Cloning and Phylogenetic Analysis of Coat Protein of Barley yellow dwarf virus Isolates from Different Regions of Pakistan

Barley yellow dwarf virus (BYDVs) is an emerging threat for wheat and may seriously threaten its production, especially as climate change may result in increased infestation by aphids, the insect vectors of the virus. To assess the possibility of using pathogen‐derived resistance against the virus, the genetic diversity of BYDVs originating from different wheat‐growing areas of Pakistan where its incidence has been higher was investigated. Wheat samples with suspected symptoms of BYDVs were screened for the presence of Barley yellow dwarf and Cereal yellow dwarf viruses (B/CYDVs) subgroup 1 (Barley yellow dwarf virus‐PAV, BYDV‐MAV, BYDV‐SGV) and subgroup II (BYDV‐RPV, CYDV‐RPV, BYDV‐GPV) by PCR using basic multiplex oligonucleotides designed on coat protein (CP) of the virus. Of 37 samples tested, 13 were positive for BYDV subgroup I and only one sample was positive for BYDV subgroup II. Samples positive for subgroup I were further tested by PCR, and results showed that 10 samples were positive for BYDV‐PAV and three for BYDV‐MAV. DNA sequences of CP region of nine isolates (BYDV‐PAV) were determined and compared with available sequences in databases. Sequence analysis showed that three isolates (from Fatehjang, Nowshera and Attock districts) had maximum identity (92.8–94.6%) to BYDV‐PAS, and six isolates (from Peshawar, Islamabad Swabi and Faisalabad districts) had maximum identity (99.3–99.7%) to BYDV‐PAV. Thus BYDV‐PAV species may be dominant in northern wheat‐growing areas of Pakistan. The conserved nature of the BYDVs suggests that pathogen‐derived resistance strategies targeting the coat protein of the virus are likely to provide protection under field conditions.     

Virus disease in wheat predicted to increase with a changing climate

Current atmospheric CO₂ levels are about 400 μmol mol^?1 and are predicted to rise to 650 μmol mol^?1 later this century. Although the positive and negative impacts of CO₂ on plants are well documented, little is known about interactions with pests and diseases. If disease severity increases under future environmental conditions, then it becomes imperative to understand the impacts of pathogens on crop production in order to minimize crop losses and maximize food production. Barley yellow dwarf virus (BYDV) adversely affects the yield and quality of economically important crops including wheat, barley and oats. It is transmitted by numerous aphid species and causes a serious disease of cereal crops worldwide. This study examined the effects of ambient (aCO₂; 400 μmol mol^?1) and elevated CO₂ (eCO₂; 650 μmol mol^?1) on noninfected and BYDV‐infected wheat. Using a RT‐qPCR technique, we measured virus titre from aCO₂ and eCO₂ treatments. BYDV titre increased significantly by 36.8% in leaves of wheat grown under eCO₂ conditions compared to aCO₂. Plant growth parameters including height, tiller number, leaf area and biomass were generally higher in plants exposed to higher CO₂ levels but increased growth did not explain the increase in BYDV titre in these plants. High virus titre in plants has been shown to have a significant negative effect on plant yield and causes earlier and more pronounced symptom expression increasing the probability of virus spread by insects. The combination of these factors could negatively impact food production in Australia and worldwide under future climate conditions. This is the first quantitative evidence that BYDV titre increases in plants grown under elevated CO₂ levels.     

An overview of stripe rust of wheat (Puccinia striiformis f. sp. tritici) in Pakistan

Stripe rust (yellow rust) caused by Puccinia striiformis f. sp. tritici has been an important disease of wheat in the Indian subcontinent since 1786. Currently, it prevails across all the wheat growing areas from north to south in the country. Due to the favourable weather conditions, the northern uplands have been historically hit by the severe disease epidemics. These epidemics caused significant losses to national wheat production. Acquisition of broader virulence pattern by the pathogen poses a serious threat to national agriculture. Although the deployed national wheat varieties have adequate resistance, these are developed around few major genes and are vulnerable to the new evolving strains of the pathogen. Utilisation of race non-specific durable resistance and seedling resistance via gene pyramiding, based on the current virulence scenario of the pathogen should provide sustainable control. This review focuses on the national milestones that recognise the economic significance of the disease and current status of stripe rust and its management in Pakistan.     

