Cytoplasmic effects of Brassica napus and B. juncea on extreme temperature stresses of B. carinata
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Alloplasmic lines of Brassica carinata were developed from the interspecific crosses B. napus × B. carinata and B. juncea × B. carinata followed by repeated backcrossing to B. carinata as the recurrent male parent up to the BC7 generation. The BC7 generations with cytoplasm of B. napus and B. juncea were designated NC-7 and JC-7, respectively, and the corresponding euplasmic lines were designated CN-7 and CJ-7, respectively. Four lines (NC-7 vs. CN-7 and JC-7 vs. CJ-7) were grown in a closed vinyl greenhouse at 55 °C and outdoors during winter in two cold regions of China (−3 to −10 °C) to investigate the heat and cold tolerance of the alloplasmic and euplasmic lines. Plants with the cytoplasm of B. napus showed lower leaf chlorophyll content and little difference in heat tolerance, whereas plants with the cytoplasm of B. juncea showed higher severity of heat injury compared with that of the euplasmic lines with cytoplasm of B. carinata. Alloplasmic plants with cytoplasm of B. napus and B. juncea showed decreased cold tolerance compared with that of euplasmic lines with cytoplasm of B. carinata. The difference in cold tolerance also was observed in the lethal temperature of the alloplasmic and euplasmic plants. The results suggest that tolerance of extreme temperature stress was controlled mainly by the nucleus but also was affected by the cytoplasm. Interaction between the maternal genome and nucleus was also observed.
KeywordsCold resistance Heat tolerance Lethal temperature Alloplasmic effect Chlorophyll fluorescence Wilt index
We express our sincere gratitude to Prof. Dr. Masahiro Kato, Laboratory of Plant Breeding, Faculty of Agriculture, Ehime University, Japan, for providing pertinent criticism from the beginning of this research to submission of the manuscript. We also thank the Tianjin Kernel Agricultural Science & Technology Co., Ltd for support.