双列杂交分析简介(续完)

表5设计类型配合力方差分析模式变异原因自由度(df)平方和气55)均方(MS) C ,O / M ︸一 忿 95,.M MM , 序,.八乙555 552gcaSCa机误P一1于p(p一1)ab(e一1)弓c“万CaM‘Ms4机误工P一1于p(p一3)ab(e一1)55‘55555。‘红be亚(a一1)(b一1)55、,-_M‘一‘ be =‘,“,如MM表5续期望均方(EMS)F模型工模型亚I兀Q,+‘p+2,‘击,子g,!al+a士+(p+2)。吞Mg/M一:Q:+~」一一 P(P一1)口名千资“乙az+O若 口名Ms/M。:a忿+(P一2) 1(P一1)O,+a了+(p一2)a委Mg/M。-Mg/Ms g艺.O名+ 2。。—‘二‘二5万.p(P一3)‘(rG名+a毒Ms/M。-Ms/M、。‘O盆…     

多种小麦蛋白质酸性聚丙烯酰胺凝胶电泳方法研究

研究了离子强度、缓冲液 p H、慢离子浓度、凝胶浓度等因素对小麦蛋白质 APAGE分离效果的影响 ,采用 L1 6 ( 41× 2 1 2 )正交试验进行了条件优化 ,所建立的甲酸盐 APAGE方法 ,具有分辩率高、重复性好的特点 ,可通过改变凝胶浓度实现不同蛋白的分离研究。因而此法在小麦蛋白分离、遗传研究、品种鉴定等方面具有广阔的应用前景     

免耕生产中棉花叶面喷施B和K溶液进行土壤缓冲的增产效应

为了评估免耕棉花生产中缓冲叶片 B和 /或 K溶液的作用 ,在粉砂壤土中进行了试验。叶片处理 :(1 )每公顷施用 B 0 .1 1 kg,不缓冲 ;(2 )每公顷施用B0 .1 1 kg,缓冲到 (a) p H6和 (b) p H4;(3)每公顷施用 K4.1 kg,不缓冲 ;(4)每公顷施用 K4.1 kg,缓冲到 (a) p H6和 (b) p H4;(5)每公顷施用 B0 .1 1 kg K4.1 kg;不缓冲 ;(6)每公顷施用 B0 .1 1 kg K4.1 kg;缓冲到 (a ) p H6和 (b) p H4;(7)对照 ,不处理。结果表明 ,叶片 K和 /或 B溶液缓冲到 p H4,第一次收获量和总皮棉产量多于未缓冲的或溶液缓冲到 p H6;B K溶液、K溶液、B溶液缓冲…     

北方设施条件下辣木及改良品种生长差异性分析

北方地区利用温室栽培辣木(Moringa oleifera Lam.)及其2个改良品种‘PKM1’和‘PKM2’,通过分析表观生长量、养分含量以及光合特性等指标的差异性,筛选适宜北方温室种植的辣木品种。结果表明:PKM1的高生长和增粗生长均显著快于辣木和PKM2(p0.05),在定干前(71 d)三者平均株高依次为115.7、80.2、81.0 cm,地径依次达17.47、13.27、15.08 mm。植株养分季节变化,PKM1养分状况要优于辣木和PKM2,在5月份,PKM1叶片中全氮(44.32 mg/g)、全钾(12.73 mg/g)含量显著高于其它2个品种(p0.05),全磷和可溶性糖含量品种间无显著性差异;7月份,PKM1可溶性糖显著高于其它2个品种;光合特性分析,3个品种在弱光条件下的光量子利用效率及光补偿能力差异不显著(p0.05),随着光强增加,光量子的转化能力出现显著性差异,PKM1的最大净光合速率(A_(max))显著高于辣木和PKM2(p0.05),最高达23.84μmol CO_2/(m~2·s)。可见,北方设施条件下,PKM1的生长速度、养分状况、光合能力均表现最好,较适宜北方温室栽培。     

