Evaluation Of Wheat Germplasms For Acid And Aluminum Tolerance

When soil pH lower than 5.5,it is defined as acidic soil.Red,yellow,and red and yellow soils are naturally formed acid soils.On the other hand,as the environment changes, acid rain(pH below 5.6) highlight the problem to even more seriously,leading to an increased soil acidification area.Aluminum(Al) is one of the most abundant elements on earth.In the acidic pH conditions,combined aluminum can easily change to freely aluminum ions and finally injure to the roots of the crops.However,when corps cultivated on non-acidic soils it is not easily injured by aluminum toxicity.As a result,when crop are cultivated in acid soils,it will face an unavoidable reality that is prone to aluminum toxicity and the growth of frustration and eventually lead to yield loss.Therefore,it is very crucial to improve the crop yields on acid soil.The wheat production in South China has been plagued by this issue.Red and yellow soil are the major soil types for South China tropical and subtropical regions,mainly in the south of the Yangtze River,Yunnan and Guizhou provinces as well as south of Sichuan, Tibet,Hubei,Anhui and Jiangsu provinces.At the same time,China Southern is also against the most serious acid rain areas,including the Yangtze River to the south of the Sichuan Basin,Guizhou,Hunan and Fujian and Guangdong provinces,is second only to North America,Europe and the world's third largest acid rain area.In the southwest of wheat area,complex geography,climate,combined with less sunshine,serious pests and diseases,lead to wheat breeding being difficult task.Attention has never been paid to the wheat genetic studies on Al tolerance in southern China.Thus,in this study,we evaluated the wheat germplasms for Al-tolerance.The main results were as follows:1.In order to compare the differences in acid and aluminum tolerance among Sichuan wheats,three types of nutrient culture solutions,pH7.00 culture solutions(neutral),pH4.50 culture solution(acid) and pH4.50 +50μM/L Al³⁺ culture solutions(aluminum cintained acid),were used to treat 45 Sichuan wheat cultivars,53 landraces,as well as 26 local breeding lines.Higher variations were observed in the root regenerate length(RRL) in each of three groups of Sichuan wheats,and the tendency was similiar in three groups of Sichuan wheats.The mean RRL in the neutral pH7.00 culture solution was the longest, whereas that of the aluminum contained pH4.50 culture solution was the shortest.The RRLs among treatments were significantly different or different from each other except for there was no diffferance in pH7.00 and pH4.50 treatment in local breeding lines.In pH7.00, pH4.50 and aluminum contained pH4.50,the mean RRLs among Sichuan wheat cultivar were 7.93,7.59 and 5.83cm,respectively,and the mean RRLs were 7.26,6.82 and 4.92cm for wheat landraces and were 8.01,7.84 and 5.57cm for local breeding lines,respectively. Higher variations were also observed in acid tolerance index.Among Sichuan wheats,the acid tolerance indexes were higher than 0.80,indicating that Sichuan wheats had the strong capacity of acid tolerance.The acid tolerance index of cultivars varied from 0.82 to 1.29, with an average of 0.96,and 12(26.67%) of them were not less than 1.00.The acid tolerance index of landrances varied from 0.93 to 1.24,with an average of 1.05 and 38 (71.70%) of them were not less than 1.00.The acid tolerance index of breeding lines varied from 0.83 to 1.15,with an average of 0.98 and 12(46.15%) of them were not less than 1.00. There were rich diversities in Al tolerance index for three groups of Sichuan wheats.The Al-tolerant index of cultivars varied from 0.55 to 1.00,with an average of 0.78,and 12 (26.67%) of them showed much better aluminum tolerance than CS,a known tolerance wheat resource.It is interesting that the wheat cultivars register by country show much better aluminum tolerance than the others.The Al-tolerant index of landraces ranged from 0.50 to 1.03,with an average of 0.73,and 9(16.98%) of them showed the same or superior Al-tolerant as CS.The Al-tolerant index of breed lines varied from 0.50 to 0.93,with an average of 0.72,and 5 lines(19.23%) showed the same or much better aluminum tolerance as CS.When compared the RRLs among the three wheat groups,there was no siginificant difference between wheat cultivars and breeding lines in each of the treatments but both significantly higher than that of the corresponding treatment for wheat tandraces.For acid tolerance index,there was siginificant difference between wheat cultivars and breeding lines,but both were smaller than that of wheat landrances.For Al-tolerance index,there were no difference between Sichuan wheat landraces and breeding lines,but both were smaller than that of the wheat cultivars.When compared the acid tolerance