Effects of Epichloë endophyte infection on growth,physiological properties and seed germination of wild barley under saline conditions

Wild barley (Hordeum brevisubulatum) is a grass that inhabits alkalized meadows in northern China. An asexual Epichloë bromicola endophyte was detected in seeds and leaf sheaths in all wild barley samples from Gansu Province, China. In this research, we determined the effects of the E. bromicola endophyte on growth, physiological properties and seed germination of wild barley under salt stress through a set of experiments. Our results demonstrate that endophyte-infected (E+) plants produced more tillers, higher biomass and yield, higher chlorophyll content and superoxide dismutase activity than endophyte-free (E−) plants under high salt stress. Seed germination parameters of E+ biotype were significantly higher than those of E− plants when NaCl concentration reached 200 and 300 mM. Our results demonstrate that E. bromicola endophytes increased tolerance to salt stress in wild barley by increasing seed germination and growth, and altering plant physiology.     

Detection of endophytic fungi in Festuca spp. by means of tissue print immunoassay

Many wild and cultivated grasses live in mutualistic symbiosis with endophytic fungi of the genera Neotyphodium and Epichloë. These associations are of agronomic importance because endophytes may induce a range of beneficial effects for the host plant but also produce alkaloids detrimental to livestock. Conventional detection of endophytes by means of histological staining is time‐consuming and not suited for large numbers of samples. Therefore, in order to simplify the detection of endophytic fungi the utility of tissue print immunoassay (TPIA) was studied and compared with the commonly used microscopic analysis. Ecotypes collected from natural grassland habitats and plants from field experiments were analyzed for endophyte infection. Both methods provided similar results. Based on stained or non‐stained mycelium in tissue prints, endophyte‐infected (E +) and endophyte‐free (E‐) tillers and inflorescences of Festuca pratensis, F. arundinacea and F. rubra were clearly distinguishable. Prints of cross sections of tillers allow the precise localization of endophyte infection within the plant tissues. Because TPIA allows the examination of endophytes in individual branches and segments of inflorescences it is a useful method for dissemination studies. Tissue print immunoassay appears to be a reliable method suited for routine work in research, practical grassland management and selection of defined E + or E‐ material for breeding.     

The Effect of Late-terminal Drought Stress on Yield Components of Four Barley Cultivars

Barley (Hordeum vulgare L.) is an important winter cereal crop grown in the semiarid Mediterranean, where late‐terminal drought stress during grain filling has recently become more common. The objectives of this study were to investigate the growth performance and grain yield of four barley cultivars under late‐terminal drought stress under both glasshouse and field conditions. At grain filling, four barley cultivars (Rum, ACSAD176, Athroh and Yarmouk) were exposed to three watering treatments: (1) well‐watered [soil maintained at 75 % field capacity (FC)], (2) mild drought stress at 50 % FC, (3) severe drought stress at 25 % FC in the glasshouse experiment and (1) well‐watered (irrigated once a week), (2) mild drought (irrigated once every 2 weeks), (3) severe drought (non‐irrigated; rainfed) in the field. As drought stress severity increased, gross photosynthetic rate, water potential, plant height, grain filling duration, spike number per plant, grain number per spike, 1000‐grain weight, straw yield, grain yield and harvest index decreased. In the glasshouse experiment, the six‐row barley cultivars (Rum, ACSAD176, and Athroh) had higher grain yield than the two‐row barley cultivar (Yarmouk), but the difference was not significant among the six‐row cultivars under all treatments. In the field experiment, Rum had the highest grain yield among all cultivars under the mild drought stress treatment. The two‐row cultivar (Yarmouk) had the lowest grain yield. In general, the traditional cultivar Rum had either similar or higher grain yield than the other three cultivars under all treatments. However, the yield response to drought differed between the cultivars. Those, Rum and ACSAD176, that were capable of maintaining a higher proportion of their spikes and grains per spike during drought also maintained a higher proportion of their yield compared with those in well‐watered treatment. In conclusion, cultivar differences in grain yield were related to spike number per plant and grain number per spike, but not days to heading or grain filling duration.     