甘蓝型油菜BnPex16p基因cDNA的克隆与表达

利用模式植物拟南芥AtPex16p/sse1基因序列与油菜数据库BBSRC BrassicaDB比对,得到甘蓝型油菜(Brassica napus)同源EST序列,拼接出油菜Pex16p基因全长cDNA电子克隆,然后设计全长引物,以甘蓝型油菜种子cDNA为模板,克隆Pex16p基因,得到全长为1 101bp的cDNA,编码366个氨基酸的蛋白,命名为BnPex16p。BnPex16p基因序列与拟南芥AtPex16p/sse1同源,其蛋白与拟南芥同源蛋白具有完全相同的PTS2型过氧化物酶体定位肽,进化关系相近。半定量PCR(RT-PCR)发现BnPex16p基因在油菜幼嫩的根、茎、叶和种子中均有高丰度表达,在种子发育过程的中期和后期表达水平增加,暗示该基因在油脂的积累中有重要作用。     

不同外形、年份六堡茶品质变化分析

通过对不同外形、年份的六堡茶进行产品质量与主要化学成分的跟踪监测，以期为六堡茶深入研究奠定理论基础。结果表明：不同外形的六堡茶随陈化年份的推移其茶多酚、氨基酸、水浸出物、茶黄素及茶红素等物质呈逐渐下降的趋势；茶褐素随着陈化年份的递增得到积累，呈上升趋势；咖啡碱在陈化过程中呈波动性变化，总体变化不大；品质综合得分随年份增长呈上升趋势。不同外形、年份对六堡茶茶多酚、氨基酸、水浸出物、咖啡碱含量变化有显著(p＜0.05)或极显著性影响(p＜0.01)，外形对茶色素含量及品质变化无显著性影响，年份对茶黄素含量变化有显著性影响(p＜0.05)，对茶红素、茶褐素及最终综合品质评分影响极显著(p＜0.01)。     

连栽桉树人工林土壤有机碳氮储量及其分布特征

采用时空互换法,以广西东门林场不同栽植代数(1、2和3代)桉树人工林和邻近区域马尾松人工林为研究对象,分析桉树人工林连栽过程中土壤有机碳、全氮含量和储量及其分布特征。结果表明:(1)在0~20 cm土层,马尾松和1代、2代、3代桉树人工林有机碳含量分别为17.06、15.70、14.47和13.16 g/kg,土壤全氮含量分别为0.895、0.841、0.778和0.715 g/kg,均呈现随栽植代数的增加而下降的趋势,但在20~40 cm土层,马尾松和各栽植代数桉树林土壤有机碳和全氮含量无显著差异。(2)马尾松、1代、2代和3代桉树人工林0~40 cm土壤有机碳储量分别为66.84、56.57、52.97和50.81 t/hm~2,土壤全氮储量分别为3.78、3.33、3.09和2.98 t/hm~2,其中马尾松林和2、3代桉树林有机碳和全氮储量之间存在显著性差异(p0.05)。(3)相关分析表明,马尾松和不同栽植代数桉树人工林土壤有机碳含量与全氮含量均存在极显著相关性(p0.01),土壤有机碳、全氮与C/N之间也存在显著的相关关系(p0.05)。     

刚果12号桉叶片化感物质的初步分离分析

对刚果12号桉鲜叶中的化感物质采用水蒸气蒸馏和超临界二氧化碳萃取2种方法进行提取分离，并运用GC／MS分析技术对提取物进行分析鉴定。2种方法共分离鉴定出119个化学组分，其中20个组分完全相同，其它的完全不同，主要成分有α—桉叶油醇(α-eudesmol)、β—桉叶油醇(β—eudesm01)、对伞花烃(p—cymene)、香树烯(aromadendrene)、水芹烯(phellandrene)、4-萜品醇(4-terpineol)、苍术醇(hinesol)、反式石竹烯(trans—caryophellene)等。其中桉叶油醇类的含量在这2种提取方法中分别占了34．36％和31．40％。因此，桉叶油醇在刚果12号桉的化感作用中可能处于举足轻重的地位。是否如此有待今后进一步的研究。     

