Genetic Variation for Salinity Tolerance in Pakistani Rice (Oryza sativa L.) Germplasm

Soil salinity is one of the major production constraints. Development and planting of salt‐tolerant varieties can reduce yield losses due to salinity. We screened 185 rice genotypes at germination stage in petri dishes under control, 50, 100 and 150 mm salt stress, and at seedling stage in Yoshida's hydroponic nutrient solution under control, 50 and 100 mm salt stress. At germination stage, 15 genotypes including Nona Bokra, Sonahri Kangni, 7421, 7423 and 7467, whereas at seedling stage, 28 genotypes including Nona Bokra, Jajai‐77, KSK‐133, KSK‐282, Fakhr‐e‐Malakand, Pakhal, IR‐6, Khushboo‐95, Shahkar and Shua‐92 were found salt tolerant. Basmati‐370, Mushkan, Homo‐46 and accessions 7436, 7437 and 7720 were sensitive to salinity at both germination and seedling stage. We further screened a subset of 33 salt‐tolerant and salt‐sensitive genotypes with SSR markers. Four SSR markers (RM19, RM171, RM172 and RM189) showed significant association with two or more of the studied traits under 50, 100 and 150 mm salt stress. These markers may be further tested for their potential in marker‐assisted selection. The salt‐tolerant genotypes identified in this study may prove useful in the development of salt‐tolerant rice varieties in adapted genetic background.     

Improving the Drought Tolerance in Rice (Oryza sativa L.) by Exogenous Application of Salicylic Acid

Drought stress encumbers the rice growth predominantly by oxidative damage to biological membranes and disturbed tissue water status. In this study, the role of salicylic acid (SA) to induce drought tolerance in aromatic fine grain rice cultivar Basmati 2000 was evaluated. SA was applied as seed and foliar treatments. For seed treatment, rice seeds were soaked in 50, 100 and 150 mg l⁻¹ aerated solution of SA for 48 h and then dried back. Treated and untreated seeds were sown in plastic pots in a phytotron. At four leaf stage, one set of plants was subjected to drought stress, while the other remained well watered. Drought was maintained at 50 % of field capacity by watering every alternate day. For exogenous application, SA was applied 50, 100 and 150 mg l⁻¹ at five leaf stage. In the control, SA was neither applied exogenously nor as seed treatment. Drought stress severely affected the seedling fresh and dry weight, photosynthesis, stomatal conductance, plant water relations and starch metabolism; however, SA application improved the performance of rice under both normal and stress conditions. Drought tolerance in rice was well associated with the accumulation of compatible solutes, maintenance of tissue water potential and enhanced potency of antioxidant system, which improved the integrity of cellular membranes and facilitated the rice plant to sustain photosynthesis and general metabolism. Foliar treatments were more effective than the seed treatments. Foliar application with 100 mg l⁻¹ (FA 100) was the best treatment to induce the drought tolerance and improve the performance under normal and stress conditions compared with the control or other treatments used in this study.     

水稻苗期耐Cd胁迫的QTL定位分析

[目的]进行水稻苗期耐Cd胁迫的QTL初步定位。[方法]（1）以Lemont（美国）和Dular（印度）杂交建立的重组自交系（RILs）群体,包括123个家系和亲本在内,用含有0.2mg/L镉的水培液进行处理,以不加镉培养的水培液作为对照,考察了叶绿素含量、根长、株高、叶长等4个性状,并转换成抗性指数,用于评价水稻对Cd污染的抗性指标。（2）在已构建的以109个引物为基础的遗传图谱上进行复合区间定位。[结果]（1）共检测到9个加性QTLs,涉及1,2,3,11等4条染色体,其中,以叶绿素抗性指数为指标,检测到3个与耐Cd有关的QTLs 分别位于第2,3,11染色体上,解释了14%,9%,9%的表型变异;（2）以根长抗性指数为评价指标,只定到1个位于第1染色体上控制耐Cd的QTLs,解释了9%的表型变异; （3）用株高抗性指数进行定位,共有3个与耐Cd相关的QTLs,位于1,1,11染色体上,分别解释了10%,27%,10%的表型变异;（4）而以叶长抗性指数进行水稻秧苗耐Cd性表现的QTL定位,结果发现也有2个QTLs与其耐Cd 反应有关,它们分别位于1,11染色体上,解释了21%,12%的表型变异。分析表明,在采用不同评价指标所检测到的9个与耐Cd相关的QTLs中,有7个集中于第1和第11染色体上,其中第1染色体上有4个,第11染色体上有3个。（结论）以株高和叶绿素抗性指数为评价指标,检测到的QTLs最多,根长抗性指数为评价指标的最少。研究还发现在第1和第11染色体上的相同区间内同时检测到以不同抗性指数为评价指标的多个与耐Cd相关的QTLs,推测它们可能是功能相同的几个紧密连锁的非等位基因,也可能就是同一等位基因的不同表现形式,从而也说明了该评价指标用于基因定位的准确性和可行性。     

