Cold tolerance at the early growth stage in wild and cultivated rice

The present study was conducted to understand the pattern of variation and the genetic bases for cold tolerance at the early growth stage in Asian rice. The genetic variation was investigated at the germination, plumule and seedling stages among 57 strains including cultivated rice (Oryza sativa ssp. indica and ssp. japonica) and its wild progenitor (Oryza rufipogon). The significant differentiation of cold tolerance was observed among the taxonomically divided groups. At the germination stage, both indica and japonica subspecies tended to be more tolerant than O. rufipogon, whereas at the plumule and seedling stages, ssp. japonica tended to be more tolerant than ssp. indica and O. rufipogon. Furthermore, in cold tolerance at the plumule stage, the clinal variation across the latitude of origins was observed within O. rufipogon and ssp. japonica, suggesting that the current pattern of variation seems to have been shaped by both their phylogenetic histories and on-going adaptation to the local environments. QTL analysis between O. sativa ssp. japonica (tolerant) and O. rufipogon (susceptible) revealed five putative QTLs for cold tolerance at the plumule and seedling stages but not at the germination stage. Substitution mapping was also carried out to precisely locate the two major QTLs for cold tolerance at the plumule stage, which could be used for improvement of tolerance to cold stress in ssp. indica.     

Identification of quantitative trait loci for cold tolerance during the germination and seedling stages in rice (Oryza sativa L.)

Low temperature is a serious abiotic stress affecting rice production in subtropical and temperate areas. In this study, cold tolerance of rice at the germination and seedling stages were evaluated using one recombinant inbred line (RIL) population derived from a cross between Daguandao (japonica), with highly cold-tolerant at the seedling stage, and IR28 (indica), with more cold-tolerant at the germination stage, and the quantitative trait loci (QTL) mapping was conducted using the multiple interval mapping (MIM) approach. Continuous segregation in low temperature germinability (LTG) and cold tolerance at the seedling stage (CTS) were observed among the RIL populations. Most RILs were moderately susceptible or tolerant at the germination stage, but were susceptible at the seedling stage. No significant relationship was found in cold tolerance between the germination and seedling stages. A total of seven QTLs were identified with limit of detection (LOD) >3.0 on chromosomes 3, 8, 11 and 12, and the amount of variation (R ²) explained by each QTL ranged from 5.5 to 22.4%. The rice LTG might be regulated by two minor QTLs, with the CTS controlled by one major QTL [qCTS8.1 (LOD = 16.1, R ² = 22.4%)] and several minor loci. Among these loci, one simultaneously controls LTG (qLTG11.1) and CTS (qCTS11.1). Several cold-tolerance-related QTLs identified in previous studies were found to be near the QTLs detected here, and three QTLs are novel alleles. The alleles from Daguandao at six QTLs increased cold tolerance and could be good sources of genes for cold tolerance. In addition, only one digenic interaction was detected for CTS, with a R ² value of 6.4%. Those major or minor QTLs could be used to significantly improve cold tolerance by marker-assisted selection (MAS) in rice.     

Characterization and identification of cold tolerant near-isogenic lines in rice

To exploit the genetic mechanism of cold tolerance in rice, cold tolerant near-isogenic lines (NILs) were developed by backcrossing Kunmingxiaobaigu (KMXBG), reported to be the most cold-tolerant variety at the booting stage, as donor, with the cold sensitive Japanese commercial japonica variety, Towada. Comparisons of cold tolerance-related traits between five BC₆F₅ NILs and recurrent parent Towada under cold treatment and normal temperatures at the booting stage showed that the differences between the NILs and Towada were significant only for spikelet fertility-related traits. Analyses of cold tolerance in the NILs at the budding (germination), seedling and booting stages indicated both correlated effects and differences. Lines 1913-4 and 1916-1 showed strong and stable tolerance at all three stages. Whole genome marker screening showed that the proportion of genetic background recovery was more than 98%. Seventeen markers from KMXBG were introgressed in two or more NILs, and cold tolerance genes were possibly present in these marker regions. The NILs should be excellent materials for both rice improvement and map-based cloning of cold tolerance QTLs.     