怒江峡谷地区草果经济产量与品质对环境因子和栽培措施的响应

采用测产、气象色谱-质谱联用(GC-MS)和参与性农村快速评估(PRA,Participatory Rural Appraisal)研究了怒江峡谷地区草果经济产量和品质对环境因子和栽培措施的响应以及种植草果对当地少数民族经济、生态的影响。结果表明:江西草果经济产量(3 167.10±436.09 kg/hm2)极显著高于江东(413.16±210.46 kg/hm2)(p0.01),品质差异不显著;山凹草果经济产量(7 499.40±324.52 kg/hm2)显著高于山脊(5 350.40±1 248.06 kg/hm2)(p0.05),山凹草果桉树脑含量(19.956 mg/g)显著高于山脊(1.5 mg/g)(p0.05);不同混农林模式的草果经济产量由高到低依次为天然林+草果(F+A)人工林+草果(A+A)玉米+草果(M+A)(p0.05),产量分别为5 678.6±690.97 kg/hm2、3 547.4±78.01 kg/hm2、135.12±46.18 kg/hm2,玉米+草果混农林模式下草果桉树脑含量(3.333 mg/g)显著高于其余模式(p0.05);6年生草果经济产量(5 678.6±690.97 kg/hm2)显著高于7年生草果的经济产量(2 869.10±208.10 kg/hm2)(p0.05),7年生草果精油出油率和桉树脑含量略高于6年生草果,但差异不显著(p0.05);管理强度强(1 756.60±474.89 kg/hm2)的草果经济产量高于管理一般(413.16±210.46 kg/hm2)的草果,但差异不显著,品质差异也不显著。从2007年种植草果至2013年马吉乡粮食播种面积下降了28.70%,人均收入增加了248.04%,家庭年收入(r=0.793**)和年支出(r=0.535**)与草果种植面积呈正相关。     

番木瓜环斑病毒弱毒株的构建及分析

弱毒株是利用交叉保护防治植物病毒病害的关键限制因子。通过对马铃薯Y病毒属病毒(强、弱毒株)的全长及部分氨基酸序列比对分析,筛选出在亲本强毒株PRSV-LM的P1和HC-Pro基因上的8个可能与致病性相关的氨基酸突变位点(I_(309)、K_(481)、K_(598)、R_(728)、F_(753)、L_(754)、N_(787)和D_(944))。采用定点突变和Gibson拼接法,分别成功构建了4种含有2个突变位点(L_(754)和N_(787))、4个突变位点(I_(309)、K_(481)、F_(753)和D_(944))、6个突变位点(I_(309)、K_(481)、F_(753)、L_(754)、N_(787)和D_(944))和8个突变位点(I_(309)、K_(481)、K_(598)、R_(728)、F_(753)、L_(754)、N_(787)和D_(944))的PRSV-LM全长c DNA侵染性克隆突变体:p Gprsvm~2、p Gprsvm4、p Gprsvm6和p Gprsvm8。经人工接种、病症观察和RT-PCR检测,4种突变体克隆均能系统性侵染非转基因番木瓜植株,除克隆p Gprsvm~2的病症表现与亲本强毒株PRSV-LM一致外,其他多位点突变的克隆p Gprsvm4、p Gprsvm6和p Gprsvm8在番木瓜植株上的病症严重程度出现依次减弱,而克隆p Gprsvm8的病症最弱,且延迟2周发病。本实验初步验证了6个氨基酸突变位点(I_(309)→S、K_(481)→Q、K_(598)→E、F_(753)→L、R_(728)→I和D_(944)→N)与PRSV-LM的病症表现及致病力相关,其中K_(598)→E和R_(728)→I可能是影响致病性的关键位点。     