兼抗抗白粉病和黄矮病小麦育种材料的创造与鉴定

白粉病和黄矮病是小麦生产上的重要病害,近几年来这两种病害经常在我国一些小麦产区同时发生。为解决该问题,本研究通过杂交、回交方法将抗黄矮病的Bdv2基因（源自于YW642）和抗白粉病的Pm21基因（源自于CB037）聚合在一起,育成了兼抗黄矮病和白粉病的小麦新材料。通过田间抗病性鉴定与分子标记辅助选择相结合,得到聚合了Bdv2基因和Pm21基因的BC1代小麦22株,F2代小麦51株。农艺性状调查显示,这些含Pm21和Bdv2基因的双抗白粉病和黄矮病小麦新材料的农艺性状优于感病植株和原先的亲本,可以在小麦白粉病和黄矮病兼性抗病育种中作为优异种质资源加以利用。     

Interaction Of Barley Yellow Dwarf Virus and Fusarium culmorum (W. G. Sm.) Sacc. in Winter Wheat

The barley yellow dwarf virus (BYDV) epidemics, which occurred predominantly in northern Germany in 1988–90 and caused unusual yield losses of wheat, prompted our study on interactions of BYDV and Fusarium culmorum. At the late stages of plant development (EC 55/65) infections with BYDV resulted in a lower yield reduction of wheat plants than infections with F. culmorum. Combined infections at flowering resulted in severer yield reduction, indicating additive effects of the two pathogens. However, if wheat infected by BYDV at stage EC 25/35 was secondarily inoculated with the fungus at EC 55/65 the yield was less reduced than in combined infections at EC 55/65. Our results proved that the susceptibility of wheat plants to F. culmorum is increased when infection by BYDV takes place during the late stages of growth. These results correspond to observations during 3 years of the epidemic in Germany. In these years BYDV was spread mainly during the late spring, resulting in a severe secondary infection by the fungus. From the results of these investigations it may be concluded that during the years of BYDV epidemic the yield of wheat was reduced to an economically important extent because of the fungal infection, which was favoured by the virus infection.     

Genetic diversity of common bean (Phaseolus vulgaris L.) ecotypes from Pakistan using Simple Sequence Repeats

Common bean (Phaseolus vulgaris L.) is a legume crop grown all over the world and is a very important food of mountain population of Pakistan for protein intake. The Western Himalayan Mountains are rich in biodiversity including unexplored landraces of the common bean crop. Unfortunately, very little attention has been given to this valuable crop in Pakistan, and it is being exported, majorly from Ethiopia, to meet the country’s requirements. The exploitation, utilization, preservation and multiplication of existing germplasm within the area are very important for sustainable production of the crop and enhancing the nutrition value for the local community in mountain regions. A research study was conducted for evaluation of biological diversity of common bean landraces from Azad Kashmir and Northern areas of Pakistan using morpho-physiological and molecular markers. Thirty-five common bean ecotypes along with one check variety were collected from different altitudes of Azad Kashmir and Northern Pakistan and screened for biological diversity. Morphological characterization revealed high genetic diversity in parameters including stem anthocyanin, growth type, days to flowering, pods/plant and 100 seeds weight. Genomic characterization using SSR markers, for allelic diversity evaluation among germplasm, also provided diverse profile with 83.3% polymorphism in banding pattern. The bulk of gene pool diversity evaluated within bean landraces may help to initiate breeding program for common bean improvement.     

