Genotype × environment interactions for wheat grain yield and antioxidant changes in association with drought stress

The phenotypic performance of a genotype is not necessarily the same under diverse agro-ecological conditions. Two commercial wheat cultivars and 33 wheat landrace varieties were selected for screening drought tolerance and the investigation of genotype × environment interactions (GEI). The study site experiences drought stress at reproductive stages. Fully irrigated along with two drought stress trials at early heading (EHS) and 50% heading stages (HDS) were performed in 2 years. The highest antioxidant and proline contents were accumulated under EHS. Reduction in cell membrane stability in EHS was 90.9% in 2011–2012. The lowest grain yield belonged to EHS (3.2 t ha^?1) while the highest (6.8 t ha^?1) was observed in the irrigated trial. GEI analysis indicated that the Pinthus’s coefficient was not an efficient index for screening GEI. Positive correlations were found between GEI parameters such as regression deviation, Wricke’s ecovalence and Shukla’s variance. Regression coefficients over trials ranged from 0.65 to 1.42, indicating genotypes had different responses to environmental changes. Regression models, GEI variances and grain yield showed that some varieties (KC4557, KC4862, KC3891, KC4495, and KC4633) had higher stability under drought stress and fully irrigated conditions and can be involved in breeding programs for drought stress tolerance.     

Relationship of Creep-Recovery and Dynamic Oscillatory Measurements to Durum Wheat Physical Dough Properties

Durum wheat gluten strength is important in determining extrusion properties and pasta cooking quality. Durum wheats varying in strength were tested using an alveograph and a 2-g micro-mixograph, both widely accepted techniques for determination of physical dough properties. Doughs from the 2-g micro-mixograph were characterized by dynamic oscillatory and large deformation creep tests using a controlled stress rheometer. Mechanical properties obtained from both testing regimes were strongly correlated with many of the parameters provided by the alveograph and micro-mixograph. Maximum strain attained after 5 min creep ranged from <5% for the strongest least extensible cultivar to >25% for the weakest cultivar, with a coefficient of variation among replicates of <10%. Storage modulus (G′) at 2 Hz ranged from ≈7,000 Pa for the weakest cultivar to >16,000 Pa for the strongest, least extensible cultivars, with a coefficient of variation of <6%. Tan δ (G″/G′) values were ≈0.4 for the strongest versus >0.5 for the weakest cultivars, indicating the larger contribution of the elastic component in the strong cultivars. The rheometer allows discrimination of durum wheat cultivars of varying gluten strength while requiring less sample than traditional physical dough testing techniques.     

Symbiotic efficiency and compatibility of native rhizobia in northern Thailand with different soybean cultivars

Symbiotic efficiency and compatibility of 81 isolates of native bradyrhizobia from irrigated areas in northern Thailand with four soybean cultivars and one cowpea cultivar were evaluated under laboratory conditions. Effectiveness and / or compatibility of the tested isolates were compared with those of a standard strain (Bradyrhizobium japonicum CB 1809) by using plants grown on plastic seed bags. Effectiveness of the isolates was also estimated using uninoculated control plants grown in a nitrogen-free solution. Nodulation of a wide range of host plants by the majority of the tested isolates was observed, which agreed well with the results of our previous field experiment (Shutsrirung et al. 2002: Soil Sci. Plant Nutr., 48, 491–499). Up to 75% of the tested isolates induced a higher growth efficiency than that of the uninoculated control in association with one of the tested cultivars, Black soybean. Comparision with uninoculated control plants, enable to estimate the proportion of the tested isolates leading to effective growth promotion (E + e) of each cultivar, namely, Black soybean (local Thai cultivar), 75%; Cowpea, 82%; SJ5 (commercial Thai cultivar), 33%; Bragg (US cultivar), 33%; and Improved Pelican (US cultivar), 9%. These results indicated that although isolates with a high infectiveness with both “Asian-type” and “US-type” soybeans could be found, a high frequency of isolates leading to inefficient nodules was observed in the US cultivar, suggesting the presence of genetic differences in the soybean cultivars that express high-preference (efficient nodules) or low-preference (inefficient nodules) for a certain group of tested isolates. Based on the results of this laboratory experiment together with our previous field experiment, native rhizobial populations in the irrigated area of northern Thailand could be separated into three groups; Group 1: rhizobium strains showing a high effectiveness with only Asian cultivars, Group 2: strains showing a high effectiveness with only US origin cultivars, and Group 3: strains showing a high effectiveness with both Asian and US origin cultivars. The majority of the native rhizobial populations belonged to Group 1. The isolates in Group 3 may display a high potential for manipulating useful rhizobial inoculant.     