水稻耐低磷胁迫研究进展

土壤中有效磷缺乏是制约水稻生产的主要因素之一。利用磷效率不同的水稻基因型选育磷高效水稻品种,是解决水稻磷营养问题的一种更为经济、环保的途径。本文简要论述了水稻耐低磷胁迫的机理及磷高效基因型筛选体系,重点综述了近年来水稻磷效率相关性状的QTL定位分析结果,以期为水稻耐低磷研究及磷高效水稻品种的选育提供参考。     

水稻耐低磷种质的筛选与鉴定

本研究对281份不同的水稻（Oryza sativa L.）品种（品系）进行了耐低磷筛选和鉴定。在大田种植条件下,通过水稻部分性状耐低磷系数（－P/+P）的变异范围、平均值以及它们间的相关性分析,认为相对籽粒产量、相对成熟期的地上部生物重、相对植株分蘖期的分蘖数是较好的耐低磷筛选和评价的指标。并提出以偏低含磷量大田初筛及     

Exogenous Application of Abscisic Acid Improves Cold Tolerance in Chickpea (Cicer arietinum L.)

Chickpea suffers cold stress (<10 °C) damage especially during reproductive phase resulting in the abortion of flowers and pods, poor pod set, and reduction in seed yield and seed quality. One of the ways in modifying cold tolerance involves exogenous treatment of the plants with chemicals having established role in cold tolerance. In the present study, the chickpea plants growing under optimum temperature conditions (28/12 °C, as average maximum and minimum temperature) were subjected to cold conditions of the field (10–12/2–4 °C; day/night as average maximum and minimum temperature) at the bud stage. Prior to exposure, these plants were treated exogenously with 10 μm abscisic acid (ABA) and thereafter again after 1 week of exposure. The stress injury measured in terms of increase in electrolyte leakage, decrease in 2,3,5-triphenyl tetrazolium chloride reduction %, relative leaf water content and chlorophyll content was observed to be significantly mitigated in ABA-applied plants. A greater pollen viability, pollen germination, flower retention and pod set were noticed in ABA-treated plants compared with stressed plants. The seed yield showed considerable improvement in the plants treated with ABA relative to the stressed plants that was attributed to the increase in seed weight, greater number of single seeded pods and reduction in number of infertile pods. The oxidative damage measured as thiobarbituric acid-reactive substances was lesser in ABA-treated plants that was associated with greater activities of superoxide dismutase, catalase, ascorbate peroxidase, ascorbic acid, glutathione and proline in these plants. It was concluded that cold stress effects were partly overcome by ABA treatment because of the improvement in water status of the leaves as well as the reduction in oxidative damage.     

水稻突变体的创制

为功能基因组学研究提供较好的基础材料,利用0.75%甲基磺酸乙酯溶液和γ射线双重诱变处理‘晋恢21’M1、‘中花11’、LR001种子进行研究。结果表明,经过M2筛选,获得716份叶、茎、穗、粒等性状变异的突变体,突变频率较高,达1.79%,还获得一些如不分蘖、多分蘖、白化苗、mini-plant、稀粒、花器官等极具研究价值的突变类型。双重诱变可以获得各种类型的突变体,所有的突变类型在3种材料中均有出现,说明该技术可为功能基因组研究提供大量的实物材料。     

水稻耐低磷种质的苗期筛选与鉴定

从以成恢448为轮回亲本，M401为供体亲本构建的回交后代BC₁F₆筛选出的耐低磷材料（GP9）和低磷敏感材料（GP14）及其亲本用于盆栽试验，设置P2（2.31 mg/kg）、P30（30 mg/kg）和P80（80 mg/kg）3个磷处理水平，以P80处理为对照计算性状相对值，研究不同磷处理浓度对供试材料6个生物学性状的影响。结果表明，P2处理较P30处理更能反映不同材料性状相对值间的差异，宜用于苗期耐低磷筛选。P2处理时，GP9与GP14及其亲本播种后52 d、59 d和66 d的相对分蘖数差异均达极显著水平，建议采用相对分蘖数作为水稻苗期耐低磷筛选的主要鉴别指标。同时，运用相对叶面积、相对绿叶数和相对叶龄进行综合评定。     

Interaction of Phosphate and Salinity on the Growth and Yield of Rice (Oryza sativa L.)

