Management Of Rust Research Articles

Virulence and Diversity of Puccinia striiformis f. sp. tritici Populations in Northwestern and Southwestern Oversummering Regions of China.

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is the most devastating fungal disease affecting wheat in China, particularly in the northwestern (Qinghai, Gansu, and Ningxia) and southwestern (Sichuan, Yunnan, and Guizhou) oversummering regions. In this study, 302 isolates collected from these six provinces were analyzed using virulence testing and single-nucleotide polymorphism (SNP) markers. Virulence testing on 19 Chinese differentials identified 38 previously reported and 49 novel races. CYR34 was the most prevalent race in both the northwestern and southwestern oversummering regions, with frequencies of 24.00% and 21.05%, respectively. In the northwestern oversummering region, the prevalence of CYR32 (10.70%) and G22-14 (10.67%) was nearly identical, whereas in the southwestern oversummering region, CYR32 (13.20%) and G22-14 (9.87%) exhibited significant differences. Additionally, 112 races were identified using 18 Yr single-gene differentials, although none of the isolates showed virulence to either Yr5 or Yr15. The virulence diversity of Pst populations was greater in the southwestern than in the northwestern oversummering region, as indicated by the differential sets. Further molecular analysis with 20 pairs of polymorphic KASP-SNP markers confirmed that the southwestern Pst population exhibited higher genetic diversity than the northwestern population. Both virulence phenotypes and genotype data demonstrated that the Pst population was more diverse in the southwestern oversummering region, despite presence of the exchange of Pst sources between regions. In addition, mutant isolates indicating resistance to tiadimefon fungicide were detected in both regions. This study provides a systematic comparison of Pst populations in the northwestern and southwestern oversummering regions based on virulence phenotyping and SNP marker genotyping, and the findings are crucial for the integrated management of wheat stripe rust in these regions and across the country.

Respuesta de la roya (Hemileia vastatrix) frente a condiciones climáticas y aplicaciones de fungicidas en el cultivo de café (Coffea arabica) bajo sombra

Coffee leaf rust (Hemileia vastatrix) was first reported in 1869 on a plantation on the island of Sri Lanka, Asia, and has since spread to all coffee-growing regions far from its center of origin. The coexistence between the coffee plant, primarily Coffea arabica, and the fungus Hemileia vastatrix leads to coevolution, which manifests in significant genetic variability in the plant’s resistance to the disease and the fungus’s virulence towards the plant (Avelino and Rivas, 2013). The trophic relationships between the fungus and the host are influenced by soil moisture, fruit load, genetic resistance, precipitation, relative humidity, and temperature; these are the main factors affecting plant colonization (Filho and Astorga, 2015). In this study, the behavior of H. vastatrix was recorded through sampling to describe the relationship between disease incidence and environmental conditions, such as precipitation, temperature, and relative humidity, over an 18-month period at the Santa Lucía Experimental Farm (FESL) in Heredia, Costa Rica. The main findings demonstrated that the use of triazole fungicides and copper hydroxide can maintain disease incidence below 7%, despite contributions to its development from precipitation and increased temperatures, but not from increased relative humidity. Proper management of coffee leaf rust and the presence of shade can help reduce the incidence of the disease in the coffee plantation at FESL.

Profiling of Phakopsora pachyrhizi transcriptome revealed co-expressed virulence effectors as prospective RNA interference targets for soybean rust management.

Soybean rust (SBR), caused by an obligate biotrophic pathogen Phakopsora pachyrhizi, is a devastating disease of soybean worldwide. However, the mechanisms underlying plant invasion by P. pachyrhizi are poorly understood, which hinders the development of effective control strategies for SBR. Here we performed detailed histological characterization on the infection cycle of P. pachyrhizi in soybean and conducted a high-resolution transcriptional dissection of P. pachyrhizi during infection. This revealed P. pachyrhizi infection leads to significant changes in gene expression with 10 co-expressed gene modules, representing dramatic transcriptional shifts in metabolism and signal transduction during different stages throughout the infection cycle. Numerous genes encoding secreted protein are biphasic expressed, and are capable of inhibiting programmed cell death triggered by microbial effectors. Notably, three co-expressed P. pachyrhizi apoplastic effectors (PpAE1, PpAE2, and PpAE3) were found to suppress plant immune responses and were essential for P. pachyrhizi infection. Double-stranded RNA coupled with nanomaterials significantly inhibited SBR infection by targeting PpAE1, PpAE2, and PpAE3, and provided long-lasting protection to soybean against P. pachyrhizi. Together, this study revealed prominent changes in gene expression associated with SBR and identified P. pachyrhizi virulence effectors as promising targets of RNA interference-based soybean protection strategy against SBR.