Starch Granule Size Distribution from Seven Wheat Cultivars Under Different Water Regimes

Seven wheat cultivars with different starch contents were used as materials to investigate the distribution of grain starch granule size under irrigated and rainfed conditions. In mature grains, the diameter of starch granules was 0.37–52.6 μm, and the percent volume distribution showed a two‐peak curve with the mean particle diameter of 5 (B‐type) and 25 μm (A‐type) at each peak. The volume percentages of A‐ and B‐types were 52.7–65.5% and 34.5–47.3%, respectively. A two‐peak curve is also shown in percent surface area distribution of starch granules, but only one peak in percent number. Both irrigated and rainfed conditions had a significant effect on the starch granule size distribution of the seven cultivars. As compared with irrigated treatment, rainfed treatment affected the distribution of starch granules in grains of all cultivars through increasing the volume percentage and surface area percentage of 2–9.8 and <9.8 μm starch granules and decreasing those of >9.8 and >18.8 μm starch granules. The soil water deficit also decreased the contents of amylose and starch in grains and increased protein content, indicating that different water regimes had an evident effect on grain quality. According to correlation coefficients (r), the contents of amylose, starch, and protein in grains was significantly correlated with the volume percentage of starch granules with different diameter ranges.     

Purple versus green‐leafed Ocimum basilicum: Which differences occur with regard to photosynthesis under boron toxicity?

This study was undertaken to investigate how different cultivars of sweet basil (Ocimum basilicum) responded to boron (B) excess. Two purple‐leafed and eight green‐leafed cultivars were hydroponically grown for 20 d with 0.2 or 20 mg L^–1 B in the nutrient solution. Leaf B concentration, gas exchanges, chlorophyll a fluorescence, and oxidative stress were determined at the end of the treatment along with the severity of leaf necrosis. A range of tolerance to B toxicity was found: the green cultivars were more susceptible than the purple‐leafed ones characterized by a higher constitutive anthocyanin concentration. In all the genotypes B excess resulted in oxidative stress as determined by accumulation of malondialdehyde by‐products (MDA), reduced photosynthesis, and the occurrence of leaf burn. A close correlation was found between leaf B accumulation and oxidative stress, as well as between oxidative stress and the severity of leaf burn. Net photosynthesis (P_n) was reduced due to both stomatal and nonstomatal limitations in the green cultivars whereas the reduction of P_n in the purple leaves was only attributable to stomatal factors. Chlorophyll a fluorescence revealed a decrease in the maximum quantum yield of PSII (F_v/F_m) and in the electron transport rate (ETR) in plants grown with B excess although less reduction was observed in the purple genotypes. The quantum yield of PSII (Φ_PSII) decreased as a result of B toxicity only in the green cultivars. It is concluded that anthocyanins are involved in attenuation of the negative effects of B toxicity.     

Water and temperature dynamics in a clay soil under winter wheat: influence on straw decomposition and N immobilization

Summary Winter wheat grown on a clay soil was subjected to one of four treatments. The control was not irrigated; the drought treatment had screens to divert rainwater; the irrigation and irrigation/fertilization treatments were irrigated using a drip-tube system with liquid fertilizer (200 kg N ha^-1 year^-1) applied daily in the irrigation/fertilization treatment according to predicted plant uptake. All other treatments also received 200 kg N, but as a single application of bag fertilizer. Soil temperature was monitored. Soil moisture was measured using gravimetric samplings and a capacitance method. Litter bags with barley straw were buried at 10 cm depth in the spring and sampled repeatedly during the growing season. Decomposition rates were calculated assuming exponential decay and that water-soluble components were immediately decomposed or leached from the litter bags. Rates were highly dependent on soil moisture, and the constants ranged from 0.11% day^-1 in the drought treatment to 0.55% day^-1 in the irrigation/fertilization treatment. A simulation model with driving variables based on Q ₁₀ temperature dependence and a log/linear relationship between soil water tension and activity was fitted to the data. The control and drought treatments showed high climate-corrected decomposition constants. The high values were attributed to low and erratic mass loss due to drought, and to low precision in the conversions from water content to tension in the dry range. The irrigated treatments showed good fits, and there was little or no difference in decomposition rates between the two irrigated treatments. The N dynamics of the straw differed considerably between treatments, and the ranking of plots in terms of net immobilization in the straw was control>irrigation/fertilization>irrigation>drought.     

