1. Yield gains and agronomic traits ofmaize varieties released in Chinaduring the past six decades Shihuang Zhang, Xiaoke Ci, Mingshu Li, Jiashun Xu, Degui Zhang, Xiaoling Liang (CAAS, Beijing, China) xkc-99@yahoo.com.cn Maize Center, ISC, CAASChinese Academy of Agricultural Sciences

2. Maize yield12.0 AmericaArgentina China VietnamMyanmar10.0 8.0 6.0 4.0 y=107x+974y=38x+4586 2.0 0.0 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95 97 99 01 03 05 07 09 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 20 20 20 20 20YearsData from FAO Chinese Academy of Agricultural Sciences 3. Problems in maize breeding Strategies for more effective breedingThe research since 2005 Chinese Academy of Agricultural Sciences 4. materials1950sGolden queen, Xiaolihong, Yinglizi, Baimaya1960sSishuang 1HD409 Weier156US131970sXindan 1, Zhongdan 2, Zhengdan2, Qundan105,Jidan1011980sYedan 4, Huang417, Shendan 7Danyu13Yedan 2,Nongda60, Tiedan 41990sBenyu 9, Yedan13, Sidan19, Zhengdan14Yedan19,Jidan159, Nongda3138, Nongda108, Ludan50, Jidan1802000sZhengdan958Xianyu335Shendan16Ludan981,Denghai 9 Chinese Academy of Agricultural Sciences 5. design The trial design was a randomized completeblock in a split plot arrangement withdensity as main plot and hybrid as subplot. Subplots consisted of two rows 0.6 m apartand 4 m long. Chinese Academy of Agricultural Sciences 6. Year Densities30 000 plants/ha2005-2006 45 000 plants/ha60 000 plants/ha15 000 plants/ha2007-2009 45 000 plants/ha75 000 plants/haChinese Academy of Agricultural Sciences 7. LocationsUrumchi Shenyang BeijingXinxiangSanyaChinese Academy of Agricultural Sciences 8. Objectives yield gains and its association with plant densities agronomic trait changes accompanied with yield N utilization and its association with released decade and stay-green provide a basis for designing more effective future breeding strategies Chinese Academy of Agricultural Sciences 9. I. Yield gain and its association with plant densitiesi Genetic yield gainii Tolerance to stress Chinese Academy of Agricultural Sciences 10. 1. Genetic contribution to total yield gains from 1970-2000 12.00 Total yield gain Yield of the 2000s hybrids at 75 000 plants/ha Gengtic yield gain 10.00 C8.00 Yield of the 1950s OPVs at 75 000 plants/ha CD breedingcontributionB6.0053%4.00 A2.00 Yield of the 1950s OPVs at 15 000 plants/ha0.001940 1950 19601970 198019902000 2010YearThe method from Tollenaar (2002)Ci et al. Euphytica, acceptedOpen pollination varieties (OPVs) Chinese Academy of Agricultural Sciences 11. Genetic yield gain Tolerance to stress 12. 1. Tolerance to stress Yield at different densities12.0 15 000 45 00010.0 75 000 y = 0.11 x - 205.03 R2 = 0.97 8.0y = 0.09 x - 177.52 R2 = 0.95 6.0 4.0y = 0.06 x - 111.74 R2 = 0.91 2.0 0.0194019501960 1970198019902000 2010YearCi et al. Euphytica, acceptedChinese Academy of Agricultural Sciences 13. Yield gain increased significantly with increasingplant densities.New hybrids have more tolerance to stress fromthe 1950S to 2000S. (Here, Tolerance to stress includeshigh densities, diseases, insects and so on) Chinese Academy of Agricultural Sciences 14. 2. Tolerance to high densities Yield in Urumchi16.016.00 30 00015 000 y = 0.084x - 15645 000 45 000 14.0014.0 R2 = 0.71 75 000 y = 0.040x - 66 60 000R2 = 0.34412.0012.0 y = 0.124 x - 236 R2 = 0.91 10.00y = 0.049x - 8710.0R2 = 0.5924 8.00 8.0 y = 0.103x - 1966.00y = 0.046x - 84 R2 = 0.91 R2 = 0.7079 6.0 4.00 4.02.0019601970 1980 1990 2000 2010 1960 1970 1980 1990 2000 2010Year Ci et al. Crop Science, 2010 Chinese Academy of Agricultural Sciences 15. 