Evaluation of salt tolerance in rice genotypes by physiological characters

The use of physiological characters as selection criteria in salt tolerance breeding requires the identification of the contribution each individual character makes to salt tolerance. Rice genotypes were evaluated for salt tolerance in terms of grain yield and physiological characters. Plants of twelve genotypes were grown in sand tanks in a greenhouse and irrigated with Yoshida nutrient solution. Sodium chloride and calcium chloride (5:1 molar ratio) were added at two concentrations to give moderate (4.5 dS m^-1) and high (8.3 dS m^-1) salinity treatments. One set of plants was harvested at 635 ^°Cċd (accumulative thermal time) after planting to determine LAI and mineral ion concentrations. Another set of plants was allowed to grow to maturity. High genotypic diversity for LAI and shoot ion contents was observed. LAI contributed the most to the variation of the grain yield under salt stress. Significant correlations between LAI and yield components in both salt-tolerant and-sensitive genotypes further confirmed the significant contribution of LAI to grain yield. K-Na selectivity increased with increasing salinity. Conversely, Na-Ca selectivity decreased with increasing salinity. Significant correlations were identified between grain yield and both Na-Ca and K-Na selectivity. Highly significant (p<0.001) correlations were identified between Na-Ca selectivity and the rankings among genotypes for grain yield. Thus, Na-Ca selectivity could be one salt tolerance component and an useful selection criterion in screening for salt tolerance. This revised version was published online in July 2006 with corrections to the Cover Date.     

Germination characters and early seedling growth of wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) genotypes under salt stress conditions

Screening of wheat genotypes as salt tolerance through seed germination and early seedling growth is crucial for their evaluation. Seeds of 20 wheat genotypes were germinated in Petri dishes on a sand bed irrigated with saline (15 dS m_-1) and control solutions for 10 days and also tested at different salinity levels (control, 4, 6, 8, and 10 dS m^-1) which were artificially developed in the soil for 30 days. At 10 days, germination percentage, rate of germination, co-efficient of germination, germination vigor index, shoot length, root length, and seedling dry weight were found to be affected due to salinity. Salt tolerance index (STI) for seedling dry weight maintained a significant positive correlation with rate of germination, germination vigor index, shoot length, and root length, which indicates that these parameters could be used as selection criteria for screening wheat genotypes against salt stress. Significant differences in shoot length, root length, and seedling dry weight in 30-day-old seedlings were observed among selected wheat genotypes as well. From the overall observation of germination characters and early seedling growth, it was concluded that the wheat genotypes including Gourab, Shatabdi, Bijoy, Prodip, BARI Gom 26, BAW 1186, and BAW 1189 showed better salt tolerance as compared to others.     

Characterization and genetic control of germination-emergence responses of grain sorghum to salinity

Summary When grain sorghum is grown in saline soils, one cause of low yield is poor crop establishment. The objectives of this study were to assess the response of grain sorghum to salinity in the germination-emergence stages, study the inheritance of salt tolerance at this stage, and determine the relative contribution to final emergence of salt effects during imbibition, and after onset of germination. Twelve inbred lines and 18 F1 hybrids, resulting from an incomplete 6×6 factorial mating design, were tested for germination and emergence in folded paper at 10 salt concentrations, from 1.8 to 36 dSm^-1. The mean EC₅₀ (the electrical conductivity at which the variable score declines by 50%) for emerged seedlings production was 21.2 dSm^-1. Large genotypic differences were observed for salt tolerance at germination and emergence stages, which were not related to the viability of seeds, and poorly related to seed weight (considered as an estimate of intrinsic seed vigor). In the hybrids, these differences were due to SCA and female GCA for emergence, and female GCA for germination, though the male GCA was also significant for both characters. Line per se performance was significantly correlated to individual GCA estimates for emergence, but not for germination. Heterosis was only detected in three crosses for final emergence and in one cross for germination. The genetic differences in final emergence were mainly due to effects occurring after the onset of germination rather than a consequence of effects during imbibition.     