Determination of the rate and frequency of Natura 250 EW fungicide for the management of cedar rust from Gesho (Rhamnus prinoides) in the north west Amhara Region, Ethiopia

Rhamnus prinoides (Gesho) is grown in the homesteads of farmers in western Amhara. The leaves, twigs, and stems of Gesho are indispensable ingredients in traditional beverages. Its production has recently suffered from cedar rust caused by the fungus Gymnosporangium. To manage this disease, different fungicides have been recommended. Therefore, this research was designed to determine the rate and frequency of the use of the Natura 250 EW system for managing this disease in Gesho during 2020. Five application rates of Natura 250 EW and three spray frequencies were used as treatments to manage the disease in infected Gesho plants via the Randomized Complete Block Design (RCBD). Statistically significant differences (P ≤ 0.05) were found between treatments for most parameters. Among these 0.75 litter ha-1 treatments, two spray applications resulted in the lowest severity and greatest relative efficacy, followed by three spray applications of 0.50 litter ha−1 at Bahir Dar Zuria district. However, at Yilmana Densa district, the lowest severity and greatest relative efficacy were found for the 0.75 litter ha−1 spray, followed by the 0.50 litter ha−1 spray, compared with the other treatments. Even though 0.75 litter ha−1 had greater relative efficacy and lower disease severity than the other treatments, there was no statistically significant difference between the three sprays of 0.50 litter ha−1 at both locations. Therefore, three sprays of Natura 250 EW at 0.50 litter ha−1 in 15-day intervals should be recommended and demonstrated for the management of cedar rust disease on Gesho.

Virulence, structure, and triadimefon sensitivity of the Puccinia striiformis f. sp. tritici population in Shaanxi Province, China.

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is the most destructive fungal disease affecting wheat in China, especially in Shaanxi Province, an important epidemiological region connecting the western Pst over-summer regions and the central and eastern spring epidemic regions in the country. In the present study, 291 Pst isolates from Shaanxi Province were studied for their virulence using two sets of wheat differentials, population structure using single-nucleotide polymorphism (SNP) markers, and sensitivity to fungicide. When the isolates were tested on the Chinese differentials of 19 wheat cultivars, 72 races were identified, which belonged to three groups, including the Guinong 22 group (48.45%), Hybrid 46 group (31.62%), and Suwon 11 group (19.93%). The three most predominant races were CYR34 (15.46%), G22-14 (11.68%), and CYR32 (10.65%). When the isolates were tested on the 18 Yr single-gene differentials, 95 races were identified, but none of the isolates were virulent to either Yr5 or Yr15. Cluster analyses of the virulence data based on the two sets of differentials and the SNP marker data consistently separated the Shaanxi Pst population into two clusters in the central part and southern part of the Province. Triadimefon sensitivity testing across different concentrations showed a broad range of half-maximal effective concentration (EC50) values, from 0.03 to 5.99 μg mL-1, with a mean EC50 of 0.46 μg mL-1. The majority of isolates (90.72%) were sensitive to the fungicide. The correlation analyses of the virulence, SNP marker, and the triadimefon sensitivity data showed no significant correlations, except a logarithmic relationship between the EC50 value and the number of avirulence factors. This study is the first to determine the relationship of virulence and SNP markers with triadimefon sensitivity in a regional Pst population.The findings provide valuable insights for breeding resistant wheat cultivars and integrated management of stripe rust.

Wheat Stripe Rust Inoculum from the Southwest Dispersed to the East Huang-Huai-Hai Region through Southern Anhui in China.

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is a continuous threat to global wheat production. In 2021, the epidemic of wheat stripe rust in China affected approximately 4.5 million hectares, resulting in severe yield losses. When confronted with the epidemic, tracing the sources of the pathogen can offer valuable insights for disease prevention and control. This study was conducted to analyze the genetic structure, aerodynamics, geographical features, and cultivation practices of the pathogen population in various wheat-producing regions, and to further reveal the spread patterns of the stripe rust pathogens in China. The findings indicated an overall trend of the pathogen dissemination from the west to the east. The pathogen was primarily spread from the northwestern region to the Huang-Huai-Hai region through the Guanzhong Plain and the NanXiang Plain. Meanwhile, the pathogen was also spread eastward from the southwestern region to the lower reaches of the Yangtze River, utilizing the Jianghan Plain as a bridge and the Yangtze River Valley in southwestern Anhui as the main pathway. Furthermore, the pathogen spread northward into Shandong under the driving force of the southeast winds. The findings of this study may provide valuable insights for the integrated management of wheat stripe rust in China.