30 000 y = 0.103x - 196 r = 0.9615 000 y = 0.046x - 84 r = 0.8445 000 y = 0.124x - 236 r = 0.9545 000 y = 0.049x - 87 r = 0.7760 000 y = 0.084x - 156 r = 0.8475 000 y = 0.040x - 66 r = 0.58No significant difference between regressioncoefficient at different densities.Hybrids improved slightly in tolerance to high densities.Hybrids did not attain greater tolerance to higher densities of60,000 to 75,000 plants/ha as yet in China. Ci et al. Crop Science, 2010Chinese Academy of Agricultural Sciencesc 16. 3. The Contribution of Stress ToleranceLocationsEnvironmentGenetic yield gain Beijing a typical environment increased efficiency in with serious biotic and grain productionabiotic stress improved tolerance tostress increased efficiency inabundant sunshine andgrain productionUrumchi few diseases and insects improved tolerance toHigh densitiesChinese Academy of Agricultural Sciences 17. compareBeijing Xinjiang30 000 plants ha-1 y = 0.064x - 121 y = 0.103x 19645 000 plants ha-1 y = 0.116x - 222 y = 0.124x - 23660 000 plants ha-1 y = 0.155x - 301 y = 0.084x - 156 The contribution of stress-tolerance to genetic yield gains was 46% at 60,000 plants/ha based on the difference of regression coefficient between Beijing and Urumchi Ci et al. Crop Science, 2010Chinese Academy of Agricultural Sciences 18. CompareBeijingXinjiang15 000 plants ha-1 y = 0.041x 75y = 0.046x 8445 000 plants ha-1 y = 0.119x 226y = 0.049x 8775 000 plants ha-1 y = 0.151x - 288 y = 0.040x - 66The contribution of stress tolerance to geneticyield gains was 74% at 75,000 plants/haCi et al. Crop Science, 2010Chinese Academy of Agricultural Sciences 19. Summary With increasing plant densities, the contribution ofstress tolerance to total yield gain increased. Yieldimprovement has occurred at a slow pace at densitiesof 60,000 and 75,000 plants/ha in China. Further increasing maize yield will be achievedthrough higher plant populations, and this will requirebreeding for greater stress tolerance. Chinese Academy of Agricultural Sciences 20. Agronomic trait changesaccompanied with yield Plant traits Ear traitsChinese Academy of Agricultural Sciences 21. 260120255 115250 110Plant height (cm) Ear height (cm)245240105y = 0.85x + 105235R2 = 0.07 y = 3.0x + 232100230 R2 = 0.4895225Plant heightEar height220 901950 1960 1970 1980 1990 20001950 1960 1970 1980 1990 2000 Year of release(11 environments, 2007-2009)Ci et al. Euphytica, accepted Chinese Academy of Agricultural Science 22. 7477 7376 7275 74 71 y = 0.74x + 6873Days 70 R2 = 0.47y = 0.66x + 71 72 R2 = 0.39 69 71 68 70 67 69 66 Days to anthsis68Days to silking 65 (Days to67 (Days to1950 1960 1970 1980 anthsis) 200019901950 1960 19701980 1990 silking)2000Year of release (11 environments , 2007-2009) Ci et al. Euphytica, accepted Chinese Academy of Agricultural Science 23. 100009000) 2Leaf area per plant (cm8000 larger plant size and7000 later maturity,especiallyy = 443x + 5526from the 1980s6000R2 = 0.785000 Leaf area per plant40001950 1960197019801990 2000 Year of release(11 environments , 2007-2009)Ci et al. Euphytica, acceptedChinese Academy of Agricultural Science 24. 50 49 48Leaf angle 47y = -0.76x + 50 R2 = 0.58 46 45 44Leaf angle 431950 1960 19701980 19902000Year of release(11 environments , 2007-2009) Ci et al. Euphytica, acceptedChinese Academy of Agricultural Science 25. 5.015 000 y = -0.02x + 2.1 r=-0.314.5 45 000 y = -0.07x + 2.8 r=-0.6475 000 y = -0.19x + 3.7 r =-0.854.03.53.02.52.01.5ASI1.01950 1960 1970 1980 1990 2000 Year of release(11 environments , 2007-2009)Ci et al. Euphytica, acceptedChinese Academy of Agricultural Science 26. 4125402039 y = 0.29x + 39 15y = -0.8x + 20R2 = 0.35 R2 = 0.333810375Tassel length Tassel branch number360 1950 19601970 1980 1990 20001950 1960 197019801990 2000Year of release (11 environments , 2007-2009)Ci et al. Euphytica, acceptedChinese Academy of Agricultural Science 27. 