Relationship of characteristics of culm construction to lodging resistance and yield of Fujian-bred super-rice cultivars

Lodging is common issue in rice production that influences not only rice yield but quality as well. In recent years, contradictions in high yields and lodging resistance have increased with increasing plant height and rice panicle weight, which has in turn greatly impacted rice production. Experiments were therefore conducted to study the relationships of characteristics of culm construction to lodging resistance and yield components of Fujian-bred super-rice cultivars. The study was necessary to lay the basis for breeding lodging-resistant varieties and high-yield cultivation in Fujian Province. The experiment consisted of 4 super-rice cultivars ("Ⅱ youming 86", "Ⅱ youhang 1", "Teyouhang 1" and "Ⅱ youhang 2") confirmed by China's Ministry of Agriculture and the "Shanyou 63" cultivar as the control. In the field experiment, conventional methods were used and 20 representative stem per cultivar selected at maturity stage. Length, diameter, wall thicknesses of different internodes and yield were measured, and breaking-resistant strength, bending moment and loading index calculated in the experiment. The results showed that most internodes of super-rice cultivars were longer than CK. However, the first internodes (from the top) of "Ⅱ youming 86" was significant shorter than CK. Also most of the internode diameters of super-rice cultivars were little different from CK. Most of the internode wall thickness of super-rice cultivars were also smaller than CK, except for the first internodes (from the top) of "Ⅱ youming 86" which were significant greater than CK. Lodging indexes of super-rice cultivar internodes were greater than CK, with most being significantly difference. However, all lodging indexes for cultivars were below 200, indicating strong resistance to lodging. Breaking-resistance strengths of three elongation internodes near stem base were significantly correlated with internode wall thickness. Lodging index of each internode was significantly or highly significantly negatively correlated with corresponding internode wall thickness. However, lodging index was not significantly correlated with plant height, internode length and diameter. This suggested that lodging resistance of the tested cultivars largely depended on internode wall thickness. As panicle length was significantly positively correlated with internode wall thickness, increasing base elongation internode wall thickness was beneficial to longer panicle breeds. To strengthen lodging resistance capacity, it was necessary to search for non-dwarf lodging-resistance traits, especially thick wall culm, during super-rice breeding.