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1.
转2-Cys Prx基因烟草抗氧化酶和PSII电子传递对盐和光胁迫的响应 总被引：5，自引：0，他引：5
以转2-Cys Peroxiredoxins (2-Cys Prx)基因的烟草(Nicotiana tabacum)为材料,非转基因烟草为对照,调查盐和光胁迫对转基因烟草幼苗叶片抗氧化酶和叶绿素荧光特性的影响,揭示2-Cys Prx基因在植物抗逆方面的功能。结果表明,弱光(200 μmol m–2 s–1)下,随着盐浓度增大,转基因烟草和对照的SOD活性皆增加,APX活性变化不大,H2O2含量稍有升高;强光(1000 μmol m–2 s–1)下,随着盐浓度增大,转基因烟草SOD活性增强,APX活性下降,H2O2含量增加缓慢,而对照的H2O2含量迅速升高,转基因烟草叶片的PSII电子传递速率(ETR)、最大光化学效率(Fv/Fm)和实际光化学效率(ФPSII)均高于对照,而且PSII电子受体侧的受抑制程度明显低于对照。结果暗示在强光和盐胁迫使APX活性降低的情况下,2-Cys Prx可有效清除细胞中过量H2O2,增强光合电子传递链的稳定性,特别是PSII电子受体侧的电子传递,有效减轻盐和高光胁迫引起的PSII光抑制。 相似文献
2.
水稻生育后期叶片早衰突变体的光合特性与叶绿体超微结构观察 总被引：2，自引：0，他引：2
以旗叶早衰的水稻突变体(psf)与其野生型对照(浙恢7954)为材料,对两者在水稻抽穗开花后旗叶衰老过程中的光合速率、叶绿素荧光和叶绿体超微结构比较分析表明,旗叶早衰突变后的每穗实粒数、结实率、千粒重和单株产量均不同程度降低,以对每穗实粒数和结实率的影响程度最明显; 在水稻灌浆期间,psf旗叶的叶绿素含量、叶绿素a/b值、净光合速率(Pn)、PSII潜在活性(Fv/Fo)和最大光化学效率(Fv/Fm)均比其野生型对照明显降低,且随着抽穗开花后天数的推移,供试材料间的差异幅度呈逐渐拉大趋势; psf叶肉细胞中的叶绿体排列、形态大小及其类囊体结构在水稻抽穗开花期基本正常,但随着叶片衰老过程的推进,psf叶肉细胞中的叶绿体相继会出现沿细胞壁周缘化、外部形态缩皱变形、嗜锇颗粒增多变大、类囊体膜系统退化、片层结构完全解体等变化。其中,叶绿体沿叶肉细胞壁排列的周缘化与外形结构的球状化表现,与叶绿体类囊体膜系统损伤和开始降解之前的净光合速率(Pn)下降有关,而由类囊体膜系统受损所带来的Fv/Fm和Fv/Fo下降过程,则相对滞后于Pn和叶绿素含量下降的起始时间。 相似文献
3.
水分胁迫下外源ABA提高甘蔗抗旱性的作用机制 总被引：14，自引：0，他引：14
以抗旱甘蔗品种ROC22为材料,调查水分胁迫及胁迫加喷施脱落酸(ABA)对甘蔗内源ABA合成及相关生理生化作用的影响。结果表明,干旱及干旱加外施ABA的条件下,甘蔗内源ABA合成水平上升,但干旱加ABA处理增幅更显著,甘蔗叶内的脯氨酸(Pro)、H2O2、丙二醛(MDA)含量增加,而ABA处理能缓解MDA的积累,使其含量处于低水平,ABA处理能防止叶绿素降解并对干旱引起的最大光能转化效率(Fv/Fm)、PSII实际量子效率(ΦPSII)下降有明显的缓解作用。干旱条件下,H2O2的积累伴随着抗氧化作用的酶CAT、GPX、GR和APX的活性提高,而ABA处理能进一步提高这些相关酶的活性而逐渐降低H2O2的含量,表明干旱条件下,外施ABA能增强甘蔗的抗氧化防护系统,提高抗旱性。 相似文献
4.
