Lodging resistance characteristics of high-yielding rice populations

• Differences of rice lodging affected by nitrogen (N) under different eco-sites were significant.
• For the lower lodging index (LI) rice populations, N primarily decreased the stems stiffness.
• For the higher LI rice populations, N mainly impacted the morphological parameters of the basal stems.

The main objectives of this paper were to explore effective ways of improving the lodging resistance of high-yield rice populations and the lodging resistance capacity responses of different rice populations to nitrogen. Field experiments were conducted at the following two eco-sites: Taoyuan (a special high-yield eco-site) in Yunnan province and Danyang (representative eco-site of the middle and lower Yangtze) in Jiangsu province, China in 2011 and 2012. A super indica hybrid rice called ‘Y Liangyou 2’ was grown at each eco-site under different N levels. The lodging index at Taoyuan was significant lower than that at Danyang. The heavier dry weight per cm of leaf sheath and higher proportion of cellulose and lignin in the basal stems enhanced the stem strengths at Taoyuan, in spite of the smaller culm diameter and thinner wall thickness. The shorter elongated internodes of the basal stems were responsible for the lower plant height and the height of center of gravity. In addition, the lodging index at Taoyuan was affected significantly by nitrogen. With increasing nitrogen, the plant height, the height of the center of gravity, dry weight per centimeter (cm) of basal stems (culms and leaf sheaths), bending stress and carbohydrate content were more susceptible to nitrogen. At Danyang, the responses of morphological and physiological parameters to nitrogen tended to level off, the lodging resistance was primarily related to the morphological characteristics of the basal stem. These results suggested that an improvement in the lodging resistance of high-yield rice populations could be achieved by the suitable plant height with the optimum configuration of internodes, namely, shorter basal stems and a longer peduncle, and by increasing stem stiffness, which was primarily attributed to higher proportions of structural carbohydrates (e.g., cellulose and lignin) and greater plumpness of the leaf sheaths.