Seasonal Changes in Carbohydrate and Protein Content of Seeded Bermudagrasses and Their Effect on Spring Green‐Up

The widespread use of warm‐season turfgrasses in transition zones of Europe, such as northern Italy, has been hampered by the long dormancy periods. To encourage the conversion from cool‐ to warm‐season grasses, research is needed to identify cultivars that exhibit early spring green‐up. A 2‐year study was conducted at the agricultural experimental farm of Padova University from November 2006 to October 2008 to compare water‐soluble carbohydrate and protein content in stolons of four bermudagrass [Cynodon dactylon (L.) Pers.] cultivars and determine their effect on spring green‐up. Samples of ‘La Paloma’, ‘NuMex Sahara’, ‘Princess 77’ and ‘Yukon’ were collected monthly, and water‐soluble carbohydrates (WSC) and crude protein (CP) content of stolons were measured. Dry weight values of WSC and CP for each cultivar were regressed against days needed to reach 80 % green cover in spring (D80). ‘Yukon’ exhibited the highest rhizome dry weight and WSC content during the winter months and was the fastest to reach 80 % green cover. Conversely, ‘Princess 77’ was the slowest cultivar to green‐up in both years. Regression analysis revealed a stronger relationship between D80 and WSC than between CP content and D80.     

DROUGHT STRESS: Soil Water Availability Alters the Inter‐ and Intra‐Cultivar Competition of Three Spring Wheat Cultivars Bred in Different Eras

Competition for water generates a classic aspect of the tragedy of the commons, the ‘race for fish’, where crops must allocate more resource to acquisition of the limiting resource than is optimal for crop yield allocation. A pot experiment using a simple additive (target–neighbour) design was conducted to examine the above‐ground and below‐ground growth of three spring wheat (Triticum aestivum L.) cultivars when grown alone and in mixtures at three levels of water availability. The effects of competition and water availability were compared by observing patterns of growth, biomass allocation and below‐ground outcomes. Competitive interactions were investigated among cultivars ‘HST’, ‘GY602’ and ‘LC8275’, target plant of each cultivar grown without neighbouring plants are referred to herein as control plant and one target plant of each cultivar sown surrounded either by same or another cultivar as intra‐ or inter‐cultivar competition. Competitive ability was assessed as the response ratio (lnRR) between the target plant surrounded by six other plants and the target plant in isolation. Our results showed that the cultivar ‘HST’, released over a century ago, produced a higher biomass and grain yield than the more recently released cultivars ‘LC8275’ and ‘GY602’ when grown as isolated plants with sufficient water supply. However, competition for resources from neighbours led to target plant biomass and grain yield being significantly reduced relative to controls in all three cultivars, particularly in ‘HST’. When subjected to intra‐cultivar competition, the two recently released cultivars ‘LC8275’ and ‘GY602’ had higher grain yields and water use efficiency for grain than ‘HST’ in all three water regimes. The landrace ‘HST’ had better and significantly linear relationships between biomass and biomass allocation, root length and specific root length, whereas the recent and modern cultivars had much more water‐related species‐specific changes in root morphology and allocation patterns. These results suggest that crop traits that influence competitive ability, such as biomass allocation to roots and root plasticity in response to drought have changed in modern wheat cultivars because of breeding and selection.     

Root distribution patterns of peanut genotypes with different drought resistance levels under early‐season drought stress

Drought severely limits crop yield of peanut. Yet cultivars with enhanced root development enable the exploration of a greater volume of soil for water and nutrients, helping the plant survive. Root distribution patterns of three genotypes (ICGV 98305, ICGV 98324 and Tifton‐8) were compared when grown in well‐watered rhizoboxes and when grown in rhizoboxes where an early‐season drought was imposed using rain‐exclusion shelters. The treatments were arranged in a completely randomized design with three replications, and the experiment was conducted during two seasons at the Field Crop Research Station of Khon Kaen University, in Khon Kaen, Thailand. The root system of ICGV 98305, when grown under drought, had a significantly higher root length in the 30–110 cm deep soil layers and less roots in the 0–30 cm soil layers when under drought than when grown under well‐watered conditions. Roots of Tifton‐8 had the largest reductions in root length in upper soil layer and reduced in most soil layers. Tifton‐8 grown under drought was smaller than under well‐watered control for all root traits, showing negative response to drought. The peanut genotypes with high root traits in deeper soil layer under early‐season drought might contribute to drought avoidance mechanism.     