QTL mapping for tolerance of anaerobic germination from IR64 and the aus landrace Nanhi using SNP genotyping

Direct seeding is becoming more popular mainly due to its labor-saving nature. However, flooding during germination caused by unleveled fields and unpredicted heavy rain can prevent crop establishment. On the other hand, flooding just after sowing protects the seeds from rats and birds and is also a viable means of weed control. Thus, the development of varieties able to tolerate flooding during germination, referred to as anaerobic germination (AG), is essential. A study was conducted to identify QTLs associated with tolerance of flooding during germination from an F_2:3 mapping population derived from the cross of IR64 and the tolerant aus landrace Nanhi. Phenotyping was performed by counting the rate of seedling survival of 300 lines under the stress. Selective genotyping was employed by genotyping the 48 most tolerant and 48 most susceptible lines using a 384-plex SNP Indica/Indica set on the Illumina BeadXpress Reader, resulting in 234 polymorphic markers for the study. A major QTL for AG derived from Nanhi, named qAG7, was detected on chromosome 7 with an LOD of 13.93 and 22.3 % of the phenotypic variance explained. A second QTL of smaller effect, qAG11, was also derived from Nanhi, while one QTL with an increased effect from IR64 was detected on chromosome 2 (qAG2.1). The QTLs detected in this study can be used to further elucidate the mechanisms underlying AG tolerance in rice, and can also be used in marker-assisted selection and QTL pyramiding to provide higher AG tolerance to enable improved crop establishment in direct-seeded systems.     

水稻籼型不育系萌发期和幼苗期的耐盐性评价

为了鉴定水稻籼型不育系在不同生育阶段的耐盐性,筛选出适合耐盐杂交水稻新组合测配的强耐盐不育系,笔者分别在萌发期、幼苗期对8个水稻籼型不育系进行耐盐性鉴定,以耐盐品种FL478、盐敏感品种IR29为对照。结果显示：盐胁迫对水稻种子的萌发起到抑制作用,抑制效应随盐浓度的提高而增强,10 g/L NaCl浓度胁迫能较好反映水稻不育系萌发期耐盐性的差异。‘沪旱7A’、Y58S在萌发期的耐盐性最好,与FL478均属于1级,具极强的耐盐性;‘荃9311A’的盐害级别为3级,具强耐盐性。盐胁迫对水稻幼苗的生长也起到明显的抑制作用,8 g/L NaCl浓度胁迫下的枯叶率性状能较好反映水稻不育系幼苗期耐盐性的差异,‘沪旱11A’与耐盐对照FL478耐盐性相仿。     

直播早籼稻品种芽期耐冷性鉴定研究

低温胁迫是水稻生产面临的重要非生物胁迫之一,鉴定水稻种质资源芽期耐冷性,筛选耐冷品种对水稻生产具有重要意义。以江西地区主推的33份早籼杂交稻品种和8份常规稻为试验材料,设置12个芽期低温胁迫处理,以死苗率为指标探讨了早籼稻芽期耐冷性的适宜鉴定方法。同时在8℃低温处理10d,恢复生长后调查其成苗率、苗高、根长、根数、地上部生物量、根系生物量和根冠比。运用主成分分析、模糊隶属函数法和聚类分析法来探讨直播早稻芽期的耐冷性评价方法及筛选耐冷品种。结果表明,8℃低温处理10d,直播早籼稻品种死苗率的方差和变异幅度大,能较好地鉴别品种间耐冷性差异,是直播早籼稻芽期耐冷性鉴定的最合理方式;杂交稻品种的耐冷性强于常规稻;低温胁迫后成苗率、苗高、根长、根数、地上部生物量、根系生物量和根冠比基本低于25℃对照处理;利用主成分分析将7个单项指标转化为3个独立的综合指标（CI₁、CI₂、CI₃）,主成分分析表明,根系生物量和地上部生物量最能代表直播早籼稻对低温胁迫后的响应情况,可作为芽期耐冷性鉴定的评价指标。通过聚类分析,将41份早籼稻品种划分为3类,筛选出陵两优7108、两优287、锦两优816等9份强耐冷品种,株两优1号、潭两优83、株两优22等15份中度耐冷品种,温229、中早33、五丰优157等17份冷敏感品种。这些品种可以进一步为耐冷育种和生产服务。     