Drought Effect on Grain Number and Grain Weight at Spike and Spikelet Level in Six‐Row Spring Barley

Water is the primary regulator of yield formation in cereals. The effect of water limitation and its timing on development of yield components were studied in detail at spike and spikelet level in spring barley (Hordeum vulgare L.). An experiment with three watering treatments (control watering, CONT; drought prior to pollination, DR1 and terminal drought, DR2) was set up in a large greenhouse (20 × 30 m). In addition to watering treatments, two NPK fertilizer application rates (0 and 120 kg N ha^?1) were used to investigate the fertilizer effect. The drought effect exceeded the effect of fertilizer application for grain number and single grain weight (SGW). DR1 reduced the number of grains, whereas DR2 reduced both SGW and the number of grains. Resuming the watering at pollination (DR1) restored photosynthesis and enhanced grain filling, resulting in almost similar SGW in DR1 and CONT plants. Spikelets in the upper mid‐section of the spike dominated yield formation in all treatments. This was particularly emphasised in DR1 plants as 58 % of the grain yield was produced in spikelets 3–5, whereas in DR2 and CONT plants it was 39 % and 36 %, respectively. Hence, drought prior pollination strongly reduced yielding capacity (=grain number) in apical and basal spikelets. DR1 and DR2 reduced substantially grain yield and grain N yield resulting in low nitrogen use efficiency.     

Effect of Water Stress on Physiological Attributes and their Relationship with Growth and Yield of Wheat Cultivars at Different Stages

The effects of water stress on physiological attributes of drought‐sensitive (Kalyansona) and drought‐tolerant (C‐306) wheat cultivars were studied in a pot experiment. Water stress was imposed by withholding irrigation at boot and anthesis stages. Leaf water potential, leaf osmotic potential and leaf turgor potential (measured with pressure chamber and osmometer), as well as leaf diffusive resistance, leaf transpiration rate and leaf‐to‐air transpiration gradient (measured with a steady‐state porometer) were measured diurnally. Growth and yield parameters were recorded after harvesting of the crop. Triplicate data were analysed using a completely randomized design and correlations amongst these parameters were computed. Water stress was found to reduce diurnal leaf water potential and leaf osmotic potential in both the genotypes but leaf osmotic potential was significantly higher in the drought‐tolerant cultivar C‐306 than in the drought‐sensitive cultivar Kalyansona. Positive turgor was recorded in both the genotypes under water stress and non‐stress conditions. Water‐stressed plants showed significantly lower turgor potential than control plants. In diurnal observations, water‐stressed plants exhibited significantly higher leaf diffusive resistance in both genotypes at both stages. The diffusive resistance of C‐306 was predominantly higher than that of Kalyansona. Water stress decreased leaf transpiration rate at both stages but the reduction was higher at the anthesis stage. The leaf‐to‐air temperature gradient was much higher in C‐306 than in Kalyansona at the boot stage but at the anthesis stage genotypic variation was non‐significant. The capacity to maintain cooler foliage was lower at the anthesis stage than at the boot stage in both the cultivars. Shoot dry weight, number of grains, test weight, grain yield, biological yield and harvest index decreased to a greater extent when water stress was imposed at the anthesis stage, while imposition of water stress at the boot stage caused a greater reduction in plant height and number of tillers. Similarly, water stress caused a smaller reduction in growth, yield and yield attributes in C‐306 than in Kalyansona. In general, the correlation coefficient of grain and biological yield with water potential and its components was positive and highly significant. Similarly, turgor potential was also correlated positively and significantly with grain yield at both the stages, but with biological yield it was significant only at the anthesis stage. A negative and significant correlation was obtained for diffusive resistance and leaf‐to‐air temperature gradient with grain yield at the boot and anthesis stages. The rate of transpiration was also positively and significantly correlated to grain and biological yields at both the stages. Amongst the yield attributes, number of leaves and number of tillers were positively correlated at the anthesis stage, whereas leaf area and shoot dry weight were significantly correlated with grain and biological yields at both the stages.     

