Soybean (Glycine max L.) has been extensively cultivated in maize-soybean relay intercropping systems in southwest China. However, during the early co-growth period, soybean seedlings suffer from severe shading by maize resulting in lodging and significant yield reduction. The purpose of the present research was to investigate the reasons behind severe lodging and yield loss. Therefore, four different soybean genotypes (B3, B15, B23, and B24) having different agronomic characteristics were cultivated in intercropping and monocropping planting patterns. The results showed that under different planting patterns, the stem resistance varied among genotypes (P < 0.01). The lodging resistance index of B3, B15, B23, and B24 genotypes was 70.9%, 60.5%, 65.2%, and 57.4%, respectively, under intercropping, among which the B24 genotype was less affected by the shade environment as there was little decrease in the lodging resistance index of this genotype under intercropping. The lignin content of B23 and B24 was significantly higher than that of B3 and B15 under both planting patterns. Under intercropping, the hemicellulose content of B23 and B24 stems was significantly higher than that of B3 and B15. Compared to the monocropping, the content of mannose in the structural carbohydrate of soybean stems was decreased in all genotypes except B23, but the difference was not significant. The content of xylose in the structural carbohydrate of soybean stems was significantly higher than that in B3 and B15. Mannose content showed no significant difference among genotypes. The arabinose content of B24 was significantly higher than that of B3, B15, and B23. The effective pod number, seed number per plant, seed weight per plant and yield of soybean plants were significantly decreased under intercropping. Conclusively, manipulation of structural and nonstructural carbohydrate rich soybean genotypes in intercropping systems could alleviate the yield loss due to lodging.

College of Agronomy Sichuan Agricultural University 211 Huimin Road Wenjiang District Chengdu 611130 P R China

College of Agronomy Sichuan Agricultural University 211 Huimin Road Wenjiang District Chengdu 611130 P R China and Sichuan Engineering Research Center for Crop Strip Intercropping System Key Laboratory of Crop Ecophysiology and Farming System in Southwest China Sichuan Agricultural University Chengdu P R China

Department of Plant Physiology Slovak University of Agriculture 94976 Nitra Slovakia and Department of Botany and Plant Physiology Faculty of Agrobiology Food and Natural Resources Czech University of Life Sciences Prague 165 00 Prague Czech Republic

School of Agriculture Food and Wine The University of Adelaide PMB1 Glen Osmond Adelaide 5064 Australia

К A Timiryazev Institute of Plant Physiology Russian Academy of Sciences Botanicheskaya St 35 Moscow 127276 Russia and Institute of Basic Biological Problems Russian Academy of Sciences Institutskaya St 2 Pushchino Moscow Region 142290 Russia and Department of Plant Physiology Faculty of Biology M 5 Lomonosov Moscow State University Leninskie Gory 1 12 Moscow 119991 Russia and Zoology Department College of Science King Saud University Saudi Arabia and Institute of Molecular Biology and Biotechnology Azerbaijan National Academy of Sciences Matbuat Avenue 2a Baku 1073 Azerbaijan and Department of Molecular and Cell Biology Moscow Institute of Physics and Technology Institutsky lane 9 Dolgoprudny Moscow region 141700 Russia

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