Self-compatibility in plum cultivars released from a breeding program in Serbia

• The self-compatible status of fifteen plum cultivars developed at Fruit Research Institute, Čačak were determined. • Pollen viability in vitro as well as in vivo were investigated. • Air temperature had the great influence on the tested reproductive parameters. • Based on the obtained results cultivars were cosidered as self-compatible, partially self-compatible and self-incompatible. • Aniline blue staining is useful method for testing growth of pollen tubes. The breeding program at the Fruit Research Institute, Čačak has released eighteen plum cultivars. Over two years, the self-compatibility of fifteen of these cultivars was determined, with open pollination used as a comparison. Pollen germination in vitro was tested in each cultivar. For observing pollen tube growth in vivo , self- and open pollinated pistils were fixed on the 3, 6 and 10 days after pollination or full flowering. Fixed samples were stained with fluorochromic stain aniline-blue and observed under the microscope. In both pollination treatments initial and final fruit set was determined. In six cultivars, average two-year pollen germination was above 31 %, while in the other cultivars it was below 27.0 %. In both years, pollen tube growth in the majority of cultivars finished after ten days (except ‘Jelica’, ‘Čačanska Rana’, ‘Čačanska Najbolja’, and ‘Čačanski Šećer’) with penetration into the nucellus. Pollen tube growth in both treatments was better in the Year 2, when the mean daily temperature was 5°C higher. The slower pollen tube growth of the abovementioned cultivars, except for ‘Jelica’, was followed by low initial fruit set. The highest rate of final set was found in ‘Krina’ and ‘Zlatka’ (36.9 % and 35.5 %), whereas in ‘Čačanska Rana’, ‘Čačanska Najbolja’ and ‘Čačanski Šećer’ no fruit were harvested. Plum cultivars developed at Čačak are self-compatible (‘Čačanska Lepotica’, ‘Čačanska Rodna’, ‘Valjevka’, ‘Valerija’, ‘Mildora’, ‘Boranka’, ‘Krina’, ‘Zlatka’, ‘Pozna Plava’) or partially self-compatible (‘Jelica’, ‘Timočanka’, ʻNada’), or self-incompatible (‘Čačanska Rana’, ‘Čačanska Najbolja’, ‘Čačanski Šećer’).