Selection of wheat genotypes for biomass allocation to improve drought tolerance and carbon sequestration into soils

The biomass allocation pattern of plants to shoots and roots is a key in the cycle of elements such as carbon, water and nutrients with, for instance, the greatest allocations to roots fostering the transfer of atmospheric carbon to soils through photosynthesis. Several studies have investigated the root to shoot ratio (R:S) biomass of existing crops but variation within a crop species constitutes an important information gap for selecting genotypes aiming for increasing soil carbon stocks for climate change mitigation and food security. The objectives of this study were to evaluate agronomic performance and quantify biomass production and allocation between roots and shoots, in response to different soil water levels to select promising genotypes for breeding. Field and greenhouse experiments were carried out using 100 genotypes including wheat and Triticale under drought‐stressed and non‐stressed conditions. The experiments were set‐up using a 10 × 10 alpha lattice design with two replications under water stress and non‐stress conditions. The following phenotypic traits were collected: number of days to heading (DTH), number of productive tillers per plant (NPT), plant height (PH), days to maturity (DTM), spike length (SL), kernels per spike (KPS), thousand kernel weight (TKW), root biomass (RB), shoot biomass (SB), root to shoot ratio (R:S) and grain yield (GY). There was significant (p < 0.05) variation for grain yield and biomass production because of genotypic variation. The highest grain yield of 247.3 g/m² was recorded in the genotype LM52 and the least was in genotype Sossognon with 30 g/m². Shoot biomass ranged from 830 g/m² (genotype Arenza) to 437 g/m² (LM57), whilst root biomass ranged between 603 g/m² for Triticale and 140 g/m² for LM15 across testing sites and water regimes. Triticale also recorded the highest R:S of 1.2, whilst the least was 0.30 for wheat genotype LM18. Overall, drought stress reduced total biomass production by 35% and R:S by 14%. Genotypic variation existed for all measured traits useful for improving drought tolerance, whilst the calculated R:S values can improve accuracy in estimating C sequestration potential of wheat. Wheat genotypes LM26, LM47, BW140, LM70, LM48, BW152, LM75, BW162, LM71 and BW141 were selected for further development based on their high total biomass production, grain yield potential and genetic diversity under drought stress.     

Thermal phenotyping of stomatal sensitivity in spring barley

Thermometry and thermography are alternative methods used for measuring stomatal conductivity via transpirative cooling. However, the influence of mixed soil–plant information contained in thermal images compared to thermometric spot measurements on the measurement quality and relationships to agronomic traits remains unclear. To evaluate their respective influence, canopy temperature was measured simultaneously by two infrared thermometers (thermometry), which were oriented oblique to the plant canopy and mounted on a tractor, and a hand‐held, nadir oriented thermal camera (thermography) in irrigated and drought‐stressed spring barley cultivar trials in 2011. Canopy temperatures were separated from soil temperatures and extracted from the thermal images by matching thermal and RGB images. Thermometric measurements conducted at the beginning of shooting during a stable period of high radiation were more closely related to total plant biomass and straw yield at harvest than thermography under both irrigated and drought‐stressed conditions. Taking into account the results of this evaluation, thermometry was used for assessing the agronomic importance of stomatal sensitivity, the earliness of stomatal closure, of spring barley cultivars subjected to different water supply in 2013. In this year, 16 spring barley cultivars were grown under mild drought stress and rainfed conditions. A stomatal sensitivity index was derived relating canopy temperatures of the cultivars grown under rainfed and drought‐stressed conditions to each other. Under rainfed conditions, stomatal sensitivity was negatively related to grain protein yield with a coefficient of determination of R² = .43. Under increasing terminal drought stress, positive regression slopes of stomatal sensitivity to grain yield, biomass yield and culms/m² were observed with coefficients of determination amounting to R² = .22, .31 and .36, respectively. Stomatal sensitivity negatively impacts agricultural production under well‐watered conditions, but maintains productivity under conditions of terminal drought.     