Photosynthetic water‐use efficiency of irrigated winter and summer crops in a typical mountain oasis of northern Oman

The millenia‐old existence of traditional, surface‐irrigated Omani mountain oases implies a remarkable sustainability of such systems in a hyperarid environment. This study was conducted in the mountain oasis of Balad Seet, situated in the Al‐Jabal‐al‐Akhdar mountains of northern Oman, to investigate the water‐use efficiency (WUE) of these oases and how farmers regulate it. In 2005, gas exchange of single leaves of 9–16 plants was measured for the most important perennial field crop alfalfa in both February and August, for the typical winter crop oat in February, and the dominating summer crop sorghum in August. The measurements were conducted five times a day in subplots irrigated the evening before and in the surrounding control plots, where plants had been withheld from irrigation for 14–16 d. Water deficit at the end of the irrigation interval reduced the stomatal conductance (g_s) strongly in summer alfalfa, oat, and sorghum, but only slightly in winter alfalfa. In oat, the reduction of net photosynthetic rate (P_N) at the end of the irrigation cycle was caused mainly by stomatal closure, in sorghum by nonstomatal factors and in summer alfalfa by both, whereas P_N in winter alfalfa remained unaffected. The ratio of net photosynthetic rate to stomatal conductance (P_N/g_s), the “intrinsic water‐use efficiency”, increased in all investigated crops in response to drought because of a stronger reduction of g_s than of P_N. This increase was small in winter alfalfa, but much stronger in oat, sorghum, and summer alfalfa. The data indicate that alfalfa maintains a relatively high CO₂ assimilation rate year‐round, contributing to a relatively high annual dry‐matter production. The decrease of the light intensity in the late afternoon caused by the shading effect of the surrounding mountains diminishes the crop evapotranspiration in the oasis.     

Nutrients uptake and water use efficiency of drip irrigated maize under deficit irrigation

Little is known about nutrient uptake during different growth stages of drip irrigated maize under deficit irrigation. A 2-year field study in the semi-arid region of Upper Egypt was carried out in a randomized complete block design with five replications during the summer of 2016 and 2017. Maize plants were irrigated with 100, 80, or 60% of water requirements. Maize growth was negatively affected by the lower water supply. Total uptake of nitrogen (N), phosphorus (P), and potassium (K) by maize irrigated with I₁₀₀ increased by 21, 25, and 21% compared to that irrigated with I₆₀. I₈₀ reduced the grain and straw yield by 8 and 17% compared to I₁₀₀. Under deficit irrigation water was used efficiently more than full water supply. NPK requirements of drip irrigated maize under deficit irrigation are less than those irrigated by full water supply thus help to sustain the environmental ecosystem and increased the economic returns.     

Response of Cotton to Irrigation Methods and Nitrogen Fertilization: Yield Components,Water‐Use Efficiency,Nitrogen Uptake,and Recovery

Efficient crop use of nitrogen (N) fertilizer is critical from economic and environmental viewpoints, especially under irrigated conditions. Cotton yield parameters, fiber quality, water‐ and N‐use efficiency responses to N, and irrigation methods in northern Syria were evaluated. Field trials were conducted for two growing seasons on a Chromoxerertic Rhodoxeralf. Treatments consisted of drip fertigation, furrow irrigation, and five different rates of N fertilizer (50, 100, 150, 200, and 250 kg N /ha). Cotton was irrigated when soil moisture in the specified active root depth was 80% of the field capacity as indicated by the neutron probe.

