Abstract
Improved lodging resistance is important for achieving high yield in irrigated environments. This study was conducted to determine genotypic variation in lodging resistance and related morphological traits among winter wheat cultivars planted at two densities, and to identify key traits associated with lodging resistance. Lodging performance of 28 genotypes, including 24 released cultivars and four advanced lines, was evaluated at 250 plants per square meter and 500 plants per square meter in Shandong province during the 2008-2009 and 2009-2010 crop seasons. At the higher density, the average grain yield was 2.6% higher, even though lodging score rose by as much as 136%. The higher planting density increased lodging through increased leaf area index (LAI), plant height, center of gravity and length of basal internodes, and reduced grain weight per spike and diameter of the lower two stem internodes. LAI, center of gravity and diameter of first internodes, as the important indicators for lodging resistance, were significantly correlated with lodging score, with R= 0.62, 0.59 and -0.52 (P<0.01), respectively. Plant pushing resistance was significantly associated with diameter and length of the first internodes (R = 0.71-0.77, P<0.01), indicating it could be used to assess the strength of the lower stem. Higher planting density could be used to select genotypes with lodging resistance in irrigated environments. Cultivars carrying high plant density tolerance and high yield potential, such as Jimai 22 and Liangxing 66, were recommended as leading cultivars for production as well as elite crossing parents for further increasing yield potential in the Yellow and Huai Valleys Winter Wheat Zone in China.
Highlights
Lodging arising from permanent displacement of plant shoots from upright stature is a complex phenomenon that interferes with photosynthate transportation and dry matter accumulation
Grain yield was significantly affected by genotypes, years, planting densities and genotype  year interaction, but no significant effects by genotype  planting density and genotype  year  planting density interaction which was mainly due to the two growing-season conditions (Fig. 1) and the zero lodging in 12 genotypes under both planting densities (Table 2)
Higher planting density was accompanied by slight increases in grain yield, but with a significantly increased lodging risk
Summary
Lodging arising from permanent displacement of plant shoots from upright stature is a complex phenomenon that interferes with photosynthate transportation and dry matter accumulation. It reduces photosynthetic potential, provides a favorable environment for fungal growth and leaf disease development, and increases agronomic costs and causes yield loss[1]. Provides a favorable environment for fungal growth and leaf disease development, and increases agronomic costs and causes yield loss[1] It can reduce grain yield by up to 80% and significantly decrease bread-making quality[2,3]. New cultivars must carry resistance to major diseases such as powdery mildew, have excellent performances under both full and reduced irrigations, with acceptable processing quality for Chinese noodles and steamed bread
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