Evaluation the effects of dextromethorphan and midazolam on morphine induced tolerance and dependence in mice

The main aim of this study was to evaluate the effects of dextromethorphan and midazolam and their combination on morphine tolerance and dependence in mice. In the present study, different groups of mice were rendered randomly and received morphine (50 mg kg(-1), s.c.), morphine (50 mg kg(-1), s.c.) + Dextromethorphan (25, 50 and 75 mg kg(-1), i.p.), morphine (50 mg kg(-1), s.c.) + midazolam (0.5, 1 and 2 mg kg(-1), i.p.), morphine (50 mg kg(-1), s.c.) + [Dextromethorphan (25 mg kg(-1), i.p. ) + midazolam (0.5 mg kg(-1), i.p.)] once a day for four days. Tolerance was assessed by administration of morphine (9 mg kg(-1), i.p.) on fifth day. Withdrawal symptoms (markers for dependence) was assessed by administration of naloxone (4 mg kg(-1), i.p.) 2 h after co-administration of morphine with either Dextromethorphan or midazolam or their combination. Results showed that pretreatment with Dextromethorphan or midazolam decreased the degree of tolerance and withdrawal symptoms significantly. Additionally co-administration ofDextromethorphan and midazolam couldn't decreased the tolerance and dependence significantly. From these results it may concluded that Dextromethorphan and midazolam alone or in combination could prevent the development of morphine induced tolerance and dependence. These effects can be related to the N-Methyl-D-Aspartate (NMDA) receptor antagonist behavior of Dextromethorphan and GABA-receptor agonist property of midazolam.     

18个优质小麦品种(系)Glu-1、Glu-3和Gli-1位点的基因变异特点

为给小麦品质育种提供参考信息,选用我国18份有影响的优质面条和面包小麦品种或种质资源，通过分步法SDS-PAGE和改良A-PAGE分析了其Glu-1、Glu-3、Gli-1位点的基因变异特点。结果表明，由Glu-1住点控制的高分子量谷蛋白亚基共14种图谱，其中，Glu-A1位点上优质亚基1和2^＊分别占61．1％和11．1％，Glu—B1位点上优质亚基14＋15、7＋8、17＋18、13＋16分别占27．8％、27．8％、22．2％、5．6％．Glu_D1位点上优质亚基5＋10占55．6％。Glu—A1、Glu—B1、Glu-D1位点上均为优质亚基的品种（系）有陕451（1，7＋8，5＋10）、95鉴5104（1,14＋15，5＋10）、陕优412（2^＊，7＋8，5＋10）、绵阳89-47（2^＊，13＋16，5＋10）以及中优16、冀5099、绵优1号、绵优2号（1，17＋18,5＋10），占参试品种的44．4％。由Glu-3位点控制的低分子量谷蛋白亚基共12种图谱，小偃6号、PH82-2、陕253、80356、95鉴5104、郑农33等6个品种皆为“a，d，c”；由G1i-1位点控制的醇溶蛋白共12种图谱，小偃6号、PH82-2、陕优225、陕253、80356、中优16、95鉴5104等7个品种皆为“O，new，i”，即发现在Gli-B1位点是一个新等位基因。     

Effect of adding ketamine to pethidine on postoperative pain in patients undergoing major abdominal operations: a double blind randomized controlled trial