Complementing cultural weed control with plant allelopathy: Implications for improved weed management in wheat crop

Wheat (Triticum aestivum L.) is an important cereal crop in Pakistan which is suffering from major grain production loss because of weed infestations. Control of weeds by herbicides is a primary weed management tool in wheat crop which can be detrimental to the environment and grain produce. Development of an efficient and eco-friendly alternate to the herbicidal weed control, testing the effectiveness of cultural weed control (crop row orientation, selected wheat genotypes and hand weeding) and plants water extracts was undertaken for weed control in wheat. An experiment was run under field conditions in winter season in 2016–2017 and in 2017–2018 in Khyber Pakhtunkhwa Province, Pakistan. The repeated experiment was each time undertaken using a randomized complete block design with a double split plot arrangements at the New Developmental Farm, University of Agriculture, Peshawar, Pakistan. The crop row orientations used were assigned to the main plots. The wheat genotypes used were assigned to the sub-plots. The allelopathic water extracts and hand weeding were assigned to the sub-sub plots. The averaged mean values for row orientations of both the years revealed lowest weed density (95.7 weeds m^?2), highest grains per spike (47.3), 1000 grains weight (44.7 g) in north to south row orientation. The averaged mean values of weed density (101.6 weeds m^?2), grains per spike (48.2), 1000 grains weight (45.9 g), crude protein content (12.793%), crude fat content (1.533%) and ash content (1.586%) were greater for the wheat genotype Pirsabaq-2013 and Atta-Habib-2010. Water extract of S. halepense, P. hysterophorus, H. annuus and hand weeding showed significantly lower weed density (84.0 to 93.3), grains per spike (50.9 to 48.3), 1000 grains weight (48.3 to 46.2 g), grains protein content (12.280 to 12.209%), grains crude fat content (1.471 to 1.464%) and grains ash content (1.523 to 1.515%). Interaction effect of different tested weed control treatments i.e. N-S × Pirsabaq-2013 and Atta-Habib-2010 × water extract of S. halepense, P. hysterophorus and H. annuus were found to show further reduction in weed density and enhance grains per spike and grains nutrition contributing parameters. Our results show that sowing wheat genotypes Pirsabaq-2013 and Atta-Habib-2010 in north-to-south row orientation, and application of water extract of S. halepense, P. hysterophorus, H. annuus can give an effective weed management and increased quality grain yield of wheat.     

Introgression and characterization of barley yellow dwarf virus resistance from Thinopyrum intermedium into wheat.

Wheatgrasses (species of Agropyron complex) have previously been reported to be resistant to barley yellow dwarf virus (BYDV). To introgress this resistance into wheat, Triticum aestivum x Thinopyrum (Agropyron) intermedium hybrids were advanced through a backcrossing program and reaction to BYDV, as determined by enzyme-linked immunosorbent assay (ELISA), is reported for the first time in backcross populations of wide hybrids between wheat and wheatgrasses. ELISA values revealed highly resistant to highly susceptible segregants in backcrosses. BYDV resistance was expressed in some backcross derivatives. Continued selection, based on cytology and ELISA in each generation, eliminated most of the unwanted wheatgrass chromosomes and produced self-fertile BYDV resistant wheat lines. The BYDV resistant lines with 2n = 42 had normal chromosome pairing similar to wheat, and their F1 hybrids with wheat had two univalents. DNA analyses showed that the source of alien chromatin in these BYDV resistant wheat lines is distinguishable from that in other Th. intermedium derived BYDV resistant wheat lines. Chromosome pairing and restriction fragment length polymorphism analyses indicated that the 42 chromosome resistant Purdue wheat lines are substitution lines in which chromosome 7D was replaced by a chromosome from Th. intermedium that was carrying gene(s) for BYDV resistance.     

Crop production structure and stability under climate change in South America

Southern South America is expected to play an increasingly important role in global food production, but climate change could seriously threaten it. Here we have analysed long‐term historical data for major crops (rice, oats, barley, sunflower, soybean, sorghum, wheat, maize) at subnational scale to (a) look for common features among crop yield dynamics, evaluating their structure and implications for the persistence of that crop; (b) address complex crop responses to changes in environmental growing conditions; and (c) identify climate impact hotspots that are crucial for adaptation and mitigation. We have proposed a novel methodological approach based on dynamics systems in order to understand the processes behind annual crop yield fluctuations. We report the results of general patterns in the internal process (biophysical adjustments by rapid negative feedbacks) regulating crop production and analyse how it influences crop persistence and yield ceilings. The structure of a crop yield dynamic system defines its behaviour, but climate variations could displace it from yield equilibrium and affect its stability. Our findings suggest that weather conditions have a stronger impact on yield growth at high rather than at low yield levels (non‐additive impacts). This allows agriculture management to be refined and applied more efficiently, weakening the relationship between crop productivity and climate change and predicting the response of crop production to yield‐improvement strategies. We have identified those crops and regions which are most vulnerable to the current climate change trends in southern South American agroecosystems. Our results allow us to point to new ways to enhance self‐regulatory success, maximising the efficiency of crop production and reducing climate impacts. We have discussed important implications for crop management and climate change mitigation in an area where agriculture plays a key role in its socioeconomic and ecologic dimensions.     

