Mikropropagacija slabo bujne podloge za krušku Pyrodwarf

The paper describes the protocol for micropropagation in vitro of low vigorous pear rootstock Pyrodwarf. Aiming at developing efficient protocol for micropropagation of this genotype, the influence of BAP concentration and/or type of auxins (IBA or NAA), on multiplication index, fresh and dry weight of shoots was examined. The effect of type of auxins on rooting parameters was monitored as well. Increase in BAP concentration from 0.5 to 1 mg l-1 in combination with NAA instead of IBA significantly increased regeneration capacity of shoots, especially multiplication index. Shoots rooted on medium with IBA displyed significantly higher capacity for rhizogenesis, in comparison with those grown on medium containing NAA at equal concentration. The percentage of acclimatization under the ‘mist’ system in green house was 90,9% for shoots rooted in vitro.U radu je prikazan protokol za mikropropagaciju in vitro slabo bujne podloge za krušku Pyrodwarf. U cilju razvijanja protokola za brzu i efikasnu mikropropagaciju ovog genotipa, ispitan je uticaj promene koncentracije BAP i/ili vrste auksina (IBA ili NAA) na parametre multiplikacije, svežu i suvu masu izdanaka, kao i uticaj vrste auksina na parametre ožiljavanja. Povećanje koncentracije BAP sa 0,5 na 1 mg l-1 i promena vrste auksina (NAA, umesto IBA) uticali su na značajno povećanje regenerativne sposobnosti izdanaka naročito izražene kroz indeks multiplikacije. U fazi ožiljavanja utvrđeno je da je efikasnost rizogeneze izražena kroz sve parametre veća na medijumu sa IBA, nego na medijumu sa istom koncentracijom NAA. U uslovima „mist“ izmaglice procenat aklimatizacije izdanaka ožiljenih in vitro je iznosio 90,9%

S-GENOTYPING OF SOME SWEET CHERRY CULTIVARS RELEASED WITHIN BREEDING PROGRAMMES IN THE BALKAN REGION

Sweet cherry cultivars generally exhibit S-ribonuclease (S-RNase)-based gametophytic selfincompatibility and require pollination with pollen of compatible genotypes, which are indispensable to stable fruit production. Therefore, the determination of S-genotype provides relevant information for sweet cherry breeders and growers. The aim of this study was to identify the S-allelic constitution and incompatibility group in eight sweet cherry cultivars which were named and released at Fruit Research Institute, Čačak, Republic of Serbia (‘Asenova Rana’ and ‘Čarna’), Research Station for Fruit Growing, Iasi, Romania (ʻAlexusʼ, ʻBuciumʼ and ʻMargoniaʼ) and Fruit Growing Institute, Plovdiv, Republic of Bulgaria (ʻKossaraʼ, ʻRosalinaʼ and ʻRositaʼ). The use of the polymerase chain reaction (PCR) method with consensus primers for the second introns of S-RNase, as well as primers specific for S1S7 and S9 alleles enabled determination of the following S-genotypes in the assessed cultivars: S1S2 (ʻAlexusʼ), S1S4 (ʻČarnaʼ), S2S9 (ʻKossaraʼ and ʻRositaʼ), S3S6 (ʻBuciumʼ), S3S9 (ʻAsenova Ranaʼ and ʻRosalinaʼ) and S5S6 (ʻMargoniaʼ). In addition, the S-genotypes of two parental cultivars were reported in this manuscript for the first time ‘Boambe de Cotnari’ (S2S7) and ‘Ranna Tcherna’ (S1S2). Based on the obtained S-allelic constitutions, the assessed cultivars were assigned to the following incompatibility groups: I, II, VI, IX, XI, XIV, XV, XVI and XLIII. The results generated in this study provide a valuable resource for cross design in developing new cultivars and for orchard management in the efficient high-yielding fruit production

Viability of Embryo Sacs and Fruit Set in Different Plum (Prunus domestica L.) Cultivars Grown under Norwegian Climatic Conditions