Effects of Zinc Deficiency and Drought on Grain Yield of Field-grown Wheat Cultivars in Central Anatolia

Drought stress and zinc (Zn) deficiency are serious abiotic stress factors limiting crop production in Turkey, especially in Central Anatolia. In this study, the effects of Zn deficiency and drought stress on grain yield of 20 wheat cultivars (16 bread wheat, Triticum aestivum; four durum wheat, Triticum durum cultivars) were investigated over 2 years under rainfed and irrigated conditions in Central Anatolia where drought and Zn deficiency cause substantial yield reductions. Plants were treated with (+Zn: 23 kg Zn ha⁻¹, as ZnSO₄·7H₂O) and without (−Zn) Zn under rainfed and irrigated conditions. Both Zn deficiency and rainfed treatments resulted in substantial decreases in grain yield. Significant differences were determined between both bread wheat and durum wheat cultivars in terms of drought stress tolerance. Considering drought sensitivity indices over 2 years, the bread wheat cultivars Yayla‐305, Gerek‐79, Dagdas‐94 and Bolal‐2973 were found to be more drought‐tolerant than the other cultivars under both −Zn and +Zn treatments. Especially the durum wheat cultivars Cakmak 79 and Selcuklu 97 showed much greater drought susceptibility under Zn deficiency, and irrigation alone was not sufficient to obtain satisfying grain yield without Zn application. The results indicate that sensitivity to Zn deficiency stress became more pronounced when plants were drought‐stressed. The effect of irrigation on grain yield was maximized when Zn was adequately supplied, leading to the suggestion that efficient water use in Central Anatolia seems to be highly dependent on the Zn nutritional status of plants.     

Effect of Formative Phase Drought on Different Classes of Shoots, Shoot Mortality, Cane Attributes, Yield and Quality of Four Sugarcane Cultivars

Field experiments were conducted at Coimbatore, India to study the effect of three levels of drought (severe, moderate and no drought) during the formative phase (60–150 days after planting; DAP) of sugarcane on the tillering, the conversion of shoots to millable canes, cane attributes and the quality of different classes of shoots in four sugarcane cultivars (Co 8021, Co 419, Co 8208 and Co 6304)_the different classes of shoots studied were: mother shoots (which emerged 0–30 DAP), early tillers (30–60 DAP), mid‐season tillers (60–150 DAP) and late tillers (150 DAP). The results indicated that drought during the formative phase reduced the total number of shoots and their conversion to millable canes at harvest. Drought also reduced the cane length, number of inter‐nodes and single cane weight of different classes of shootsand the subsequent total cane yield. Irrespective of drought treatments, Co 8021, a high‐tillering, thick‐stalked cultivar, gave the highest cane yield despiteits higher shoot mortality, while Co 8208, a low‐tillering, thin‐stalked cultivar, gave the lowest cane yield despite its lower shoot mortality. Thus a moderate level of shoot mortality is clearly necessary to obtain higher millable canes and subsequently higher cane yield. Mother shoots and early tillers together contributed most of the total number of millable canes (84.5 %) and of the total cane yield at harvest (86.2 %). The contribution of late tillers to the number of millable canes and cane yield was, however, negligible, especially in cultivars Co 6304 and Co 8208. There was a gradual reduction in stalk attributes such as cane length, number of internodes, single cane weight and commercial cane sugar percentage as the physiological age of shoots decreased. This study emphasizes the need for a cultivar with the optimal characteristics of early tillering (like Co 8021 and Co 6304) and maximum conversion to millable canes (like Co 8208) and provides information relevant to breeders making decisions on crossing programmes to produce improved cultivars for drought conditions.     

