Population characteristics of super-high-yielding wheat under rice stubble in Huanghuai area

Studies on population characteristics of super-high-yielding wheat have recently attracted significant researches. These studies have revealed large differences in wheat population structure in different super-high-yielding wheat areas. The area of wheat under rice stubble in the Huanghuai region has reached 1.3 million hm², accounting for about 10% of cultivated wheat area in the Huanghuai region. Significant differences have been noted in the growth characteristics and ecological environments between dryland wheat and wheat under rice stubble. Current studies on population characteristics of wheat under rice stubble have focused mainly on production levels of 8 000 kg·hm^-2. Super-high-yielding wheat (yield is higher than 9 000 kg·hm^-2) was still in the infancy development stage, and studies on population characteristics of super-high-yielding wheat under rice stubble in Huanghuai area were less to be reported. To understand the population characteristics of super-high-yielding wheat-after-rice system in Huanghuai region, growth and yield formations of three semi-winter wheat varieties ('Lianma 6', 'Jimai 22' and 'Yannong 19') were investigated under high-yield (CK) and super-high-yield (SHY) cultivation measures. The results showed that wheat varieties had more grains per spike and higher 1000-grain weight under SHY than under high-yield wheat CK. There was no significant difference in spike number per unit area between SHY and CK. Compared with those under CK, wheat exhibited fewer tillers at the early growth stage (from tillering to jointing) but with higher rate of productive tillers to total tillers under SHY. While leaf area index and photosynthetic potential of SHY were lower than those of CK at the early growth stage, these attributes were significantly higher after heading. There was no significant difference in accumulated dry matter weight between SHY and CK at the early growth stage. Root-to-shoot ratio and root exudate amount under SHY were higher than those under CK at heading, milking and waxing stages. Also grain-to-leaf ratio, percent matter translocation from stem and sheath, and harvest index under SHY were higher than those under CK. Analysis of various attributes of rice yield and population showed that for SHY wheat in Huanghuai region, spikes per unit area, grains per spike, 1000-grain weight, productive tiller rate, total dry matter weight at maturity stage, grain weight/leaf area ratio, root/shoot ratio at heading stage, root exudate amount, harvest index were greater than 700×10⁴·hm^-2, 32, 42 g, 45%, 20 t·hm^-2, 14 g·cm^-2 (i.e., mg grain weight per cm2 leaf area), 0.28, 7.1 g·m^-2·h^-1, 0.45, respectively; while leaf area index at heading stage was 6.5 7.0.