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ARTICLE

Observation of Flowering Process of Grape (Vitis vinifera L.)—Insight into the Starting of Pollination of Flower Hiding in Calyptras (Cap)

Yue Wang^1,#, Xiujie Li^2,#, Yusen Wu², Zhonghui Cai¹, Bo Li², Zhaosen Xie^1,*

1 College of Horticulture and Landscape Architecture, Yangzhou University, Yangzhou, 225009, China
2 Shandong Academy of Grape, Shandong Academy of Agricultural Sciences, Jinan, 250100, China

* Corresponding Author: Zhaosen Xie. Email:
# These authors contributed equally to this work and should be considered co-first authors

Phyton-International Journal of Experimental Botany 2023, 92(6), 1859-1871. https://doi.org/10.32604/phyton.2023.027067

Received 12 October 2022; Accepted 09 January 2023; Issue published 11 April 2023

Abstract

It is generally agreed that many Vitis vinifera L. cultivars are self-fertile, where self-pollination often occurs before capfall in a process called cleistogamy. Therefore, it is difficult to identify the right time to remove stamens before self-pollination during the cross-breeding of grape. For this paper, we observed the process of grape flowering and measured the pollen viability and stigma receptivity of grape flowers of ‘Shine Muscat’ in order to identify the starting time of self-pollination before capfall and to provide useful information for improving the efficiency of cross-breeding. The results demonstrate that the anther is not cracked during the visible clusters and separated clusters stages. Meanwhile, in the separated floral buds, flowering begins, and full bloom stages, the pollen viability is 60.7%, 73.2% and 80.3%, respectively; however, at the berry set stage, pollen viability drops to zero. The top of the mature stigma is composed of a layer of nearly cylindrical papillary cells, and the stigma receptivity for pollen changes with the development of flowers: in particular, no reaction was observed in the visible clusters stage; weak positive reaction at the separated clusters stage; strong positive reaction at the separated floral buds, flowering begins, and full bloom stages; and no reaction at the berry set stage. In the separated floral buds stage, pollen tubes were seen germinating in the style. In the flowering begins stage, more pollen tubes were observed at the entry of the ovary. During the full bloom stage, most pollen tubes elongated into the ovary base and some entered the pearl hole. At the berry set stage, newborn endosperm nucleus could be seen in the ovule. From the above, we can conclude that the initiation time of closed fertilization for ‘Shine Muscat’ grape can be judged as the separated floral buds stage, and it is best to discard the stamen before the separated floral buds stage when conducting cross-breeding.

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