Compatibility and synchrony between specialized tissues of the pistil, female gametophytes and male gametophytes, are necessary for successful pollination, fertilization, and fruit set in angiosperms. The aim of the present work was to study the development and viability of embryo sacs, as well as fertilization success, in relation to the fruit set of the cultivars ‘Mallard’, ‘Edda’, ‘Jubileum’, and ‘Reeves’, under specific Norwegian climatic conditions. Emasculated, unpollinated, and open-pollinated flowers were collected at the beginning of flowering, and on the 3rd, 6th, 9th, and 12th days after flowering, from all four plum cultivars over two years (2018/2019). Ovaries were dehydrated, embedded in paraffin wax, sectioned, stained, and observed under a light microscope. Results showed the existence of synchronization between successive phases in the development of the embryo sac and individual phases of flowering. All plum cultivars had higher percentages of viable embryo sacs, fertilized embryo sacs, and fruit set in 2018 than in 2019. These differences may be related to the very low temperatures during the post-full-flowering period in 2019, and to the low adaptation of some studied cultivars to unfavorable conditions. In our study, the cultivar ‘Jubileum’ showed the highest percentage of viable embryo sacs, fertilized embryo sacs, and fruit set compared to other cultivars, i.e., the best low-temperature adaptation

The effective pollination period of European plum (Prunus domestica L.) cultivars in western Norway

This study evaluated the effective pollination period (EPP) in four European plum (Prunus domestica L.) cultivars (‘Mallard’, ‘Edda’, ‘Jubileum’, and ‘Reeves’) during two years (2018–2019) under the environmental conditions in western Norway. The pollination of plum cultivars was carried out one, three, five, seven, and nine days after anthesis (DAA) with a pollen mix of two compatible cultivars (‘Victoria’ and ‘Opal’). Initial, middle-season, and final fruit set was recorded after one month and two months after pollination and just before the harvest, respectively. On average from both years cultivar ‘Jubileum’ had the highest fruit set when pollinated one, three, five, seven, and nine DAA (33.23%, 30.83%, 8.47%, 3.08%, and 1.15%, respectively), which was more than two folds higher fruit set than in the other studied cultivars. Cultivar ‘Jubileum’ showed significantly reduced fruit set between pollination on five and nine DAA, while cultivars ‘Mallard’, ‘Edda’, and ‘Reeves’ had markedly reduced fruit set if pollinated three to five DAA, implying that the EPP in ‘Jubileum’ was five days while in the rest it was three days. Variation of weather conditions during the flowering period in both years did not have a major effect on the receptivity of stigmas in the studied plum cultivars, which means that the existing differences in the length of EPP is maternal-genotype dependent

Breeding systems, hybridization and continuing evolution in Avon Gorge Sorbus

BACKGROUND AND AIMS: Interspecific hybridization and polyploidy are key processes in plant evolution and are responsible for ongoing genetic diversification in the genus Sorbus (Rosaceae). The Avon Gorge, Bristol, UK, is a world ‘hotspot’ for Sorbus diversity and home to diploid sexual species and polyploid apomictic species. This research investigated how mating system variation, hybridization and polyploidy interact to generate this biological diversity. METHODS: Mating systems of diploid, triploid and tetraploid Sorbus taxa were analysed using pollen tube growth and seed set assays from controlled pollinations, and parent–offspring genotyping of progeny from open and manual pollinations. KEY RESULTS: Diploid Sorbus are outcrossing and self-incompatible (SI). Triploid taxa are pseudogamous apomicts and genetically invariable, but because they also display self-incompatibility, apomictic seed set requires pollen from other Sorbus taxa – a phenomenon which offers direct opportunities for hybridization. In contrast tetraploid taxa are pseudogamous but self-compatible, so do not have the same obligate requirement for intertaxon pollination. CONCLUSIONS: The mating inter-relationships among Avon Gorge Sorbus taxa are complex and are the driving force for hybridization and ongoing genetic diversification. In particular, the presence of self-incompatibility in triploid pseudogamous apomicts imposes a requirement for interspecific cross-pollination, thereby facilitating continuing diversification and evolution through rare sexual hybridization events. This is the first report of naturally occurring pseudogamous apomictic SI plant populations, and we suggest that interspecific pollination, in combination with a relaxed endosperm balance requirement, is the most likely route to the persistence of these populations. We propose that Avon Gorge Sorbus represents a model system for studying the establishment and persistence of SI apomicts in natural populations