Combining Ability And Correlation Of Kernel Dry-down And Grain Filling Rate In Maize

It will be a effective way to increase yield and quality of maize by selecting and planting inbreds with fast dry-down and high grain filling rate in the northeast spring maize growing area in China . Past study mainly emphasized on grain filling rate and other physiological characters shows that inbred lines with fast dry-down and high grain filling rate have important effect in maize breeding. Nine inbred lines were used to mating crosses by Griffing's design 2 ,the combining ability of grain filling and dry-down rate, the correlation with yield were analysed. The potential value of these inbred lines and hybrids were estimated and the breeding design are discussed. The main results are dicussed in the following:1. The significant differences of combining ability of grain filling and dry down rate for kernel, ear stalk and ear husk were observed among inbred lines in the four stages of grain filling. There were also have significant differences in the same inbred line and hybrid among the four stages of grain filling.2 The combining ability of grain filling rate: in inbred HR705 was lower in all of the four stages. The elite combination for inbred HR705 appeared in the cross with inbred MO17. Inbred MO17 had lower combining ability at the stageⅠand stageⅡ, but having higher combining ability at the stageⅢand stageⅣ. The better combinations of it appeared in crosses with inbred HR705 and Huangzaosi. The combining ability of inbred HR11 was higher in the first 3 stages and lower in the last stage. The better combinations of it emergence in the crosses with inbred HR304 and K10. Inbred Huangzaosi had higher combining ability in all of the four stages. The better combinations of it were those crossed with inbred MO17 and HR112. Inbred HR304 had higher combining ability in the first 2 stages and lower combining ability in the later stages. The better combinations of it were crosses with inbred MO17 and i HR11. The combining ability of inbred Dan340 was lower at the stage I and higher at other stages. The better combinations of it were those crossed with inbred MO17, Huangzaosi and HR304. The combining ability of inbred HR112 was higher in all of the four stages. The better combinations of it were those crossed with inbred Huangzaosi and Dan340. The combining ability of inbred K10 was lower at the stageⅠand stageⅡ, higher at the stageⅢand stageⅣ. The better combination of it was the crosse with inbred HR11. Inbred HR106 had lower combining ability in all of the four stages. The better combinations of it were crosses with inbred HR304 and K10. The special combining ability of filling rate were higher in the lines with higher general combining ability of filling rate. There were also many hybrids with higher special combining ability but the general combining ability of their parents were lower. We should pay much attention to special combining ability in the breeding.3. The combining ability of dry down rate: dry down rate of kernel, ear cob and husk were measured. The combining ability values of inbred line HR705 , HR304 and HR112 were lower and negative in all of these characters. The combining ability of inbred line 2, HR11, Huangzaosi and HR106 were higher and positive in all of these characters. The combining ability effects of inbred line Dan340 and K10 were negative in some characters and positive in the others. The special combining ability had more differences.in 9 inbreds. The physiological and natural dry down rate were highest in the hybrid HR112XHR106. The dry down rate of husk was highest in the hybrid Huangzaosi×HR106. 4. Correlation and path analyze: it showed that grain-filling rate, dry-down rate had high correlation with main agronomy traits. Grain filling rate had positive correlation with plant yield. The correlative coefficients was higher at stageⅢthan that at stageⅡand stageⅠ. Grain filling rate was positive correlated with yield of per plant, kernels on each ear, kernels per row, ear length, 100-grain weight, volume weight, ear diameter and rows in each ear in sequence. Plant yield had positive direct path coefficient to kernels per ear, grain filling rate at stageⅢ, days to silk, grain filling rate at stage I, 100-grain weight, grain filling rate at stageⅡ, durable time of grain filling in sequence. Kernel natural dry-down rate were positively correlative with ear stalk dry-down rate, husk dry-down rate and water content of husk at harvest and significant negative correlation with the ear traits. Husk dry down rate had the biggest positive path coefficient to water contain of ear husk at harvest and 100 grain weights had the biggest negative value to naturally dry down rate.5. The breeding materials with high grain filling rate should have high grain filling rate in the first three stages, especially in stageⅡand stageⅢ. They should also have bigger size of kernel and large kernel number in each ear. The husk selection was the key in all of the ear traits Inbred lines and hybrids with husk in proper length, narrow width, small area and less layers should be selected.