谷子地方品种发芽期和苗期对NaCl胁迫的反应和耐盐品种筛选

用150 mmol L^-1和200 mmol L^-1NaCl溶液鉴定194份来自河南、山东、河北等地的谷子地方品种的耐盐性,筛选出红谷、小黄谷、三变丑等11份耐盐性较强的品种,野谷5号和洋谷对盐胁迫比较敏感;不同品种发芽率、根和芽生长表现不同。发芽相对盐害率与苗期株高和第一片真叶面积相对盐害率没有显著相关性,但发芽期耐盐性差的品种野谷5号和洋谷在苗期耐盐性也较差。芽期耐盐性强的红谷、小黄谷和三变丑在150~200 mmol L^-1下苗期株高相对盐害率小于野谷5号和洋谷,三变丑的株高相对盐害率低于红谷和小黄谷,在高浓度下小黄谷的叶面积相对盐害率最小。     

Identification of pearl millet [Pennisetum glaucum (L.) R. Br.] lines tolerant to soil salinity

Crop tolerance to salinity is of high importance due to the extent and the constant increase in salt-affected areas in arid and semi-arid regions. Pearl millet (Pennistum glaucum), generally considered as fairly tolerant to salinity, could be an alternative crop option for salt affected areas. To explore the genotypic variability of vegetative-stage salinity tolerance, 100 pearl millet lines from ICRISAT breeding programs were first screened in a pot culture containing Alfisol with 250 mM NaCl solution as basal application. Subsequently, 31 lines including many parents of commercial hybrids, selected from the first trial were re-tested for confirmation of the initial salinity responses. Substantial variation for salinity tolerance was found on the basis of shoot biomass ratio (shoot biomass under salinity/ non-saline control) and 22 lines with a wide range of tolerance varying from highly tolerant to sensitive entries were identified. The performance of the genotypes was largely consistent across experiments. In a separate seed germination and seedling growth study, the seed germination was found to be adversely affected (more than 70% decrease) in more than half of the genotypes with 250 mM concentration of NaCl. The root growth ratio (root growth under salinity/control) as well as shoot growth ratio was measured at 6 DAS and this did not reflect the whole plant performance at 39 DAS. In general, the whole plant salinity tolerance was associated with reduced shoot N content, increased K⁺ and Na⁺ contents. The K⁺/Na⁺ and Ca⁺⁺/Na⁺ ratios were also positively related to the tolerance but not as closely as the Na⁺ content. Therefore, it is concluded that a large scope exists for improving salt tolerance in pearl millet and that shoot Na⁺ concentration could be considered as a potential non-destructive selection criterion for vegetative-stage screening. The usefulness of this criterion for salinity response with respect to grain and stover yield remains to be investigated.     

Screening sorghum genotypes for salinity tolerant biomass production

Genetic improvement of salt tolerance is of high importance due to the extent and the constant increase in salt affected areas. Sorghum [Sorghum bicolor (L.) Moench] has been considered relatively more salt tolerant than maize and has the potential as a grain and fodder crop for salt affected areas. One hundred sorghum genotypes were screened for salinity tolerance in pots containing Alfisol and initially irrigated with a 250-mM NaCl solution in a randomized block design with three replications. Subsequently 46 selected genotypes were assessed in a second trial to confirm their responses to salinity. Substantial variation in shoot biomass ratio was identified among the genotypes. The performance of genotypes was consistent across experiments. Seven salinity tolerant and ten salinity sensitive genotypes are reported. Relative shoot lengths of seedlings were genetically correlated to the shoot biomass ratios at all stages of sampling though the relationships were not close enough to use the trait as a selection criterion. In general, the whole-plant tolerance to salinity resulted in reduced shoot Na⁺ concentration. The K⁺/Na⁺ and Ca²⁺/Na⁺ ratios were also positively related to tolerance but with a lesser r ². Therefore, it is concluded that genotypic diversity exists for salt tolerance biomass production and that Na⁺ exclusion from the shoot may be a major mechanism involved in that tolerance.     

Identification and Characterization of Salt Tolerance of Wheat Germplasm Using a Multivariable Screening Approach

Salinity is one of the major limitations to wheat production worldwide. This study was designed to evaluate the level of genetic variation among 150 internationally derived wheat genotypes for salinity tolerance at germination, seedling and adult plant stages, with the aim of identifying new genetic resources with desirable adaptation characteristics for breeding programmes and further genetic studies. In all the growth stages, genotype and salt treatment effects were observed. Salt stress caused 33 %, 51 % and 82 % reductions in germination vigor, seedling shoot dry matter and seed grain yield, respectively. The rate of root and shoot water loss due to salt stress exhibited significant negative correlation with shoot K⁺, but not with shoot Na⁺ and shoot K⁺/Na⁺ ratio. The genotypes showed a wide spectrum of response to salt stress across the growth stages; however, four genotypes, Altay2000, 14IWWYTIR‐19 and UZ‐11CWA‐8 (tolerant) and Bobur (sensitive), exhibited consistent responses to salinity across the three growth stages. The tolerant genotypes possessed better ability to maintain stable osmotic potential, low Na⁺ accumulation, higher shoot K⁺ concentrations, higher rates of PSII activity, maximal photochemical efficiency and lower non‐photochemical quenching (NPQ), resulting in the significantly higher dry matter production observed under salt stress. The identified genotypes could be used as parents in breeding for new varieties with improved salt tolerance as well as in further genetic studies to uncover the genetic mechanisms governing salt stress response in wheat.     

