Study On Genetic Improvement Effect Of Density Tolerance And Lodging Resistance Of Maize Reid Germplasm

Corn,as the most important grain crop,its yield directly affects the development of China’s agricultural economy and food security.Cultivating and promoting dwarf and dense varieties and increasing planting density are effective agronomic measures to increase corn yield.However,increasing density also brings the risk of higher lodging rate,which leads to decreased yield and quality of corn.In this study,Reid improved series J567,J1428,J1033,J1072,J1598,and SY125 were used as female parents.Non-Reid backbone series J1865,J1838,J1144,J1174,and J1185 were used as male parents for hybridization and combination.Under the density of60,000 plants/hm^2,75,000 plants/hm²and 90,000 plants/hm²,the net photosynthetic rate of ear leaf,leaf area of top three leaves,lodging resistance and major agronomic traits of 30combinations were studied.The results are as follows:（1）The results of ear leaf photosynthetic characteristics showed that the net photosynthetic rate of ear leaf decreased with the increase of density and growth process after silking in all combinations.Comprehensively under three densities,the combination H25 had the highest net photosynthetic rate of ear leaf,and the combination H16 had the lowest decrease（43.83%）of net photosynthetic rate of ear leaf.（2）The results of top three leaf area showed that from silking to maturity stage,the leaf area increased first and then decreased with the increase of planting density,and reached the highest at 75000 plants/hm².The combination H23 had the largest increase（18.41%）of top three leaf area under 60,000 plants/hm².The combination H15 had the largest increase（27.93%）under75,000 plants/hm².The combination H16 had the largest increase（20.46%）under 90,000plants/hm².（3）The results of lodging resistance showed that the stem tensile strength of combination H15（SY125/J1838）performed well under 60,000-90,000 plants/hm².The stem crushing strength of the 2nd,3rd and 5th internodes of combination H11（J567/J1865）performed well under 90,000 plants/hm².The stem puncture strength of the 2nd,3rd and 5th internodes of combination H30（J1428/J1185）performed well under 90,000 plants/hm².The stem diameter of combination H3（SY125/J1144）performed well under 90,000 plants/hm².Combination H5（J567/J1144）had the smallest ear height coefficient under 90,000 plants/hm²,showing the best performance.It shows that Reid improved series J1428,J567 and SY125 are easy to develop combinations with higher yield.（4）The results of hybrid vigor showed that under three densities,the combination H25（J1598/J1185）had the highest hybrid vigor of grain yield per plant and kernel number per row.The combination H7（J1598/J1865）had the highest hybrid vigor of 100-kernel weight.The combination H19（J1598/J1174）had the highest hybrid vigor of row number,indicating that Reid improved series J1598 is easy to develop combinations with higher yield.（5）The results of general combining ability showed that under three densities,Reid improved series J1598 had higher positive general combining ability of 100-kernel weight,ear weight and grain yield per plant.Improved series SY125 and J1428 had higher effect values of general combining ability of stem tensile strength,puncture strength and stem crushing strength.The results of specific combining ability showed that under three densities,the combination H19 had the highest effect value of specific combining ability of grain yield per plant.The combination H6（J1428/J1144）had the highest effect value of specific combining ability of100-kernel weight.The combination H10 had the highest effect value of specific combining ability of kernel number per row.The combination H15 had the highest effect value of specific combining ability of stem tensile strength.The combination H13 had the highest effect value of specific combining ability of stem crushing strength.The combination H20 had the highest effect value of specific combining ability of stem puncture strength.（6）The comprehensive results showed:The combinations composed of Reid improved series J1598 had the best performance in hybrid vigor of grain yield per plant and combining ability of yield-related traits such as 100-kernel weight and ear weight,showing application potential.The combinations composed of Reid improved series J1428,J567 and SY125 had the best performance in combining ability of lodging resistance-related traits,showing potential in breeding for lodging resistance.