18.012.015 000y = -0.50x + 4.8 r=-0.94 15 000 y = -1.12x + 6.4 r=-0.84 16.045 000y = -1.09x + 8.4 r=-0.72 45 000 y = -1.47x + 8.7 r=-0.9210.0 14.075 000y = -1.72x + 14.0 r=-0.88 75 000 y = -0.96x + 7.2 r=-0.8212.08.0lodging (%)10.0 root lodging 6.0 8.0 6.04.0stalk lodging 4.02.0 2.0 0.00.0 1950 1960 1970 1980 1990 2000 1950 1960 1970 1980 1990 2000 Year of release(11 environments , 2007-2009) Ci et al. Euphytica, accepted Chinese Academy of Agricultural Science 28. Summary Earlier maturity, shorter plant stature andmore tolerance to root and stalk lodgingunder high density will be required forfurther yield improvement 29. Plant traits Ear traitsChinese Academy of Agricultural Science 30. 254.6 4.4 20 4.2 y = 0.75x + 16 15 R2 = 0.876cmy = 0.11x + 3.8 4.0 R2 = 0.83 10 3.8 5 3.6 Ear lengthEar diameter 0 3.41950 1960 1970198019902000 1950 1960 1970 19801990 2000 Year of release (11 environments , 2007-2009)Chinese Academy of Agricultural Science 31. 15.5454015y = 0.25x + 1435 R2 = 0.9030 y = 1.3x + 3214.5 R2 = 0.61252014151013.5 Row number per ear5Kernel number per row13 0 1950 1960 19701980 1990 20001950 1960 1970 19801990 2000Year of release(11 environments , 2007-2009)Chinese Academy of Agricultural Science 32. 4035In America Kernel number per ear have noKernel weight (g)30 increase. increased grain yield y = 1.9x + 2425 R2 = 0.88 was contributed to increased20 kernel weight (Duvick 2005).1510 In China kernel weight and kernel number5 hundred kernel weight per plant (larger ear size).0 1950 19601970 19801990 2000 Year of release(11 environments , 2007-2009) Chinese Academy of Agricultural Science 33. 84 83.583 82.582y = 0.19x + 82 R2 = 0.12 81.581 80.580 shelling percentage Percentage barrenness 79.5 (shelling1950 1960 1970 198019902000 percentage) Year of release(11 environments , 2007-2009)Chinese Academy of Agricultural Science 34. Grain yield per plant250200Grain yield per plant (g) grain yield per plant had150y = 23x + 82 R2 = 0.94 improved greatly, but tolerance to high100 densities had not. This is opposite to that in the United States (Tollenaar and50 Lee, 2002; Duvick, 2005) Yield per plant 01950 19601970 1980 19902000 Year of release (11 environments , 2007-2009)Chinese Academy of Agricultural Science 35. Summary Yield gain in China mainly was due toyield improvement per plant. Plant andear traits mentioned also reflected thiscase. Chinese maize yield improvement canbenefit from agronomic strategies athigher densities. 36. N utilization and itsassociation with releaseddecade and stay-greenChinese Academy of Agricultural Sciences 37. 1. N requirement for 100 kg grain production(2010, Beijing)Golden QueenZD2YD13ZD958 (Yuan & Mi et al., unpublished data)Chinese Academy of Agricultural Sciences 38. 2. N concentration of grain in Chinese maize hybrids (2010, Beijing)2010 Beijing Golden Queen Grain N concentration (g/kg) ZD2YD13 R2=0.4049 ZD958 Year of release (Yuan & Mi et al., unpublished data)Chinese Academy of Agricultural Sciences 39. 3. Stay-green degree(2010, Beijing)Yellow-typeMiddle-typeStay-green degree (%)Stay-greenR2=0.464Year of release(Yuan & Mi et al., unpublished data)Chinese Academy of Agricultural Sciences 40. 4. Contribution of leaf N to grain N In Chinese maize hybrids released during the past 60ysThe control(2010, Beijing)Contribution of leaf N to grain N YellowMiddleStay-green R2=0.5954 R2=0.1522(%) R2=0.0587Stay-green (%)(Yuan & Mi et al., unpublished data)Chinese Academy of Agricultural Sciences 41. SummaryNewer hybrids improved in N efficiency,But contribution of leaf N to grain N reducedin newer hybrids because of increased stay-green. 42. Chinese Academy of Agricultural Sciences