Morphological and biochemical responses of Balanites aegyptiaca to drought stress and recovery are provenance‐dependent

Balanites aegyptiaca is a drought‐tolerant tree naturally distributed in Africa and has a high potential for biofuel production and livelihood. To understand the plant tolerance to drought stress, B. aegyptiaca plants collected from five provenances were subjected for 4 weeks to drought stress through different regimes of soil volumetric water content (VWC, i.e. 25% control, 15% as moderate and 5% as a severe drought stress) followed by 2‐week recovery. Morpho‐physiological responses as well as the changes in antioxidant defences under water stress and recovery were investigated. Drought stress significantly reduced plant biomass‐related parameters, stomatal conductance, quantum efficiency and increased leaf temperature. Each provenance showed specific patterns of stress response reactions that were detected in a cluster analysis. The large leaf area and a high level of lipid peroxidation in Cairo provenance increased its sensitivity to severe drought. For provenances El‐Kharga and Yemen, the highest tocopherol contents and the highest catalytic activities of ascorbate peroxidase (SOD), catalase (CAT), glutathione reductase (GR) and dehydroascorbate reductase (DHAR) were recorded. These traits contributed to the high drought tolerance of these two provenances in comparison with the other provenances. All plants recovered from stress and showed specifically increased activity of glutathione‐S‐transferase (GST) as a repair mechanism. Results showed that the drought tolerance level in B. aegyptiaca is provenance‐dependent.     

Improving resistance against terminal drought in bread wheat by exogenous application of proline and gamma‐aminobutyric acid

Scarcity of water is a severe constraint, which hinders the wheat productivity worldwide. However, foliage application of osmoprotectants may be useful in reducing the drought‐induced yield losses in wheat (Triticum aestivum L.). In this study, potential of foliage applied osmoprotectants (proline, gamma‐aminobutyric acid) in improving the performance of bread wheat against terminal drought was evaluated. Both proline and gamma‐aminobutyric acid (GABA) were foliage applied at 50, 100 and 150 mg/L at anthesis stage (BBCH‐identification code‐ 61), in two bread wheat cultivars viz. Mairaj‐2008 and BARS‐2009. After 1 week of foliage application of these osmoprotectants, drought was imposed by maintaining the pots at 35% water holding capacity. Imposition of drought caused significant reduction in the grain yield of both tested bread wheat cultivars; nonetheless, foliage applied osmoprotectants at either concentration improved the chlorophyll contents, accumulation of proline, glycinebetaine and total soluble phenolics and reduced the malondialdehyde contents, which resulted in better stay green, maintenance of grain weight and grain number under drought stress, thus resulting in better grain yield, water‐use efficiency and transpiration efficiency in both wheat cultivars. However, foliage applied proline at 150 mg/L, and GABA at 100 mg/L was most effective than other concentrations of these osmoprotectants. Performance of cultivar Mairaj‐2008 was quite better than cultivar BARS‐2009. In crux, foliar application of proline and GABA at pre‐optimized rate can be opted as a shotgun approach to improve the performance of wheat under terminal drought.     

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.     