Effect of BYDV Infection on the Cell Surface Glycoproteins in Common Wheat,Wheatgrass and Octoploid Wheat-Wheatgrass

Changes in the cell surface glycoproteins in common wheat 3B-2, Agropyron intermedium and octoploid wheat-wheatgrass Zhong 5 after the inoculation with barley yellow dwarf virus (BYDV) were sdudied using electron microscopy and ruthenium red staining. The results indicated that, after the inoculation with BYDV, different changes in cell surface glycoproreins were observed in the plant species with different levels of resistance. In A. intermediurn which is immune to BYDV, inoculation with BYDV did not cause significant change in cell surface glycoprotein layer. In cotoploid wheat-wheatgrass Zhong 5 which is highly resistent to BYDV, BYDV infection caused significant thickening in most cell surface glycoprotein layer. In common wheat 3B-2 which is susceptible to BYDV, BYDV infection did not cause thickening in cell surface glycoprotein layer, but in most cells, glycoproteins on the cell surface were partially peeled off or disappeared completely. Therefore, it is suggested that the glycoproteins on cell surface play certain roles in BYDV resistance. The phenomenon of the thickening of cell surface glycoprotein layer caused by BYDV infection was possibly a resistant reaction to the virus.     

The Role of Maize in the Epidemiology of Barley Yellow Dwarf Virus in Northeast Spain

Barley yellow dwarf virus has been detected in maize by indirect enzyme-linked immunosorbent assay (ELISA) and by immunospecific electron microscopy (ISEM). Samples of maize collected in September 1988, 1989 and 1990 showed that this crop is an important reservoir of BYDV; MAV-like isolates were the most common although PAV-like and RPV-like isolates were also present. Earlier research in Spain had shown that PAV-like isolates were predominant. Thus the evidence from this work that MAV was the main isolate, and very widely spread, is important for future research on BYDV epidemiology in Spain.     

气候变化对我国华北地区冬小麦发育和产量的影响

验证作物模型在我国华北冬小麦主产区是否适应的基础上,采用作物模型与气候模式相结合的研究方法,定量化地模拟预测了未来100年气候变化对华北冬小麦生产的影响.结果表明,从2000～2004年,华北地区冬小麦产量的模拟值与实测值的变化趋势基本一致,且生育期和产量变化不大.未来100年内华北地区冬小麦的生长期可能会有所缩短,平均缩短8.4 d;产量也会有不同程度的下降,平均减产10.1％.适当采取应对措施可以有效降低冬小麦的减产趋势.     

Tripartite Interactions of Barley Yellow Dwarf Virus,Sitobion avenae and Wheat Varieties

The tripartite interactions in a pathosystem involving wheat (Triticum aestivum L.), the Barley yellow dwarf virus (BYDV), and the BYDV vector aphid Sitobion avenae were studied under field conditions to determine the impact of these interactions on aphid populations, virus pathology and grain yield. Wheat varietal resistance to BYDV and aphids varied among the three wheat varieties studied over two consecutive years. The results demonstrated that (1) aphid peak number (APN) in the aphid + BYDV (viruliferous aphid) treatment was greater and occurred earlier than that in the non-viruliferous aphid treatment. The APN and the area under the curve of population dynamics (AUC) on a S. avenae-resistant variety 98-10-30 was significantly lower than on two aphid-susceptible varieties Tam200(13)G and Xiaoyan6. (2) The production of alatae (PA) was greater on the variety 98-10-30 than on the other varieties, and PA was greater in the aphid + BYDV treatment on 98-10-30 than in the non-viruliferous aphid treatment, but this trend was reversed on Tam200(13)G and Xiaoyan6. (3) The BYDV disease incidence (DIC) on the variety 98-10-30 was greater than that on the other two varieties in 2012, and the disease index (DID) on Tam200(13)G was lower than on the other varieties in the aphid + BYDV and BYDV treatments in 2012, but not in 2011 when aphid vector numbers were generally lower. (4) Yield loss in the aphid + BYDV treatment tended to be greater than that in the aphid or BYDV alone treatments across varieties and years. We suggested that aphid population development and BYDV transmission tend to promote each other under field conditions. The aphids + BYDV treatment caused greater yield reductions than non-viruliferous aphids or virus treatment. Wheat varietal resistance in 98-10-30 affects the aphid dispersal, virus transmission and wheat yield loss though inhibits aphid populations from increasing.     

