Relationship between lodging and mechanical characteristics of winter wheat stem under different yield levels

Understanding the relationship between the structure of the base node and mechanics of lodging resistance would be helpful to solve the contradiction of high-yield and lodging. In order to identify the relationship between the yield and lodging, the biomechanical properties (such as kink force of inertia, cross sectional moment of inertia, young modulus bending rigidity and bending strength) of basal second internodes and morphological traits were measured with the SANS-CMT6104 multifunctional testing machine controlled by computer, in 21 wheat fields, which have different yield levels in late-maturing winter wheat area in Jinzhong, Shanxi Province. The results showed that under the different production levels, with the excessive increase of the basic seeding number and the peak number of tiller in jointing stage, the lodging rate of groups was greater, lodging time was earlier, the grain number per spike and the weight of 1 000 grain were reduced significantly in particularly, the yield was decreased. Moreover, it showed that wheat production in the area was constrained by natural conditions and plant system. The reasonable basic seeding amount and the highest number of the tiller after re-green stage determined by the appropriate irrigation and fertilizer regulation were two important critical values of wheat groups with relations to high-yield and no lodging. The relationship between lodging and the morphology of base second internodes was defined. All the biomechanical indictors were negatively related to the indexes of wheat stem such as plant height and spacing bending section, while positively to dry weight, diameter and wall thickness of stem. With the excess increase of basic seeding amount, the number of highest tiller in joint stage was increased, and mechanics load of basal stem was decreased, which led to lodging. Two biomechanical properties including bending strength and elasticity modulus, which were close to lodging resistance of internodes, quality of population, morphosis of plant and yield structure, were screened out, and were regarded as reference indexes for lodging resistance or plant type breeding and high yielding population framework designed.