Effects of Reciprocal Recurrent Selection on Grain Yield in Two Tropical-Temperate Maize Synthetic Populations Tuxpeño-Reid and Suwan-Lancaster

Reid, Lancaster, Tuxpeno and Suwan are the most common maize (Zea mays L.) germplasms. Reid × Lancaster and Suwan × Tuxpeno are very important heterotic patterns in temperate areas and tropical areas, respectively. Broadening the genetic basis of maize has usually been conducted in inter-populations formed by crossing temperate and tropical germplasms. Reciprocal recurrent selection (RRS) is a breeding procedure to improve the inter-populational cross of two base populations. The objective of this study was to evaluate the direct and indirect effects of reciprocal recurrent selection on grain yield in the TR (Tuxpeno-Reid) and SL (Suwan-Lancaster) maize populations. The populations and the inter-populational crosses of each selection cycle, as well as two commercial hybrids, were evaluated in four environments. The effect of mean grain yield on TR × SL inter-population crosses was 4.63% (or 0.365 Mg·ha-1) cycle-1. The grain yield of SL increased by 2.78% (or 0.20 Mg·ha-1) cycle-1, but the grain yield of TR essentially did not change. Most changes in other agronomic traits occurred in the desired direction. After 3 selection cycles, the ear tip-barrenness length decreased in TR × SL, TR and SL by 39.70%, 37.50% and 24.57%, respectively, which indicates that the increase in grain yield may be largely due to a decreasing ear tip-barrenness length. The mid-parent heterosis of grain yield of the inter-populational cross increased from 15.49% to 25.96% from C0 to C3. The mean grain yields of TRC3 × SLC3 were 100.01% and 103.88% of the mean grain yields of the commercial single-crosses GD8 and QD16, respectively. The results suggest that Tuxpeno-Reid × Suwan-Lancaster may be possible new heterotic patterns in the southern region of China.

Comparisons of Three Recurrent Selection Methods in the Improvement of Maize Populations

The maize population Csyn 4 was improved for three cycles with three recurrent selection methods MS1, MS1-HS, and MHSRRS in northern China. A total of 40 NC Ⅱ testcrosses were made by four testers with Csyn 4 and 10 improved populations, which were evaluated in four environments in the cropping season of 2005. Analysis of variance indicated a significant progress （P〈 0.05） in yield and other chief agronomic traits in the improved populations and testcrosses, demonstrating that the three recurrent selection methods were effective for increasing grain yield of testcrosses and improvement of general combining ability in maize population. The average grain yield increase of population Csyn 4 in MS1, MS1-HS, and MHSRRS recurrent selections was 266.7 kg ha^-1 （5.3%）, 288.0 kg ha^-1 （5.7%）, and 231.3 kg ha^-1 （4.6%） per cycle, while the grain yield of S 1 progeny of population for Csyn 4 was increased by 420.0 kg ha^-1 （10.9%）, 376.0 kg ha^-1 （9.8%）, and 414.7 kg ha^-1 （10.8%） per cycle in MS1, MS1-HS, and MHSRRS recurrent selections, respectively. Linear responses （b） in the MS1, MS1-HS, and MHSRRS recurrent selections were the same as the realized responses of the selection （G） for grain yield increase of Csyn 4 and S1 progeny of the populations. The grain yield of testcrosses increased by 3.3-5.2% on average per cycle. The value of heterosis did not display any differences amongst the different cycles of selections. The GCA for yield component traits of population Csyn 4 was improved significantly by means of three selection methods, whereas the GCA for plant height, ear height, days to silking, and days to pollen did not show significant increase in the recurrent selections. GCA for the number of tassel branches were decreased in the selections, while GCA for the number of plant leaves were increased, but the difference was not significant.

改良HS相互轮回选择法对两个玉米群体的改良

对MZZ3(改良中综 3号 )、MZZS4 (经 4轮MS1改良的中综 4号群体 )完成了 2轮改良半同胞 (HS)相互轮回选择。结果表明 ,两群体以籽粒产量为主要选择目标 ,经两轮改良HS相互轮回选择 ,与各测验种间的测交组合产量、杂种优势都获得了逐轮提高。测交组合产量每轮增益 (ΔG)在 2 85kg hm2 (5 .5 % )到 6 88kg hm2 (13.0 % )之间。同时 ,两群体ΔG都以MZZS4C2×MZZ3Cn和MZZ3C2×MZZS4Cn最大 ,其次为掖 4 78×MZZ3Cn、P178×MZZ3Cn及黄早四×MZZS4Cn、丹 340×MZZS4Cn ;杂种优势每轮增益 (ΔG)在 193kg hm2 到 4 2 1kg hm2 之间。两群体一般配合力均得到了显著改良 ,MZZ3从C0的 - 5 17提高到C2的 5 10 ,MZZS4从C0的 - 5 0 9提高到C2的 4 94。同时 ,两群体间的特殊配合力也逐轮提高。不仅如此 ,还改良了群体与测交种 (含同类种质 )的特殊配合力。从特殊配合力的获得量看 ,MZZS4C2×MZZ3Cn、MZZ3C2×MZZS4Cn最大 ,其次为掖 4 78×MZZ3Cn、P178×MZZ3Cn及黄早四×MZZS4Cn、丹 340×MZZS4Cn。杂种优势、测交组合产量的变化与配合力完全一致。改良HS相互轮回选择可同时改良群体S1、S2后代的产量 ,MZZ3每轮群体S1后代获得 10 2 %的增益 ,S2后代获得 12 .7%的增益 ;MZZS4每轮群体S1后代获得 11.8%的增益 ,S2后代获得