中国高粱地方种质芽期苗期耐盐性筛选及鉴定

日益严重的土壤盐渍化对现代农业生产造成了巨大的危害。高粱既是世界五大粮食作物之一,又是耐盐性很强的抗逆作物。开展高粱耐盐性研究、筛选出一批综合耐盐能力优良的高粱品种对开发利用盐渍化土地、增加粮食产量和维持农业可持续发展具有重要意义。本研究对110份中国高粱地方品种分别进行了芽期200 mmol L~(-1)和苗期100 mmol L~(-1)的NaCl胁迫试验,测定芽期发芽势、发芽率以及苗期的相对叶绿素含量(SPAD)、苗长、根长、苗鲜重、根鲜重、苗干重、根干重等指标。计算芽期、苗期盐胁迫下性状值占对照性状值的百分比表明,参试品种芽期相对发芽势、相对发芽率范围分别为0～98.89%、23.65%～101.79%,盐胁迫下相对发芽势变化差异显著。苗期相对叶绿素含量、相对苗长、相对根长、相对苗鲜重、相对苗干重、相对根鲜重、相对根干重变化范围分别为59.53%～99.91%、52.47%～95.23%、47.87%～100.14%、27.43%～95.28%、30.48%～98.26%、21.62%～100.34%、31.46%～102.13%。采用隶属函数值分析和主成分分析2种方法结合聚类分析对参试高粱芽期和苗期的耐盐能力综合评定,鉴定出芽期高度耐盐材料22份,耐盐材料32份;苗期高度耐盐材料37份,耐盐材料41份;其中,来自内蒙古的朝阳棒槌(00003011)和来自北京的白鞑子帽(00001081)等10个品种在芽期和苗期均表现高度耐盐,可作为后续全生育期耐盐鉴定和耐盐育种的优异资源。对芽期隶属函数值排名以及苗期F值排名结果进行相关性分析表明,芽期与苗期耐盐性没有显著相关性;主成分分析结果表明,反映生物量的指标如苗干重、根鲜重可作为苗期大量材料耐盐鉴定的评价指标。     

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.     

Sunflower seed yield as influenced by some agronomic and seed characters

Summary An investigation was made to the interrelationships of agronomic and seed characters and their effect upon seed yield. Twenty genotypes of sunflower (Helianthus annuus L.) from diverse origin were studied in spring and autumn season, 1989.Most of the studied characters exhibited different relationships in spring and autumn seasons. The correlations between plant height and oil content, 100-achene weight and number of achenes per head and plant height and head diameter were, however, consistent in both seasons and across the seasons. Stepwise multiple regression analysis identified six relevant characters on which path analysis was done.Path analysis indicated that yield components like head diameter, number of achenes per head and 100-achene weight had comparatively smaller direct effects on seed yield (0.22, 0.15 and 0.23, respectively). Days to physiological maturity, plant height and oil content had relatively stronger direct effects on seed yield (0.33, 0.38 and 0.29, respectively). Days to physiological maturity, plant height and head diameter had considerable indirect effects. Head diameter, 100-achene weight and number of achenes per head were indentified as selection criteria for yield improvement.     

Evaluation of seedling selection for salinity tolerance in potato (Solanum tuberosum L.)