Assessing morphological characteristics of elite cotton lines from different breeding programmes for low temperature and drought tolerance

Cotton breeders in the United States strive to develop region‐specific genotypes adapted to low temperatures and variable soil moistures during early‐season planting. Nine elite upland cotton germplasm (Gossypium hirsutum L.) lines, representing public breeding programmes from nine states across the cotton belt, were evaluated for cold and drought stresses during seed germination and seedling growth stages. Lines were subjected to three treatments, such as low temperature well‐watered (22/14°C, WW), optimal temperature drought stress (30/22°C, DS) and optimal temperature well‐watered (30/22°C, WW; control), to examine genotypic variability for cold and drought tolerance. The treatment including drought stress was irrigated at 50% of the control. Shoot and root traits measured at 25 days after planting were significantly affected by drought and low temperature, where significant genetic variability among lines was observed for both shoot and root parameters. Response indices were developed to quantify variation in the degree of tolerance among the lines to low temperature and drought. Accordingly, OA‐33 was identified as the most low‐temperature‐tolerant line and Acala 1517‐99 as the most drought‐tolerant line. Identification of both cold‐ and drought‐tolerant genotypes suggests existing genotypic variability could provide breeders the opportunity to improve cultivar response to early‐season drought or cold conditions.     

Evaluation of Cold Tolerance in NERICAs Compared with Japanese Standard Rice Varieties at the Reproductive Stage

New Rice for Africa (NERICA) is a general name for interspecific rice varieties derived from a cross between the high‐yielding Asian rice (Oryza sativa L.) between locally adapted African rice (Oryza glaberrima Steud.). Eight NERICAs were evaluated for cold tolerance (CT) at the reproductive stage and compared with their O. sativa parents and three Japanese standard rice varieties over 3 years. Cold tolerance was evaluated based on the filled grain ratio (FGR) after cold water irrigation. The FGR was greatly reduced by cold water irrigation. NERICA 1, 2 and 7 had higher FGR (51.9–57.9 %), while NERICA 6, 15 and 16 had lower FGR (6.2–14.5 %). NERICA 1, 2 and 7 were less affected by cold stress, with a 31 % mean reduction in FGR, while NERICA 6, 15 and 16 were greatly affected, with their FGRs being reduced by more than 80 %. NERICA 3 and 4 were moderately affected by cold stress, with about 45 % reduction rate in FGR. FGR significantly influenced the grain weights of the varieties with strong positive correlations (r = 0.83–0.91; P < 0.001), and thus, similar trends in grain weights were observed. Grain weights were reduced by 61.7–96.4 % under cold stress. NERICA 1, 2 and 7 showed significantly better performance than NERICA 3 and 4, while NERICA 6, 15 and 16 performed poorly under cold water irrigation. The Japanese varieties Koshihikari (very tolerant) and Ozora (moderately tolerant) were more affected by cold water irrigation than NERICA 1, 2 and 7. On the basis of the mean reduction rate (%) in FGR under cold stress, the varieties were classified as follows: NERICA 1, 2 and 7 as tolerant; NERICA 3 and 4 as moderately tolerant; and NERICA 6, 15 and 16 as susceptible to cold stress. However, NERICA 7 grain yields were lower under cold stress due to both greatly reduced number of panicles per plant and number of spikelets per panicle. Therefore, NERICA 1 and 2 are suitable candidates for production in the highland regions of East Africa and should be promoted for production.     

水稻新质型不育系幼苗期耐冷性及其生理生化特性的质核效应

为了探明水稻新质型不育系幼苗期耐冷性特点,以一套同质异核不育系（G软香A,G华香1A,G华香2A）和一套同核异质不育系（G软香A,Y软香A,WA软香A）为材料,采用光照培养箱培养的方法,鉴定和评价了3~4叶期幼苗的耐冷性,并分析了低温胁迫后不育系幼苗丙二醛(MDA)含量、过氧化物酶(POD)活性以及幼苗生物量的变化。结果表明：供试不育系的耐冷性分级可分为4级,其中G华香2A的耐冷性最强（1级）,Y软香A的耐冷性最差（9级）。就同质异核不育系而言,G华香2A耐冷性最强,G华香1A次之,G软香A中等,表现出细胞核对耐冷性的效应。就同核异质不育系而言,WA软香A耐冷性强,G软香A耐冷性中等,Y软香A耐冷性极弱,表现出细胞质对耐冷性的效应。因此,水稻不育系的耐冷性受到细胞质和细胞核基因的共同影响。幼苗MDA含量、POD的活性以及幼苗期水稻苗高、根数、鲜重等生物量等性状都与耐冷性有关。耐冷性越强的不育系,经低温处理后其幼苗MDA相对含量越低,POD相对活性越低,生物量相对鲜重越大,即说明耐冷性越强的不育系,经低温处理后较之对照幼苗的MDA含量增加量较小,POD活性增强程度小,生物量下降较少。     