Field efficacy of novel fungicides against chickpea rust (Uromyces ciceris-arietini)

The host resistance in present-day chickpea cultivars against rust disease is lacking thus, the present study was carried out during the winter (rabi) seasons of 2019–20 and 2020–21 at Regional Research Station, ICAR-Indian Institute of Pulses Research, Dharwad, Karnataka to explore effective fungicides for the management of chickpea rust. All fungicides found to reduce chickpea rust severity, but differences in efficacy were observed throughout the study. Present studies revealed that two sprays of 0.1% azoxystrobin 18.2% + difenoconazole 11.4% sc fungicide at 15 days interval minimizes the rust severity to the tune of >77% and achieved a benefit cost (B:C) ratio of 2.32 i.e. in terms of monetary value farmers could get a net income of ₹35268/ha. Thus, timely spraying of identified modern fungicide combination can be taken advantage for better control of chickpea rust.

Management of Rust in Wheat Using IPM Principles and Alternative Products

Overall, there is a major wish that European farmers implement integrated pest management (IPM), particularly to reduce dependence on pesticides. In the European Rustwatch project, partners conducted nineteen trials across nine different countries during 2020 and 2021 to investigate different IPM strategies, focusing on controlling rust diseases in winter wheat. The trials included the use of varieties with contrasting levels of resistance, variety mixtures, reduced fungicide rates, thresholds, and Decision Support Systems (DSSs), and testing alternative products to fungicides. Sixteen trials developed yellow rust (Puccinia striiformis f. sp. tritici) infections, and six trials developed brown rust (Puccinia triticina) infections. Resistant varieties proved highly effective in keeping down yellow rust infection, and variety mixtures also effectively reduced infection levels and stabilized yields. Rust was fully controlled using 25% of standard fungicide rates, even under high disease pressure. Using DSSs provided sufficient control of rust diseases and resulted in competitive net economic returns due to fewer fungicide applications. The alternative products tested included two biological control agents and four alternative chemistries, which all gave inferior and insufficient control against rust compared with chemical fungicides. The trial work demonstrated that there are good and reliable options for including IPM into disease control in wheat.

SSR‐based analysis of structural variation of the Russian population of Puccinia striiformis f. sp. tritici in 2019–2021

AbstractThe importance of monitoring and management of yellow rust, caused by Puccinia striiformis f. sp. tritici (Pst), has markedly increased in Russia over recent years because of intensifying negative effects of this destructive disease on wheat production. The Pst virulence survey was conducted in 2019–2021 in the European (North‐West, Volga, North Caucasus) and Asian (Siberia) parts of Russia, and the same 109 isolates have been genotyped here with 20 SSR markers. Fifty‐three multilocus genotypes (MLGs) were detected, seven of which occurred in two or more regions. The most frequent MLG was found in three European Pst collections (except Dagestan) and Siberia. SSR‐based variation within the regional collections was low because many MLGs were closely related. Nevertheless, each collection contained relatively different small genotype groups. No clear geographic structure of the Russian Pst population was observed because the five studied regional collections shared groups of similar genotypes. The most singular SSR genotype was identified in the North‐West collection, but genotypes of four invasive isolates belonging to the PstS2 temperature‐adapted aggressive strain did not considerably differ from others. The observed heterozygosity at all SSR loci exceeded the expected one in all regional Pst collections, which could imply asexual reproduction of the pathogen. Both the SSR and virulence analyses demonstrated similar patterns of relationships between the regional Pst collections, although the magnitude of differences between the collections was larger for virulence pathotypes. However, no significant association was established between the virulence pathotypes and SSR genotypes because multiple pathotypes had the same genotype and vice versa.