吐丝期干旱胁迫对玉米生理特性和物质生产的影响 总被引：10，自引：0，他引：10
以玉米品种郑单958 (抗旱性强)和陕单902 (抗旱性弱)为材料,采用抗旱池栽控水试验,研究了叶片光合特性、保护酶活性以及干物质转运对吐丝期干旱胁迫的响应。结果表明,在吐丝期干旱胁迫下2个品种产量分别降低39.10%和44.87%;叶片净光合速率(Pn)和气孔导度(Gs)显著下降,胞间CO2浓度(Ci)先升后降。PSII最大光化学效率(Fv/Fm)、实际量子产额(ΦPSII)、光化学猝灭(qP)降低,非光化学猝灭(qN)升高;抗氧化酶(SOD、POD和CAT)活性先升高后降低,而丙二醛(MDA)含量一直升高。说明吐丝期干旱胁迫增加了花前营养器官贮藏同化物转运量(率)及其对籽粒转运的贡献率;但郑单958受干旱影响程度小于陕单902。说明抗旱品种郑单958具高抗氧化酶活性清除活性氧,使得膜脂过氧化程度轻,维持较高的光化学效率,延长叶片光合功能期,促进花前营养器官贮藏同化物转运量对籽粒的贡献率。这可能是其在干旱胁迫下仍能获得较高产量的重要原因之一。 相似文献
5.
施钾对不同转基因棉花品种光合特性及产量和品质的影响 总被引：3，自引：1，他引：2
在田间试验条件下,研究了施钾对转Bt+CpTI基因抗虫棉中棉所41、转Bt基因抗虫棉国抗1号和常规棉泗棉3号光合特性和产量及品质的影响。结果表明,施用钾肥能不同程度地提高不同转基因棉花品种的叶绿素含量、叶面积指数(LAI)、叶片净光合速率(Pn)、气孔导度(Gs)、叶绿素荧光动力学参数PSⅡ、最大光化学量子效率(Fv/Fm)、PSⅡ潜在光化学活性(Fv/Fo),从而提高棉花叶片的光合性能。施钾还提高了转基因棉花干物质量及分配到生殖器官的比例,增加了棉花总成铃数、铃重和衣分;施钾处理的中棉所41、国抗1号和泗棉3号的皮棉产量较未施钾处理分别增加5.8%,11.8%和7.0%,棉纤维的主要品质指标也得到改善。转Bt基因抗虫棉国抗1号比转Bt+CpTI基因抗虫棉中棉所41和泗棉3号对钾肥更为敏感。 相似文献
6.
低温胁迫下聚糖萘合剂对玉米幼苗光合作用和抗氧化酶活性的影响 总被引：7，自引：0，他引：7
采用盆栽试验, 以郑单958和丰单3号为材料, 研究了低温胁迫对玉米幼苗光合作用、叶绿素、叶绿素荧光参数和抗氧化酶活性的影响, 以及聚糠萘合剂(PKN)的调控效果。结果表明, 低温胁迫下, 玉米幼苗的光合作用和光系统II光化学最大效率受到抑制; 超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性降低; 过氧化氢、超氧阴离子的产生速率及丙二醛(MDA)含量显著升高。PKN处理提高了低温胁迫下玉米幼苗净光合速率(Pn)、气孔导度(Gs)、光系统II光化学的最大效率(Fv/Fm)、叶绿素含量(Chl a+Chl b)。低温处理7 d, ZDTR和FDTR的Pn、Gs、Fv/Fm、Chl a+Chl b分别比各自的对照提高了88.95%和61.11%、593.33%和1 741.67%、111.50%和145.16%、36.61%和54.03%; PKN处理延缓了SOD、POD、CAT活性的降低, 低温胁迫7 d, PKN处理使郑单958和丰单3的SOD、POD、CAT活性分别比对照高了292.59%和632.98%、295.07%和360.54%、254.55%和265.45%; 同时降低了过氧化氢、超氧阴离子的产生速率及MDA的含量。表明PKN处理有利于提高玉米幼苗的抗冷性。 相似文献
7.
