栗属杂交F1代生长与枝条性状遗传变异及杂种优势分析

为探索栗属杂交F₁代幼林期生长、枝条性状遗传变异规律及杂种优势,并为栗属育种亲本选配及早期选择指标筛选奠定理论基础,该研究以锥栗、板栗种内和种间9个杂交组合子代及其亲本为材料,在分析F₁代幼林期生长、枝条性状遗传变异规律及杂种优势的基础上,利用SSR分子标记检测7个亲本的遗传距离,进而分析栗属杂交子代生长、枝条性状杂种优势与亲本遗传距离间的关系。结果显示：(1)栗属杂交F₁代生长、枝条性状均存在较高的遗传变异,各性状组合间F值的变动范围为5.08~22.03,组合内的变异系数范围为6.60%~27.69%;各性状广义遗传力均在0.5以上,性状受遗传影响较大;除地径外,其他性状遗传传递力均大于100%,性状遗传稳定性较高;各性状中亲优势率为-6.01%~44.40%,且F₁代生长、枝条性状存在普遍的超亲分离现象。(2)28对引物在7个亲本中共检测出115个多态性等位位点,每对引物的等位基因数3~5个不等,平均每对引物等位基因数为4.1个,多态性程度较高;Shannons 指数(I)、多态性信息含量(PIC)的平均值分别为1.25、0.674,亲本遗传多样性较为丰富。(3)相关分析表明,杂交子代一年生枝长、一年生枝粗及节间距的杂种优势与亲本遗传距离均存在显著的线性关系,并随遗传距离增大杂种优势增强。     

陆地棉产量性状QTLs的分子标记及定位

用我国的高产栽培品种泗棉3号和美国栽培品种TM-1为材料,构建F₂和F_2∶3作图群体,应用301对SSR引物和1040个RAPD引物,对产量性状QTLs进行了分子标记筛选,结果共筛选出了37对SSR多态性引物和10个RAPD多态性引物的49个位点,鉴定出了控制产量性状变异的主效QTLs。定位于第9染色体的连锁群,分别具有控制铃重、衣分和籽指的主效QTLs,铃重的2个QTLs分别解释F_2∶3群体表型变异的18.2%和21.0%;在F₂群体检测到的1个衣分QTL解释表型变异的25%,另一个衣分QTL在F₂群体和F_2∶3群体都检测到,解释F₂群体衣分的24.9%的表型变异,解释F_2∶3群体衣分的5.9%的表型变异;在F_2∶3群体铃重的一个QTL的同一位置同时检测到一个籽指QTL,它解释15.6%的表型变异,是一因多效或是紧密连锁的两个QTLs,有待进一步研究。本研究标记的产量性状主效QTLs可用于棉花产量性状的标记辅助选择。     

小麦雌性育性的主基因+多基因混合遗传分析

选用普通小麦中3种不同生态型育性正常品种与雌性不育系XND126杂交构建3个F2组合, 连续两年对3组合P₁、P₂、F₁和F₂雌性育性进行调查, 利用植物数量性状主基因+多基因混合遗传模型的4世代联合分析方法分析了小麦雌性育性的遗传。结果表明: 小麦雌性育性受两对主效基因+多基因联合控制, 两对主效基因之间存在互作效应。     

水稻的耐淹性状及其Sub1基因

近4年来, 水稻(Oryza sativa L.)耐淹性状及其分子机理的研究取得了长足的进展。水稻植株的耐淹性状主要由Submergence-1 (Sub1) 基因控制。Sub1通过调节乙烯和赤霉素介导的反应, 抑制淹水期间的伸长生长和减缓碳水化合物消耗来控制耐淹性状。文章介绍了水稻应对淹涝胁迫的两种策略, 影响耐淹性状的主要生理因素, Sub1基因定位以及它控制耐淹性状的机理; 阐述了Sub1基因在我国杂交水稻生产方面的应用前景。     