The role of phosphorus application on growth and yield of rice under saline conditions was studied in a set of two experiments, one in nutrient and the other in soil culture. In experiment 1, the effect of inorganic phosphate (P_i) on the growth and ionic relations of four rice cultivars, varying in salt tolerance and phosphorus use efficiency, grown in nutrient solution with and without 50 mol m^?3 NaCl was measured in a 2 week trial. The growth of all rice cultivars was affected to different degrees due to external P, in the presence of salt. External P, concentration up to 100 μM in the presence of NaCl caused stimulation of all growth parameters (shoot, root, tillering capacity), above this concentration P, had an inhibitory effect. Salt-induced P toxicity was exhibited at a much lower P, concentration (10 μM) by the salt sensitive cultivar. Increasing the supply of phosphorus (from 1 to 100 μM P_i) to the saline medium tended to decrease the concentrations of Na¹ and CI in all cultivars except IR 1561. Shoot concentrations of these saline ions were much lower in the salt tolerant and moderately salt tolerant rice cultivars. Shoot P and Zn concentrations showed an increasing trend in the presence of external P, and salt in the rooting nr -idium but most strikingly P: Zn ratio was lower in salt tolerant and moderately salt tolerant cultivars. Significantly higher concentrations of Na⁺, P and CI, and lower concentrations of Zn, were determined in the shoots of salt sensitive cultivars when exposed to salt stress in the presence of P_i Results were confirmed in naturally salt-affected soils of two different types (saline-sodic and saline) where paddy yield of NIAB 6 (salt tolerant) and IR 1561 (salt sensitive) showed improvement through moderate phosphorus supply (18 kg P ha^?1).     

Effect of Prohexadione Calcium on Growth Components and Endogenous Gibberellins Contents of Rice (Oryza sativa L.)

Prohexadione calcium (Pro‐Ca) is a novel plant growth regulator that inhibits the late stages of gibberellins (GAs) biosynthesis in plants, thus reducing the vegetative growth of the plant. Pro‐Ca was applied to field‐grown rice cultivar Ilpumbyeo to evaluate its effect on growth and yield components and endogenous GAs, when applied at different rates and timings. This study illustrated that Pro‐Ca application decreased the internode length, stem length, panicle length, shoots fresh weight and stem lodging index, while stem breaking force was increased in all treatments. The effect of Pro‐Ca was more pronounced in 20 ppm concentration than 10 ppm. The number of panicles m⁻², ripened grain ratio and 1000 grain weight and milled rice yield parameters, increased with the application of Pro‐Ca, though the number of grains per panicle decreased insignificantly. The endogenous bioactive GA₁ contents significantly decreased with the application of Pro‐Ca, as the GA biosynthesis was interrupted at later stages, when GA₂₀ conversion to GA₁ was blocked, thus drastically reducing GA₁ and GA₈ levels, but only insignificant changes were observed for intermediates from GA₁₂ to GA₂₀. The levels of the endogenous GAs in rice shoots were measured by GC‐MS‐SIM using ²H₂‐labelled GAs as internal standards. Present results also illustrated that early application of Pro‐Ca was more effective than its late application for effective control of different growth parameters and thus reducing lodging in rice plants.     

CaM和TFP对水稻早期胚胎离体发育的影响

研究了不同浓度的外源钙调素(calmodulin, CaM)和钙调素拮抗剂TFP (trifluoperazine)对水稻授粉后3~5 d胚胎离体发育的影响。结果表明：（1）CaM对水稻3~5 d胚胎离体发育的调控具有时间和浓度效应。较高浓度的CaM (10^-6~10^-5 mol/L)对不同时期的水稻胚胎发育均具一定抑制作用,CaM浓度越大,抑制作用越强;培养基中外加10^-7 mol/L CaM时,不同时期的水稻胚胎均表现出最佳的生长速度和最高的正常胚胎诱导频率;在相同的CaM条件下,胚龄越大,胚胎离体生长越快,正常胚胎诱导频率及总诱导频率越高。（2）较高浓度的TFP抑制水稻3~5 d胚胎的离体生长和发育,其作用亦有时间和浓度的效应,胚胎越小,抑制作用越强;TFP浓度增加,抑制作用增强,不同发育时期的胚胎生长速度及正常胚胎诱导频率、总诱导频率均逐渐下降。     