Summary Salt-tolerance in potato (Solanum tuberosum L.) was selected on the basis of germination and survival of seed sown in trays of perlite suspended in either 75 or 150 mM NaCl. Salinity reduced the germination of seed. Genetic differences in salt-tolerance were apparent with salt reducing germination more in seed collected from cv. Cara than in that collected from cv. Maris Piper. Progeny from the seedling selection were then grown to maturity to produce tubers.The relative tolerance of the parental cultivars and of unselected and selected progeny to long-term exposure to salinity was examined in a pot experiment in which plants were irrigated with either fresh water or 50 mM NaCl solution from one week after plant emergence. In this experiment, salinity significantly reduced leaf conductance, total dry matter production and partitioning of assimilate to tubers. Salinity reduced dry matter production and assimilate partitioning to tubers to a greater extent in Cara than in M. Piper. Progeny selected for short-term salt-tolerance did not exhibit greater long-term salt-tolerance than unselected progeny, and both were more sensitive than M. Piper.These results demonstrate genetic variation in salt-tolerance in potato. However, although there was a correlation between the performance of the parent to long-term salinity and survival of progeny in the seedling selection, there was no correlation between short- and long-term salt-tolerance. This suggests that characters underlying short-term tolerance may contribute to long-term tolerance but do not of themselves confer long-term tolerance. Future progress in selecting for improved salt-tolerance depends on understanding the effects of salinity on the physiological processes underlying growth and carbon partitioning.     

Using Growth and Ionic Contents of Wheat Seedlings as Rapid Screening Tool for Salt Tolerance

High germination percentage with vigorous early growth is preferred for harvesting good wheat stand under saline soils. Therefore, an attempt for rapid screening of wheat genotypes for salt tolerance was made in this study. Eleven wheat genotypes including salt tolerant check Kiran-95were subjected to salinity (120 and 160 mMNaCl) along with non-saline control. Results showed a gradual decrease in seed germination and restricted seedling growth in tested wheat genotypes in response to increasing NaCl concentration in nutrient solution. Among the genotypes, NIA-AS-14-6 and NIA-AS-14-7 exhibited more sensitivity towards the salt stress at the germination stage but NIA-AS-14-6 performed quite satisfactorily later on at the seedling stage. Wheat genotypes NIA-AS-14-2, NIA-AS-14-4, NIA-AS-14-5, NIA-AS-14-10, and Kiran-95 showed better performance in term of root-shoot length, plant biomasses (fresh and dry), K⁺:Na⁺ ratio with least Na⁺ content, and high accumulation of K⁺ at higher levels of NaCl stress. On the basis of overall results, the categorization of genotypes was carried out as sensitive, moderately tolerant, and tolerant. Wheat genotypes NIA-AS-14-2, NIA-AS-14-4, NIA-AS-14-5, NIA-AS-14-10, and Kiran-95 grouped as tolerant, moderately salt tolerant group comprised of NIA-AS-14-1, NIA-AS-14-3, NIA-AS-14-6, and NIA-AS-14-8, whereas, NIA-AS-14-7 and NIA-AS-14-9 were found sensitive to salt stress. Principal component analysis revealed that components I and II contributed 70 and 16.5%, respectively. All growth parameters are associated with each other except RDW. In addition to growth traits, low Na⁺ and improved K⁺ content with better K⁺:Na⁺ ratio may be used for screening of salt tolerance in wheat as potential physiological criteria.     

Comparative study of the Nicotiana species with respect to water deficit tolerance during early growth

Sixty Nicotiana species were examined for tolerance against various osmotica for seed germination and seedling growth in vitro. The species showed a wide variety of tolerance, and based on the results of the in vitro tests, 31 species were selected and further evaluated for salt and drought tolerance in a glasshouse. The degrees of tolerance of germination among the 57 species toward NaCl were approximately related to those toward mannitol, indicating that the osmolarity plays a majorrole in seed germination. However, the responses during the seedling growth differed in NaCl and mannitol or drought, and there was no correlation between salt and drought tolerance. Based on the responses in vitro and in the glasshouse, N. paniculata and N. excelsior were selected as the salt tolerant species, and N. arentsii as the salt sensitive species. The degrees of accumulation of dry matter and of Na⁺ in the leaves were different in the two tolerant species; during NaCl treatment, N. paniculata and N. arentsii accumulated less dry matter relative to the control plants than N. excelsior, and N. paniculata accumulated more Na⁺ in its leaves than N. excelsior and N. arentsii. It is assumed that the two salt tolerant species have different mechanisms for tolerance to the salt. This revised version was published online in July 2006 with corrections to the Cover Date.     

