrid genotypes were selected between 2011 and 2012 from crosses between local commercial cultivars (Shams, Shahroudi, and Ordoubad) and four foreign self-compatible pollen parents (Palumella, San Castrese, Cafona and Vitilo). The experimental orchard was established in 2016 at the Meshkin-Dasht Horticultural Research Station, Karaj, Iran. Data analysis over two consecutive fruiting years, 2019 and 2020, confirmed the self-compatibility genotype and phenotype of the hybrid genotypes. Significant differences (p < 0.05 and p < 0.01) were observed among genotypes as well as significant genotype × year interactions for bloom onset, bloom duration, and self-pollinated fruit set. The average blooming duration was about 13 days, and the average fruit set following self-pollination was more than 17%. These traits are important for commercial apricot production. The mean pollen germination rate of 48% indicated that these hybrids had high fertility potential under self-pollination conditions.
Keywords: Apricot, phenology, pollination, pollen tube, Sc-allele, breeding.
Introduction
Pollination is very important for economic fruit production in the Rosaceae family, particularly for apricot. While self-incompatibility serves as an evolutionary strategy for genetic diversity, it presents a significant challenge in modern, single-cultivar orchards by limiting fruit set. Consequently, effective pollination management such as planting cross-compatible cultivars or adopting self-compatible cultivars is essential to maximize fruit yield without expanding cultivation area. Recent research highlights the importance of identifying self-compatibility in various apricot genotypes. Zarrinbal et al. (2018) confirmed self-compatibility in some apricot genotypes, including the Iranian hybrid AD731 and European cultivars, Canino, San Castrese, Palumella and Cafona. Furthermore, molecular advancements have strengthened these efforts. Liu et al. (2018) utilized S-RNase primers to identify S-alleles in Chinese apricot genotypes, distinguishing between self-incompatible and self-compatible types. To overcome the economic constraints imposed by self-incompatibility (SI) in local apricot cultivars in Iran, crossbreeding scheme has been design designed and implemented.
The objective of this research was to evaluate the phonological and reproductive traits, and determination self-compatibility of seven apricot hybrid genotypes.
Materials and Methods
Seven apricot hybrid genotypes, selected from a crossbreeding program aimed at developing superior self-compatible genotypes, were evaluated in an experimental orchard in Meshkin-Dasht Research Field Station, Horticultural Sciences Research Institute, Karaj, Iran. These genotypes were derived from crosses between Iranian local apricot cultivars; Shams, Shahroudi, and Ordoubad as female parents and four Italian commercial cultivars; Palumella, San Castrese, Cafona, and Vitillo as pollen donors. For the purpose of further testing and reporting, the studied hybrids are designated as SHAR-06, SHAR-51, SHAR-57, SHAR-64, SHMS-26, SHMS-65, and SHMS-88, considering their maternal lineage.
Phenological traits were recorded based on the percentage of open flowers on the canopy. Onset of blooming was defined when 10% of flowers were open and the end of blooming (petal fall) stage was recorded when approximately 80-90% of the petals had abscised from the flowers, in accordance with the BBCH-scale; stone fruit. Self-compatibility was evaluated by bagging branches for controlled self-pollination and recording final fruit set under field conditions (Burgos et al., 1993).
Pollen viability was verified through `in vitro' germination on standard agar media, and pollen tube growth in self-pollinated pistils was monitored on cut branches using aniline blue fluorescence microscopy. Finally, S-alleles were determined via PCR-based S-RNase genotyping following the specific consensus primer protocols established for apricot.
Results and Discussions
The results revealed significant (P<0.05%) differences in fruit set among the studied apricot genotypes. Genotype SHAR-06 exhibited the highest fruit set, whereas control cultivars showed significantly lower values. This variation in fruit set is a critical factor in apricot breeding, as it often reflects the level of self-compatibility or the efficiency of pollen-pistil interactions. The observed differences in fruit set could be attributed to the genetic variation in S-alleles, which governs self-incompatibility (SI) in Prunus armeniaca (Andres and Duran, 1998). Higher fruit set percentages in certain genotypes suggest a higher potential for self-compatibility, a trait highly sought after in intensive orchard management (Zarrinbal et al., 2018).
Significant differences were also observed in the timing of blooming. The timing of blooming is a genetically controlled trait influenced by environmental factors such as temperature. The mean blooming onset varied from 1 to 8.5 days after early flowering control cultivar. Furthermore, the blooming duration (flowering period) showed significant differences among genotypes. Genotypes with a prolonged blooming period, such as SHMS-26 and SHMS-65 might provide a wider window for successful pollination, which could potentially mitigate the risks of environmental stresses during flowering stage. The relationship between blooming onset and duration is a key component of the flowering phenology that determines the synchronization of pollen availability and stigma receptivity (Milatović et al., 2013).
In conclusion, the significant variation in phenological traits and fruit set among the seven apricot hybrid genotypes indicated wide genetic basis for these traits. The genotypes that showed stable blooming onset and duration combined with high fruit set should be considered for being used in apricot breeding programs for development of self-compatible apricot hybrids.
References
Andres, M.V. and Duran, J.M. 1998. Self-incompatibility in Spanish clones of apricot (Prunus armeniaca L.) tree. Euphytica, 101, pp.349-355. DOI: 10.1023/A:1018325517208
Liu, M., Hou, P., Zhang, L., Dong, Y. and Zong, W. 2018. S-genotype characterization of 10 Kernel-apricots native to China. The Journal of Horticultural Science and Biotechnology, 94(2), pp.237-242. DOI: 10.1080/14620316.2018.1478679
Milatović D., Nikolić D., Fotirić-Akšić M. and Radović A. 2013. Testing of self-(in)compatibility in apricot cultivars using fluorescence microscopy. Acta Scientiarum Polonorum Hortorum Cultus, 12(6), pp.103-113. DOI: 10.1080/14620316.2007.11512215
Zarrinbal, M., Soleimani, A., Baghban Kohnehrouz, B. and Dejampour, J. 2018. Self-compatibility in some apricot (Prunus armeniaca L.) genotypes. Crop Breeding Journal, 8(1 & 2), pp.49-59. DOI: 10.22092/cbj.2018.122435.1025
کلیدواژهها [English]
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