Hydroxamic acids affecting barley yellow dwarf virus transmission by the aphid Rhopalosiphum padi

2,4-Dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA), a hydroxamic acid (Hx) occurring in wheat, was shown to deter feeding by the aphid Rhopalosiphum padi (L.), and to reduce BYDV transmission to the plant. Dual choice tests with wheat leaves showed the preferential settlement of aphids on leaves with lower levels of DIMBOA. Electric monitoring of aphid feeding behaviour showed that in seedlings with higher DIMBOA levels fewer aphids reached the phloem and they needed longer times to contact a phloem vessel than in those with lower levels. When aphids carrying BYDV were allowed to feed on wheat cultivars with different DIMBOA levels, fewer plants were infected with BYDV in the higher DIMBOA cultivars than in the lower ones. Preliminary field experiments showed a tendency for wheat cultivars with higher Hx levels to be more tolerant to infection by BYDV than lower Hx level ones.     

中国作物种质资源引进与流出研究

引进国外种质、促进粮食生产,对中国至关重要。中国每年从世界各地引进大量的作物遗传资源,如水稻、小麦、玉米、马铃薯、甘薯,当然主要是从国际农业研究磋商组织(CGIAR)各中心引进的。同时,中国也向国际农业研究磋商组织各中心和其他国家提供了许多作物遗传资源(如大豆),为世界做出了巨大贡献。种质资源的流动有利于中国,因此中国应该与国际农业研究磋商组织各中心和其他国家加强合作,组织专家系统研究并争取尽快加入《粮食和农业植物遗传资源国际条约》,强化统一管理,规范种质资源引进与输出,建立共享机制,推进种质资源共享。     

Interaction between barley yellow dwarf virus and rust in wheat, barley and oats, and the effects on grain yield and quality

In three separate experiments, the upper leaf surface of the fifth formed leaf of wheat cv. Highbury, the fourth and fifth leaves of barley cv. Julia and the third and fourth leaves of oat cv. Mostyn were inoculated in a spore settling tower with wheat brown rust (Puccinia recondita f. sp. tritici), barley brown rust (P. hordei) or oat crown rust (P. coronata f. sp. avenae), respectively. Fewer pustules developed on distal portions of leaves of plants infected with barley yellow dwarf virus (BYDV) than on similar portions of leaves from virus-free plants. There were no significant differences in the number of pustules on proximal leaf portions. In barley and oats, the number of pustules on distal leaf portions was negatively correlated with the amount of yellowing of the leaf areas scored. In wheat, symptoms of BYDV were mild and leaves were little affected by yellowing. The latent period of rust on wheat and oats was not affected by BYDV. In barley, BYDV reduced the latent period of rust on leaf 5, but not on leaf 4, and reduced it on proximal, but not distal, leaf portions. In other experiments, BYDV reduced the yield of wheat and oats by 44% and 66%, respectively, while BYDV-infected barley was almost sterile. The appropriate rust reduced the yield of wheat, barley and oats by 33%, 13% and 86%, respectively. When infected with both BYDV and rust, yield of wheat and oats was reduced by 63% and 91%, respectively. Neither BYDV nor rust affected the percentage crude protein content of wheat grain, nor did rust affect that of barley. In oats, BYDV and rust each significantly increased crude protein of grain, but rust infection of BYDV-infected plants tended to reduce it.     