开放式臭氧浓度升高条件下不同敏感型小麦品种的光合特性 总被引：6，自引：0，他引：6
利用亚洲首个开放式臭氧浓度升高平台(O3FACE),以臭氧敏感品种烟农19和臭氧耐性品种扬麦16为试材,研究了小麦光合特性对O3浓度升高的响应,并分析了不同敏感型小麦品种响应差异的可能原因。结果表明,O3浓度升高并持续处理75 d后,小麦旗叶的净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)均显著下降,其中扬麦16的降幅(27.9%、37.5%和27.9%)明显小于烟农19 (61.1%、68.0%和57.4%);而Ci基本维持恒定。说明O3FACE下小麦旗叶Pn下降是气孔因素和非气孔因素共同作用的结果,其中非气孔因素起决定性作用。叶绿素荧光分析表明,两个品种的PSII最大光化学量子产量(Fv/Fm)、PSII潜在活性(Fv/Fo)、光化学猝灭(qP)和光化学反应速率(Prate)等荧光参数均呈下降趋势,而非光化学猝灭(NPQ)和热耗散速率(Drate)呈上升趋势;可溶性蛋白和核酮糖-1,5-二磷酸羧化酶/加氧酶(Rubisco)则与荧光参数及Pn的变化趋势一致。由此可见,RuBP的羧化限制和PSII光系统损伤可能是O3胁迫下小麦旗叶Pn下降的主要非气孔因素。此外,O3FACE下扬麦16各参数的变幅均小于烟农19,扬麦16较高的蒸腾速率和较小的Rubisco含量降幅可能是其维持光合机构功能的重要原因。 相似文献
8.
干旱胁迫下PEPC过表达增强水稻的耐强光能力 总被引：1，自引：0，他引：1
以过表达磷酸烯醇式丙酮酸羧化酶(PEPC)的水稻为材料,研究了不同程度干旱胁迫下开花期剑叶光合作用的光响应过程、叶绿素荧光参数、色素含量和活性氧代谢。结果表明,在干旱特别是重度干旱胁迫下,野生型水稻在强光下净光合速率迅速下降,而转Zmppc基因水稻没有明显的下降现象; 而且表示光化学活性的叶绿素荧光参数Fv/Fm、ΦPSⅡ和qP下降程度低,说明PEPC增强了干旱胁迫下水稻抵御强光胁迫的能力。这可能是因为干旱胁迫下转Zmppc基因水稻玉米黄质含量高,光系统对过剩光能的耗散能力强,能够保护光系统免受过剩光能的伤害,从而减小O2?产生速率; 同时干旱胁迫下转PEPC基因水稻抗氧化酶SOD、POD和CAT活性高,能有效清除活性氧,减轻膜质过氧化。 相似文献
9.
室外盆栽条件下盐胁迫对甜高粱光系统II活性的影响 总被引：3，自引：0，他引：3
室外盆栽条件下, 设置2个NaCl浓度(100 mmol L–1和200 mmol L–1), 调查盐胁迫对甜高粱光合特性和光系统II (PSII)活性的影响。结果表明,叶片Na+离子含量与Na+/K+比随盐浓度增加和处理时间延长而增加。净光合速率(Pn)、光系统II开放反应中心天线转化效率(Fv¢/Fm¢)、光化学猝灭系数(qP)和光系统II实际光化学效率(ΦPSII)随盐浓度的增加而降低,非光化学猝灭(NPQ)随盐浓度增加而增加;100 mmol L–1处理组的Pn、Fv¢/Fm¢、qP和ΦPSII随处理时间延长有所恢复,但200 mmol L–1处理组无此现象。光系统II (PSII)最大光化学效率(Fv/Fm)在100 mmol L–1 NaCl处理时影响较小,但在200 mmol L–1 NaCl处理时明显下降。短期盐胁迫未影响荧光诱导动力学曲线,而200 mmol L–1 NaCl处理5 d后荧光诱导动力学曲线O-K和O-J相上升。进一步研究证明,PSII的失活速率在两个盐浓度下均无明显变化,而修复速率在200 mmol L–1盐浓度处理5 d后降低明显。因此,认为室外盆栽条件下盐胁迫造成甜高粱碳同化能力降低并改变PSII激发能分配;叶片Na+离子含量的大幅增加会导致PSII活性下降及光抑制,这与PSII失活速率无关,主要是失活PSII修复速率受抑制的结果。这对理解户外盐胁迫条件下C4作物的光抑制机制具有一定意义。 相似文献
10.