Differences between wheat genotypes in damage from freezing temperatures during reproductive growth

Cereal crops in the reproductive stage of growth are considerably more susceptible to injury from freezing temperatures than during their vegetative growth stage in the fall. While damage resulting from spring-freeze events has been documented, information on genotypic differences in tolerance to spring-freezes is scarce. Ninety wheat genotypes were subjected to a simulated spring-freeze at the mid-boot growth stage under controlled conditions. Spring-freeze tolerance was evaluated as the number of seeds per head at maturity after plants were frozen at −6 °C. Plants that froze, as confirmed by infrared (IR) thermography, died shortly after thawing and consequently the heads did not mature. Only in plants that had no visible freezing (super-cooled) were heads able to reach maturity and produce seeds. In plants that super-cooled four genotypes had significantly higher seed counts after being exposed to freezing than three with the lowest. In addition, significant differences between genotypes were found in whole plant survival among those that had frozen. Genotypes with high whole-plant freezing survival were not necessarily the same as the super-cooled plants with the highest seed counts. Spring-freeze tolerance was not correlated with maturity suggesting that improvement in freezing tolerance could be selected for without affecting heading date. Spring-freeze tolerance was not correlated with freezing tolerance of genotypes of plants in a vegetative state, either under non-acclimated or cold-acclimated conditions indicating that vegetative freezing tolerance is not a good predictor of spring-freeze tolerance.     

Genetic variation in drought tolerance at seedling stage and grain yield in low rainfall environments in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Genetic architecture of seedling drought tolerance is complex and needs to be better understood. To address this challenge, we developed a protocol to identify the most promising drought-tolerant genotypes at the seedling stage in winter wheat. A population of 146 recombinant inbred lines (F₉) derived from a cross between wheat cultivars, ‘Harry’ (seedling drought tolerant) and ‘Wesley’ (seedling drought susceptible) were used in this study. All genotypes were sown in three replications in a randomized complete block design under controlled conditions in a greenhouse. Seven traits were scored and grouped into tolerance traits; days to wilting, leaf wilting, and stay green and survival traits; days to regrowth, regrowth, drought survival rate, and recovery after irrigation. Three selection indices were calculated (1) tolerance index, (2) survival index, and (3) drought tolerance index (DTI). The same set of genotypes were also tested for grain yield in two low rainfall environments for two seasons. High genetic variation was found among all genotypes for all seedling traits scored in this study. Correlations between tolerance and survival traits were weak or did not exist. Heritability estimates ranged from 0.53 to 0.88. DTI had significant phenotypic and genotypic correlations with all seedling traits. Genotypes were identified with a high drought tolerance at the seedling stage combined with high grain yield in low rainfall. Breeding for tolerance and survival traits should be taken into account for improving winter wheat drought tolerance at seedling stage. The selected genotypes can be used for to further improve drought tolerance in high yielding wheat for Nebraska.     

Genetic variation in seed production and its components in four cultivars of the pasture grass Setaria sphacelata

Variation in seed production and its components was investigated between and within four cultivars of the pasture grass Setaria sphacelata, in two experiments over two years, as a basis for future cultivar improvement. The study sought to determine the basis for the considerable differences in seed production of the four cultivars Nandi, Narok, Solander and Kazungula, to determine the extent of genetic variation in the four cultivars in attributes which contribute to seed yield, and to investigate genotypic consistency in seed production over years and seasons. Each experiment comprised 50 genotypes of each cultivar. In the first experiment, plants were harvested a set number of days after median flowering date whereas in the second experiment, which was unreplicated, each genotype was harvested a set number of days after it had flowered. In the first experiment, seed yields were generally highest for Kazungula, lowest for Narok and intermediate for Nandi and Solander. All measured attributes contributing to seed yield exhibited a high order of variation between and within cultivars, but the basis for the large difference in seed yield per plant between cultivars was tiller fertility rather that total tiller number. Averaged over the four harvests, there was a six fold to > 100–fold intra-cultivar genetic range in seed production, associated with differences in tiller fertility, which were associated with differences in date of first flowering. Broad sense heritability for seed yield averaged 0.68 for the four cultivars and showed little change over the four harvests. Genotypes which produced high seed yields in summer were also more productive of seed in autumn and the 0ore productive genotypes in the first year were also more productive in the second year. Cultivars differed in the relative importance of factors which contributed to the high seed yield of high-yielding genotypes. In the second experiment, genotypes with a high seed yield also generally had the highest tiller fertility, even though all genotypes were harvested the same number of days after first flowering. Within-cultivar correlations in seed yield between the two experiments were generally significant and the elite 20% of genotypes from this experiment had 1.2–2.9 times the seed yield of the same genotypes with a very different harvesting regime in the first experiment. It is concluded that opportunities exist in all four cultivars for improvement in seed production and that the selection criterion offering the best opportunity for advance would be fertile tiller number. In Narok, Solander and Nandi, this would result in increased tiller fertility, whereas in Kazungula, it would result in an increase in total tiller number. This revised version was published online in July 2006 with corrections to the Cover Date.     

