Selection and characterization of wheat genotypes for saline soils prone to water‐logging

Wheat (Tritcum aestivum L.) genotypes were screened and characterized for performance under salt stress and/or water‐logging. In a solution‐culture study, ten wheat genotypes were tested under control, 200 mM–NaCl salt stress and 4‐week water‐logging (nonaerated solution stagnated with 0.1% agar), alone or in combination. Shoot and root growth of the wheat genotypes was reduced by salinity and salinity × water‐logging, which was associated with increased leaf Na⁺ and Cl^– concentrations as well as decreased leaf K⁺ concentration and K⁺ : Na⁺ ratio. The genotypes differed significantly for their growth and leaf ionic composition. The genotypes Aqaab and MH‐97 were selected as salinity×water‐logging‐resistant and sensitive wheat genotypes, respectively, on the basis of their shoot fresh weights in the salinity × water‐logging treatment relative to control. In a soil experiment, the effect of water‐logging was tested for these two genotypes under nonsaline (EC = 2.6 dS m^–1) and saline (EC = 15 dS m^–1) soil conditions. The water‐logging was imposed for a period of 21 d at various growth stages, i.e., tillering, stem elongation, booting, and grain filling alone or in combinations. The maximum reduction in grain yield was observed after water‐logging at stem‐elongation + grain‐filling stages followed by water‐logging at grain‐filling stage, booting stage, and stem‐elongation stage, respectively. Salinity intensified the effect of water‐logging at all the growth stages. It is concluded that the existing genetic variation in wheat for salinity × water‐logging resistance can be successfully explored using relative shoot fresh weight as a selection criterion in nonaerated 0.1% agar–containing nutrient solution and that irrigation in the field should be scheduled to avoid temporary water‐logging at the sensitive stages of wheat growth.     

Effectiveness of potassium in mitigating the salt-induced oxidative stress in contrasting tomato genotypes

To check the efficacy of potassium in alleviating oxidative stress under salt stress, salt-tolerant (Indent-1) and salt-sensitive (Red Ball) tomato (Lycopersicon esculentum Mill.) genotypes were exposed to three levels of sodium chloride (NaCl) (0, 75, 150 mM) and two levels of potassium (4.5 and 9 mM) in solution and foliar form. Thirty days of treatments revealed that increasing NaCl stress increased lipid peroxidation (malondialdehyde, MDA) and correspondingly the activity of antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT; and glutathione reductase GR) in both genotypes. However, higher potassium (K) level in solution or foliar spray during the salt-induced stress decreased MDA and antioxidant activity and increased the growth in salt-tolerant genotype than in the salt-sensitive genotype. Decrease in MDA concentration, activity of antioxidant enzymes, and increase in the growth of tomato plants by the application of potassium under salt stress suggest that potassium is an effective ameliorating agent against salt-induced oxidative damage.     

Yield potential and salt tolerance of quinoa on salt‐degraded soils of Pakistan

Quinoa is recently introduced to Pakistan as a salt‐tolerant crop of high nutritional value. Open field trials were conducted to evaluate its performance on normal and salinity/sodicity‐degraded lands at two locations of different salinity/sodicity levels, S₁ (UAF Farm, Normal Soil), S₂ (Paroka Farm UAF, saline sodic), S₃ (SSRI Farm, normal) and S₄ (SSRI Farm, saline sodic) during 2013–2014. Two genotypes (Q‐2 and Q‐7) were grown in lines and were allowed to grow till maturity under RCBD split‐plot arrangement. Maximum seed yield (3,062 kg/ha) was achieved by Q‐7 at normal field (S₁) soil which was statistically similar with yield of same genotype obtained from salt‐affected field S₂ (2,870 kg/ha). Furthermore, low yield was seen from both genotypes from both S₃ and S₄ as compared to S₁ and S₂. Q‐7 was best under all four conditions. Minimum yield was recorded from Q‐2 (1,587 kg/ha) at S₄. Q‐7 had higher SOD, proline, phenolic and K⁺ contents, and lower Na⁺ content in leaves as compared to Q‐2. High levels of antioxidants and K⁺/Na⁺ of Q‐7 helped to withstand salt stress and might be the cause of higher yields under both normal and salt‐affected soils. Seed quality (mineral and protein) did not decrease considerably under salt‐affected soils even improved seed K⁺, Mg²⁺ and Mn²⁺.     

Silicon-induced changes in growth,ionic composition,water relations,chlorophyll contents and membrane permeability in two salt-stressed wheat genotypes

We investigated the effect of exogenously applied silicon (Si) on the growth and physiological attributes of wheat grown under sodium chloride salinity stress in two independent experiments. In the first experiment, two wheat genotypes SARC-3 (salt tolerant) and Auqab 2000 (salt sensitive) were grown in nutrient solution containing 0 and 100 mM sodium chloride supplemented with 2 mM Si or not. Salinity stress substantially reduced shoot and root dry matter in both genotypes; nonetheless, reduction in shoot dry weight was (2.6-fold) lower in SARC-3 than in Auqab 2000 (5-fold). Application of Si increased shoot and root dry weight and plant water contents in both normal and saline conditions. Shoot Na⁺ and Na⁺:K⁺ ratio also decreased with Si application under stress conditions. In the second experiment, both genotypes were grown in normal nutrient solution with and without 2 mM Si. After 12 days, seedlings were transferred to 1-l plastic pots and 150 mM sodium chloride salinity stress was imposed for 10 days to all pots. Shoot growth, chlorophyll content and membrane permeability were improved by Si application. Improved growth of salt-stressed wheat by Si application was mainly attributed to improved plant water contents in shoots, chlorophyll content, decreased Na⁺ and increased K⁺ concentrations in shoots as well as maintained membrane permeability.     