高粱耐冷种质的鉴定及利用评价

为了满足高粱育种对耐冷基础材料的需求,解决高粱播后遇低温造成幼芽受冻、幼苗萎焉进而影响高粱产量的问题,对238份高粱种质资源进行了高粱芽期、苗期耐冷性鉴定与评价,从中筛选出芽期耐冷种质15份,苗期耐冷种质11份。印度材料IS-2867和中国育成种TC1383-2、E671在芽期、苗期均为耐冷一级抗性,其中TC1383-2是中国高粱育种常用的恢复系,其耐冷特性对于耐冷品种的选育具有利用价值。结果表明,地方品种、育成种和国外品种的耐冷性存在差异,无论芽期还是苗期,在中国地方品种中都有较高比例的耐冷资源,说明在中国地方品种中挖掘耐冷种质的潜力较大。     

不同生育期水稻耐冷性的鉴定及耐冷性差异的生理机制

以粳稻9516、H45、武育粳、转PEPC基因水稻、Kitaake、苏沪香粳，籼稻扬稻6号、香籼、IR64，培矮64S以及杂交稻粤优938、汕优63、X07S/紫徽100、两优培九等14个水稻品种为材料，分别鉴定了芽期（胚根1 cm, 胚芽0.5 cm）、苗期（三叶）和孕穗期的耐冷性，同时选取南京对水稻播种敏感的自然低温条件，进行低温鉴定。结果表明，芽期存活率、苗期的枯死率和孕穗期结实率均为可靠的水稻耐冷性鉴定指标。进一步从叶片的光合速率、PSⅡ光化学效率（F_v/F_m）、脂肪酸组分、活性氧指标(丙二醛,过氧化氢和超氧阴离子和抗氧化物质(抗坏血酸和谷胱甘肽)的变化等方面，研究耐冷性不同的水稻的耐冷生理机制。表明耐冷的水稻品种武育粳含较多的不饱和脂肪酸，在低温逆境下，膜的流动性愈大，低温对其伤害愈小；对杂交稻汕优63而言，其叶内抵御逆境的保护系统抗坏血酸和谷胱甘肽的循环被较大地激活，特别是谷胱甘肽再生的高速运转，与不耐冷的品种香籼相比，汕优63叶内的过氧化物质累积较少，其耐冷性表现中等。看来水稻叶片维持高的脂肪酸不饱和指数和谷胱甘肽的周转循环能力是水稻耐冷的重要特征。     

Analysis of decision-making coefficients of the lint yield of upland cotton (Gossypium hirsutum L.)

Cold water irrigation and growth in low temperature phytotron are two commonly used methods to evaluate cold tolerance of rice at the seedling stage and the cold sensitive seedlings exhibit different injury symptoms, respectively. However, so far no one has systematically dissected the differences of cold tolerance at seedling stage in rice under the two cold environments. We used a recombinant inbred line (RIL) population derived from a cross of a cold-tolerant japonica cultivar, Lijiangxintuanheigu and a cold sensitive indica cultivar, Sanhuangzhan-2 for this study. The cold sensitive seedlings exhibited leaf yellowing after cold water irrigation and leaf rolling during growth in the low temperature phytotron. Leaf yellowing and leaf rolling in RILs was significantly correlated, but the correlation coefficient was low. A total of four quantitative trait locus (QTLs) on chromosomes 1, 6, 9 and 12 were detected using leaf yellowing and percent seedling survival as indicators of cold tolerance after cold water irrigation, while five QTLs on chromosomes 7, 8, 9, 11 and 12 were detected using leaf rolling and percent seedling survival as indicators of cold tolerance during growth in the low temperature phytotron. The two QTLs, qCTS-9 and qCTS-12 were detected using different evaluation indicators under the two cold environments. Our results suggest that rice cold tolerance mechanisms at the seedling stage differ between the two environments, but the detection of common QTL implies the existence of overlap in the metabolic pathways for cold tolerance. The two common QTLs have potential value in rice breeding.     

