[Effects of planting density on the grain yield and source-sink characteristics of summer maize].

Taking high-yielding summer maize cultivars Zhengdan 958 (ZD 958) and Denghai 661 (DH 661) as test materials, this paper studied the effects of different planting density (22500, 45000, 67500, 90000, and 112500 plant x hm(-2)) on the grain yield and source-sink characteristics of the cultivars in four regions, i.e., Shandong Agricultural University, Wenkou, Yanzhou, and Laizhou. At the planting density 112500 plant x hm(-2), the grain yield and the biomass of the cultivars were the highest, being 19132 and 36965 kg x hm(-2), respectively. Comparing with those at the planting densities 22500 and 67500 plant x hm(-2), the grain yield at the planting density 112500 plant x hm(-2) was increased by 72% and 48%, and the biomass was increased by 152% and 112%, respectively. With the increase of planting density, the leaf area index (LAI) increased significantly, while the leaf area per plant (LA), the maximum number of filaments, the grains per ear, and the 1000-grain weight all decreased. The harvest index and the grain-leaf ratio decreased with increasing planting density, but no significant change was observed when the planting density was higher than 67500 plant x hm(-2), suggesting that at higher planting densities, summer maize could improve their grain yield via increasing population sink.

[Study on the relationship between inheritance and immature embryo culturing capacity of maize inbreds].

The immature embryo culturing capacity of maize is crucially important to maize improvement by transgenic approach. The hereditary variation regularity of maize embryo culturing capacity is not very clear yet. The research aims to study the relationship between inheritance and immature embryo culturing capacity of maize inbreds. By culturing immature embryos of 22 maize inbreds, embryonic callus induction efficiency and regenerating plant efficiency were analyzed with cluster analysis method. And the genetic relationships of 22 inbreds were analyzed using 14 SSR primers with good polymorphism. Results showed that 22 inbreds were classified into three groups. The average embryonic callus efficiency and regenerating plant efficiency of the inbreds with good culturing capacity were 85.0% and 86.7% respectively. The average embryonic callus efficiency and regenerating plant efficiency of the inbreds with middle culturing capacity were 41.3% and 53.1% respectively. The average embryonic callus efficiency and regenerating plant efficiency of the inbreds with bad embryo culturing capacity were 2.14% and 2.75% respectively. 22 inbreds were clustered based on 110 polymorphic loci and classified into 4 genetic groups based on GS (genetic similarity) = 0.75. The consistencies were 91%, 82% and 91% for the clustered results of the single character (embryogenic callus efficiency and regenerating plant efficiency) and both characters respectively. t test showed that immature embryo culturing capacity was significantly different between different genetic groups. Therefore, the immature embryo culturing capacity could be correctly estimated by polymorphic loci from the 14 SSR primers. The clustering method by the SSR provided a basis for forecasting and selecting the immature embryo culturing capacity of maize inbreds.