Seed cotton yield was higher than the national average (3,928 kg/ha) by at least 12% as compared to all treatments. Lint properties were not negatively affected by the irrigation method or N rates. Water savings under drip fertigation ranged between 25 and 50% of irrigation water relative to furrow irrigation. Crop water‐use efficiencies of the drip‐fertigated treatments were in most cases 100% higher than those of the corresponding furrow‐irrigated treatments. The highest water demand was during the fruit‐setting growth stage. It was also concluded that under drip fertigation, 100–150 N kg/ha was adequate and comparable with the highest N rates tested under furrow irrigation regarding lint yield, N uptake, and recovery. Based on cotton seed yield and weight of stems, the overall amount of N removed from the field for the drip‐fertigated treatments ranged between 101 and 118kg and 116 and 188 N/ha for 2001 and 2002, respectively. The N removal ranged between 94 and 113 and 111 and 144 kg N/ha for the furrow‐irrigated treatments for 2001 and 2002, respectively.     

Effectiveness of foreign bradyrhizobia strains in enhancing nodulation, dry matter and seed yield of soybean (Glycine max L.) cultivars in Nigeria

 Field experiments were conducted to investigate the performance of three soybean cultivars with five foreign bradyrhizobia strains in different regions. The experiments at the two sites were designed with soybean (Glycine max L.) cultivars as the main factor and bradyrhizobia strains (USDA 136, TAL 122, USDA 6, TAL 377 and TAL 102) as the sub-factor. The experiments were arranged in randomised complete block design with four replications. Results show that nodule number, nodule dry weight and shoot dry weight, total N and seed yield were significantly increased when soybean cultivars were inoculated with foreign bradyrhizobia in two locations in the south east of Nigeria. At 63 days after planting the percentage increase in nodule number and dry weight after inoculation of soybean cultivars with bradyrhizobia strains ranged from 71 to 486% and from 0 to 200%, respectively. The percentage increase in shoot dry matter, %N and total N after bradyrhizobia inoculation ranged between 2–130%, 18–62% and 35–191%, respectively at Awka, and at the Igbariam site the percentage increase in shoot dry weight, %N and total N ranged between 3–76%, 0–43% and 19–125%, respectively. Seed yields after bradyrhizobia inoculation of soybean cultivar TGX 1485–1D at Igbariam ranged between 1.20 and 2.18 t ha^–1 against the uninoculated plants, which had seed yields of 1.05 t ha^–1. The poorest yield response after inoculation with bradyrhizobia strains was observed in soybean cultivar M-351, with a seed yield ranging from 0.60 to 0.98 t ha^–1. The fact that foreign bradyrhizobia strains were more effective than the indigenous strains for all the parameters studied suggests that there is a need to use bradyrhizobia inoculants for increased soybean production in Nigeria. The variations in the strain performance with the different soybean cultivars at the two sites, emphasises the need for careful Bradyrhizobium spp. strain selection. The fact that inoculation response was cultivar- and site-specific suggests that strategies for improving inoculation response in soybean cultivars should also consider the soil environment where the soybean is to be produced. Received: 25 May 1999     

Uptake of sulfur by four cotton cultivars grown under field conditions

There has never been an intensive study of the sulfur (S) nutrition of cotton (Gossypium hirsutum L.) when grown under field conditions. Field studies were conducted on two non‐irrigated soils to evaluate the S‐uptake characteristics of four selected cotton cultivars that are representative of those produced in the Southern United States. Four cultivars with diverse genetic backgrounds, Deltapine 90, Coker 315, Paymaster 145, and Stoneville 825 were grown on a Norfolk fine sandy loam (fine loamy, siliceous, thermic, Typic Kandiudults) and a Decatur silt loam (clayey, kaolinitic, thermic, Rhodic Paleudults). Whole plants were collected at two‐week intervals over the growing season starting at 15 days after planting. The plants were partitioned into leaves, stems, burs, seed, and lint, and analyzed (except for lint) for S. Total S uptake when averaged over both soils and all four cultivars was 20.4 (±9.4) kg/ha [or 2.7 (±0.7) kg S per 100 kg lint produced]. Sulfur uptake on the Norfolk soil (15.6 (±8.5) kg/ha) was lower compared to the Decatur soil [25.1 (±7.9) kg/ha]. There were no cultivar differences in total S uptake on the Norfolk soil, but total S uptake on the Decatur soil was affected by the interaction between sampling date and cultivar. The concentration of S and S uptake by some plant parts were affected by the interaction between sampling date and cultivar, however, cultivar differences were not consistent among soils or over the growing season. Maximum daily accumulation of S occurred during the final two week sampling period at the end of the growing season (cumulative heat unit 1193–1444) during which an average of 29.5% of the total S was accumulated.     