IGF2基因对鸡生长及屠体性状的影响及印记状况的研究

以明星肉鸡和丝毛乌骨鸡杂交产生的F₂代鸡群为实验材料, IGF2基因作为控制鸡生长、屠体性状主基因的候选基因, 通过PCR-SSCP方法对IGF2基因多态性进行检测. 该基因外显子2中有一个单核苷酸多态性位点, 即71位碱基由C突变为G. 对F₂鸡群个体进行了基因型鉴定, 经方差分析表明：该基因对部分生长、屠体性状有显著性影响(如胸角宽、腺胃重、半净膛重等). 研究表明该基因可能调控鸡生长、屠体性状的表达, 或与控制生长、屠体性状的主基因连锁. 进一步分析发现, 正反交结果不一致, 即杂合子AB(父本等位基因在前)出生重、胸肌重较杂合子BA高, 而腹脂重后者较前者高. 另选丝毛乌骨鸡家系做IGF2印记状况检测, 杂合子与纯合子进行正反交, 然后检测后代基因型并选取杂合子, 利用RT-PCR-SSCP检测表达情况, 结果表明, 鸡的IGF2基因不受印记控制. 交互效应可能是由于其他遗传因素作用的结果.     

水稻紫色柱头的遗传分析与基因定位

rdh是四川农业大学水稻研究所通过组织培养和连续自交得到的一个具有红色籽粒和紫色柱头,遗传上稳定的籼稻材料。抽穗期在rdh与3个无色柱头品种蜀恢527、蜀恢368和蜀恢168之间分别做正反交,结果显示F1群体在柱头颜色上正反交之间没有明显区别,全部是紫色的。F2群体发生分离成为两组,一组具有紫色柱头,另一组具有无色柱头。每一个F2群体的紫色柱头对无色柱头均适合3：1的比例,表明rdh紫色柱头性状的遗传是由一对显性核基因控制的。组合rdh／蜀恢527 F2分离群体中40个具有紫色柱头的显性单株和284个具有无色柱头的隐性单株构成定位群体。从两个亲本rdh和蜀恢527提取的基因组DNA,用涵盖水稻整个基因组的252对微卫星标记作引物扩增片段。结果发现有78对微卫星标记在两亲本之间具有多态性。然后用这78对标记作引物,扩增亲本、F1、F2显性单株和F2隐性单株、,结果显示位于水稻第6染色体的RM276、RM253以及RM111与rdh紫色柱头基因有连锁关系。再用RM276、RM253以及RM111作引物扩增剩余的全部具有无色柱头的隐性单株。结果表明：在RM276的扩增产物中,有20个单交换和2个双交换;在RM253中有2个单交换：在RM111中有3个单交换。因此,rdh紫色柱头基因被定位于水稻第6染色体。根据公式P=（h＋2b）／2n,计算得到微卫星标记RM276,RM253和RM111与rdh紫色柱头基因的遗传距离分别是4．2cM、0．35cM以及0．53cM。根据已经发表的RM276、RM253和RM111在第6染色体上的位置以及计算得到的rdh与RM276、RM253和RM111之间的遗传距离,构建了部分连锁图谱,并暂时将这个紫色柱头基因命名为Ps-4。     

水稻寡分蘖突变体的遗传分析和基因定位

从籼粳交组合“圭630/02428”的花培后代中获得一份寡分蘖突变体G069,其主要特征是分蘖速度慢,最高分蘖数少,成熟叶片叶尖、叶缘黄化.用突变体作母本与02428杂交,并以02428作轮回亲本与杂交后代突变型单株回交构建BC₂F₂.对BC₂F₂进行调查和遗传分析,确认突变体G069寡分蘖特性和叶片黄化现象受同一隐性基因控制.以BC₂F₂分离群体为基础,应用SSR标记和RFLP标记进行连锁分析,将寡分蘖基因定位于第2染色体的RFLP标记C424和S13984之间,分别相距2.4和0.6cM.该基因暂定名为ft1.     

