|Authors: ||S. Kawano, Y. Li, M. Yahata, H. Kunitake|
|Keywords: ||aniline blue staining, SI-like response, pistil culture system, pollen tube growth, stylar crude protein extract|
Temperature has a clear effect on pollen germination and pollen tube growth.
Recently, researchers have reported a relationship between self-incompatibility (SI) and temperature.
However, the detailed behavior and mechanisms of this relationship have not been completely clarified in Citrus. In the present study, to reveal the relationship between SI and temperature in Citrus cultivars, we investigated pollen germination and pollen tube behavior using in vitro pistil and mature pollen systems under controlled environmental chamber conditions of 25, 30 and 35°C. We first evaluated pollen tube growth for one week in in vitro detached pistils of the SI cultivar LSQUOHyuganatsuRSQUO (Citrus tamurana hort.
Ex Tanaka) after self- or cross-pollination.
LSQUOHassakuRSQUO (C. hassaku) and LSQUOBanpeiyuRSQUO pummelo [C. maxima (Burm.) Merr.] were used as compatible cultivars.
Pollen tube growth was observed one week after pollination using aniline blue staining and a fluorescent microscope.
Results indicated incompatible pollen tubes stopped in the upper part of styles at 25°C, whereas they reached the base of the styles at 30°C, similar to the behavior of compatible pollen tubes at 25°C. To investigate improvement of the SI-like responses of pollen tubes under different temperature conditions, we examined the inhibition of pollen tube growth and morphological changes of tube tips using the mature pollen culture of LSQUOHyuganatsuRSQUO (Abe et al., in press). The pollen was treated with stylar crude extract protein of LSQUOHyuganatsuRSQUO to simulate the SI-like response.
Pollen tubes with the SI treatment showed tip inflation, content leakage and abnormal tip twisting at 25°C, and tube growth was inhibited.
However, at 30°C, these SI-like responses were suppressed.
These results suggested that temperature might be a trigger for avoiding SI reaction in Citrus.
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