Nitrogen fertilization of warm‐season turfgrasses irrigated with saline water from varying irrigation systems. 1. Quality,spring green‐up and fall colour retention

A 3‐year study was conducted at New Mexico State University in Las Cruces, NM, to investigate the effects of different fertilization treatments on turf performance when water conservation strategies are applied. These strategies include the use of non‐potable saline irrigation water and the use of efficient subsurface irrigation systems. Two low water use warm‐season grasses, “Princess 77” bermudagrass (Cynodon dactylon L.) and “Sea Spray” seashore paspalum (Paspalum vaginatum O. Swartz), were irrigated with either potable [Electrical Conductivity (EC) = 0.6 dS/m] or saline (EC = 3.1 dS/m) water from either an overhead or a subsurface drip irrigation (SDI) system. Four different fertilizers, liquid slow release, granular slow release, granular urea and liquid urea, were applied at two rates: 10 and 20 g N m^?2 year^?1 for “Sea Spray” and 20 and 30 g N m^?2 year^?1 for “Princess 77.” Spring green‐up, summer quality and fall colour retention were determined using digital image analysis, visual quality ratings and normalized difference vegetation index. Generally, subsurface drip‐irrigated grasses were slower to green‐up than overhead irrigated ones. “Sea Spray” irrigated from the SDI system took 18, 28 and 15 days longer to reach 80% green cover in 2010, 2011 and 2012, respectively, than their sprinkler‐irrigated counterparts. The combination of “Princess 77” and overhead irrigation reached 80% green cover 35 (in 2010), 34 (in 2011) and 12 (in 2012) days faster than SDI‐irrigated “Princess 77.” Fertilization rate and type had no effect on summer turfgrass quality of “Princess 77” irrigated from a sprinkler system throughout the research period reaching ratings of greater than 7 during all 3 years. Similar results were observed for “Princess 77” irrigated from a SDI system during 2010 and 2011. Summer quality of sprinkler‐irrigated “Sea Spray” was negatively affected by liquid fertilization. During two of three summers, visual quality of plots fertilized with either liquid slow release or liquid urea was lower than “Sea Spray” fertilized with granular fertilizer. Further research is needed to investigate the effect of fertilization on bermudagrass and seashore paspalum over a wider nitrogen range including both granular and foliar products.     

Increasing pre‐acclimation temperature reduces the freezing tolerance of winter‐type faba bean (Vicia faba L.)

Autumn‐sown winter‐type faba bean (Vicia faba L.) has been shown to have a yield advantage over spring sowing. Still, adoption of this overwintered pulse crop remains limited in temperate locations, due to inadequate winter hardiness. This research sought to understand how the prevailing temperature during emergence and seedling development, that is pre‐acclimation, influences freezing tolerance. Seedlings grown under a controlled “warm” 17/12°C (day/night) pre‐acclimation environment were initially less freezing tolerant than those grown under a “cold” 12/5°C temperature treatment. Stem and particularly root tissues were primarily responsible for slower cold acclimation, and there was a genotype specific response of above‐ground tissues to pre‐acclimation treatment. Both above and below‐ground tissues should be tested across a range of pre‐acclimation temperatures when screening faba bean germplasm for freezing tolerance.     

Agronomic performance of winter wheat grown under highly divergent soil moisture conditions in rainfed and water‐managed environments

Even in the temperate climates of Europe, increasing early season drought and rising air temperature are presenting new challenges to farmers and wheat breeders. Sixteen winter wheat (Triticum aestivum L.) genotypes consisting of three hybrids, six line cultivars and two breeding lines from Germany as well as five line cultivars from France, Austria, Slovakia, Hungary and the Ukraine (referred to as “exotic” lines) have been included in this study. The genetic materials were evaluated over three growing seasons under a range of soil moisture regimes at the three North German sites Braunschweig (irrigated and drought‐stressed), Warmse (rainfed) and Söllingen (rainfed). The average grain yields in the twelve growth environments (water regime × season combinations) ranged from 6.1 to 13.5 t ha^?1. The exotic lines showed little evidence of specific phenological adaptation to drought although they are frequently faced with water scarcity in their countries of origin. The hybrids and German lines exhibited higher regression coefficients (b_i) to environmental means than the exotic lines, indicating particular adaptation to favourable growing conditions. The phenotypical correlations of grain yield between the various environments were high, ranging for instance from 0.6 to 0.8 for the irrigated and drought‐stressed environments at Braunschweig. It is thus expected that in the foreseeable future continued selection aiming at high yield potential will suffice as a means to counter the expected increase in droughts.     