Independent and Combined Effects of Soil Warming and Drought Stress During Anthesis on Seed Set and Grain Yield in Two Spring Wheat Varieties

Increase in soil temperature together with decrease in soil moisture during anthesis of spring wheat (Triticum aestivum L) crops is predicted to occur more frequently in a future climate in Denmark. The objective of this study was to investigate the responses of two Danish spring wheat varieties (Trappe and Alora) to soil warming (H), drought (D) and both (HD) during anthesis. The plants were grown in pots in a climate‐controlled glasshouse. In H, the soil temperature was increased by 3 °C compared with the control (C). In both D and HD treatments, the plants were drought‐stressed by withholding irrigation until all of the transpirable soil water had been depleted in the pots. Results showed that, particularly under D treatment, Alora depleted soil water faster than Trappe. In both varieties, flag leaf relative water content (RWC) was significantly lowered, while spikelet abscisic acid (ABA) concentration was significantly increased by D and HD treatments. Compared with the C plants, D and HD treatments significantly reduced ear number, ear to tiller ratio, shoot biomass, grain yield, harvest index and seed set but hardly affected tiller number and 1000‐kernel weight, whereas H treatment alone only decreased shoot biomass and reduced seed set. When analysed across the varieties and the treatments, it was found that the reduction in seed set was closely correlated with the increase in spikelet ABA concentration, indicating that D and HD treatments induced greater spikelet ABA concentrations might have caused seed abortion. It was concluded that the grain yield reduction under D and HD treatments during anthesis in spring wheat is ascribed mainly to a lowered seed set and wheat varieties (i.e. Alora) with more dramatic increase in spikelet ABA concentration are more susceptible to D and HD treatment.     

Effects of Mild and Severe Drought Stress on Photosynthetic Efficiency in Tolerant and Susceptible Barley (Hordeum vulgare L.) Genotypes

Drought stress is one of the most important abiotic factors which adversely affect growth, metabolism and yield of crops worldwide. The objective of this study was to determine the effects of drought stress on photosynthesis in barley and examine the differential responses of photosynthetic apparatus in relatively tolerant (Yousof) and susceptible (Morocco) barley genotypes. Plants were subjected to different levels of soil water availability including control, mild and severe drought stress. In both genotypes, drought stress led to decrease in chlorophylls, β‐carotene and stomatal conductance accompanied by decrease in CO₂ assimilation rate. Significant increase in α‐tochoperol content was only observed in Yousof cultivar under drought stress. Initial slope and plateau phase of CO₂ response curve of drought‐stressed plants as well as polyphasic chlorophyll a fluorescence transient curve (OJIP test) and fast fluorescence induction kinetics were influenced by drought stress. These parameters were more affected in Morocco cultivar by drought stress compare with Yousof. Drought stress also resulted in reduction of D1 protein content in both genotypes and accelerated photoinhibition process. Based on our results, stomatal conductance is the main factor limiting photosynthesis in Yousof genotype under mild drought stress. However, in Morocco, in addition to stomatal limitation, damage to photosystem II (PSII), reduced electron transport and carboxylation efficiencies were important parts of limitation in photosynthesis. Severe drought stress resulted in structural and biochemical impairment of light‐dependent reactions as well as carboxylation process of photosynthesis in both genotypes. Alpha‐tocopherol showed an important protective role against drought stress in Yousof cultivar as a relatively drought‐tolerant cultivar.     

Nitrogen Sustains Seed Yield of Quinoa Under Intermediate Drought

Quinoa (Chenopodium quinoa Willd.) is a promising crop for food security in dry areas. Studies have been conducted to define nitrogen (N) fertilization levels and to understand the responses of quinoa to drought, but little is known about the response of this crop to N fertilization under drought stress. The aim of this study was to investigate whether N fertilization could improve quinoa yield and physiology under limited water. A greenhouse experiment was carried out with quinoa grown at four N fertilization levels (0, 0.2, 0.4 and 0.6 g N pot^?1) and two watering treatments (progressive drought and full irrigation; 10 and 98 % of pot water holding capacity, respectively). Results of this experiment showed that N may confer a certain degree of drought tolerance to quinoa as seed quality and yield of N‐fertilized plants were not affected by drought stress. Responses such as faster stomatal closure, reduced leaf water potential, higher leaf abscisic acid (ABA) concentration and particularly an improved N remobilization in N‐fertilized plants may have played a role in sustaining seed yield in the drought‐stressed treatment. These results under controlled conditions serve as a basis to elucidate drought tolerance mechanisms activated with N fertilization and to define the use of N in management practices under semi‐arid environments.     

