Analysis On Improvement Effect Of Combinations With Improved Inbreds Using CIMMYT Maize Germplasm

Introducting exotic germplasm was an effective way to improve hereditary basis of maizegermplasm in China and to enrich hereditary basis of available inbreds. The tropic and subtropicgermplasm from CIMMYT have higher combining ability and heterosis, but they were difficultyutilized in high latitude region such as Heilongjang province because of photoperiod sensibility.They should be improved through making semi-exotic germplasm with local inbeds. The hybridsDongnong250, Dongnong251 and Longdan13 were planted widely in the No.2 and No.3accumulative temperature zone of Heilongjiang Province. In this study the parents of these hybridswere used to making semi-exotic germplasm and some improved inbreds were selected from them.Some combinations of these improved inbreds with the other parents were made and tested in field.Some lines from CIMMYT germplasm Pob101 were crossed with one of the parents above and alsotested in field. The yield and some agronomic traits were compared with original hybrids and therelationship among these traits were studied by correlation and path analysis to guide theimprovement and utility of exotic germplasm especially CIMMYT germplasm in Heilongjiangprovince. The main results were as followed:1.The performance of combinations of improved inbreds selected from semi-exoticgermplasm by introducing CIMMYT germplasm Pob45 to the parent inbreds of hybrids inHeilongjiang province crossed with the other parents were various. The yield of 16.7％combinations of the improved He344's from semi-exotic germplasm accessed with Pob45 andimprovement He344 (the female parent of Dongnong251) crossed with Dongs 112 (the male parentof Dongnong251) were higher than the CK variety Dongnong251. The yield of 33.3％combinations of the improved Ji846's from semi-exotic germplasm introduced Pob45 and K10 (thefemale parent of Lomgdan13) crossed with improved Ji846 (the male parent of Dongnong250)were higher than the CK variety Dongnong250. But the yield of combinations of 444 (the femaleparent of Dongnong250) crossed with the improved Ji846 weren't higher than CK Dongnong250.Agrononmic traits of combinations which parental inbreds came from semi-germplasm introducedPob45 were highly improved. The plant height and ear height of combinations with improved Ji846were lower than CK variety. Tassel ramification numbers, leaf area of whole strain,shellingpercentage, 100-kernal weight had apparently improved effects in partial combinations. The plantheight, ear height, tassel ramification numbers of combinations with improved He344 wassignificantly improved. Therefore, The Pob45 were used to improve yield and correlative traits ofavailable germplsm. 2 The performance of combinations of improved inbreds selected from semi-exoticgermplasm by introducing Pob45 germplasm to the female parent inbreds of Domgnong250 andLongdan13 weren't significant.Only yield of two hybrids using improved inbreds 444×Ji846 wereover CK. Dongnong250. But the yield of combinations of improved inbreds K10 didn't exceed toCK Longdan13. Partial agronomic traits had significant effect, such as 100-kernel weight, shellingpercentage, Kernel per row, Ear length. Pob46 germplasm should be used in different directions inthe future.3 CIMMYT germplasm Pob101 was an early population. The days to poliination, the days tosilking and the maturity of the combinations of inbred lines from Pob101×He344 was 6 days, 7daysand 14 days earlier than the CK Longdanl3 respectively. Pobl01 may be used in early varietybreeding of com.