不同株型品种冬小麦NDVI 变化特征及产量分析

冬小麦不同株型品种和灌溉类型是影响产量遥感估测的重要因素, 对二者的实时监测可以提高产量的估测精度。结合遥感数据(MODIS 数据)与非遥感数据(GPS 数据和外业调查资料), 研究了不同株型品种冬小麦在水、旱地条件下归一化差值植被指数(NDVI)的动态变化特征, 分析了不同生育时期NDVI 与产量之间的关系。结果表明: 冬小麦不同株型品种间NDVI 随生育时期的变化具有明显一致性, 呈“小-大-小”变化趋势; 拔节期至孕穗期不同株型品种冬小麦NDVI 差异显著, 披散型品种高于紧凑型品种, 该时期为准确识别冬小麦株型的最佳时期。水、旱地同一种株型的冬小麦品种在整个生育时期NDVI 均值差异较显著, 均表现为水地冬小麦高于旱地冬小麦, 尤以抽穗初期最为明显。水旱地冬小麦不同生育时期NDVI 与产量相关性均以抽穗初期为最高, 但用抽穗初期和灌浆期NDVI 与产量的复合回归方程进行产量预测比用抽穗初期NDVI 与产量的回归方程效果好, 旱地冬小麦尤为明显。     

Effects of nutrient levels on growth and quality of radish (Raphanus sativus L.) grown on different substrates

Radish grown in sand or granulated rockwool was irrigated with nutrient solutions of different concentrations. The EC value in the root environment aimed at ranged between 1.0 and 6.0 dS/m at 25°C. Four crops were grown, three crops in the spring‐summer season and one crop in winter. For the spring‐summer grown radish highest plant weights were obtained with EC values in the root environment of about 2 dS/m. In the winter grown crop an EC value between 2 and 4 gave highest plant weights. With too low EC values the yield reduction was more serious in winter than in spring‐summer. High EC values reduced yield especially in the spring‐summer season. In winter, the number of blind plants was strongly affected by the EC value. The bulb/leaf ratio was higher on sand than on rockwool and increased with EC value. Sponginess appeared in the spring‐summer crops and was reduced by increasing EC values. The mineral absorption of the radish was equal for the different crops. The water absorption, however, differed a factor four between winter and spring‐summer. So the nutrient absorption concentration in winter was about four times higher in winter than in spring‐summer.     

Growth stimulation and nitrogen supply to wheat plants inoculated with Azospirillum brasilense

Twelve Azospirillum brasilense strains isolated from wheat (Triticum aestivum L.) roots were compared for root colonization, growth stimulation, and nitrogen (N) supply to young wheat plants cv. Klein Chamaco grown in sterile nutrient solutions without N. All the strains inoculated colonized both the root surface and interior, and most strains stimulated root and shoot growth, although the degree of stimulation was different for the different strains. Some strains increased the total N content of roots and tops at the end of the experiment, in one case up to 80% of the uninoculated plants, while others produced no effect on N content. No correlation could be found between growth stimulation or the amount of N supplied to the plant with the degree of root colonization. When the most efficient strain for N fixation was inoculated to different wheat cultivars, it stimulated growth and supplied N to the five cultivars tested, although the degree of root colonization, growth stimulation and N supply showed differences among the cultivars. Our results suggest that there exists the potential of A. brasilense to supply N to wheat plants in considerable amounts, although an adequate strain are still to be identified.     