Einfluß von Monoethanolamin auf den Ertrag von Kulturpflanzen

Effect of monoethanolamine on yield of crops
I. Studies on the effect of monoethanolamine on the grain yield and the nitrogen household in cereal plants (pot experiments)
The effect of monoethanolamine (EA, applied as foliar spray, 10 mg per pot) on grain yield and yield components was investigated in pot experiments with spring barley, winter wheat, and winter rye. Under conditions of a moderate drought stress the applied EA increased the grain yield of spring barley from 5 % to 7 % (significance only at α= 0.05). A stimulating effect of EA on the grain yield of winter wheat and winter rye was also obtained.
The positive influence of EA on the grain yield of spring barley was reproducible under the conditions of a limited water supply in small-scale plot experiments (increase of yield about 9 %).
In case of spring barley and winter rye the increase of the grain yield by EA, applied at growth stage 31 (= DC 31) was connected with a greater number of ear-bearing tillers. The increase of the winter wheat yield resulted from more grains per ear of the tillers.
The enhanced formation of tiller grain mass and total tiller biomass by EA was in correlation with a higher nitrogen import into tillers (r = 0.8⁺). Since an export of N from the main shoots into the tillers was not observed a higher N uptake (≥ 6 %) was calculated from N balances. After a fertilization with ¹⁵N-labelled fertilizers the additional ¹⁵N uptake was 13 % to 20 %.
Possible stress reducing activities caused by EA are discussed.     

Understanding physiological and morphological traits contributing to drought tolerance in barley

Drought stress is a major limiting factor for crop production in the arid and semi‐arid regions. Here, we screened eighty barley (Hordeum vulgare L.) genotypes collected from different geographical locations contrasting in drought stress tolerance and quantified a range of physiological and agronomical indices in glasshouse trails. The experiment was conducted in large soil tanks subjected to drought treatment of eighty barley genotypes at three‐leaf stage and gradually brought to severe drought by withholding irrigation for 30 days under glasshouse conditions. Also, root length of the same genotypes was measured from stress‐affected plants growing hydroponically. Drought tolerance was scored 30 days after the drought stress commenced based on the degree of the leaf wilting, fresh and dry biomass and relative water content. These characteristics were related to stomatal conductance, stomatal density, residual transpiration and leaf sap Na, K, Cl contents measured in control (irrigated) plants. Responses to drought stress differed significantly among the genotypes. The overall drought tolerance was significantly correlated with relative water content, stomatal conductance and leaf Na⁺ and K⁺ contents. No significant correlations between drought tolerance and root length of 6‐day‐old seedling, stomatal density, residual transpiration and leaf sap Cl^? content were found. Taking together, these results suggest that drought‐tolerant genotypes have lower stomatal conductance, and lower water content, Na⁺, K⁺ and Cl^? contents in their tissue under control conditions than the drought‐sensitive ones. These traits make them more resilient to the forthcoming drought stress.     

Endophyte Infection May Affect the Competitive Ability of Tall Fescue Grown with Red Clover

Cool-season grasses infected with Neotyphodium endophytes may be more persistent and competitive than non-infected plants. In a greenhouse experiment, two tall fescue ( Festuca arundinacea Schreb.) cloned genotypes (DN2 and DN11) with different growth characteristics and endophyte status (E−, non-infected; E+, infected) were grown in monocultures and in full competition with red clover ( Trifolium pratense L.) cv. Reddy Red for 20 weeks. When grown in monoculture, endophyte infection reduced the root dry matter (DM) of DN2 (16 %) and DN11 (5 %) when compared to E− plants, while shoot DM was not affected. In full competition with red clover, root and shoot DM of tall fescue were not influenced by endophytes, but cumulative herbage DM yield was less in E+ than in E− plants. Root growth of red clover was significantly depressed (22 %) in competition with E+ plants of DN2 compared to E− plants, but was not affected when plants were grown in competition with DN11. The relative yield total (RYT) did not differ from 1.0 in red clover mixtures with E− plants of DN2 and DN11, and with E+ plants of DN11, indicating competition between the competitors for the same resources. In contrast, RYT was less than 1.0 in the red clover/DN2 E+ mixture, suggesting a negative interaction between the competitors. Endophyte infection increased the competitive ability of DN2 but reduced that of DN11 when compared to E− plants. Because the concentration of pyrrolizidine alkaloids in roots of E+ plants of DN2 was twice that found in roots of DN11 (1083 and 536 μg g⁻¹, respectively), we suggest that pyrrolizidine alkaloids might influence the competitive ability of some endophyte–tall fescue associations through a possible allelopathic effect on companion species.     

