Homozygous transgenic rice lines expressing GNA with enhanced resistance to the rice sap-sucking pest Laodelphax striatellus

Homozygous transgenic rice lines expressing snowdrop lectin, Galanthus nivalis agglutinin (GNA), were investigated for resistance to the rice small brown planthopper (SBPH), Laodelphax striatellus, an important rice sap‐sucking pest causing yield losses and serving as vector for some important rice viruses. Insect bioassay results revealed that both the GNA‐expressing homozygous lines tested significantly inhibited SBPH by decreasing its survival, its overall fecundity and retarding development. This is the first report on homozygous transgenic rice lines expressing GNA conferring enhanced resistance to SBPH. This result suggests that transgenic rice expressing GNA will be useful in rice pest resistance breeding, as an alternative to conventional breeding for the control of SBPH, and potentially alleviating damage caused by the viruses it transmits.     

Genetics of thermosensitive genic male sterility in rice

Summary Inheritance of thermosensitive genic male sterility (TGMS) in Norin PL12 and IR32364TGMS and their allelic relationship were studied from F₁, F₂ testcross (TC) and F₃ generations of the crosses made with the two mutants and several fertile tester parents. F₂, TC and F₃ segregation behavior for pollen and spikelet fertility indicated that the TGMS trait in the two mutants was controlled by a single recessive gene. Allelic relationship studies indicated that TGMS genes of the two mutants were different. Since TGMS gene in Norin PL12 has been designated as tms ₂ , the TGMS gene present in IR32364TGMS is tentatively designated as tms ₃ (t) until allelic test is done with another TGMS gene (tms ₁ ) reported from China in a line 5460S seeds of which were not available.     

Chromosomal location of fertility restoring genes for ‘wild abortive’ cytoplasmic male sterility using primary trisomics in rice

Summary Identification and location of fertility restoring genes facilitates their deployment in a hybrid breeding program involving cytoplasmic male sterility (CMS) system. The study aimed to locate fertility restorer genes of CMSWA system on specific chromosomes of rice using primary trisomics of IR36 (restorer), CMS (IR58025A) and maintainer (IR58025B) lines. Primary trisomic series (Triplo 1 to 12) was crossed as maternal parent with the maintainer line IR58025B. The selected trisomic and disomic F₁ plants were testcrossed as male parents with the CMS line IR58025A. Plants in testcross families derived from disomic F₁ plants (Group I crosses) were all diploid; however, in the testcross families derived from trisomic F₁ plants (Group II crosses), some trisomic plants were observed. Diploid plants in all testcross families were analyzed for pollen fertility using 1% IKI stain. All testeross families from Group I crosses segregated in the ratio of 2 fertile: 1 partially fertile+partially sterile: 1 sterile plants indicating that fertility restoration was controlled by two independent dominant genes: one of the genes was stronger than the other. Testcross families from Group II crosses segregated in 2 fertile: 1 partially fertile+ partially sterile: 1 sterile plants in crosses involving Triplo 1, 4, 5, 6, 8, 9, 11 and 12, but families involving triplo 7 and triplo 10 showed significantly higher X² values, indicating that the two fertility restorer genes were located on chromosome 7 and 10. Stronger restorer gene (Rf-WA-1) was located on chromosome 7 and weaker restorer gene (Rf-WA-2) was located on chromosome 10. These findings should facilitate tagging of these genes with molecular markers with the ultimate aim to practice marker-aided selection for fertility restoration ability.     

Genetic analysis of a CSR10 (indica) × Taraori Basmati F3 population segregating for salt tolerance using ISSR markers

Segregation for salinity tolerance and ISSR markers based molecular polymorphism were investigated in a F₃ plant population raised via single-seed descent method from a cross between salt-tolerant indica rice variety CSR10 and salt-susceptible premium traditional Basmati rice variety Taraori Basmati HBC19. A total of 130 F₃plants were evaluated individually for salinity tolerance on 1–9 scale on the basis of seedling growth parameters; the average score ranged between 1.7 to 8.3. Frequency distribution curve obtained using the salinity tolerance data of F₃ population and a chi-square analysis, showed a good fit to a normal distribution. Eleven plants each in the category of salt-tolerant and salt-susceptible were selected from the segregating F₃ population for ISSR marker analysis. A total of 149 bands (4–11 bands per primer) ranging from 200 to 3530 bp were scored for the two rice varieties and the selected CSR10 × HBC19 segregating F₃ plants using 26 ISSR primers. Of these, 89 were monomorphic and 60 were polymorphic. Of the 60 polymorphic bands,36 and 20 bands were specific to CSR10 andHBC19 respectively. The remaining four bands were amplified using UBC primers 810,848, 853 and 886 and present in only some of the CSR10 × HBC19 F₃ plants. Notably, ISSR primers with dinucleotide repeat motif and 5'-anchored end amplified more number of bands (7.0 bands/primer) compared to3'-anchored dinucleotide primers (5.4bands/primer), but 3'-anchored dinucleotide primers revealed higher level of polymorphism (2.6 polymorphic bands/primer) compared to 5'-anchoreddinucleotide primers (1.43 polymorphic bands/ primer). While distribution of majority of the polymorphic bands were more or less in the expected ratios in salt-tolerant and/or salt-sensitive F₃segregating plants, but some of the bands amplified using UBC ISSR primers 823, 825,826, 849, 853, 864, 866 and 884 showed highly skewed distribution. Such polymorphic bands stand greater chances of having a linkage with the genes/ QTLs for salinity tolerance and shall be the target for further studies. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Deterioration of Eating and Cooking Quality Caused by High Temperature During Grain Filling in Early-Season indica Rice Cultivars