Aerial canopy temperature differences between fast‐ and slow‐wilting soya bean genotypes

Drought stress limits crop growth and yield in soya bean (Glycine max [L.] Merr.), but there are relatively few tools available to assess the ability of different genotypes to tolerate drought. Aerial infrared image analysis was evaluated as a potential tool for identifying drought tolerance in soya bean. Drought effects were evaluated from late vegetative to mid‐reproductive stages of soya bean development in an experiment with ten genotypes including five slow‐ and five fast‐wilting genotypes that were from a population derived from Benning×PI416937. There were two deficit irrigation levels for 2 years and one deficit irrigation level for the third year along with a fully irrigated control level. When the canopy was completely closed, relative canopy temperature was determined using an infrared camera taken from an aerial platform 50–75 m above the experiment. As water availability decreased, the relative canopy temperature generally increased. Moreover, slow‐wilting soya bean genotypes generally had lower canopy temperature compared to fast‐wilting genotypes, and grain yield was generally positively associated with cool canopy temperatures. The results indicate that the determination of canopy temperature is a promising tool for rapid characterization of drought‐related traits in soya bean.     

Morphological and Physiological Responses of Plantain (Plantago lanceolata) and Chicory (Cichorium intybus) to Water Stress and Defoliation Frequency

Plants are often subjected to periods of water stress. There are little data examining the effect of water stress on the forage species Plantago lanceolata and Cichorium intybus. In two pot experiments with P. lanceolata and C. intybus, morphological responses under optimum, dry, and very‐dry water treatments with weekly, fortnightly and 3‐weekly defoliation intervals and physiological responses under optimum and very‐dry water treatments were measured. A third experiment compared the rooting depths of P. lanceolata and C. intybus under field conditions. These findings suggest that both P. lanceolata and C. intybus can survive and continue to grow under water stress conditions with the main differences between the two species being attributable to morphological characteristics (root mass, taproot diameter and shoot mass fraction) rather than differences at a physiological level. Overall, the results suggest plantain may be more productive under moderate drought due to its greater shoot mass fraction, whereas chicory may be more productive and persistent under severe drought due to its greater root mass, taproot diameter and root depth under field conditions.     

Effects of contrasting seasonal growth patterns on composition and persistence of mixed grass‐legume pastures over 5 years in a semi‐arid Australian cropping environment

Perennial grass‐based pastures are uncommon in phased cropping rotations in south‐eastern Australia, where rainfall often limits production and persistence. The high reliance on pure legume‐based pastures limits overall pasture productivity and has adverse effects on environmental parameters such as weed incursion and ground cover. A field experiment was monitored over 5 years to examine the relative productivity of the temperate perennial grasses, phalaris (Phalaris aquatica) and cocksfoot (Dactylis glomerata) and determine whether contrasting seasonal activity enhances their persistence when grown in mixtures with lucerne (Medicago sativa) and annual legumes. Phalaris swards were shown to increase cumulative aboveground biomass by up to 96% and 32%, and in year 5 reduce annual grass emergence by between sevenfold and threefold compared to annual legume and lucerne/annual legume mixed swards, respectively. Only swards that included phalaris maintained ground cover above 70% in each autumn of the experimental period. Swards based on the highly summer dormant cocksfoot cultivar, Kasbah, were generally less productive over all, despite the cocksfoot showing a high level of persistence and good recovery following drought. Grass‐based swards that included lucerne were observed to produce ~35% greater legume biomass than a sward sown only to annual legumes. Cumulative legume biomass was greatest in lucerne swards in the absence of perennial grasses. The experiment was unable to demonstrate a consistent benefit in production and persistence associated with contrasting seasonal growth patterns. However, mixtures containing a range of functional types were consistently shown to enhance productivity over the duration of the experiment compared to less diverse swards. The potential to substantially increase forage productivity and ground cover, while reducing incursion by annual grass weeds, by including well‐adapted perennial grasses in mixtures with lucerne and annual legumes should be utilized.     

