Comparative analysis of growth and photosynthetic characteristics of (Populus simonii × P. nigra) × (P. nigra × P. simonii) hybrid clones of different ploidides.

Xiyang Zhao,Yonghong Cui,Chuanping Yang,Mengran Liu,Ying Li,Mi Zheng,Jing Jiang,Yanshuang Sun,Shuchun Li,Guifeng Liu,Fuwei Wang,Xiuyan Bian,Rongling Wu

doi:10.1371/journal.pone.0119259

Abstract

To evaluate differences among poplar clones of various ploidies, 12 hybrid poplar clones (P. simonii × P. nigra) × (P. nigra × P. simonii) with different ploidies were used to study phenotypic variation in growth traits and photosynthetic characteristics. Analysis of variance showed remarkable differences for each of the investigated traits among these clones (P < 0.01). Coefficients of phenotypic variation (PCV) ranged from 2.38% to 56.71%, and repeatability ranged from 0.656 to 0.987. The Pn (photosynthetic rate) photosynthetic photon flux density (PPFD) curves of the 12 clones were S-shaped, but the Pn-ambient CO2 (Ca) curves were shaped like an inverted “V”. The stomatal conductance (Gs)-PPFD and transpiration rate (Tr)-PPFD curves had an upward tendency; however, with increasing PFFD, the intercellular CO2 concentration (Ci)-PPFD curves had a downward tendency in all of the clones. The Pn-PPFD and Pn-Ca curves followed the pattern of a quadratic equation. The average light saturation point and light compensation point of the triploid clones were the highest and lowest, respectively, among the three types of clones. For Pn-Ca curves, diploid clones had a higher average CO2 saturation point and average CO2 compensation point compared with triploid and tetraploid clones. Correlation analyses indicated that all investigated traits were strongly correlated with each other. In future studies, molecular methods should be used to analyze poplar clones of different ploidies to improve our understanding of the growth and development mechanisms of polyploidy.

Highlights

Poplars (Populus spp.) are some of the most important economic tree species in the temperate regions of the world [1, 2]
The phenotypic variation (PCV) of different growth traits ranged from 12.60% to 43.36%, with the value of basal diameter (BD) being the lowest and that of stem fresh weight (SFW) being the highest, respectively
Tetraploid poplar clones did not show superiority to diploid poplar clones in growth traits, which agreed with the results of Comai [34] who indicated that because of the ploidy increase, increased numbers of chromosomes led to increased numbers of cells and nuclei, thereby increasing the possibility of producing aneuploidy in meiosis and mitosis, resulting in epigenetic instability

Summary

Introduction

Poplars (Populus spp.) are some of the most important economic tree species in the temperate regions of the world [1, 2]. Breeders have paid close attention to different ploidy level (diploid, triploid and tetraploid) breeding in forest trees because of the huge growth of forestry. In research on different types of polyploids, triploid poplars are often characterized as having fast growth, large leaves, vigor and low fertility compared with their diploid counterparts [23]. With the aim of obtaining high growth rate and highly resistant offspring, P. simonii × P. nigra and P. nigra × P. simonii were selected as parents. Colchicine was used in the crossing experiment and many offspring were obtained with different ploidies. Our primary objectives were to explore the variation in growth, photosynthesis and chlorophyll fluorescence traits among hybrid clones with different ploidies, and to provide a theoretical basis for polyploid poplar clone selection

Methods

Results

Discussion

Conclusion