Flexible Strategies for Coping with Rainfall Variability: Seasonal Adjustments in Cropped Area in the Ganges Basin

One of the main manifestations of climate change will be increased rainfall variability. How to deal with this in agriculture will be a major societal challenge. In this paper we explore flexibility in land use, through deliberate seasonal adjustments in cropped area, as a specific strategy for coping with rainfall variability. Such adjustments are not incorporated in hydro-meteorological crop models commonly used for food security analyses. Our paper contributes to the literature by making a comprehensive model assessment of inter-annual variability in crop production, including both variations in crop yield and cropped area. The Ganges basin is used as a case study. First, we assessed the contribution of cropped area variability to overall variability in rice and wheat production by applying hierarchical partitioning on time-series of agricultural statistics. We then introduced cropped area as an endogenous decision variable in a hydro-economic optimization model (WaterWise), coupled to a hydrology-vegetation model (LPJmL), and analyzed to what extent its performance in the estimation of inter-annual variability in crop production improved. From the statistics, we found that in the period 1999–2009 seasonal adjustment in cropped area can explain almost 50% of variability in wheat production and 40% of variability in rice production in the Indian part of the Ganges basin. Our improved model was well capable of mimicking existing variability at different spatial aggregation levels, especially for wheat. The value of flexibility, i.e. the foregone costs of choosing not to crop in years when water is scarce, was quantified at 4% of gross margin of wheat in the Indian part of the Ganges basin and as high as 34% of gross margin of wheat in the drought-prone state of Rajasthan. We argue that flexibility in land use is an important coping strategy to rainfall variability in water stressed regions.     

The barley yellow dwarf virus in Ukraine

Barley yellow dwarf virus (BYDV) has been identified in the Central region of the Ukraine. BYDV infection in winter wheat crops was shown to be highly harmful. There were no winter wheat cultivars being resistent to BYDV and tolerant cultivars occured rarely. In particular seasons BYDV may give rise to widescale epithoties.     

A review of research on Sunn Pest {Eurygaster integriceps Puton (Hemiptera: Scutelleridae)} management published 2004–2016

Wheat is an important food crop that provides over 40% of the per capita dietary supply of calories and proteins in many developing countries. Wheat production has a crucial role in food security and the global economy. With the world's population estimated to reach 9.6 billion by 2050, the demand for wheat is expected to increase 60%. Sunn Pest, Eurygaster integriceps Puton (Hemiptera: Scutelleridae), is one of the major constraints to wheat production in Central and West Asia, Eastern Europe and North Africa. The economic impact of Sunn Pest is around 42 million USD for the region and that is only the cost of the chemicals used for its management. Application of chemical insecticides has been the main strategy for management of Sunn Pest. However, emergence of resistance in Sunn Pest populations against most pesticides and increased awareness of their adverse impacts on the environment have prompted investigation of alternative approaches. This review provides information on the most current literatures on Sunn Pest management with emphasis on practices such as application of chemical insecticides, insect growth regulators (IGRs) and anti-juvenile hormones, use of Sunn Pest egg parasitoids, entomopathogenic nematodes, entomopathogenic fungi, use of digestive enzyme inhibitors and development of resistant wheat varieties.     

小麦背景下 BYDV抗性携带染色体的遗传行为

在鉴定遗4212中BYDV抗性携带染色体的染色体组起源以及被代换小麦染色体的基础上,研究了BYDV抗性携带染色体补偿小麦染色体的能力以及传递率等问题.结果表明,BYDV抗性携带染色体能较好补偿小麦第2、第5以及第7部分同源群的染色体;在二体代换系中,该染色体优先取代2D小麦染色体、而非2A、2B小麦染色体;(77-5433×遗4212)自交F2群体中共出现10种染色体组成类型,其中一种为非预期类型,染色体数目变异较大而结构变异较少;该染色体的传递率以及携带该染色体配子的传递率分别为56.3%和33%,低于理论值75%和50%;并结合遗4212染色体组成鉴定结果探讨了相关结果产生的原因.染色体原位杂交是研究小麦背景下外源染色体遗传行为快速而准确的方法.