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.     

水稻芽期与幼苗前期耐碱性状QTL定位

利用包含120个株系的籼粳交来源(春江06/TN1)的加倍单倍体群体, 在Na₂CO₃胁迫下, 以发芽期和幼苗前期的相对发芽势等10个性状作为耐碱性评价指标, 进行水稻耐碱性的QTL定位。相关性分析表明, 相对发芽势和相对发芽率显著正相关, 相对苗高、相对根数和相对根长之间显著正相关。采用QTLNetwork统计软件共定位到14个加性QTL和13个上位性QTL。在第3染色体RM251~RM3280间有2个QTL, 在第7染色体RM3286~RM1279区域有3个QTL; 在第1、2和7染色体同一位置同时检测到2个上位性QTL, 在第12染色体RM1246~RM5199之间集中了4个上位性QTL, 耐碱数量基因表现出一因多效或紧密连锁现象。耐碱性盐QTL可能包括两类, 一类与K+、Na+等离子胁迫有关, 另一类与高pH胁迫有关。不同类型的水稻品种都具有一些耐碱基因, 可以通过有性杂交和分子标记辅助选择的方法选育优良的耐碱品种。     

Effect of Sodium Chloride on Germination and Seedling Characters of Different Types of Rice (Oryza sativa L.)

The rice eultivars grown in the tropies and sub-tropics can be broadly categorized as aromatic small grain, local coarse grain and modern high yielding varieties (HYV). The first two categories are traditional rice, and are generally palatable. The aromatic rice has better market value than HYV rice, yet farmers are unwilling to expand its cultivation because of the low yield potential. One possibility to expand the cultivation of traditional rice is o t find stress tolerant cultivars for growing in marginal land. The salinity tolerance of nine rice cultivars representing three from each type of aromatic small grains, local coarse grains and HYV types, was analysed at germination and early seedling stage. Seeds were placed for germination and the seedlings were allowed to grow for nine days at NaCl concentrations of 0, 50, 100, 150 and 200 mM. NaCl decreased the germination index (GI), speed of germination, seedling height and seedling dry matter weight. Seedling characteristics were decreased more than GI. In general aromatic small grain type showed more salt sensitivity than the other two types. Among the nine cultivars Shakkorkhora (aromatic type) showed the least salt tolerance in relation to germination and seedling characters while the other two cultivars of the same group showed tolerance as high as the tolerant cultivars in other types. Generalization of group salt tolerance of rice, therefore, has little value from the agronomic point of view at least at early growth stage. As the number of cultivars employed in this study was only three from each type it is suggested that more cultivars be considered for the purpose of salt tolerant improvement programme of various types of rice.     

High resolution genotyping by restriction enzyme-phased sequencing of advanced backcross lines of rice exhibiting differential cold stress recovery

Advanced backcross rice lines MIb 4853-9 and 6885-2 harbor major seedling cold tolerance QTL qCTS4 and qCTS12 from the temperate japonica M202 in the genetic background of the indica IR50. Previous studies have shown that these lines exhibit the same tolerance, based on visual ratings, under constant and intermittent exposure to cold stress. However, some differences between the MIb lines with regard to physiological stress indicators are observed under constant exposure and a clear difference is detected using a cold stress recovery assay. Genotyping with over 120 SSR markers did not detect any polymorphisms. Here we report using a reduced representation sequencing method called Restriction Enzyme Site Comparative Analysis to identify M202 introgressions unique to each MIb line as candidate loci for the cold stress recovery trait.     