To determine the effect of adding ketamine to pethidine in reducing post-operative pain in patients undergoing major abdominal operations, in a double blind randomized controlled trial, 100 patients aged 15-60 years who were candidate for elective major abdominal surgery allocated into two groups of pethidine + ketamine group (5 mg pethidine and 0.25 mg kg(-1) ketamine) or pethidine and placebo group (10 mg pethidine and NS) according to the regimen prescribed in postanesthesia care unit. Severity of pain (using visual analogue scale), prescribed dose of pethidine and side effects were recorded until 24 h after operation. Regarding post-operative pain, pethidine + ketamine group showed significant lower scores in all the times except 0 min, 2, 6 and 16 h. Nausea was significantly less frequent amongst pethidine + placebo group at times of 0, 15, 30 and 45 min (p < 0.05). Comparison of two groups did not show significant differences in prescribed pethedine dose in 0, 9, 12, 16, 20 and 24 h (p > 0.05). Yet, the mean dose of administered pethidine as rescue analgesic was significant lower in pethidine + ketamine group compared to pethidine + placebo group (112 +/- 31.5 mg vs. 133.5 +/- 24.5 mg, p < 0.001). In conclusion, our results showed that co-administration of ketamine and pethidine in postanesthesia care unit will improve postoperative pain and reduce narcotic consumption. It may, however, increase rate of postoperative nausea in the first hour after operation.     

Association Study of rs1333040 and rs1004638 Polymorphisms in the 9p21 Locus with Coronary Artery Disease in Southwest of Iran

Background:

Coronary artery disease (CAD) is a multifactorial and heterogenic disease. Recently, genome-wide association studies have reported that rs1333040 (C/T) and rs1004638 (A/T) single nucleotide polymorphisms (SNPs) in the 9p21 locus have very strong association with CAD. This study aimed to examine these associations in Southwest of Iran.

Methods:

Blood samples were collected from 200 CAD patients and 110 healthy individuals with no CAD. The association of two SNPs with CAD was evaluated by PCR and restriction fragment length polymorphism.

Results:

Chi-square test showed no association between rs1333040 SNP and CAD (X²: 4.66, df: 2, P=0.09). Also, there was no association between rs1004638 SNP and CAD (X²: 0.27, df: 2, P=0.88).

Conclusion:

No association was observed between rs1333040 and rs1004638 SNPs in the 9P21 region and CAD in Southwest of Iran. Key Words: Coronary artery disease, Single nucleotide polymorphisms, Genetic association study, Iran     

Sulfated-polysaccharide fraction from red algae Gracilaria caudata protects mice gut against ethanol-induced damage

The aim of the present study was to investigate the gastroprotective activity of a sulfated-polysaccharide (PLS) fraction extracted from the marine red algae Gracilaria caudata and the mechanism underlying the gastroprotective activity. Male Swiss mice were treated with PLS (3, 10, 30 and 90 mg·kg(-1), p.o.), and after 30 min, they were administered 50% ethanol (0.5 mL/25 g(-1), p.o.). One hour later, gastric damage was measured using a planimeter. Samples of the stomach tissue were also obtained for histopathological assessment and for assays of glutathione (GSH) and malondialdehyde (MDA). Other groups were pretreated with l-NAME (10 mg·kg(-1), i.p.), dl-propargylglycine (PAG, 50 mg·kg(-1), p.o.) or glibenclamide (5 mg·kg(-1), i.p.). After 1 h, PLS (30 mg·kg(-1), p.o.) was administered. After 30 min, ethanol 50% was administered (0.5 mL/25 g(-1), p.o.), followed by sacrifice after 60 min. PLS prevented-ethanol-induced macroscopic and microscopic gastric injury in a dose-dependent manner. However, treatment with l-NAME or glibenclamide reversed this gastroprotective effect. Administration of propargylglycine did not influence the effect of PLS. Our results suggest that PLS has a protective effect against ethanol-induced gastric damage in mice via activation of the NO/K(ATP) pathway.     

