Evaluation Of Soybean Drought Tolerance And Root Characteristics Of Drought Tolerant Soybean Varieties

To investigate effects of drought stress on morphology,yield and roottraits,twenty-four soybean varieties from Liaoning,Hebei and Shanxi Province were stressed and characterized for drought tolerancein the pot experiment during the flowering and poding periods.Identify of drought tolerance of soybean varieties.Accordingly drought-tolerant and sensitivevarieties were selected to stuty of the relationship between soybeanroot-traits and drought-tolerance,therefore providing theoretical references for breeding and producingsoybeanswhich are tolerant to drought.Results are listed as the followings: 1.morphologicaltraitsSoybean traits including plant-height,stem-weight and branch-number were reduced under drought stresses.These traits invariety Fendou62,Liaodou3,Liaodou21,Jindou31,Liaodou26 and Liaodou54 only decreased slightlyindicating these varietieswere not sensitive to the drought.However,Liaodou37,Liaodou35,Liaodou15,Liaodou32 and Tiedou40 showed significantdecrease and were characterized as drought-sensitive varieties.2.Yield traitsYield of soybean per plant were decreased under the drought stress.Varieties with small yield reduction were Liaodou21,Liaodou54,Jindou31,Liaodou3,Liaodou45,Liaodou31 and Liaodou33.However,signifcant yield decreaseswere observed in Liaodou37,Liaodou35,Liaodou15,Liaodou32 and Tiedou40.3.Evaluation of the soybean drought-toleranceThe strength of drought-tolerance was represented by calculated drought-resistance coefficients and thesubordinate function.Total of seven drought-tolerant varieties were identified,including Liao Dou 21,Liao Dou 3,Jin Dou 31,Liao Dou 33,Liao Dou 54,Liao Dou 45 and Fen Dou 62.Five varieties were not drought tolerant,Liao Dou 37,Liao Dou 35,Liao Dou 15,Liao Dou 32 and Iron Dou 40.4.Relationship between soybeanroot system and drought tolerance.The total root length,root surface area,root volume,root tip number,root dry weight and root crown ratio of different soybean varieties were at their peaksduring the flowering or drum-grain stages.The root indexes of non-drought-tolerant Liaodou 37 and Liaodou 35 reached their maximum at the flowering stage.But the drought-tolerant variety Jindou 31 and Liaodou 45 reached its maximum values at the drum-grain stage.Drought stress reduced root length,root surface area,root volume,root tip number and root dry weight of soybean.The drought-tolerant variety Jindou 31 showed very leastroot reductionunder the drought.It showed better performances in every examined root indexesthan the non-drought-tolerant varieties Liaodou 37 and Liaodou 35 at each growth stage.Drought could increase the root/shoot ratioduringthe soybean flowering and drum-grain stages.The root/shoot ratios of drought-tolerant Jindou 31 and Liaodou 45 were higher than those of non-drought-tolerant Liao Dou37 and Liaodou 35.These result ssuggested that rootcharacteristics ofdrought-tolerant soybean varieties were their well developed root systems.