Preliminary Study of Variable Rate Application – Organic Liquid Fertilizer by Using SPAD Chlorophyll Meter on System of Rice Intensification (SRI) Cultivation

Knowing actual nutrient requirements for rice plants is crucial in supplying the correct amount of fertilizer, especially nitrogen since nitrogen is one of the most key limiting nutrients in rice cultivation. A preliminary study of variable rate application (VRA) on System of Rice Intensification (SRI) planting by using organic foliar fertilizer was carried out to determine the effectiveness of precision fertilization. Foliar fertilizer was formulated based on actual nitrogen needed by rice plants using Soil-Plant Analyses Development (SPAD) chlorophyll meter measurements. The experiment was laid out in a randomized complete block design (RCBD) with four treatments (50% fixed rate, 100% fixed rate, 150% fixed rate and VRA) and four replications for each treatment. Plant growth performances (plant heights, number of tillers, number of panicle and flower) and yield performances (grain yield, number of grain, 1000-grain weight and number of spikelets) were recorded during the study. The results showed that foliar application of VRA resulted in significantly higher yield performances; grain yield (13.65 g), number of grain (807.50), 1000-grain weight (16.79 g), and number of spikelets (7.50) compared to uniform fertilizer applications. VRA treatments had the highest SPAD readings at every planting stage during the experiment; however, a high nitrogen supply was needed during the mid-tillering stages (35 DAT) compared to other fertilizer rates. Besides, VRA application shows the most savings in term of total nitrogen supply (415 µg) compared to uniform rates application; 50% fixed rate (400 µg), 100% fixed rate (810 µg), and 150% fixed rate (1210 µg).     

Genetic Variation in Cadmium Accumulation and Tolerance among Wheat Cultivars at the Seedling Stage

Exploitation of genetic differences to select wheat cultivars’ pollution-safe from cadmium (Cd) contamination requires better understanding of Cd uptake and translocation patterns. For this purpose, 15 wheat cultivars were grown in nutrient solution and exposed to four levels of Cd, i.e., 0, 15, 30, and 45 µM. The plants were harvested after 2 weeks of Cd exposure. Root and shoot relative dry matter (DM) was decreased in most of the cultivars, but some cultivars did not exhibit any toxic symptoms. The lowest Cd concentration in shoots was recorded for Lasani-2008 and Iqbal-2000 while the highest for Sehar-2006 and Inqlab-91. Both root absorption and translocation accounted for regulating Cd concentration in shoots. There was no relationship between relative DM and Cd concentrations in roots and shoots. The results suggest that wheat cultivars with low shoot Cd concentration but higher tolerance, i.e. Lasani-2008 and Iqbal-2000, could be used in breading programs for low Cd wheat.     

A high virulence and pathotype diversity of Puccinia striiformis f.sp. tritici at its centre of diversity,the Himalayan region of Pakistan

Information on the pathogen virulence profile and diversity across locations is crucial for host germplasm improvement and deployment. The rapid acquisition of virulence to host resistance by the wheat yellow/stripe rust pathogen (Puccinia striiformis f.sp. tritici: PST), makes it crucial to know about its virulence and pathotype diversity. Recent studies have shown the plausible centre of origin of the pathogen in the Himalayan region, with Pakistan being the most ancestral to all other worldwide populations. To assess the status of virulence and pathotype diversity in the Himalayan region of Pakistan, a set of 127 PST infected wheat samples from eight locations were collected, multiplied and pathotyped using a set of 36 differential lines from the world set, European and Chinese sets, and 9 Avocet Yr isolines. Virulence (Vr) was recorded to 18 out of 24 tested yellow rust resistance (Yr) genes, while a total of 53 pathotypes were detected out of 127 isolates tested. Virulence was found to the resistance genes rarely deployed in Pakistan (Vr8) or even worldwide level (Vr5), while virulence to Vilmorin 23 (Yr3+) was absent in Pakistan, which is common in Europe. None of the pathotypes was dominant across all locations, however, no clear spatial structuring was observed for the studied locations. Our results suggested a high virulence and pathotype diversity in line with the previously proposed potential role of sexual recombination in the temporal maintenance of PST in the Himalayan region of Pakistan. This information should be useful in host resistance gene improvement and deployment.     

