| White corn,as a staple food in the part of southwest mountainous district,was very slow in the replacement of varieties.Although there are abundant white grain corn germplasm resources in the southwest mountainous areas,there are relatively few relevant reports on these resources.Therefore,the studying of the genetic diversity of white corn germplasm resources is of great significance to exploring the breeding of white corn.This experiment combined with the heterotic pattern of “temperate Germplasm×Tropical Germplasm(Subtropical)” that was suitable for corn eco-regions in Southwest Mountainous Areas,and used 45 white corn inbred lines that introduced from the outside and 4 standard testers(Ye478,Mo17,Dan340,and Huangzaosi)as experimental materials,and utilized the NCII incomplete diallel design to generate 294 crosses,and launched a joint identification test at Xinjin county in Sichuan province(attitude 450m),Jushan county in Guizhou province(attitude 1250m)and Luquan county in Yunnan province(attitude 2250m),these are three locations with different altitude and environment,in a year.Combining with SSR molecular markers,preliminary studies were conducted on the heterosis groups of 45 white corns,the general combining ability of the 10 quantitative traits,the heritability and the grain yield per plant of crosses,and the following results were obtained:1.36 amplified primers with clear bands were selected from 120 pairs of SSR primers and a total of 167 allelic variations were detected in 49 materials,with the variation range was 2 to 11,and the average number of allelic variations detected at each tested site was 4.6.The Polymorphic Information Content(PIC)ranged from 0.34 to 0.86,with an average of 0.64.The Genetic Similarity varied from 0.5269 to 0.9401,with an average of 0.6793.when the threshold was 0.667,We could divide the 45 white corn inbred lines into 6 groups,according to the genetic similarity coefficient matrix and the UPGMA method,as well as referencing the main heterosis groups of the 4 standard testers.2.In the case of fixed testers,clustered with special combining ability.When the threshold was 12.01,42 tested lines can be divided into 6 groups using special combining ability to cluster,which was lack of SPT compared with the result of SSR clustering.There were certain changes in the other groups,but the overall trend was consistent with the results of SSR clustering.In practice,the two methods should be combined with each other,and specific application should be based on the specific performance of the material.3.Synthesizing the general combining ability effects of 10 traits of the 45 white-grain maize inbred lines and its field performance,6 white-grain maize inbred lines(White 2、5008、8072、GY156、GY435and SC122)with high general combining and excellent comprehensive traits were screened out,which can be focused on the testing in the practice breeding.Among them,"White 2 and SC122" are both suitable for the male parent due to its slightly spread plant type,while the other four materials are more suitable for the female parent due to its relatively compact plant type and appropriate plant height."5008 and GY435" both belong to the materials with thick ear diameter and multi-rows ear,the "8072and GY156" both belong to the materials with long ear length and multi-ear row.4.The genetic parameters of 10 quantitative traits of 45 white maize inbred lines were estimated and the narrow heritability in descending sequence were row number per ear(79.57%)> ear height(63.35%)> plant height(63.26%)> ear diameter(56.05%)> ear length(53.30%)> kernel rate(49.27%)> 100-kernel weight(33.15%)> kernels per row(31.23%)> ear barren tip(21.31%)> grain yield per plant(18.26%).Among them,the generalized heritability and narrow heritability of the five traits: ear length,ear diameter,row number per ear,plant height and ear height were all greater than 50%,so that it should be selected in the early generation.The generalized heritability and narrow heritability of the four traits of baldness,kernel number per row,100-kernel weight,and grain yield per plant were both less than 50%,so that it should not be selected in the early generation.5、Through the analysis of the grain yield per plant between cross and the control check,we selected two crosses,8072 × SC122 and GY435 × SC122,both of which were disease-resistant and steady increase in production at Jushan county in Guizhou province and at Luquan in Yunnan province,with average increase value was 2.6% and 4.8%,respectively,and were suitable for planting in the high altitude ecological region of Yunnan and Guizhou.And screened out the strong superiority crosses of GY435 × Mian 817,with an average increase of 7.8% at Xinjin and Jushan and was suitable for planting in low elevation and middle elevation ecological areas in Sichuan and Guizhou.And selected out a high-yield cross of 8072 × Mian 817,with increase production reached to 10.6% and was suitable for the plain ecological area in Sichuan. |