The effect of temperature during grain filling on eating and cooking quality of early-season indica rice was investigated by using four cultivars with different amylose content. Starting from flowering stage until maturity, the plants of all cultivars were subjected to two temperature treatments, referred as optimum (mean daily air temperature, 22 °C) and high (32 °C) temperature regimes. The results showed that the effect of high temperature on apparent amylose content and gel consistency in milled rice was cultivar-dependent. Under high temperature, amylose content increased for cv. Jiayu353 and remained little changed for cv. Guangluai4, which had intrinsically higher amylose content, and decreased for cv. Zhefu49 and cv. Jiazao935, which had lower amylose content. By contrast, high temperature reduced or kept stable gel consistency values for cultivars with higher amylose content and increased gel consistency values for those with lower amylose content. Moreover, high temperature significantly increased the gelatinization temperature of all cultivars. Pasting profiles and X-ray diffraction pattern of rice were also affected by temperature. The results suggest that high temperature during grain filling change the component and crystalline structure of starch and result in deterioration of eating and cooking quality for early-season indica rice.     

转甜菜碱醛脱氢酶基因水稻种子萌发和苗期耐盐性的研究

用0.0、3.0、5.0g/L NaCl对2个转甜菜碱醛脱氢酶(BADH)基因水稻51-22、52-7与受体亲本中花8进行萌发期盐胁迫试验.结果表明,盐胁迫下转基因材料受抑程度小于受体亲本,尤以52-7表现明显.用0.0、3.0、5.0g/L NaCl对51-22、52-7和中花8在幼苗期进行14 d盐胁迫试验.结果表明,低盐胁迫时幼苗受盐害较小,高盐胁迫时转基因材料耐盐性优于受体亲本;在盐胁迫7 d后,转基因材料体内脯氨酸含量明显高于受体亲本,同一品种随盐度增大,脯氨酸含量升高.     

温度对水稻光敏、温敏核不育基因表达影响的研究

在温度和光照自动控制的生物人工气候箱内研究了温度对安农S-1等6个温敏（Thermo-sensitive)不育材料和农垦58S等4个光敏(Photo-sensitive)不育基因表达的影响。结果表明：温敏不育材料在高温（昼温31℃，夜温28℃）条件下为不育，在低温（昼温24℃，夜温22℃）条件下为可育。它们对温度敏感的时期在花粉母细胞形成期至单核花     

不同Xa21转基因杂交稻组合的大田试验与分析

在北京、四川和江苏等地对Xa21转基因杂交稻进行了大田释放实验. 分别对转基因纯合的3个恢复系明恢63-Xa21、盐恢559-Xa21和C418-Xa21与各种不育系配组的23个杂交组合进行了抗性和农艺性状分析. 在不同的杂合遗传背景下转基因Xa21稳定遗传和高效表达, 所有杂交组合均具有对白叶枯病的广谱抗性. 转基因恢复系配制的杂交组合与     

水稻早世代稳定特异性的研究

利用9个具有早世代稳定遗传特性的水稻品系和7个栽培稻作为主体亲本杂交配组，在130个组合F2群体963个株系中，发现28个组合中出现73个稳定株系。遗传分析表明水稻早世代稳定既不是质量性状遗传也不是数量性状遗传，是按株群分离的遗传方式，出现稳定株系的组合F1群体发生了分离，F2群体中既有性状不分离的稳定株系又有孟德尔     

抽穗扬花期高温胁迫对不同耐热性水稻生理指标的影响

高温热害对水稻生产造成了巨大的损失,其危害机理研究刚刚起步。为了研究不同耐热性水稻在高温胁迫下主要生理指标的变化情况,对其生理指标与耐热性的关系进行分析。结果表明:不同品种的水稻,耐热性存在差异,可以通过耐热系数筛选不同的耐热品种;高温胁迫对不同耐热性水稻的生理指标有较大的影响,绝大多数的生理指标随高温处理时间延长,表现出先增大,达到峰值后下降的趋势;耐热性强的水稻品种,各个生理指标的峰值出现的较晚,耐热性差的品种,较早达到峰值;耐热系数和生理指标相关分析表明耐热系数除与MDA含量呈正相关关系外,与各生理指标上呈负相关关系,其中与CAT酶活性相关系数到达了-0.75222**。高温胁迫下,水稻水稻生理指标会发生很大的变化;每个生理指标基本都有峰值出现,表明生物体高温热害是应激物质等调节存在反馈机制;高温胁迫时生理指标变化与耐热性有一定的相关性。