Barley varieties in semi‐controlled and natural conditions—Response to water shortage and changing environment

The yield potential of 60 spring barley varieties was examined under controlled drought and natural conditions in the years 2011–2013. The studied varieties were genotyped with the 1536‐SNP barley oligonucleotide assay. In experiments with controlled drought conditions, the grain yield, 1,000‐grain weight, number of productive tillers and length of the main stem were measured. Physicochemical properties such as the specific surface area, water adsorption energy, fractal dimension and nanopore radius of the plant leaves were determined and correlated with yield‐forming traits. Field trials were conducted over 3 years at 14 locations, where along with the yield‐related traits, monthly rainfall and average temperature were monitored. Five varieties of high yield and five varieties relatively stable under both semi‐controlled and natural conditions were distinguished. The yield‐related traits observed in various locations were related to environmental variables relevant to water availability. The sum of the rainfall in April and May was negatively correlated with the 1,000‐grain weight and positively with the plant height. Positive relationships were found between plant height and temperatures in June and July. Five markers detected earlier as linked to the quantitative trait loci in the mapping populations were identified to have a coherent effect among varieties of various pedigree.     

Photosynthesis and Remobilization of Dry Matter in Wheat as Affected by Progressive Drought Stress at Stem Elongation Stage

With increasingly erratic rainfall patterns particularly in drought‐prone production systems, the capacity of plants to recover productively from drought spells becomes an important feature for yield stability in rainfed agriculture. Consequently, effects of water management at the stem elongation stage on partitioning and remobilization of dry matter, alteration in photosynthesis and water‐use efficiency (WUE), and yield components of wheat plants were studied in a glasshouse pot experiment. The plants were subjected to three soil moisture regimes: well watered during all phenological stages (WW), drought affected during stem elongation and post‐anthesis stages (DD) and drought affected during stem elongation and rewatered at post‐anthesis stage (DW). Total dry weight substantially decreased by both drought treatments. However, DD plants allocated relatively higher assimilates to roots whereas DW plants remobilized them to the grains. Drought applications resulted in a decrease of grain yield and thousand grain weight while reduction was more pronounced in DD treatment. Relative contribution of post‐anthesis photosynthesis to dry matter formation in grain was higher in WW treatment (72.6 %) than DD (68.5 %) and DW (68.2 %) treatments. Photosynthetic rate, gas exchange and transpiration decreased whereas leaf (photosynthetic) and plant level WUE increased with drought applications. However, all these parameters were rapidly and completely reversed by rewatering. Our findings showed that partitioning of dry weight to grain increases with rewatering of wheat plants subjected to drought during stem elongation phase, but the relative contributions of remobilization of stem reserves and post‐anthesis photosynthesis to grain did not change. Moreover, rewatering of plants at booting stage after a drought period lead to full recovery in photosynthesis and WUE, and a significant although partial recovery of yield components, such as grain yield, TGW and harvest index.     