模拟酸雨胁迫下硅对髯毛箬竹光合特性的影响

以髯毛箬竹为试验材料,研究了模拟酸雨胁迫(pH 3.0)下硅对髯毛箬竹叶片叶绿素相对含量、光合作用日变化以及叶绿素荧光特性等的影响.结果表明:20和100 mg·L^-1 Na₂SiO₃预处理可以不同程度地抑制酸雨胁迫下髯毛箬竹叶片叶绿素含量的显著下降,且以100 mg·L^-1浓度处理效果最佳,叶绿素含量可提高22.7%,而高浓度(500 mg·L^-1)预处理则无缓解作用-酸雨胁迫下,髯毛箬竹光合“午休”现象加重,日平均净光合速率(P_n)、气孔导度(G_s)和气孔限制值(L_s)明显降低,而胞间CO₂浓度(C_i)增大,经过20～100 mg·L^-1硅预处理后,P_n、G_s、L_s不同程度增加,而C_i有所降低,且以100 mg·L^-1硅预处理效果最佳,日平均P_n增加39.2%.酸雨胁迫下,箬竹PSⅡ最大荧光(F_m)、最大光化学效率(F_v/F_m)、潜在活性(F_v/F_o)、有效光化学效率(F_v′/F_m′)、最大荧光产额(F_m′)、光化学淬灭系数(q_P)、非光化学淬灭系数(q_N)、PSII实际光化学效率(Φ_PSⅡ)降低,暗适应和光适应下的最小荧光产额F_o、F_o′ 则升高;而100 mg·L^-1硅预处理明显抑制了胁迫下各荧光参数的变化,F_v/F_m、F_v/F_o、F_v′/F_m′和Φ_PSⅡ分别增加35.2%、146.2%、55.0%和24.3%.说明外源适宜浓度硅预处理能有效地缓解酸雨胁迫导致的髯毛箬竹光合活性下降和光合系统损伤,从而提高胁迫下植物的光合能力.     

北京地区野生大豆种群SSR标记的遗传多样性评价

 使用40对SSR引物分析了北京地区野生大豆(Glycine soja)天然种群的遗传结构与遗传多样性。10个种群共检测到526个等位变异, 平均每对引物等位基因数为13.15个, 种群平均Shannon指数(I)为0.658, 群体平均位点预期杂合度(H_e)为0.369, 群体平均位点杂合度(H_o)为1.29 %。平均种群内遗传多样度(H_s)为0.362, 平均种群间遗传多样度(D_ST)为0.446, 基因分化程度(G_ST)为0.544。该研究显示, 中-西部生态区种群比北部和东部山区种群有较高的遗传多样性。在地理上, 环绕北京地区的太行山和燕山两大余脉区域野生大豆种群遗传分化表现出地理差异。可能是经过干旱选择而形成的有抗旱潜力的种群在遗传上表现单一化。期待该种群提供耐旱基因。     

栽培菊花与菊属-近缘属属间杂种杂交后代耐盐性的遗传分析

为了解菊花近缘种属植物耐盐性的遗传规律,对栽培菊花与菊属-近缘属属间杂种杂交后代耐盐性进行了遗传分析。以栽培菊花'韩2’为母本,大岛野路菊×芙蓉菊属间杂种为父本进行杂交,以盐害指数作为指标,通过水培法对获得的F₁群体进行耐盐性鉴定,并应用植物数量性状主基因+多基因混合遗传模型,采用单个F₂世代的分离分析方法对F₁群体耐盐性进行混合遗传分析。结果发现:F₁群体的耐盐性出现广泛分离,变异系数达53.63%,盐害指数的变异范围为3.33%-96.67%;中亲优势为2.47,未达到显著水平;将后代的耐盐性分为5个级别,其中高耐的占14.52%,耐盐的占38.70%,中耐的占30.65%,敏盐的占9.68%,高敏的占6.45%。F₁群体的耐盐性符合B-2模型,由两个主效基因控制,加性效应均表现正向增效,分别为18.06和19.13,显性效应表现负向效应,分别为-17.99和-1.44,主基因遗传率为61.14%,属高度遗传力。综合分析表明:菊花近缘种属植物耐盐性可通过杂交导入栽培菊花,实现栽培菊花耐盐性遗传改良;菊花近缘种属植物盐害指数受两对主基因的控制,主基因在F₁群体的遗传率属高度遗传力,耐盐性选育可在早期世代进行。     