index with aluminum tolerance index,the results were the same as acid tolerance index.In this study, some wheat with good aluminum tolerance,such as Chengduguangtou,Shehongqing-gangmai, Chuanmai No.32 and Chuanyu No.16 were screened out,and could be used in the improvement of wheat aluminum tolerance.2.One hounded and fifty-five Tibet wheat landraces were evaluated for acid tolerance and aluminum tolerance using three hydroponic nutrient solutions(i.e.pH7.00 culture solution,pH4.50 culture solution and pH4.50 contained 50μMAl³⁺ culture solution).The RRLs in each of treatment showed rich diversities.The RRLs for treatment pH4.50, pH7.00 and pH4.50 contained solution were different from each other,and were 7.35,7.14 and 4.41 cm,respectively.Tibet wheat had good acid tolerance.The acid tolerance indexes of Tibet wheat varied from 0.87 to 1.25,with an average of 1.03,and the acid tolerance indexes of 92 accessions(59.35%) were higher than 1.00.However,Tibet wheat showed poor aluminum tolerance.The aluminum tolerance indexes of Tibet wheat varied from 0.38 to 1.01,with a mean of 0.61.Only 7 accessions of Tibet wheat(4.51%) had the tolerance index equal to or higher than that of CS.Much better aluminum tolerance was observed in As1543 and As1242.3.For comparison the acid tolerance and aluminum tolerance among six tetraploid wheats,three treatment of pH7.00,pH4.50 and pH4.50 plus 50μM/L Al³⁺ hydroponic nutrient solutions were performed on a total of 254 accessions of Triticum turgidum ssp. dicoccoides,T.turgidum ssp.dicoccon,T.turgidum ssp.turgidum,T.turgidum ssp.durum, T.turgidum ssp.carthlicum and T.turgidum ssp.polinicum.The RRLs,acid tolerance index and aluminum tolerance index showed rich diversities either among or within subspecies.The tetraploid wheats showed good acid tolerance with an average of above 1.00 in terms of acid tolerance index.The order for acid tolerance among six subspecies were T.turgidum ssp.polinicum≥T.turgidum ssp.dicoccon> T.turgidum ssp.carthlicum≥T.turgidum ssp.dicoccoides≥T.turgidum ssp.turgidum≥T.turgidum ssp.durum.The tetraploid wheat species showed poor aluminum tolerance.However,there were great differences in aluminum tolerance among the six tetraploid wheat species.T.turgidum ssp. dicoccoides was the most tolerance specie with an average tolerance,index of 0.70,while T. turgidum ssp.dicoccon was the most sensitive specie with an average tolerance index of 0.40.The order of aluminum tolerance for tetraploid wheats were Triticum turgidum ssp. dicoccoides≥T.turgidum ssp.durum>T.turgidum ssp.turgidum≥T.turgidum ssp. polinicum≥T.turgidum ssp.carthlicum>T,turgidum ssp.dicoccon.Thought tetraploid wheats showed poor aluminum tolerance,some tolerance genotypes could be screened out. In this study,two T.turgidum ssp.carthlicum accessions(i.e.PI341800 and PI94752) with the Al-tolerance superior to Chinese Spring were found.4.Forty-five accessions of Aegilops tauschii were evaluated for aluminum tolerance using three treatments of pH4.50,pH4.50 plus 50μM/L Al³⁺,as well as pH4.50 plus100μM/L Al³⁺ hydroponic nutrient solutions.There were abundant variations in RRLs and Al tolerance index among the Ae.tauschii accessions.The RRLs at pH4.50 were the longest, while those in pH4.50 plus100μM/L Al³⁺ were the shortest.The RRLs at pH4.50 varied from 2.46 to 5.53 cm,with an average of 4.00cm.The RRLs at pH4.50 plus 50μM/L Al³⁺ varied from 0.81 to 1.72cm,with an average of 1.24cm.The RRLs at pH4.50 plus 100μM/L Al³⁺ varied from 0.36 to 1.13cm,with an average of 0.67cm.The aluminum tolerance indexes at pH4.50 plus 50μM/L Al³⁺ varied from 0.18 to 0.49,with an average of 0.33,while those at pH4.50 plus100μM/L Al³⁺ varied from 0.09 to 0.32,with an average of 0.18.When stained with hematoxylin at 50M/LAl³⁺,all of the accesions,except for As65 and As88 stained light as scale 2,were all stained heavy as scale 3,while CS stained much lighter than all of them with scale 1.Combined with hematoxylin staining and aluminum tolerance index,it was suggested that all of the Aegilops tauschii accessions were aluminum sensitive.5.Twenty synthetic wheat lines were evaluated for aluminum tolerance using pH4.50 and pH4.50 plus 50μM/L Al³⁺ hydroponic nutrient solutions.The result indicated that RRLs in each of the treatment showed higher diversity.The RRLs in pH4.50 varied from 1.07 to 5.96cm,with an average of 3.12cm,while those in pH4.50 +50μM/L Al³⁺ varied from 0.39 to 3.46cm,with an average of 1.57cm.The aluminum tolerance index of synthetic wheat varied from 0.32 to 0.79,with an average of 0.48.The aluminum tolerance indexes of 2 synthetic wheat lines were larger than 0.70,while the aluminum tolerance indexes of the remaining lines were below 0.70.These results suggested that the synthetic wheat had poor aluminum tolerance than tolerance common wheat cultivar CS.