Biomass Production,Nutritional and Mineral Content of Desiccation‐Sensitive and Desiccation‐Tolerant Species of Sporobolus under Multiple Irrigation Regimes

The development of low‐water‐input forages would be useful for improving the water‐use efficiency of livestock production in semi‐arid and arid regions. The desiccation‐tolerant (DT) species Sporobolus stapfianus Gandoger and two desiccation‐sensitive (DS) species, Sporobolus pyramidalis and Sporobolus fimbriatus (Trin.) Nees. (Poaceae), were evaluated for aerial biomass production and seed productivity under three different irrigation regimes. Sporobolus stapfianus displayed the least biomass production, whereas S. pyramidalis and S. fimbriatus produced up to 3.8‐ and 11.2‐fold greater dry biomass, respectively, at the highest irrigation rate of 12 334 l (0.01 acre‐feet). Sporobolus fimbriatus and to a lesser extent S. pyramidalis showed significant increases in biomass production in response to increased irrigation rates, whereas S. stapfianus did not. Sporobolus pyramidalis and S. fimbriatus exhibited 3.2‐ and 6.0‐fold greater seed production, respectively, in response to increased irrigation rates, whereas S. stapfianus showed only a 1.4‐fold increase. All Sporobolus species possessed forage quality traits (e.g. crude protein, fibre content) comparable to those of timothy, a forage grass grown widely in the Great Basin in the western United States. Micronutrient content exceeded the minimum requirements of beef cattle, without surpassing tolerable limits, with the exception of zinc, which appeared low in all three Sporobolus species. The low water requirements displayed by these species, combined with their acceptable forage qualities, indicate that these grasses have the potential to serve farmers and ranchers in semi‐arid and arid regions of the western United States where irrigation resources are limited.     

Genetic Analysis of Grain Yield and Other Traits of Early‐Maturing Maize Inbreds under Drought and Well‐Watered Conditions

Maize (Zea mays L.) is an important staple food crop in West and Central Africa (WCA). However, its production is constrained by drought. Knowledge and understanding of the genetics of hybrid performance under drought is invaluable in designing breeding strategies for improving maize yield. One hundred and fifty hybrids obtained by crossing 30 inbreds in sets using the North Carolina Design II plus six checks were evaluated under drought and well‐watered conditions for 2 years at three locations in Nigeria. The objectives of the studies were to (i) determine the mode of gene action controlling grain yield and other important agronomic traits of selected early inbred lines, (ii) examine the relationship between per se performance of inbreds and their hybrids and (iii) identify appropriate testers for maize breeding programmes in WCA. General combining ability (GCA) and specific combining ability (SCA) mean squares were significant (P < 0.01) for grain yield and other traits under the research environments. The GCA accounted for 64.5 % and 62.3 % of the total variation for grain yield under drought and well‐watered conditions, indicating that additive gene action largely controlled the inheritance of grain yield of the hybrids. Narrow‐sense heritability was 67 % for grain yield under drought and 49 % under well‐watered conditions. The correlations between traits of early‐maturing parental lines and their hybrids were significant (P < 0.01) under drought, well‐watered and across environments. Mid‐parent and better‐parent heterosis for grain yield were 45.3 % and 18.4 % under drought stress and 111.9 % and 102.6 % under well‐watered conditions. Inbreds TZEI 31, TZEI 17, TZEI 129 and TZEI 157 were identified as the best testers. Drought‐tolerant hybrids with superior performance under stress and non‐stress conditions could be obtained through the accumulation of favourable alleles for drought tolerance in both parental lines.     