生根剂处理对于茶树嫩枝扦插内源激素水平和繁殖的影响

为进一步探究茶树不同嫩度的嫩枝插穗根系和地上部生长适宜的生根剂处理时间及内源激素水平,本试验以3年生台茶12号嫩枝为试验材料,采用酶联免疫吸附测定法（ELISA）分析了嫩梢不同部位IAA、ZR、GA₃和ABA含量,同时研究了生根剂处理时间对插穗茎基部激素含量和茶苗扦插快繁的影响。结果表明,在茶树嫩枝顶部一芽一叶至一芽二叶初展梢（BL1）、半功能叶（L2）、第1片功能叶（L3）及其茎段（S1）、第2片功能叶（L4）及其茎段（S2）、第3片功能叶（L5）及其茎段（S3）、第4片功能叶茎段（S4）中,叶片内IAA和ABA以第2片功能叶含量最高,ZR以第3片功能叶含量最高,GA₃含量则随叶片成熟度增加而增大。茎段S1—S3中IAA含量显著高于S4,而ABA含量则为S1显著高于S2—S4。浸泡100βmg·L^-1 ABT-1号生根剂会显著提高插穗茎基部IAA含量,并使IAA/ABA和(IAA+ZR+GA₃)/ABA值增至1.0左右,从而有利于生根。其中,保留顶梢带1片和2片功能叶的插穗（F1-1、F2-1）在浸泡生根剂前期1βh内IAA含量快速增加,且IAA/ABA和(IAA+ZR+GA₃)/ABA值可增至1.0以上,其他插穗则在浸泡生根剂4βh后上述3个指标达到最大值。F1-1、F2-1浸泡生根剂0.5~1βh,摘除顶梢带1片功能叶的插穗（F1-2）浸泡生根剂4βh,F2-2、F3-1、F3-2浸泡生根剂3~4βh,IAA含量达到较高水平,而且IAA/ABA和 (IAA+ZR+GA₃) /ABA值可增至1.0左右。出苗时,平均根系活力、平均生根条数和平均茎粗增加值的最大值出现在浸泡生根剂0~2βh内,其他根系和地上部生长情况以浸泡生根剂4βh表现较好。     

大麦开颖性状的遗传分析Ⅰ.大麦开颖性状的遗传效应和遗传模型

为了研究大麦开颖性状的遗传规律，以5个开颖品种（系）（黄长芒大麦、沪1154、1430R、99-7122、扬0187）和1个闭颖品种（91单2）为亲本，采用6^2完全双列设计，配制杂种F1．开花期利用图象处理软件Adobe photoshop测量亲本及杂种F1的开颖角度，并对所测的数据进行方差分析．同时计算公共亲本的系列方差Vr和系列协方差Wr，以测验开颖性状的遗传模型．推断其显（隐）性基因频率分布特点。结果表明：（1）亲本间和杂种间的F值分别为237．71^＊＊和162．48^＊＊，表明开颖角度在亲本间和杂种间的差异均这到极显著水平；（2）Wr依Vr的回归方程为Wr=4，5128＋0．8968Vr，r=0＋9339^＊＊，回归系数与0的差异（t=5．23^＊＊，df=4）达到极显著水平，与1的差异（t=-0．60，df=4）不显著，即开颖性状的遗传符合加性-显性模型;回归截距与0的差异（t=0．86，df=4）也不显著，即开颖性状的遗传属完全显性类型；加性、显性和环境方差的估计数依次为45．922、20．321和1．210，说明加性遗传方差比非加性遗传方差更重要；开颖显性方向和程度随亲本和组合而有所不同，平均而言．开颖性状是减效基因表现为显性，即闭颖对开颖表现为显性；（3）15对正反交杂种F1中有3对的开颖角度存在正反交差异，表明大麦开颖性状有时还受到细胞质基因的影响。     

Improvement of Tissue Survival of Skin Flaps by 5α-Reductase Inhibitors: Possible Involvement of Nitric Oxide and Inducible Nitric Oxide Synthase

Background:

Skin flap grafting is a popular approach for reconstruction of critical skin and underlying soft tissue injuries. In a previous study, we demonstrated the beneficial effects of two 5α-reductase inhibitors, azelaic acid and finasteride, on tissue survival in a rat model of skin flap grafting. In the current study, we investigated the involvement of nitric oxide and inducible nitric oxide synthase (iNOS) in graft survival mediated by these agents.