Growth,morphological and yield responses of irrigated wheat (Triticum aestivum L.) genotypes to water stress

Water shortages is a major constraint in wheat production in South Africa. It is important therefore to assist irrigated wheat farmers to identify water stress tolerant growth stages in irrigated wheat genotypes. This study evaluated new wheat genotypes for water stress at different growth stages. An 8 (genotypes) × 2 (water treatments) × 3 (growth stages) factorial experiment was laid out in a randomised complete block design with three replicates. The results indicated that plant height was not affected (p > .05) by water stress at tillering and grain filling. Water stress imposed at the tillering stage reduced the number of fertile tillers (p < .05) in susceptible genotypes while at the flowering and grain filling stages all genotypes were tolerant (p > .05). Aboveground biomass was only affected (p < .05) by water stress imposed at the tillering stage. Water stress reduced grain yield on the genotypes where stress was imposed at the tillering stage (p < .05); whereas when stress was imposed at flowering and grain filling the grain yield was not reduced (p > .05). This study provided evidence to suggest that most genotypes were tolerant to water stress at the flowering and grain filling stages.     

Effect of N rate and split application on bahiagrass production

Abstract

Vegetative and reproductive growth were studied in five tomato (Lycopersicon esculentum Mill) cultivars under saline conditions imposed at the five‐leaf stage by addition of 50 mM NaCl to half strength Hoagland nutrient solution. The plants were raised in pots filled with washed quartz sand kept in a greenhouse. Stem height and number of leaves in tomato plants were significantly reduced when irrigated with saline regimes in contrast with control plants that received only the Hoagland solution. The highest number of flowers were obtained in the cultivar Pearson and the least in cultivar Strain B. Fruit set and yield were little affected by varietal differences and were not related to vegetative growth. Fruit weight was suppressed with NaCl stress, but improvement in weight was achieved when potassium (K) and calcium (Ca) were added to the saline water. The most detrimental effect of NaCl stress was the reduction of biomass yield in tomatoes. However, the relative dry weights of Pearson and Monte Carlo were increased to 60% and 54%, respectively, when NaCl was supplemented with Ca. Large varietal differences in biomass occurred among the NaCl‐treated and control plants. Tomato fruit quality (TSS) was improved by salinization.     

Variation in seed longevity of rice cultivars belonging to different isozyme groups

The storage potential of seeds harvested at different stages of maturity was studied in ten cultivars of Oryza sativa, representing six known isozyme groups, and in two cultivars of O. glaberrima. Mass maturity (the end of the seed-filling period) was attained between 14.2 and 20.2 days after anthesis (DAA). A comparison of the estimates of p ₅₀ (time in storage for viability to decline to 50%) of seeds harvested at 21, 28 and 35 DAA and stored at 35°C with 15% moisture content showed that maximum longevity was attained between 28 and 35 DAA in most cultivars. Cultivars belonging to isozyme group II survived longer than other cultivars with estimates of p ₅₀ nearly doubled. On the other hand, the floating rices of Group IV had shorter longevity. Within group VI, the upland cultivar survived longer than the lowland cultivar. Both O. glaberrima cultivars survived reasonably well, showing that African rice cultivars also differ in longevity.     

Enhancement of salinity tolerance in tomato: Implications of potassium and calcium in flowering and yield

Abstract

Five tomato (Lycopersicon esculentum Mill) cultivars were grown in sand nutrient culture experiment in a greenhouse to investigate the effects of salinity on growth and yield. Nutrient solutions were made saline with 50 mM NaCl (EC = 5.5 mS/cm or supplemented with 2 mM KNO₃ (EC = 6.8), 20 mM Ca(NO₃)₂ (EC = 7.5), and combination of potassium (K) and calcium (Ca) (EC = 8.0). Seedlings were irrigated with saline treatments commencing two weeks after transplanting. Determination of sodium (Na) and K in tomato leaves and fruits were by flame photometry. Accumulation of Na in tomato fruits was higher than in leaves under control or saline conditions for all tomato cultivars. The amount of K in the tomato leaves was higher in control than in saline‐grown plants. Addition of K and Ca to the nutrient solution resulted in a 3 to 7 fold increase in K accumulation in all cultivars tested. Stem and leaf growth were significantly reduced with salinity but growth was enhanced following irrigation when K was added to the nutrient solution. Flowering and fruit set were adversely affected by NaCl stress. Reduction of flower number was 44% relative to the control plants. Fresh fruit yield decreased by 78% when plants received 50 mM NaCl. Growth and development of tomatoes under saline conditions was enhanced in this study following the application of K to the saline nutrient solution. Amelioration in growth was also achieved when Ca was used but to a lesser extent. Our results suggest that ion accumulation and regulation of K and Ca contribute to salt tolerance and growth enhancement.     