Closing the nitrogen use efficiency gap and reducing the environmental impact of wheat-maize cropping on smallholder farms in the Guanzhong Plain,Northwest China

A high crop yield with the minimum possible cost to the environment is generally desirable. However, the complicated relationships among crop production, nitrogen (N) use efficiency and environmental impacts must be clearly assessed. We conducted a series of on-farm N application rate experiments to establish the linkage between crop yield and N₂O emissions in the Guanzhong Plain in Northwest China. We also examined crop yield, partial factor productivity of applied N (PFPN) and reactive N (Nr) losses through a survey of 1 529 and 1 497 smallholder farms that grow wheat and maize, respectively, in the region. The optimum N rates were 175 and 214 kg ha^–1 for winter wheat and summer maize, respectively, thereby achieving the yields of 6 799 and 7 518 kg ha^–1, correspondingly, with low N₂O emissions based on on-farm N rate experiments. Among the smallholder farms, the average N application rates were 215 and 294 kg ha^–1 season^–1, thus producing 6 490 and 6 220 kg ha^–1 of wheat and maize, respectively. The corresponding PFPN values for the two crops were 36.8 and 21.2 kg N kg^–1, and the total N₂O emissions were 1.50 and 3.88 kg ha^–1, respectively. High N balance, large Nr losses and elevated N₂O emissions could be explained by the overdoses of N application and low grain yields under the current farming practice. The crop yields, N application rates, PFPN and total N₂O for wheat and maize were 18 and 24% higher, 42 and 37% less, 75 and 116% higher, and 42 and 47% less, correspondingly, in the high-yield and high-PFPN group than in the average smallholder farms. In conclusion, closing the PFPN gap between the current average and the value for the high-yield and high-PFPN group would increase crop production and reduce Nr losses or the total N₂O emissions for the investigated cropping system in Northwest China.     

Effect of season and superstimulatory treatment on in vivo and in vitro embryo production in wood bison (Bison bison athabascae)

Two experiments were done using a two-by-two design to determine the effects of season and superstimulatory protocol on embryo production in wood bison. In Experiment 1 (in vivo-derived embryos), ovarian superstimulation was induced in female bison during the ovulatory and anovulatory seasons with either two or three doses of FSH given every-other-day (FSH × 2 vs. FSH × 3, respectively). Bison were given hCG to induce ovulation, inseminated 12 and 24 hr after hCG, and embryos were collected 8 days after hCG (n = 10 bison/group). In Experiment 2 (in vitro embryo production), ovarian superstimulation was induced in female bison during the ovulatory and anovulatory seasons with two doses of FSH, and in vivo maturation of the cumulus–oocyte complexes (COC) was induced with hCG at either 48 or 72 hr after the last dose of FSH. COC were collected 34 hr after hCG, and expanded COC were used for in vitro fertilization and culture. In Experiment 1, the number of follicles ≥9 mm, the proportion of follicles that ovulated, the number of CL, and the total number of ova/embryos collected did not differ between seasons or treatment groups, but the number of transferable embryos was greater (p < .05) in the ovulatory season. In Experiment 2, no differences were detected between seasons or treatment groups for any end point. The number of transferable embryos produced per bison was greatest (p < .05) using in vitro fertilization and was unaffected by season (1.5 ± 0.2 and 1.1 ± 0.3 during anovulatory and ovulatory seasons, respectively), in contrast to in vivo embryo production which was affected by season (0.1 ± 0.01 and 0.7 ± 0.2 during anovulatory and ovulatory seasons, respectively). Results demonstrate that transferable embryos can be produced throughout the year in wood bison by both in vivo and in vitro techniques, but the efficiency of embryo production of in vivo-derived embryos is significantly lower during the anovulatory season.     

苗期甘蔗氮高效基因型评价指标的筛选

本研究通过低氮压力选择,筛选出甘蔗氮高效种质,分析影响甘蔗氮高效的重要指标,为甘蔗氮高效育种及栽培提供理论依据。以58份甘蔗种质资源为材料,在苗期采用正常供氮（2 mmol/L N）和低氮（0.2 mmol/L N）处理,分析甘蔗植株形态、干重及氮素在各器官中累积分配的特征。通过主成分分析方法筛选影响甘蔗氮高效利用的重要指标,通过聚类分析对58份种质进行聚类。结果表明,低氮（0.2 mmol/L N）处理可以明显从植物形态区分不同种质的氮利用差异,58份种质低氮条件下的干重范围为0.64~14.75 g/株,氮累积量为5.53~63.00 mg/株,氮利用率范围为115.40~279.30 g/g。对低氮压力下甘蔗干重及氮累积等25个指标进行主成分分析后,提取出4个主要成分,总贡献率为92.35%。通过高、低氮条件下与氮利用效率有关的氮转移系数及基因潜力等19个指标分析后提取出5个主成分,总贡献率为82.21%。影响甘蔗氮高效的重要指标有甘蔗的干重（全株、叶、根）、氮累积量（全株、叶、茎）、氮利用率（全株、叶）、叶的相对氮利用率、茎的基因潜力、茎的相对干物质量和茎的相对氮累积量。经聚类分析后初步将58份甘蔗种质分为氮高效基因型、偏氮高效基因型、偏氮低效基因型和氮低效基因型。