引进春小麦种质耐盐性的鉴定评价

对从美国引进的28份春小麦种质经过实验室耐盐性鉴定,筛选出13份芽期相对盐害率在20%以下,苗期盐害指数在40%以下的耐盐性较强的材料,进一步在0.37%以上的盐渍化土壤上进行全生育期的耐盐性鉴定,对株高、穗长、穗数、穗粒数、千粒重等生产要素进行统计分析及逐步剔除多元回归分析,结果表明产量性状的耐盐指数与出苗率、     

Combining ability for seed yield traits of Chenopodium quinoa breeding lines

For a better understanding of the inheritance of seed yield traits in Quinoa (Chenopodium quinoa) Willd., a half-diallelic crossing experiment with six diverse but uniform breeding lines was conducted. True hybrid plants were detected by means of differences in panicle colour in 14 out of the 15 crosses performed. The agronomic performance of 14 F₂ populations and six parental lines was evaluated in field trials on fertile clay soil. General and specific combining ability of the lines (GCA and SCA) were estimated. Highly significant differences in GCA effects were found between the lines for plant height at maturity, early flowering, early maturity, seed yield and thousand seed weight. Significant SCA effects were only found for plant height at maturity. However, SCA effects were rather small and accounted for 7% of the total variance. The finding of large GCA effects and low SCA effects suggests that best selection results could be expected from crosses between the agronomic best performing genotypes. This revised version was published online in August 2006 with corrections to the Cover Date.     

棉花苗期耐低钾能力筛选指标研究及其与产量、品质的关系

以长江流域下游棉区的12个棉花主栽品种为研究材料,在人工气候室水培和田间种植条件下进行棉花苗期耐低钾能力筛选指标研究。结果表明,低钾会放大棉花苗期关于钾素吸收利用和光合碳同化等生理特性上的品种间差异幅度。土壤严重缺钾时会显著降低棉花铃数、铃重及衣分,其中铃数响应土壤缺钾最为敏感,而在铃重组成中纤维质量对土壤缺钾的响应幅度大于棉子质量。通过对比基于棉花苗期不同生理指标和最终产量与品质指标的筛选结果,发现综合考虑棉花苗期叶片SuSy活性、SPAD值和单株叶片生物量3项指标的低钾胁迫系数对棉花最终产量与品质的耐低钾能力具有较好的预测效果。通过试验筛选出低钾敏感型棉花品种泗杂3号和耐低钾型棉花品种泗棉3号,二者可作为进一步研究低钾环境下棉花产量、品质形成机理的理想试验材料。     

Assessment of tolerance to salt stress in Kenyan tomato germplasm

Tomato is an important vegetable crop in Kenya and the development of salt tolerant cultivars would enhance its productivity in the vast marginal areas of the country. This study was aimed at determining the magnitude of genotypic variability for salt tolerance in the Kenyan tomato germplasm. Pot experiments with 22 landraces and 9 market cultivars were laid out as a two and four replicate split-plot design in glasshouse in Experiments 1 and 2, respectively. Salt treatments in Experiment 1 were 0 and 5 g NaCl kg^-1 resulting into 0.5 and 9.1 dS m^-1 of the soil saturation extracts, respectively. In Experiment 2 the treatments were 0, 4, and 8 g NaCl kg^-1 soil corresponding to 0.5, 7.4, and 14.2 dS m^-1, respectively. Data were recorded on agronomic and biochemical parameters. The germplasm showed large variation for salt tolerance. Fruit and seed production at soil salinity of 14.2 dS m^-1 demonstrated that these tomatoes are fairly tolerant of NaCl. Osmotic adjustment was achieved by higher fruit electrical conductivity, brix and total titratable acidity. Low and high contents of K⁺, Ca²⁺ and Mg²⁺ within tomato tissues and soil, respectively, under salt treatment, confirmed competition and antagonism involving Na⁺ and these cations. Low Na⁺ and Cl^- contents in the fruit at 7.4 dS m^-1 revealed their exclusion and ensured production of physiologically normal seeds and nutritionally healthy fruits. Two landraces ‘Chwerotonglo’ and ‘Nyanyandogo’ were identified as salt tolerant. Comparatively, the market cultivars showed superior fruit yields despite their susceptibility to salinity. Accordingly, tolerance of landraces in combination with superior yields of the market cultivars is suitable for tomato improvement for salt tolerance. This revised version was published online in July 2006 with corrections to the Cover Date.