耐低钾玉米自交系延缓叶片衰老的生理特性 总被引：2，自引：0，他引：2
以典型的耐低钾玉米自交系90-21-3和低钾敏感玉米自交系D937为试材,采用大田试验,研究了生育后期低钾胁迫对不同自交系叶片持绿性、叶绿素含量、光合特性及叶绿素荧光参数、烯醇式丙酮酸羧化酶(PEPC)和NAD激酶(NADK)活性、保护酶活性的影响,探讨耐低钾玉米延缓叶片衰老的生理特性。结果表明,低钾胁迫持续到生育后期,90-21-3与D937相比,叶片持绿时间长,叶绿素含量下降缓慢,叶片净光合速率(Pn)高;胞间CO2浓度(Ci)和气孔限制值(LS)上升幅度小;FPSII、Fv、Fm高,而Fo明显低;PEPC和NADK活性高;MDA含量上升缓慢且维持较低水平;抗氧化酶SOD、POD和CAT活性相对较高。低钾胁迫下,90-21-3自交系延缓叶片衰老的原因可能为持绿性较好,延长了叶片功能期;光合能力强,受光抑制程度较轻;NADK活性稳定,为光反应提供电子受体NADP,同时PEPC活性较高,暗反应又能固定相对较多的CO2,从而保证了CO2的供应;光反应和暗反应的协同,使90-21-3自交系具有相对较高的光合速率,同时抗氧化酶又具有较高的活性,可有效清除活性氧。 相似文献
11.
Recent studies have indicated that spontaneous interspecies crossing commonly occurs among vascular plants, and therefore that horizontal gene flow from transgenic plants into wild relatives is unavoidable. Few surveys, however, have been conducted to determine an actual flow frequency for individual plant species. For the present estimation of gene flow among Vigna angularis complex (small red bean) plants, randomly amplified polymorphic DNA was analysed, the patterns of which differ between a cultivar, var. angularis and its wild counterpart, var. nipponensis. Cultivars and wild‐type plants were planted alternately and approximately 1% of the screened F1 beans of wild type were hybrid. These F1 hybrids were selected, allowed to self to produce F2 beans, and subsequent crossing between the F2 plants and wild type resulted in that 3.7% of the F3 generation possessed DNA fragments specific to the cultivar. These results indicate that gene flow actually occurs among V. angularis complex plants, and that transferred genes might be stably maintained by the offspring. The present observation cannot be directly applied to transgenic plants due to the lack of information as to whether or not artificially introduced genes behave as do native genes after horizontal movement. However, as gene flow is found to be inevitable in this species, specific assessment of whether or not the gene to be introduced confers a significant selective advantage to the host is critical for utilization of genetically modified plants in future. 相似文献
12.
Summary The levels of the naturally occurring insecticide 2-tridecadone (2TD) were measured in leaves of Lycopersicon hirsutum f. glabratum, L. esculentum, the interspecific F1 hybrid, the F2 and backeross generations. The wild species contains 50 times more 2TD than the cultivated tomato and the frequency distribution of the substance indicates that there is dominance for low levels of the compound. The genotype of F2 plants was determined with respect to 6 codominant isozyme markers and 4 dominant/recessive markers. Significant associations were detected between 5 of the marker genes and the level of 2TD. We interpret these results as implying linkage between marker genes and genes that control the level of 2TD. The behavior of the gene for the determinant growth habit of the plants suggests that it has a pleiotropic effect on the level of 2TD. 相似文献
13.
Tomato (Solanum lycopersicum) production in tropical and subtropical regions of the world is limited by the endemic presence of Tomato yellow leaf curl virus (TYLCV). Breeding programmes aimed at producing TYLCV‐resistant tomato cultivars have utilized resistance sources derived from wild tomato species. So far, all reported breeding programmes have introgressed TYLCV resistance from a single wild tomato source. Here, we tested the hypothesis that pyramiding resistances from different wild tomato species might improve the degree of resistance of the domesticated tomato to TYLCV. We have crossed TYLCV‐resistant lines that originated from different wild tomato progenitors, Solanum chilense, Solanum peruvianum, Solanum pimpinellifolium, and Solanum habrochaites. The various parental resistant lines and the F1 hybrids were inoculated in the greenhouse using viruliferous whiteflies. Control, non‐inoculated plants of the same lines and hybrids were exposed to non‐viruliferous whiteflies. Following inoculation, the plants were scored for disease symptom severity, and transplanted to the field. Resistance was assayed by comparing yield of inoculated plants to those of the control non‐inoculated plants of the same variety. Results showed that the F1 hybrids between the resistant lines and the susceptible line suffered major yield reduction because of infection, but all hybrids were more resistant than the susceptible parent. All F1 hybrids resulting from a cross between two resistant parents, showed a relatively high level of resistance, which in most cases was similar to that displayed by the more resistant parent. In some cases, the hybrids displayed better levels of resistance than both parents, but the differences were not statistically significant. The F1 hybrid between a line with resistance from S. habrochaites and a line with resistance from S. peruvianum (HAB and 72‐PER), exhibited the lowest yield loss and the mildest level of symptoms. Although the resistance level of this F1 hybrid was not statistically different from the level of resistance displayed by the 72‐PER parent itself, it was statistically better than the level of resistance displayed by the F1 hybrids between 72‐PER and any other resistant or susceptible line. 相似文献
14.