Methods:

A number of 42 male rats were randomly allocated into six groups: 1, normal saline topical application; 2, azelaic acid (100 mg/flap); 3, finasteride (1 mg/flap); 4, injection of L-N^G-nitroarginine methyl ester (L-NAME) (i.p., 20 mg/kg); 5, L-NAME (20 mg/kg, i.p.) + azelaic acid (100 mg/flap, topical); 6, L-NAME (20 mg/kg, i.p.) + finasteride (1 mg/flap, topical). Tissue survival, level of nitric oxide, and iNOS expression in groups were measured.

Results:

Our data revealed that azelaic acid and finasteride significantly increased the expression of iNOS protein and nitric oxide (NO) levels in graft tissue (P < 0.05). These increases in iNOS expression and NO level were associated with higher survival of the graft tissue.

Conclusion:

It appears that alterations of the NO metabolism are implicated in the azelaic acid- and finasteride-mediated survival of the skin flaps.Key Words: Finasteride, Azelaic acid, Surgical flaps, Nitric oxide, Nitric oxide synthase Type II     

Sinularones A-I, new cyclopentenone and butenolide derivatives from a marine soft coral Sinularia sp. and their antifouling activity

Nine new compounds, namely sinularones A-I (1-9), characterized as cyclopentenone and butenolide-type analogues, were isolated from a soft coral Sinularia sp., together with a known butenolide (10). Their structures were elucidated by means of spectroscopic (IR, MS, 1D and 2D NMR, CD) analysis. The absolute configurations were determined on the basis of CD and specific rotation data in association with the computed electronic circular dichroism (ECD) by time dependent density functional theory (TD DFT) at 6-31+G(d,p)//DFT B3LYP/6-31+G(d,p) level. Compounds 1-2 and 7-10 showed potent antifouling activities against the barnacle Balanus amphitrite.     

Genetic and physiological analysis of tolerance to acute iron toxicity in rice

Background

Fe toxicity occurs in lowland rice production due to excess ferrous iron (Fe²⁺) formation in reduced soils. To contribute to the breeding for tolerance to Fe toxicity in rice, we determined quantitative trait loci (QTL) by screening two different bi-parental mapping populations under iron pulse stresses (1,000 mg L⁻¹ = 17.9 mM Fe²⁺ for 5 days) in hydroponic solution, followed by experiments with selected lines to determine whether QTLs were associated with iron exclusion (i.e. root based mechanisms), or iron inclusion (i.e. shoot-based mechanisms).

Results

In an IR29/Pokkali F₈ recombinant inbred population, 7 QTLs were detected for leaf bronzing score on chromosome 1, 2, 4, 7 and 12, respectively, individually explaining 9.2-18.7% of the phenotypic variation. Two tolerant recombinant inbred lines carrying putative QTLs were selected for further experiments. Based on Fe uptake into the shoot, the dominant tolerance mechanism of the tolerant line FL510 was determined to be exclusion with its root architecture being conducive to air transport and thus the ability to oxidize Fe²⁺ in rhizosphere. In line FL483, the iron tolerance was related mainly to shoot-based mechanisms (tolerant inclusion mechanism). In a Nipponbare/Kasalath/Nipponbare backcross inbred population, 3 QTLs were mapped on chromosomes 1, 3 and 8, respectively. These QTLs explained 11.6-18.6% of the total phenotypic variation. The effect of QTLs on chromosome 1 and 3 were confirmed by using chromosome segment substitution lines (SL), carrying Kasalath introgressions in the genetic background on Nipponbare. The Fe uptake in shoots of substitution lines suggests that the effect of the QTL on chromosome 1 was associated with shoot tolerance while the QTL on chromosome 3 was associated with iron exclusion.

Conclusion

Tolerance of certain genotypes were classified into shoot- and root- based mechanisms. Comparing our findings with previously reported QTLs for iron toxicity tolerance, we identified co-localization for some QTLs in both pluse and chronic stresses, especially on chromosome 1.