水稻花粉的离体萌发

选出适合于水稻花粉萌发的液体培养基： 20%蔗糖+10%PEG4000+40 mg.L-1H3BO3+3m mol/L Ca(NO3)2+10 mg.L-1VB1, 得到80%的萌发频率。 离体萌发时, 花粉管生长很快, 在30 min内可达700 μm。 最适萌发的温度范围较宽, 27～33℃都可以得到较高的萌发频率。     

水稻苗期耐淹相关性状QTL分析

以相同淹水条件下存活率差异较大的籼稻TN1与粳稻春江06(CJ06)为亲本构建的DH群体为试材,考察了DH群体及其双亲与苗期耐淹相关的5个性状,各性状均表现为连续分布,且都存在一定数量的双向超亲遗传类型,受多基因控制。使用分子连锁图谱进行QTL分析,共检测到16个与苗期耐淹有关的QTL,包括4个中胚轴长度QTL、3个株高QTL、3     

水稻孕穗期耐热性QTLs分析

水稻籼粳亚种间杂种优势利用是提高水稻产量的重要途径。然而，异常高温或低温导致籼粳亚种间杂种育性下降是影响其优势利用的主要因素之一。本研究以USSR5（粳稻）/广解9号（籼稻）//USSR5回交群体为供试材料，构建了相应的分子连锁图谱，分别以高温处理下直接小穗育性及小穗育性热敏感指数为指标，对水稻孕穗期高温耐热性及其相对耐热性进行数量性状位点（QTLs）分析。结果表明，在第2、4和5染色体上检测到孕穗期耐热性相关的QTL各一个，对表型变异的解释率为6.4%~15.8%；在第4、8染色体上分别检测到与孕穗期相对耐热性相关的QTL，qhts-4和qhts-8，LOD值分别为3.81和2.86，对表型变异的解释率分别为16.8%和9.9%。对其进一步的上位性分析表明，有8条染色体的4对位点存在基因间互作，小穗育性耐热性除受主效QTL控制外，还受基因间互作及修饰基因的影响。     

不同水稻种质资源重要农艺性状与发芽期耐寒性鉴定研究

对106份水稻材料的12个农艺性状进行两年（2018-2019年）田间测定,比较分析不同材料间的性状及多样性指数差异,以低温处理下的发芽率为标准对水稻种质资源发芽期耐寒性进行评价。结果表明,12个农艺性状中,除了千粒重、茎粗和每穗总粒数外,其他9个性状的遗传多样性指数均小于2.00;单株产量、每穗总粒数和每穗实粒数的变异系数分别为22.08%、21.89%和22.25%,谷粒宽变异系数最小,为7.90%。共筛选出23份特异种质资源,其中大穗型品种9个,高单株产量型品种4个,籽粒细长型品种10个。聚类分析可将106份水稻材料分为3个类群,类群Ⅰ、类群Ⅱ和类群Ⅲ占比分别为15.1%、47.2%和37.7%。通过主成分分析可将12个农艺性状指标转换为5个主成分因子（PC1~PC5）,得到84.19%的累计贡献率。利用综合指标值（PC1~PC5）和相关公式得到相应模糊隶属函数和权重,最终获得综合评价种质资源农艺性状的D值,排名前10名的种质资源为77D、万恢355-2、宜恢1577、南恢533、176-15、丰788、万恢86、杨福6号、蜀恢527和176-6。低温胁迫导致水稻种子发芽率降低,种质间的发芽率存在显著差异,其中176-6、176-15、桂99和糯稻89-1发芽期耐寒性强,为1级耐寒种质。筛选到的耐寒种质和综合性状优良的种质可为培育适宜直播的新品种提供材料。     

Physiological Role of Exogenously Applied Glycinebetaine to Improve Drought Tolerance in Fine Grain Aromatic Rice (Oryza sativa L.)