Summary Resistance to fusarium wilt, incited by Fusarium oxysporum (Schlecht.) f. sp. lycopersici (Sacc.) Snyder & Hansen race 3 in tomato (Lycopersicon esculentum Mill.) was discovered in LA 716, a L. pennellii accession. A resistant BC1F3 breeding line, E427, was developed from LA 716. E427 was crossed with the susceptible cv. Suncoast and F1, BCP1, BCP2 (to Fla 7155, a susceptible parent) F2, F3, and BCP2S1 seeds were obtained. Segregation for resistance following root dip inoculation over three experiments indicated a single dominant gene controlled resistance. Five of the 12 BCP1S1's segregated more susceptible plants, whereas one of the 12 segregated more resistant plants than expected (P<0.05). Three of 23 F3 lines segregated more susceptible plants than expected while 1 of the 23 had more resistant plants than expected (P<0.05). Segregation in all other lines fit expected ratios. Five of the 23 F3's were homozygous resistant which was an acceptable fit to expectations (P=0.1–0.5). The gene symbol I
3 is proposed for resistance to race 3 of the wilt pathogen. Deviations from expected ratios in data reported here and for other breeding lines indicate an effect of modifier genes and/or incomplete penetrance. Plant age at inoculation and seed dormancy did not affect results.Florida Agricultural Experiment Station Journal Series No. 8101. 相似文献
15.
Gustavo Rubén Rodríguez Guillermo Raúl Pratta David Rodolfo Liberatti Roxana Zorzoli Liliana Amelia Picardi 《Euphytica》2010,176(1):137-147
A tomato cultivar with high quality fruit and a long shelf life is a main goal in tomato breeding and it would be achieved
using wild germplasm. The objective of this work was to explore the inheritance for fruit quality traits, especially fruit
shelf life, in three tomato crosses using a standard Argentinean cultivar (Ca, cv ‘Caimanta’), a ripening mutant (nor, homozygous
for the nor gene) of Solanum lycopersicum, and a wild cherry type (Ce, LA1385 of S. lycopersicum var. cerasiforme). The wild parent had a shorter fruit shelf life than the mutant genotype but higher than Ca. When the Ce genotype was analyzed
in hybrid combination, the F1 (Ca×Ce) was similar to the wild genotype for shelf life whereas the F1 (nor × Ce) had a longer shelf life. Both F1 crosses and backcrosses to the cherry type genotype had significantly lower fruit weight than the cultivated genotypes but
higher than the cherry type parent. In the F2 analysis, it was found that the inheritance underlying quality traits is complex since non allelic interactions were detected.
A significant additive genetic variance was found for fruit shelf life as well as for other fruit quality traits in each cross.