Thai Jasmine Rice Carrying QTLch9 (SubQTL) is Submergence Tolerant

Submergence tolerance is an important agronomic trait for ricegrown in South-East Asia, where flash flooding occurs frequentlyand unpredictably during the monsoons. Although mapping locationsof one major and several minor quantitative trait loci (QTL)were known previously, improving submergence tolerance in agronomicallydesirable types of rice has not been achieved. KDML105 is jasminerice widely grown in rain-fed lowland regions of Thailand. Thiscultivar is very intolerant of submergence stress. To improvesubmergence tolerance in this cultivar, three submergence-tolerantcultivars, FR13A, IR67819F2-CA-61 and IR49830-7-1-2-2, werecross-pollinated with KDML105. Transferring the major QTL forsubmergence tolerance was facilitated by four back-crossingsto the recipient KDML105. Molecular markers tightly linked tothe gene(s) involved were developed to facilitate moleculargenotyping. We demonstrated that individuals of a BC4F3 linethat retained a critical region on chromosome 9 transferredfrom tolerant lines were also tolerant of complete submergencewhile retaining all the agronomically desirable traits of KDML105.In addition, effects of secondary QTLch2 were detected statisticallyin back-cross progenies. Effects of secondary QTLch7 were notstatistically significant. The close association between tightlylinked markers of the tolerance locus on chromosome 9 and submergencetolerance in the field demonstrates the considerable promiseof using these markers in lowland rice breeding programmes forselecting increased submergence tolerance.     

Responses of the antioxidative enzymes in Malaysian rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) cultivars under submergence condition

The potential involvement of activated oxygen species by submergence stress was studied in two Malaysian rice cultivars, MR219-4 and MR219-9, and cultivar FR13A that is known to be tolerant to submergence. Seedlings of these three rice cultivars were subjected to different submergence periods (4, 8, and 12 days). Under 8 days of complete submergence, FR13A cultivar showed higher lipid peroxidation in terms of malondialdehyde level and activities of antioxidative enzymes, superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) when compared to the MR219-4 and MR219-9 cultivars. MR219-9 showed higher SOD, APX, and GR activities after 12 days of submergence. The levels of SOD activity indicated that detoxification of O₂^·− to H₂O₂ was maintained at a stable level throughout the submergence stress until up to 8 days and increased rapidly at 12 days of submergence. The results indicated that tolerance to submergence in rice is associated until 8 days submergence for MR219-4 and FR13A cultivars. These findings suggested that tolerance to submergence stress in rice might be proven by increased the capacity of antioxidative system. In addition, CAT activity has much higher affinity for scavenges H₂O₂ than APX. Therefore, ascorbate glutathione cycle might be more efficient to scavenge H₂O₂.     

A major locus for submergence tolerance mapped on rice chromosome 9

Submergence stress is a widespread problem in rice-growing environments where drainage is impeded. A few cultivars can tolerate more than 10 days of submergence, but the genes conferring this tolerance have not been identified. We used randon-amplified polymorphic DNA (RAPD) and restriction fragment length polymorphism (RFLP) markers to map submergence tolerance in 169 F₂ plants and the resulting F₃ families of a cross between a tolerant indica rice line, IR40931-26, and a susceptible japonica line, PI543851. IR40931-26 inherited strong submergence tolerance from the unimproved cultivar FR13A. Eight-day old F₃ seedlings were submerged for 14–16 days in 55-cm deep tanks, and tolerance was scored after 7 days recovery on a scale of 1 (tolerant) to 9 (susceptible). The tolerant and susceptible parents scored 1.5 and 8.4, respectively, and the F₃ means ranged from 1.6 to 8.9. Two bulks were formed with DNA from F₂ plants corresponding to the nine most tolerant and the nine most susceptible F₃ families. Of 624 RAPD primers used to screen the bulks, five produced bands associated with either tolerance or susceptibility. These markers were mapped to a region of chromosome 9 by linkage to RFLP markers. A submergence tolerance quantitative trait locus (QTL), here designatedSub1, was located ca. 4 cM from the RFLP marker C1232 and accounted for 69% of the phenotypic variance for the trait.     