两个玉米群体的构建及其改良效果

【目的】通过群体的创建和改良,扩大玉米种质基础,为广西玉米杂交育种提供新的优良种质。【方法】根据配合力测定和自交系的系谱分析结果和育种目标要求,分别应用37、26个优良自交系创建两个玉米基础群体GZPA和GZPB,应用经简化后的改良HS相互轮回选择法对两个群体进行遗传改良,并对其农艺性状进行测定和遗传增益分析。【结果】经改良后,两群体杂交组合4个试点的平均产量增益为7.70%,其吐丝天数、开花间隙天数、穗长、穗粗、穗行数、行粒数、出籽率、千粒重均获得一定程度的有利增益。GZPA和GZPB平均产量增益分别为5.37%和4.85%;群体GZPA的吐丝天数、开花间隙天数、出籽率为负增益,其他性状为正增益,且株高、穗粗、穗行数的增益达显著水平;群体GZPB的吐丝天数、开花间隙天数、穗长、穗粗、穗行数、行粒数为正增益,其他性状为负增益。两个群体改良前后性状变异系数变化较小。【结论】简化后的改良HS相互轮回选择法对两个群体的改良效果明显,两个群体内仍有较大的遗传变异,可作进一步改良。

桂综3号和桂苏综玉米群体相互轮回选择效果分析

【目的】对两个玉米群体桂综3号和桂苏综进行两轮相互轮回选择改良后的遗传效益进行评估,为其利用提供理论依据。【方法】以黄早4、掖478、丹340、M0174个测验种作母本,以两个玉米群体桂综3号和桂苏综不同改良群体作父本,按NCⅡ遗传交配设计组配测交种,对各轮群体、群体间杂交组合和测交种进行田间鉴定,调查产量、株高、穗位高、穗长、穗粗、穗行数、行粒数、秃尖度、出籽率和千粒重并分析配合力等。【结果】桂综3号、桂苏综及其杂交组合产量平均每轮增益分别为83kg/ha(0.85%)、645kg/ha(12.45%)和390kg/ha(5.90%);群体间杂交组合超亲优势从5.7%提高到13.5%。桂综3号的产量一般配合力效应从-5.32增加到-1.55,桂苏综的一般配合力效应从0.10增加到6.55。桂综3号、桂苏综均与掖478、丹340的特殊配合力都得到一定提高。出籽率和千粒重朝逐轮增加方向发展,秃尖度呈逐轮减少趋势,其他性状变化不明显。【结论】桂综3号和桂苏综经两轮相互轮回选择后,群体间杂交组合产量和杂种优势都逐轮增加,易与掖478、丹340等Reid、旅大红骨种质形成杂种优势模式,可继续进行相互轮回选择改良,利于在玉米育种上改良利用。

甜菜有粉系轮回选择初报——早代配合力选择

通过1989～1992年3批单株测交组合的配制和鉴定,初步揭示了甜菜有粉系早代配合力选择的方法、效果和存在的问题。选育出一般配合力较高、经济性状较优的甜研4号轮-24、A_(?)-24轮-24和81G—06轮-16等优良株系4个,高配合价基因型20余个,以及新的一轮群体3个,其中甜研4号一轮群体在主要性状方面有明显增益:根产量提高18.30％、含糖率增加2.9度,产糖量提高54.3％,褐斑病病情降低0.21级。该研究为开展甜菜配合力育种提供了一定的积累。

利用对生玉米改良群体的研究

本项试验利用pob46×对214-乙、Suwan×对4356建立两个相互全姊妹轮回选择群体,进行十代的选择鉴定,其分析结果是:就最高产组合来看,S2×P2比S1×P1增产27.3%,证明利用对生玉米做桥梁亲本有助于提高遗传进化的速度,其效率十分明显。

两个热带玉米复合群体相互轮回选择遗传改良效益研究

利用半同胞相互轮回选择法对桂综3号和桂苏综两个热带复合群体进行两轮改良后,选用黄早四、掖478、丹340、Mo17等4个测验种作母本,各轮改良群体作父本,按NCⅡ遗传交配设计组配测交种,对各轮群体、群体间杂交组合和测交种进行选择效果评价。结果表明,桂综3号、桂苏综及其杂交组合产量平均每轮增效分别为53、645、390 kg/hm2;群体组合超亲优势由5.7%提高到13.5%。C2群体与C0相比,桂综3号的产量一般配合力效应从-5.32增加到-1.55,桂苏综的一般配合力效应从0.10增加到6.55。桂综3号、桂苏综与掖478、丹340的特殊配合力都得到一定的提高。其他农艺性状随各轮对产量相互轮选择发生不同程度的变化,其中出籽率和千粒重是随轮次改良向增加方向发展,秃尖长也随着减少,其他性状变化不大。