| The Huanghuaihai Summer Maize Region is one of three largest maize production regions, and to analyze the genetic relations of common maize inbreds in our country, and study characterizations of heterotic group and patterns in this region with especial ecological conditions have a very importance to maize breeding and productions.Fifteen common maize inbreds as farther lines, and four testers (Huanzao 4, Dan340, Ye478 and Mo17) as mother lines were combined to form sixty heterosis crosses with NC-II method. According to grain yields, agronomic traits and combining ability of these crosses, genetic relation of common maize inbreds under the conditions of Huanghuaihai Summer Maize Region were studied, these crosses were divided into different cross groups, analyze property characterization and utilization value of different cross groups, further put forward instructive methods and heterotic patterns. The main results were followed:1. According to yield especial combining ability, fifteen maize inbreds were divided into four groups: Reid group included Tie 7922, Dan 9046, C8605-2, X178; Tangsipingtou included LX9801, Chang 7-2, K12 and 444; Lvdahonggu group included Lvjiukuan, Tie 9010, E28 and Danhuang 02; Lancaster group included 200B, Yu12 and P138. The results were mostly accordance with many domestic studies and pedigree source. In this study, X178 and P138 were divided into Reid and Lancaster groups, respectively, but they were from 78599, an American cross. 78599 and its lines were considered to be a novel maize cross group (P).2. Reid heterotic group was the most germplasm source of maize in Huanghuaihai Summer Maize Region. Compared with the total average values of sixty cross combinations, cross combinations from Reid group had many good traits: 1.8% longer in ear length, same in ear diameter, 7.3% fewer in row number per ear, 2.3% more in grain number per row, 7.7% more in ear grain weight, 4.4% fewer in plant height and 9.6% fewer in ear height. The results indicated that, compared with other germplasm sources, Reid contained the dwarf gene, resulting in longer ear, large grains, more rows and high combining ability. In the breeding utilization, its improvement and utilization should be emphasized, particularly in large grains, plant heights, low ear heights, etc. Main improvement on this group should be focused on the increasing in ear length, ear diameter and combining ability and yield, helpful to explore, utilize heterotic patterns from American and torrid one, and improve local germplasm with close genetic relation.3. Compared with the total average values of all cross combinations, cross combinations from Tangsipingtou group had many traits: 13.1% shorter in ear length, same in ear diameter, 5.5% more in row number per ear, 6.3% fewer in grain number per row, 8.1% fewer in ear grain weight, 2.6% lower in plant height and 0.9% lower in ear height. The results indicated that the many breeding traits: shorter ears, more row numbers, fewer grain number per row, lower grain weight, moderate ear diameter and plant height. In breeding, more row numbers and grain setting4. Compared with the total average values of all cross combinations, cross combinations from Lancaste group had many traits: 7.1% longer in ear length, 6.0% shorter in ear diameter, 8.5% more in row number per ear, 7.2% fewer in grain number per row, 2.4% fewer in ear grain weight, 3.1% higher in plant height and 2.6% lower in ear height. The results indicated that it contained many traits: long and thin ear, many row numbers per row, few row number and high height, etc. However, its cross grains had many disadvantages, such as, few row numbers, low seed setting, resulting in the limitation for yields, and it had been used in Huanghuaihai Summer Maize Region.5. Compared with the total average values of all cross combinations, cross combinations from Lvdahonggu group had many traits: 4.2% longer in ear length, 4.0% shorter in ear diameter, 12.8% more in row number per ear, 3.5% fewer in grain number per row, 2.7% fewer in ear grain weight, 3.9% higher in plant height and 3.5% lower in ear height. The results indicated that it contained low grain weight, high ear and plant heights, average combining ability. Accordingly, it possessed few fine traits and was rarely used at Huanghuaihai Summer Maize Region.6. Compared with the total average values of all cross combinations, cross combinations from P group had many fine traits: 10.28% more in grain number per row, 7.74% higher in plant height and 9.8% higher in ear height. The results indicated that P group contained long ear, many grain number per row, high plant and high ear, etc. Accordingly, it was universally utilized at Huanghuaihai Summer Maize Region. For it utilization, it should be noticed to clearly divide its situation in heterosis utilization, broad its heterosis pattern, which would unite maize germplasm, conclude heterosis pattern, reasonably use germplasm expanding, improvement and innovation.7. Especial combining abilities of fifteen maize inbred lines were analyzed and the results indicated that the sequences of high combining abilities were, Huanzao 4×Tie 7922 (1.272), Huanzao 4×Yu 12; (0.966), Ye 478×K12 (0.956) and Ye 478×LX9801 (0.890). Three of these crosses belonged to Reid×Tangsipingtou group, indicating that it had a strong heterosis. The maize cultivars, such as Zhendan958 (Zheng 58×Chang 7-2), Yedan 2 (Ye 107×Huangzao 4), Yedan 12 (Ye 478×Ye 515), Ludan 90002 (Zheng 58×LX98001), Yuyu 23 (Ye478×Chang 7-2), which are broadly planted at Huanghuaihai Summer Maize Region at present, belonged to Tangaipingtou×P cross, indicating that it is the best cross pattern at Huanghuaihai Summer Maize Region.Analysis on yields of sixty crosses indicated that yields of only five, including Huangzao 4×X178, were higher than control, implying that heterosis pattern of Huangzao 4×X178 group and Tangsipingtou Huangzao 4×P group heterosis group were significant. Recently, development of Ludan 981 (Qi 319×LX9801) and Ludan 963 (Qi 319×Ji853) also illuminated that heterosis of Tangsipingtou×P group was becoming eminent, and it was one of the most important heterosis patterns at Huanghuaihai Summer Maize Region. |
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