Identifying novel QTLs for submergence tolerance in rice cultivars IR72 and Madabaru

Short-term submergence is a recurring problem in many rice production areas. The SUB1 gene, derived from the tolerant variety FR13A, has been transferred to a number of widely grown varieties, allowing them to withstand complete submergence for up to 2 weeks. However, in areas where longer-term submergence occurs, improved varieties having higher tolerance levels are needed. To search for novel quantitative trait loci (QTLs) from other donors, an F_2:3 population between IR72 and Madabaru, both moderately tolerant varieties, was investigated. After a repeated phenotyping of 466 families under submergence stress, a subset of 80 families selected from the two extreme phenotypic tails was used for the QTL analysis. Phenotypic data showed transgressive segregation, with several families having an even higher survival rate than the FR13A-derived tolerant check (IR40931). Four QTLs were identified on chromosomes 1, 2, 9, and 12; the largest QTL on chromosome 1 had a LOD score of 11.2 and R ² of 52.3%. A QTL mapping to the SUB1 region on chromosome 9, with a LOD score of 3.6 and R ² of 18.6%, had the tolerant allele from Madabaru, while the other three QTLs had tolerant alleles from IR72. The identification of three non-SUB1 QTLs from IR72 suggests that an alternative pathway may be present in this variety that is independent of the ethylene-dependent pathway mediated by the SUB1A gene. These novel QTLs can be combined with SUB1 using marker assisted backcrossing in an effort to enhance the level of submergence tolerance for flood-prone areas.     

Mapping QTLs for submergence tolerance in rice using a population fixed for <Emphasis Type="Italic">SUB1A</Emphasis> tolerant allele

Submergence is a widespread problem of rice production, especially in low-lying areas in South and Southeast Asia. Despite the success of Sub1 mega varieties, repeated instances of prolonged and severe flooding in stress-prone areas suggests that the SUB1 gene is no longer sufficient in those regions and requires improved varieties with increased tolerance. A study was conducted to identify quantitative trait loci (QTLs) associated with submergence tolerance using 115 F₇ recombinant inbred lines (RILs) derived from the cross of Ciherang-Sub1, a popular Indonesian cultivar carrying the SUB1 gene that has relatively higher tolerance to submergence compared to the performance of most other Sub1 lines and the submergence and stagnant flooding tolerant IR10F365. As the tolerant allele at SUB1A on chromosome 9 was fixed in this mapping population, additional QTLs responsible for submergence tolerance were expected to be revealed. Genotyping with an Infinium 6K SNP chip resulted in 469 polymorphic markers that were then used for QTL mapping. Phenotyping was performed under complete submergence with two replicates. A major QTL for submergence derived from Ciherang-Sub1, named qSUB8.1, was detected on chromosome 8 with a LOD score of 10.3 and phenotypic variance of 27.5%. Additionally, a smaller QTL, also derived from Ciherang-Sub1, was detected on chromosome 2 with a LOD score of 3.5 and phenotypic variance of 12.7%. There was no digenic interaction detected between these QTLs suggesting their independent action. The QTLs detected in this study can be used in marker-assisted selection to further improve the tolerance of other Sub1 varieties.     