The genetic parameters analyzed by mean values and variances in parental, F1 and F2 and backcross generations indicated that the cross between the normal ripening cultivar and LA1385 of S. lycopersicum var. cerasiforme offers the best possibility to obtain long shelf life tomato genotypes with good fruit quality. 相似文献
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植物介导的RNA干扰引起马铃薯晚疫病菌基因的沉默 总被引：1，自引：0，他引：1
由致病疫霉(Phytophthora infestans)引起的晚疫病是最具毁灭性的马铃薯病害。为明确植物介导的RNAi沉默致病疫霉基因的有效性,本研究采用重叠延伸PCR技术克隆同时与晚疫病菌4个ces基因均同源的融合基因C1234,构建内含子连接的C1234反向重复序列植物表达载体,采用农杆菌介导法转化晚疫病易感马铃薯品种大西洋,经PCR和Southern杂交检测,获得129个转基因株系。离体叶片接种病原菌后,有97个转基因株系发病速度明显慢于野生型,接种6 d后病斑大小和霉层厚度均明显小于对照,并且叶片感病部位没有出现失绿斑,而野生型产生了明显的失绿斑。实时定量RT-PCR分析发现,发病延缓的叶片上致病疫霉4个纤维素合酶基因的表达水平明显低于野生型。本研究表明,转基因植株中产生的以晚疫病菌ces基因为靶标的ds RNA能够沉默致病疫霉相应基因表达,延缓发病进程。 相似文献
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Hrip1是从极细链格孢(Alternaria tenuissima)代谢物中分离的一种蛋白激发子。将蛋白激发子基因Hrip1转化到拟南芥,对5个T1代转基因拟南芥株系进行分子检测, 证明Hrip1基因能够在拟南芥中转录和表达。转基因植株对盐和干旱胁迫的抗性显著增强, 75 mmol L−1 NaCl和50 mmol L−1甘露醇渗透胁迫2 d, 转基因植株种子平均相对发芽率为32.1%和77.9%, 分别比野生型的增加3.72倍和5.61倍; 150 mmol L−1 NaCl和50 mmol L−1甘露醇处理拟南芥幼苗7 d后, 转基因植株平均相对根长为81.79%和93.25%, 分别是野生型的1.53倍和1.34倍。3周龄的转基因植株在250 mmol L−1 NaCl条件下胁迫20 d, 平均存活率为67%, 显著高于野生型(42%)(P<0.05); 干旱胁迫25 d后, 复水5 d转基因植株平均存活率为72%, 而野生型仅为44%。检测结果显示转基因植株叶片的抗氧化酶活性明显高于野生型, 用200 mmol L−1 NaCl和200 mmol L−1甘露醇处理24 h后, POD活性分别比野生型植株提高1.56倍和1.85倍, CAT活性分别比野生型植株提高1.64和1.86倍。说明蛋白激发子Hrip1基因在拟南芥中的表达能够改善和提高植株的耐盐抗旱能力。 相似文献
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Overexpression of a small heat‐shock‐protein gene enhances tolerance to abiotic stresses in rice 
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下载免费PDF全文 Rice (Oryza sativa L.) is one of the most important crops in the world which survives from various abiotic stresses in natural environments with specific stress‐involved genes expressed. Plant sHSPs (small heat‐shock proteins) were reported to respond to abiotic stresses. To improve the understanding of sHSPs in rice, we characterized heat‐shock‐protein gene OsHSP18.6 here. OsHSP18.6 could be induced by diverse stresses, such as drought, salt and cold, especially under heat. The gene was found expressed in root, stem, leaf, internode and spikelet. Overexpression of OsHSP18.6 results in increased thermotolerance and exhibits universal tolerance to stresses tested, including heat, drought, salt and cold. Lower levels of malondialdehyde (MDA) and greater activities of catalase (CAT) and superoxide dismutase (SOD) were observed in OsHSP18.6‐overexpression rice under heat and drought. OsHSP18.6‐overexpression lines indicated decreased sterile rates under hot weather without remarkable changes in most of other agronomic traits compared with wild‐type plants. 相似文献
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Late blight (LB), caused by the oomycete Phytophtohra infestans, is one of the most destructive diseases of tomato (Solanum lycopersicum) and other Solanaceae species. Current disease control and prevention strategies are not sufficient to control the disease in tomato. Recent germplasm screening experiments led to the identification of a new source of resistance (PI 270443) in the tomato wild species S. pimpinellifolium. This study was conducted to identify genomic regions associated with LB resistance in this accession. A large F2 population (n = 986) derived from a cross between PI 270443 and a LB-susceptible tomato breeding line (NCEBR-2) was screened for LB resistance using a highly aggressive isolate of P. infestans. Twenty-five of the most resistant and 29 of the most susceptible, but surviving F2 individuals were identified based on disease evaluations conducted in the F2 and F3 progeny populations. The selected individuals were genotyped with 153 DNA markers located across the 12 tomato chromosomes. A selective genotyping approach led to the identification of two genomic regions on tomato chromosomes 1 and 10 associated with LB resistance in PI 270443. Identification of two genomic regions associated with resistance was consistent with a previous estimate of the number of LB resistance genes in this accession. Research is currently underway to fine map the two resistance genes and incorporate them into new tomato breeding lines and hybrid cultivars. 相似文献