Analysis of genetic diversity in Tunisian durum wheat cultivars and related wild species by SSR and AFLP markers

Thirty-four durum wheat cultivars representing the Tunisian durum (Triticum durum Desf.) wheat collection and seven wild species of wheat relatives (Triticum turgidum L., T. dicoccon Schrank., T. dicoccoides (Körn) Schweinf., T. araraticum Jakubz., T. monococcum L., Aegilops geniculata Roth, and Aegilops ventricosa Tausch) were analysed with amplified fragment length polymorphism (AFLP) and microsatellite (SSR) markers. Both marker systems used were able to differentiate durum wheat cultivars from the wild relatives and to specifically fingerprint each of the genotypes studied. However, the two marker systems differed in the amount of detected polymorphisms. The 15 SSR markers were highly polymorphic across all the genotypes. The total number of amplified fragments was 156 and the number of alleles per locus ranged from 3 to 24 with an average of 10.4. Two SSR markers alone, Xwms47 and Xwms268, were sufficient to distinguish all 34 durum wheat genotypes. The five AFLP primer pair combinations analysed yielded a total of 293 bands, of which 31% were polymorphic. The highest polymorphic information content (PIC) value was observed for SSRs (0.68) while the highest marker index (MI) value was for AFLPs (7.16) reflecting the hypervariability of the first and the distinctive nature of the second system. For durum wheat cultivars, the genetic similarity values varied between 31.3 and 81% for AFLPs (with an average of 54.2%), and between 3.6 and 72.7% for SSRs (with an average of 19.9%). The rank correlation between the two marker systems was moderate, with r = 0.57, but highly significant. Based on SSR markers, highest genetic similarity (GS) values were observed within the modern cultivars (37.3%), while the old cultivars showed a low level of GS (19.9%). Moreover, the modern cultivars showed low PIC and MI values. UPGMA Cluster analysis based on the combined AFLP and SSR data separated the wild wheat species from the durum wheat cultivars. The modern cultivars were separated from the old cultivars and form a distinct group.     

Nitrogen and phosphorus requirements of different wheat plant types under dryland and irrigated conditions 1

The wheat (Triticum aestivum L.) plant type in major producing areas of the U.S. is changing rapidly from tall cultivars to high‐yielding semidwarf cultivars. Objectives of experiments were to determine if nitrogen and phosphorus nutritional requirements differ between traditional tall cultivars and modern semidwarf cultivars under dryland and irrigated conditions. ‘Larned’, a tall cultivar; ‘Newton’, a semidwarf cultivar; and ‘Plainsman V, a high‐protein semidwarf cultivar, were grown with all combinations of three nitrogen fertilizer levels (0, 84, and 168 kg N/ha) and two phosphorus fertilizer levels (0 and 90 kg P₂O₅/ha) at Colby, Kansas for two years. Three levels of irrigation—dryland, limited irrigation, and full irrigation—were applied. Grain yields were highest with 84 kg N/ha under dryland and with 168 kg N/ha under irrigation. Phosphorus increased grain yield under dryland conditions one year, but had no effect under irrigated conditions. Cultivar X nutrition interactions from differential yield responses to fertility levels occurred under the dryland and limited irrigation regimes one year. Grain protein content was increased by nitrogen fertilization under all regimes both years and was decreased only by phosphorus fertilization under dryland conditions one year. Cultivar X nitrogen interactions for grain protein occurred under all irrigation regimes. We concluded that nutrient requirements do not differ between tall and semi dwarf wheat culti‐vars under any irrigation regime. Raising the recommended level of nutrients, particularly nitrogen, should be considered for all cultivars, both tall and semidwarf.