Evaluation and development of flood‐tolerant soybean cultivars

Soybean (Glycine max [L.] Merr.) cultivars are generally sensitive to flooding stress. The plant growth is severely affected and grain yield is largely reduced in the flooded field. It is important to develop flood‐tolerant soybean cultivars for grain production in regions of heavy rainfalls worldwide. In this study, a total of 722 soybean genotypes were evaluated for flooding tolerance at R1 stages (first flower at any node) in the 5‐year flooding screening tests. Differential soybean genotypes exhibited diverse responses to flooding stress with that plant foliar damage score (FDS) and plant survival rate (PSR) ranged from 1.9 to 8.8 and 3.4% to 81.7%, respectively (p < .0001). Based on our standard of flooding evaluation, most genotypes were sensitive to flooding with 6.0 of average FDS and 38.7% of PSR. Fifty‐two soybean genotypes showed flooding tolerance and 11 genotypes were with consistent flooding tolerance during 4‐ to 5‐year continual evaluations. In the meantime, six genotypes were identified with consistent high sensitivity to flooding. The group analysis showed that genotypes from different sources had distinguishable responses to flooding stress (p < .0001). The interacting analysis of year and flooding tolerance indicated that FDS and PSR means were significantly different among 5 years due to weather temperature and flooding treatment time influences of each year (p < .0001). Furthermore, five breeding lines with high‐yielding and flood‐tolerant traits were developed using selected consistent flood‐tolerant and high‐yielding genotypes through conventional breeding approach.     

Genetic analysis and quantitative trait locus mapping of PEG‐induced osmotic stress tolerance in cotton

Water stress is one of the major abiotic stresses that adversely affect cotton production. Seedlings of 142 backcross inbred lines (BILs) derived from Pima cotton ‘Pima S‐7’ (Gossypium barbadense L.) × Upland cotton ‘Sure‐Grow 747’(G. hirsutum L.) were evaluated in two tests for plant height, fresh shoot weight and root weight under two treatments (5% PEG and water‐control conditions) using a hydroponic system in the greenhouse. The experiment in each test was a randomized complete block design with three replicates. The analysis of variance for the two tests detected significant genotypic variation in PEG‐induced stress tolerance within the BIL population and between the parents. Heritabilities were moderate to high and were higher under the control conditions than under the PEG treatment, and the three traits were also significantly and positively correlated. Based on a linkage map with 292 loci, six QTLs were detected including two for plant height, and two each for fresh shoot weight and root weight. This study represents the first report in using a permanent mapping population in genetic and linkage analysis of water stress tolerance in cotton.     

Drought Tolerance and Water‐Use Efficiency of Biogas Crops: A Comparison of Cup Plant,Maize and Lucerne‐Grass

The cup plant (Silphium perfoliatum L.) is discussed as an alternative energy crop for biogas production in Germany due to its ecological benefits over continuously grown maize. Moreover, a certain drought tolerance is assumed because of its intensive root growth and the dew water collection by the leaf cups, formed by fused leaf pairs. Therefore, the aim of this study was to estimate evapotranspiration (ET ), water‐use efficiency (WUE ) and the relevance of the leaf cups for the cup plant's water balance in a 2‐year field experiment. Parallel investigations were conducted for the two reference crops maize (high WUE ) and lucerne‐grass (deep and intensive rooting) under rainfed and irrigated conditions. Root system performance was assessed by measuring water depletion at various soil depths. Transpiration‐use efficiency (TUE ) was estimated using a model approach. Averaged over the 2 years, drought‐related above‐ground dry matter reduction was higher for the cup plant (33 %) than for the maize (18 %) and lucerne‐grass (14 %). The WUE of the cup plant (33 kg ha^?1 mm^?1) was significantly lower than for maize (50 kg ha^?1 mm^?1). The cup plant had a lower water uptake capacity than lucerne‐grass. Cup plant dry matter yields as high as those of maize will only be attainable at sites that are well supplied with water, be it through a large soil water reserve, groundwater connection, high rainfall or supplemental irrigation.     