Submergence tolerance in relation to variable floodwater conditions in rice

Flash floods adversely affect rice productivity in vast areas of rainfed lowlands in South and Southeast Asia and tropical Africa. Tolerant landraces that withstand submergence for 1–2 weeks were identified; however, incorporation of tolerance into modern high-yielding varieties through conventional breeding methods has been slow because of the complexity of both the tolerance phenotype and floodwater conditions, and the ensuing discrepancies encountered upon phenotyping in different environments. Designing an effective phenotyping strategy requires a thorough understanding of the specific floodwater characteristics that most likely affect survival during flooding. We investigated the implications of floodwater temperature and light penetration, caused by artificial shading, seasonal variation, or water turbidity, for seedling survival after submergence. Three field experiments were conducted using rice genotypes contrasting in their tolerance of submergence: FR13A and Kusuma (tolerant); Gangasiuli (intermediate); Sabita, CRK-2-6 and Raghukunwar (elongating/avoiding types); and IR42 (sensitive). We tested the hypotheses that warmer floodwater decreases plant survival and that turbid water augment plant mortality by causing effects similar to those caused by shading, by reducing light penetration. Plants survive better when water is cooler, and survival decreased at about 8% per unit increase in water temperature above 26 °C. Lower intensity of light and warmer temperatures seem to reduce biomass and increase mortality under flooding. An increase in the concentrations of O₂ and CO₂ and a decrease in water pH did not improve survival in clear unshaded water. Turbid floodwater was more damaging to rice as plant mortality increased as the percentage of silt increased, and the effects of water turbidity cannot be explained by the reduction in light penetration alone. Even the most tolerant rice cultivar, FR13A, experienced higher mortality when flooded with turbid floodwater. Correlation studies revealed that cultivars with the capacity to maintain higher biomass, higher chlorophyll, and non-structural carbohydrate concentrations after submergence had higher survival. These findings help to understand the variation observed in submergence tolerance when screening is done under different environments. The study could have implications for designing proper screening strategies and assessing the damage submergence causes across different rice-growing regions.     

Genetic analysis of salinity tolerance in rice (Oryza sativa L.)

Summary The genetics of salinity tolerance in rice was investigated by a nine-parent complete diallel including reciprocals. Test materials involved susceptible (IR28, IR29, and MI-48), moderately tolerant (IR4595-4-1-13, IR9884-54-3-1E-P1, and IR10206-29-2-1), and tolerant (Nona Bokra, Pokkali, and SR26B) parents. Twoweek-old seedlings were grown in a salinized (EC = 12 dS/m) culture solution for 19 days under controlled conditions in the IRRI phytotron. Typical characteristics of salinity tolerance in rice were found to be Na⁺ exclusion and an increased absorption of K⁺ to maintain a good Na-K balance in the shoot. Genetic component analysis (GCA) revealed that a low Na-K ratio is governed by both additive and dominance gene effects. The trait exhibited overdominance, and two groups of genes were detected. Environmental effects were large, and the heritability of the trait was low. Our findings suggest that when breeding for salt tolerance, selection must be done in a later generation and under controlled conditions in order to minimize environmental effects. Modified bulk and single-seed descent would be the suitable breeding methods. Combining ability analysis revealed that both GCA and specific combining ability (SCA) effects were important in the genetics of salt tolerance. Moderately tolerant parents — e.g., IR4595-4-1-13 and IR9884-54-3-1E-P1 — were the best general combiners. Most of the best combinations had susceptible parents crossed either to moderate or tolerant parents. The presence of reciprocal effects among crosses necessitates the use of susceptible parents as males in hybridization programs. Large heterotic effects suggest the potential of hybrid rice for salt-affected lands.     

Genes/QTLs affecting flood tolerance in rice

The adaptation of deepwater rice to flooding is attributed to two mechanisms, submergence tolerance and plant elongation. Using a QTL mapping study with replicated phenotyping under two contrasting (water qualities) submergence treatments and AFLP markers, we were able to identify several genes/QTLs that control plant elongation and submergence tolerance in a recombinant inbred rice population. Our results indicate that segregation of rice plants in their responses to different flooding stress conditions is largely due to the differential expression of a few key elongation and submergence tolerance genes. The most important gene was QIne1 mapped near sd-1 on chromosome 1. The Jalmagna (the deepwater parent) allele at this locus had a very large effect on internal elongation and contributed significantly to submergence tolerance under flooding. The second locus was a major gene, sub1(t), mapped to chromosome 9, which contributed to submergence tolerance only. The third one was a QTL, QIne4, mapped to chromosome 4. The IR74 (non-elongating parent) allele at this locus had a large effect for internal elongation. An additional locus that interacted strongly with both QIne1 and QIne4 appeared near RG403 on chromosome 5, suggesting a complex epistatic relationship among the three loci. Several QTLs with relatively small effects on plant elongation and submergence tolerance were also identified. The genetic aspects of these flooding tolerance QTLs with respect to patterns of differential expression of elongation and submergence tolerance genes under flooding are discussed. Received: 13 December 1999 / Accepted: 14 March 2000<@head-com-p1a.lf>Communicated by G. Wenzel