Effectiveness of Mulching vs. Incorporation of Composted Cattle Manure in Soil Water Conservation for Wheat Based on Eco-Physiological Parameters

Abstract The objective was to study soil water conservation and physiological growth of wheat (Triticum aestivum L.) using composted cattle manure applied either as mulch or incorporated with soil at 20 Mg ha^?1. Haruhikari, a relatively drought‐sensitive and Hongmangmai, a relatively drought‐tolerant wheat, were the cultivars studied under both adequate and deficit irrigation. Fourteen weeks after sowing (WAS), the number of tillers and leaves was significantly reduced by 19 % and 30 % respectively under deficit irrigation and Hongmangmai produced slightly (10 %) more tillers than Haruhikari. Unlike mulching, the incorporation of manure had favourable effects on plants in terms of shoot dry mass (SDM) by 36 % and number of tillers and leaves by 40 %. Haruhikari produced substantially (29 %) greater root mass under adequate irrigation but Hongmangmai produced slightly (2.7 %) more roots and responded much better to manure use whether under adequate or deficit irrigation. As a result, Hongmangmai suffered less severe reductions in tillers and biomass under water stress. In comparison, the mulched manure treatment saved 15 % and 64 % respectively more water than the control and the treatment incorporating manure, but this advantage in water‐saving did not translate to superior plant growth. Leaf water potential (ψ_l) under adequate irrigation significantly exceeded that under deficit irrigation by 27 % and the ψ_l of Haruhikari exceeded that of Hongmangmai by 15 %. However, Hongmangmai may be considered more tolerant of dehydration since it maintained much higher net photosynthetic rates (P_N) even with a lower leaf water potential. The reduction in the P_N and intracellular carbon dioxide concentration (C_i) of the cultivars under deficit irrigation was on account of decreasing stomatal conductance (g_s) and transpiration rate but on average, the g_s of Hongmangmai significantly exceeded that of Haruhikari by as much as 0.53 under adequate irrigation and 0.22 under deficit irrigation. In conclusion, we suggest that the drought tolerance of Hongmangmai was related to its superior root growth and greater ability than Haruhikari, to efficiently utilize incorporated manure for growth under water stress.     

Drought tolerance in perennial ryegrass (Lolium perenne L.) as assessed by two contrasting phenotyping systems

The objectives of this research were to establish a practicable phenotyping platform for assessing the drought stress response of perennial ryegrass (Lolium perenne L.; Lp), and to use this platform for evaluating the variation for drought tolerance among a panel of 39 diverse Lp populations. A moderate‐to‐strong correlation was assessed between the performance of plants grown in a hydroponics system, where the stress was generated by the addition of polyethylene glycol (PEG), and those grown in the field in a rainout shelter. Following the application of drought stress, tetraploid Lp populations, along with a small number of reference Festulolium and Festuca sp. accessions, were able to develop more shoot and root dry matter than diploid Lp populations. The onset of drought symptoms was also delayed within these accessions and the plants recovered better once drought had been relieved. Although most of the diploid Lp populations were drought susceptible, there was a considerable accession‐to‐accession variation for performance under drought stress conditions. Measuring biomass production and post‐drought recovery in rainout shelter experiments in combination with the assessment of root biomass accumulation in PEG‐supplemented hydroponics represented a viable means of screening Lp germplasm for drought tolerance.     

Influence of Soil Water Regimes on VA Mycorrhiza

A greenhouse trial was conducted with cassava inoculated with seven different VAM fungal species, i.e. Acaulospora longula, A. myriocarpa, Entrophospora colombiana, Glomus fasciculatum, G. manihotis, G. occultum and Scutellospora heterogama. A wet and a dry soil water regime was established to study the effect of water stress on performance of these fungi with a drought tolerant cassava clone. At harvest, N, P and K concentration was analysed in leaves, petioles, stems and roots.
In unstressed plants, five endophytes were effective whereas in stressed plants only three fungi improved growth beyond the non-mycorrhizal control. These were E. colombiana, G. manihotis and G. occultum which were most effective for P uptake under stress. Differential effects of VAM fungal species on root length and K. uptake were found. A. myriocarpa caused the greatest increase in length of feeder roots and G. occultum was one of the most effective for K uptake under both water regimes even though these fungi were not the most effective for dry matter production. Under each water regime, the concentration of N, P and K in leaves, petioles, stems and roots was influenced by the fungal species. Mycorrhizal endophytes differed in tolerance to dry soil conditions as found by root infection ratings. From the results it can be concluded that in addition to the improved P nutrition the enhanced root length and K uptake by VAM fungi may be important for drought tolerance of cassava.