Lodging Resistance And Nitrogen Regulation In Yangmai Series Varieties

The study was conducted in the Key Laboratory of Crop Genetics and Physiology of Jiangsu Province and on the Experimental Farm of Yangzhou University during the two wheat growing seasons from 2012 to 2014. It included two experiments. The first experiment was done to investigate the relationship between plant morphology, anti-lodging force, stem anatomical structures and other indicators with lodging resistance, using eight Yangmai series varieties bred in different years. With Yangmai 20, a widely extended variety, as the experimental variety, the second experiment was conducted to study the effects of different nitrogen application ratios on lodging resistance and to explore the nitrogen application techniques for anti-lodging and high-yielding. The main results were as follows:(1) The earlier the varieties were developed, the less lodging resistance was observed, indicating that newly-developed varieties have better lodging resistance and higher yield.(2) Lodging resistance varieties and lodging susceptible varieties were significantly different in the degrees of angles between the main stem and the upper 3 leaves. Compared with lodging susceptible varieties, lodging resistance varieties are smaller in the degrees of angles between the main stem and the upper 3 leaves. For the lodging resistance varieties, the leaves on the upper part of wheat plants were compactly arrayed, the degrees of angles between the main stem and the upper 3 leaves were smaller as compared with lodging susceptible varieties. The light transmittance at different heights of wheat plants was greater in lodging resistance varieties than in lodging susceptible varieties.(3) Height dwarfing of wheat varieties was beneficial to lodging resistance. The height of newly bred varieties was generally stable at 80-90 cm. Compared with lodging susceptible varieties, lodging resistance varieties were higher in wall thickness, dry weight per unit length, and the contents of lignin, cellulose, and silicon of the 1st and 2nd basal internodes. Lodging resistance varieties had more vascular bundles in basal internodes as compared with lodging susceptible varieties. There was no significant difference in the number of small vascular bundles and the layer number of thick-walled cells between the varieties developed at different ages and lodging types.(4) The lodging resistance index was negatively correlated with plant height, the length of the 2nd basal internodes (P<0.01). It was positively correlated with the contents of lignin and cellulose, the dry weight per unit length of basal internodes, and the wall thickness of the 1st and 2nd basal internodes (P<0.01). Path analysis indicated that plant height was the most important factor affecting the lodging resistance of wheat. In addition, the wall thickness of the 1st and 2nd basal internodes and the diameter of the 2nd basal internode were also the important parameters affecting lodging.(5) The grain yield and the yield components of Yangmai 20 were significantly affected by nitrogen application amount and ratios. At the same nitrogen application ratio, grain yield increased with increased nitrogen application amount less than 225 kg-hm-2 and reduced at nitrogen application amount higher than 225 kg-hm-2. The highest grain yield was achieved at the nitrogen level of 225 kg-hm-2. At the same N application amount, the highest grain yield was determined in the treatment of 5:1:2:2 (the ratio of N applied before sowing, at tillering stage, jointing stage and booting stage) and the lowest yield in the treatment of 7:1:2:0.(6) Inappropriate high basal nitrogen ratio caused excessive tillers and deteriorated population, Postponing N fertilizer application appropriately controlled the occurrence of excessive tillers, increased dry matter accumulation after anthesis and thus grain yield. Increased and earlier nitrogen fertilizer application improved LAI from over-wintering to booting. At the same N application amount, excessive nitrogen fertilizer at early stage resulted into a rapid decline in LAI after antheis and shortened the period of grain filling. As the increase in nitrogen application amount and basal nitrogen ratio, lodging resistance ability and lodging resistance coefficient became lower, which significantly increased lodging risks. At the same N application amount, lodging resistance ability and lodging resistance coefficient increased as the increase in nitrogen ratio.(7) For Yangmai 20, the planting density of 180×104-hm-2, N application amount of 225 kg-hm"2, and the proportion of 5:1:2:2 (the ratio of N amount applied before sowing, at tillering stage, jointing stage and booting stage) effectively reduced plant height and the length of basal internodes, increased the wall thickness, filling degree, and the contents of lignin, cellulose, and silicon in basal internodes. Moreover this combination of planting density and N application amount and ratio also increased the ratio of carbon to nitrogen (C/N), lodging resistance and grain yield.