Self-sterility in Camellia oleifera may be due to the prezygotic late-acting self-incompatibility.

Ting Liao,Ting Liao,De-Yi Yuan,De-Yi Yuan,Feng Zou,Chao Gao,Chao Gao,Xiao-Feng Tan,Xiao-Feng Tan,Ya Yang,Lin Zhang,Lin Zhang,Randall P Niedz

doi:10.1371/journal.pone.0099639

Ting Liao, Ting Liao + Show 11 more

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https://doi.org/10.1371/journal.pone.0099639

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Abstract

In this report, self-sterility in Camellia oleifera was explored by comparing structural and statistical characteristics following self-pollination (SP) and cross-pollination (CP). Although slightly delayed pollen germination and pollen tube growth in selfed ovaries compared to crossed ovaries was observed, there was no significant difference in the percentages of pollen that germinated and pollen tubes that grew to the base of the style. There was also no difference in morphological structure after the two pollination treatments. However, the proportions of ovule penetration and double fertilization in selfed ovules were significantly lower than in crossed ovules, indicating that a prezygotic late-acting self-incompatible mechanism may exist in C. oleifera. Callose deposition was observed in selfed abortive ovules, but not in normal. Ovules did not show differences in anatomic structure during embryonic development, whereas significant differences were observed in the final fruit and seed set. In addition, aborted ovules in selfed ovaries occurred within 35 days after SP and prior to zygote division. However, this process did not occur continuously throughout the life cycle, and no zygotes were observed in the selfed abortive ovules. These results indicated that the self-sterility in C. oleifera may be caused by prezygotic late-acting self-incompatibility (LSI).

Highlights

Camellia oleifera (Theaceae), an evergreen shrub species, is widely cultivated in southern China
Previous studies focusing on flowering biology [2], pollination biology [2], pollen viability [3,4,5,6], flower bud differentiation [7], megaspore and microspore development [8], male and female gamete development [8], and embryological development [9] have been performed in C. oleifera
Significant differences in pollen tube length at every stage over 2–48 h following SP compared to CP were observed in C. oleifera, the length increased continuously during the life cycle (Fig. 1; 2 h after pollination (AP), SSB = 0.032, df = 1, F = 21.275, P,0.05; 4 h AP, SSB = 1.696, df = 1, F = 104.585, p,0.05; 8 h AP, SSB = 9.45, df = 1, F = 432.501, p,0.05; 12 h AP, SSB = 12.586, df = 1, F = 793.236; p,0.05; 24 h AP, SSB = 17.785, df = 1, F = 257.13, p,0.05; 36 h AP, SSB = 19.984, df = 1, F = 211.022, p,0.05; 48 h AP, SSB = 22.157, df = 1, F = 14.31, p,0.05)

Summary

Introduction

Camellia oleifera (Theaceae), an evergreen shrub species, is widely cultivated in southern China. Oil from its seeds is commonly used as an edible oil with known health benefits At this time, there are approximately three million hectares of cultivated area of C. oleifera in China, with 35.2 kg of oil per acre [1]. The large number of flowers with relatively low fruit/seed sets is a serious problem and has restricted development of the oil tea industry [1] To address this issue, previous studies focusing on flowering biology [2], pollination biology [2], pollen viability [3,4,5,6], flower bud differentiation [7], megaspore and microspore development [8], male and female gamete development [8], and embryological development [9] have been performed in C. oleifera. These studies did not explore flower development or the large number of ovules that fail to mature into seeds during fruit development in nature [1,9]

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