Response of maize inbred lines to a defoliation treatment inducing tolerance to cold at germination

Defoliation during maize (Zea mays L.) kernel development has been observed to induce tolerance to cold of germinating seeds in responsive genotypes. The objectives of this study were to evaluate the response to defoliation of immature embryo and mature seed germinability at cold and to verify if the response was influenced by the developmental stage at which the treatment was applied. In three environments, six inbred lines (B73, IABO78, Lo1016, Lo964, Mo17, Os420) were defoliated (D) approximately 20 days after pollination (DAP) or not defoliated (ND). Immature embryos were excised three days after defoliation and germinated in vitro at 9 or 25 ^∘C. At maturation, kernel germination was tested at the same temperatures. Defoliation improved cold tolerance and mean time to germination (MTG) at 9 ^∘C of both embryos and kernels of Lo1016. To study the effect of kernel developmental stage on response to defoliation, plants of B73, Lo1016 and Lo964 were defoliated at 15, 18, 21, 24, 27, 30, 33, 36, and 39 DAP, or not defoliated. At the same DAP, immature grains were analyzed for dry weight, water and abscisic acid (ABA) content. In Lo1016, low amounts of kernel ABA were detected at all stages, while in Lo964 and B73 ABA increased during development. Lo1016 mature kernels showed an improvement of cold tolerance due to defoliation at all times, while the other genotypes did not. In conclusion inbred lines showed variability for mature seed and immature embryo tolerance to cold at germination and for the ability to acquire tolerance after defoliation.     

甘蓝型油菜种子萌发期耐镉性分析及耐镉材料筛选

为研究镉对甘蓝型油菜幼苗的影响,筛选出耐镉品种,以35个不同遗传背景的甘蓝型油菜品系（种）为材料,用不同浓度(1、5、10 mg/L)镉进行胁迫处理。以相对发芽势、相对正常芽苗率、根长抑制率、苗长抑制率、苗鲜重抑制率和苗含水量抑制率六大指标,通过主成分分析和隶属函数分析科学评价不同甘蓝型油菜品系幼苗耐镉性。结果表明,随着镉处理浓度的增大,胁迫对大部分油菜种子的发芽势有促进作用,而成苗率呈下降趋势;幼苗的根长和苗长的抑制均呈上升趋势;苗鲜重和苗含水量呈下降趋势;综合评价筛选出耐镉品系（种）10个,其中品系C13095-6的镉耐性最强。本研究可为甘蓝型油菜品种耐镉性筛选和耐镉育种提供理论参考。     

河北省地方水（陆）稻品种耐逆性研究

对河北省地方水（陆）稻品种耐逆性进行了鉴定,并在此基础上分析了耐寒性、耐旱性、耐盐性种质分布情况。对耐性频度较高的耐寒性、耐旱性从水、陆稻,熟期,不同稻作区等方面进行了详细研究。结果表明：耐寒、耐旱品种频度高、强度大,耐寒品种高达86.44%,高耐率23.53%;耐旱品种为48.77%,高耐率31.65%;耐盐性品种仅为6.46%,并且无高耐性和耐性品种。耐寒品种频度水稻高于陆稻,各熟期类型分布频度接近,随纬度增加、经度西移和温热条件降低而增加;耐旱性品种频度和强度均是陆稻高于水稻,早稻早熟耐性频度最高,其余熟期比较接近,河北省东北地区高,西北及冀中库淀地区低。     

Salt Tolerance of Some Oats (Avena sativa L.) Varieties at Germination and Seedling Stage

Soil salinity is the serious problem of the arid and semi-arid tracts of the world. It causes great losses to agriculture by lowering the yields of various crops. However, such soil may be utilized either after reclaimation or by growing tolerant plant species. The degree of salt tolerance varies not only with plant species but the different varieties of the same species show variation in salt tolerance. Germination and seedling stages have a bearing on plant development at later stages of growth and ultimately crop yield. Therefore, in the present investigation, twelve varieties of oats viz., Colabagh, Kent, JHO-801, JHO-802, JHO-810, JHO-815, JHO-816, S-3021, S-2688, Chauripatti, UPO-201 and Sierra were tested for their relative salt tolerance to increasing levels of salinity in those combination of salts which nearly exist in the natural salt affected soils. Seeds were sown in petri dishes and were exposed to five salinity (40, 80, 120, 160 and 200 me/L. of salts) levels. The germination percentage, root and shoot length and dry weight of the seedlings decreased with increase in salinity. In general, varieties JHO-815, JHO-802, JHO-816 and UPO-201 were found to be more tolerant at germination and seedling stages.