Styrian oil pumpkin pollen germinability at higher irradiation doses: optimization of the in vitro germination protocol and irradiation procedure

Abstract

Protocols for haploid induction in cucurbits are based on pollination with irradiated pollen, but the induction frequency is low and the majority of obtained embryos are zygotic. The longevity of Cucurbita pepo L. pollen is short even under natural conditions; following irradiation, germinability is decreased even further. This study was initiated to develop an optimal in vitro germination medium for styrian oil pumpkin (Cucurbita pepo L. subsp. pepo var. styriaca Greb.) pollen, which would enable accurate germination testing. Different pH values and the addition of sucrose, mannitol, and polyethylene glycol to the Brewbaker and Kwack germination medium were tested. The optimum medium condition was pH 9 and 12.5% (w/v) sucrose, while other tested components were not efficient. Using the optimized medium, X-ray-irradiated (100-700 Gy) pollen germinability was assessed under 2 air humidity conditions. Germinability of pollen irradiated at room humidity (RH) was generally lower than that of pollen irradiated at high humidity (HH). A major variability in pollen size (diameters ranged from 79.2 to 196.5 µm) and 2 subgroups were found in the pollen population. Following irradiation, HH conditions allowed germination of larger pollen grains than those of the nonirradiated control and RH.

Effect of different irradiation sources and doses on haploid embryoinduction in Altinbas (Cucumis melo L. var. inodorus) melons

“…In addition to Co 60 and Cs 137 , X-rays have also been used for in situ haploid induction in melon (Katoh et al, 1993;Yashiro et al, 2002;Zha, 2002) and in related species such as hull-less seed pumpkin (Košmrlj et al, 2014). In our study we found that both 200 and 300 Gy of X-ray pollen irradiations were successful in fruit set and embryo formation.…”

“…In a recent study the effect of different doses (0, 50, 100, 150, 200, 300, and 350 Gy) of X-ray on haploid induction in hull-less seed pumpkin was examined and the most effective doses were found to be 100, 200, and 300 Gy. A gradual decrease of fruit set and mean number of embryos per 100 seeds was observed at increased irradiation doses (Košmrlj et al, 2014).…”

“…Different doses of X-ray (0,50,100,150,200,300,and 350 Gy) were used for haploid induction through parthenogenesis in hull-less seed pumpkin and sufficient percentages of haploid plants were obtained (Košmrlj et al, 2013). A recent study was reported on the effect of different irradiation doses (100-700 Gy) of X-ray on pollen germination in Styrian oil pumpkin (Košmrlj et al, 2014). Cesium-137 is also found to be effective in haploid induction in melon (Lotfi et al, 2003).…”