Rice performance under drought stress is mainly impeded by oxidative damage and hampered plant water status, which may be improved by exogenous use of osmoprotectants. In this study, the role of glycinebetaine (GB) to improve drought tolerance in rice (Oryza sativa L.) cultivar Super-basmati was evaluated. GB was used both as seed and foliar application. For priming, seeds were soaked in 50, 100 and 150 mg l⁻¹ aerated solution of GB for 48 h. At four-leaf stage, one set of plants was subjected to drought stress, while the other set kept at full field capacity. Drought was maintained at 50 % of field capacity by watering when needed. For exogenous application, 50, 100 and 150 mg l⁻¹ GB levels were applied at five-leaf stage. Drought stress greatly reduced the rice growth while GB application improved it both under well-watered and drought conditions. Drought tolerance in rice was strongly related to the maintenance of tissue water potential and antioxidant system, which improved the integrity of cellular membranes and enabled the plant to maintain high photosynthesis. Foliar treatments were more effective than the seed treatments, while among the GB treatment, foliar application with 100 mg l⁻¹ was the most effective.     

籼稻米粒延伸性的遗传研究

采用包括遗传主效应和基因型与环境互作效应的三倍体遗传模型，分析了两环境下籼稻米粒延伸性的遗传基础。结果表明，米粒延伸性及其相关性状(米粒长和饭粒长)，主要受制于遗传主效应，但也受到基因型与环境互作效应的控制。在遗传主效应中又以种子基因加性效应为主，其次是母体植株的基因效应。米粒长和饭粒长的狭义遗传率都     

Exogenously Applied Nitric Oxide Enhances the Drought Tolerance in Fine Grain Aromatic Rice (Oryza sativa L.)

Drought stress is a severe threat to the sustainable rice production, which causes oxidative damage and disturbs plant water relations, while exogenously applied nitric oxide (NO) may have the potential to alleviate these effects in rice plants. In this study, the role of NO to improve drought tolerance in fine grain aromatic rice ( Oryza sativa L. cv. Basmati 2000) was evaluated. Sodium nitroprusside, a NO donor, was used at 50, 100 and 150  μ mol l⁻¹ both as seed priming and foliar spray. To prime, the seeds were soaked in aerated NO solution of respective solution for 48 h and dried back to original weight. Primed and non-primed seeds were sown in plastic pots with normal irrigation in a greenhouse. At four leaf stage, plants were subjected to drought stress except the controls, which were kept at full field capacity. Drought was maintained at 50 % of field capacity by watering when needed. Two controls were maintained; both receiving no NO treatments as foliar application or seed treatment, one under drought conditions and the other under well-watered conditions. Drought stress seriously reduced the rice growth, but both methods of NO application alleviated the stress effects. Drought tolerance in rice was strongly related to the maintenance of tissue water potential and enhanced capacity of antioxidants, improved stability of cellular membranes and enhanced photosynthetic capacity, plausibly by signalling action of NO. Foliar treatments proved more effective than the seed treatments. Among NO treatment, 100  μ mol l⁻¹ foliar spray was more effective.     

水稻中胚轴长度QTL分析

为分析水稻中胚轴伸长与赤霉素的关系及其遗传基础,以沈农265(长中胚轴)和丽江新团黑谷(短中胚轴)的RIL群体为材料,结合其连锁图谱,对水和赤霉素溶液两种培养条件下的中胚轴长度进行QTL定位。结果表明,浓度为1.50μmolL~(-1)的赤霉素可显著促进中胚轴的伸长。两种培养条件下,共检测到控制中胚轴长度的5个QTL,分布在第1、第2、第3、第6和第11号染色体上,LOD值在3.65～15.52范围内,单个QTL对表型贡献率在7%～33%之间。其中qML3、qML6和qML11在2种处理条件下均被检测到,qML1和qML2仅在水培条件下被检测到。与其他研究比较发现,主效基因qML3可以在不同群体和不同环境下稳定表达。     

Genetic Analysis of Resistance to Brown Planthopper in Rice (Oryza sativa L.)

Seventeen rice cultivate resistant to brown planthoppers were genetically analyzed using the Bangladesh insect population. Seven cultivars were found to have a single dominant gene for resistance. These genes segregated independently of the recessive resistance gene bph-5. Tae dominant resistance gene of ‘Swarnalata’ was designated Bph-6. In ten cultivars, resistance is conferred by single recessive genes. In eight cultivars, the resistance genes are allelic to bph-5. However, the recessive genes o: two cultivars are non-allelic to bph-5. The recessive gene of T12 is designated bph-7.