Inter‐row Mulch Increase the Water Use Efficiency of Furrow‐Irrigated Maize in an Arid Environment

The effect inter‐row polyethylene mulch on the water use efficiency and crop productivity of furrow‐ and drip‐irrigated maize (Zea mays L.) was evaluated in a field study. In contrast to the traditional ‘on ridge’ mulching, the inter‐row polyethylene mulch was placed in such a way that it could be easily removed for reuse since the row of plants itself was not covered but the furrows were completely covered. Irrigation needs were computed by multiplying the cumulative Class A Pan evaporation between irrigations by a crop coefficient that changed through the growing season. Our results indicate that inter‐row mulching induced earliness under both irrigation treatments. Seventy five percent of canopy density was attained in the mulched treatments contrasting with 45–61 % in the non‐mulched treatments at 34 days after sowing. Throughout the growing period, shoot biomass was significantly higher for the mulched treatments that had as well higher root biomasses. The overall estimated evaporative losses from the non‐mulched treatments were between 37 % and 39 % of the total water applied. The whole gross canopy water use efficiency in the furrow and drip mulched treatments was 64 % and 45 % higher than in the respective non‐mulched treatments. These results indicate that inter‐row polyethylene mulch is an efficient technique by which soil evaporation is reduced and plant productivity increased.     

Comparative Drought Response in Eleven Diverse Alfalfa Accessions

Alfalfa (Medicago sativa L.) production is negatively affected by drought stress. This is particularly true for alfalfa grown on non‐irrigated rangelands. Thus, the development of drought‐tolerant alfalfa cultivars is of great significance. A greenhouse study was conducted to evaluate 11 alfalfa accessions including several that are adapted to rangeland conditions and two commercial accessions, for their performance under drought condition. Water supply was adjusted based on the transpiration rate of individual plants to compensate for 100, 75, 50 or 25 % of transpirational water loss. We found that RS, a naturalized alfalfa collected from the Grand River National Grassland in South Dakota, showed the best resistance to drought condition. It showed the smallest reduction in stem elongation (36 %), relative growth rate (14 %), and shoot dry mass (40 %) production under the severest drought tested in this study relative to the non‐drought treatment. While RS showed less biomass production under well‐watered conditions, it produced similar or more shoot biomass under drought conditions compared to other accessions. Associated with the drought resistance or less sensitivity to drought, RS showed greater capability to maintain root growth, shoot relative water content, and leaf chlorophyll content compared to other accessions. Different from other accessions, RS showed increasing water use efficiency (WUE) as water deficit became severe, reaching the greatest WUE among 11 accessions. Our results suggest that RS is a valuable genetic resource that can be used to elucidate physiological and molecular mechanisms that determine drought resistance in alfalfa and to develop alfalfa with improved WUE.     

Identification and characterization of sources for photo‐ and thermo‐insensitivity in Vigna species

Cultivation of the same varieties of mungbean and blackgram across different seasons and locations is constrained by their photo‐ and thermo‐sensitive behaviour. Developing insensitive genotypes, which can fit well across all seasons, requires robust donors which would provide genes imparting this trait. This study was undertaken to identify such donors in the Vigna species. Forty‐eight accessions belonging to 13 Vigna species and eight released cultivars were evaluated under natural field conditions. Among these, two accessions, viz. V. umbellata (IC251442) and V. glabrescens (IC251372) were found photo‐ and thermo‐insensitive as these were able to flower and set pods at temperatures as high as 43.9°C and as low as 2.7°C. Pollen viability studies indicated viable pollen (>75% at 2.7°C and >85% at 41.9°C) and normal pollen tube growth at both the extremes of temperature. The identified V. glabrescens accession has long, constricted pods and dark green, mottled seeds while V. umbellata has smooth, curved pods and shining, oval, large seeds. Both these accessions can be utilized in developing photo–thermo insensitive genotypes in cultivated Vigna species.