Interference of Volunteer Corn from Different Origins and Emergence Time on Soybean Yield and Stress Metabolism

ABSTRACT: Volunteer corn occurrence with soybean is favored by the glyphosate-resistant (GR) corn cultivation preceding soybean and no-tillage systems. Volunteer corn interference causes significant losses in soybean grain yield. The levels of crop losses change with the corn density, origin, and time of emergence. High levels of weed interference in crops can result in the production of reactive oxygen species and lead to the occurrence of oxidative stress. The objectives of this study were to evaluate the effects of interference of (1) different origins (individual plants and clumps) and times of emergence of volunteer corn on soybean growth, yield components, and grain yield loss; and (2) if the volunteer corn interference causes oxidative stress in soybean. Field experiment and laboratory analyses were performed. The evaluated variables were soybean yield components, grain yield, hydrogen peroxide - H2O2 content, and antioxidant enzyme superoxide dismutase - SOD, catalase - CAT, and ascorbate peroxidase - APX activities. Volunteer corn interference reduced the yield components and soybean yield. The highest yield losses were observed with volunteer corn clumps regarding individual plants. The interference of volunteer corn emerged 10 days before or on the same day as soybean caused the greater yield losses than those emerged 10 days after, independently of its origin. The content of H2O2 and enzyme SOD, CAT and APX activities changed in soybean leaves in response to the interference of volunteer corn plants and clumps. However, the results indicate that the volunteer corn interferences does not cause oxidative stress in soybean.摘要：当大豆前茬种植抗草甘膦（glyphosate-resistant, GR）玉米并采用免耕栽培体系时，大豆田中的自生玉米发生更为频繁且严重。自生玉米的竞争干扰会导致大豆籽粒产量显著损失。产量损失程度随自生玉米密度、种群类型及出苗时间而异。作物田中的重度杂草干扰可诱导活性氧（reactive oxygen species, ROS）产生，进而引发氧化应激反应。本研究旨在探究两类干扰效应：其一，自生玉米的不同种群类型（单株与丛株）及出苗时间对大豆生长、产量构成因子与籽粒产量损失的影响；其二，自生玉米的干扰是否会引发大豆的氧化应激反应。本研究采用田间试验与室内分析相结合的方法开展实验，测定的指标包括大豆产量构成因子、籽粒产量、过氧化氢（hydrogen peroxide, H₂O₂）含量，以及抗氧化酶超氧化物歧化酶（superoxide dismutase, SOD）、过氧化氢酶（catalase, CAT）与抗坏血酸过氧化物酶（ascorbate peroxidase, APX）的活性。结果显示，自生玉米的干扰会降低大豆的产量构成因子与籽粒产量。相较于单株自生玉米，丛株自生玉米导致的产量损失更高。无论自生玉米的种群类型如何，相较于晚于大豆10天出苗的处理，与大豆同期出苗或早于大豆10天出苗的自生玉米所造成的产量损失更为显著。大豆叶片中的H₂O₂含量以及SOD、CAT、APX的活性会随单株或丛株自生玉米的干扰发生变化，但研究结果表明，自生玉米的干扰并未引发大豆的氧化应激反应。