Modern Approaches to Enhancing Rust Resistance in Wheat Leading to Global Food Security

Rust diseases pose significant threats to wheat production. The deployment of wheat cultivars endowed with rust resistance stands as the most potent strategy for effective rust management. This resistance is primarily inherited through Mendelian principles discovered in 1905, but traditional breeding methods are time-consuming. Modern strategies have emerged to develop rust-resistant wheat varieties efficiently. Marker-Assisted Selection (MAS) accelerates the breeding process through precise screening, bringing about a revolution in the creation of rust-resistant wheat varieties. Genetic engineering techniques allow the transfer of resistance genes from other species into susceptible crops, but GMO use remains controversial and regulated. Gene editing, especially with CRISPR-Cas9, is a game-changer, enabling the introduction of natural variations or inactivation of critical genes in rust pathogens, enhancing plant resistance. RNA interference (RNAi) is another promising strategy, using small RNA molecules to inhibit rust pathogen gene expression, reducing disease severity. Induced Systemic Resistance (ISR) primes plant immune systems by treating them with beneficial microorganisms or compounds, fortifying them against subsequent rust infections. Eco-friendly biofungicides with antagonistic microorganisms suppress rust infections as alternatives to chemical fungicides. The development of climate-resilient wheat varieties is essential, as they indirectly enhance rust resistance, ensuring stable production amid changing climate conditions. These efforts to improve wheat productivity and rust resistance are crucial for feeding the growing global population. Integrating modern methods with traditional breeding is key to effectively combatting rust diseases and enhancing food security.

Integrated management of stripe rust (Puccinia striiformis f. sp. tritici) and its impact on the growth and yield of bread wheat (Triticum aestivum) in Ethiopia

Bread wheat is one of the key food grains in Ethiopia. However, its production and productivity are affected by stripe rust. The objective of this study was to investigate and develop integrated management options for stripe rust using varieties and fungicide application frequency in the study area. A field experiment was conducted at Enarj Enawuga district in the Metaya Kebele farmer training center during the 2022 main cropping season. There were sixteen total treatment combinations [four bread wheat varieties (Ogolcho, Lemu, Hidase, and Local as check), and four Tilt 250 EC fungicide application frequencies (nil, 1, 2, and 3 times)]. The design of the experiment was laid out in a randomized complete block design with factorial arrangements within three replications. Both disease and yield-related data were collected and analyzed using SAS 9.4 software. The disease and yield parameters showed a significant (p < 0.01) difference, and all treated plots had higher yield and lower disease severity than untreated plots. On the untreated plots, the final mean stripe rust severity was 18.53%, 22.57%, 36.73%, and 57.63% on Ogolcho, Lemu, Hidase, and local varieties, respectively. The maximum disease control was recorded from Ogolcho variety (61.31%) with a three-time application of Tilt 250EC. Grain yield and thousand kernel weight increment were obtained at 79.72% and 17.37% from Ogolcho, 100% and 23.44% from Lemu, 94.85% and 34.54% from Hidase, and 102.85% and 49.56% from local varieties treated by three times of Tilt 250EC, respectively. A higher yield reduction and AUDPC (114 DAS) were recorded from untreated plots of local (50.70%, 2,031.49% days−1), and Hidase (48.68%, 1,020.6% days−1) varieties, receptively. The 15-day interval application frequency of Propiconazole increased the grain yield of all tested varieties and reduced stripe rust severity. The Ogolcho variety treated three times yielded the maximum net benefit (216,750 Birr/ha) with an accepted marginal rate of return (22,810%). Therefore, based on the results obtained, producers use the Ogolcho variety with three-time application of propiconazole fungicide for optimum wheat production and could be recommended to manage stripe rust in the study area.

Multiline is a strategy for homeostasis and Asian Soybean Rust Management in Agriculture

Multiline is a strategy for homeostasis and Asian Soybean Rust Management in Agriculture

Assessment of Rapeseed-Mustard Varieties for Resistance against White Rust (Albugo candida) Infection

The increasing prominence of rapeseed-mustard on the global stage as vital oilseed crop is attributed to its high yield, low moisture requirements, cost effective production, and adoptability to diverse farming condition indicating the potential for a forthcoming yellow revolution role in India's oilseed production, facing challenges from various factors affecting yield and seed quality. Notably, white rust stands out as a significant biotic stressor, causing substantial losses in both yield and seedily, 17–34% yield particularly in oil content. To address this, utilizing resistant varieties is the most cost-effective and environmentally friendly approach for disease management. However, the available resistant sources are limited. In a recent study during the Rabi seasons of 2021-22 and 2022-23, thirty rapeseed mustard genotypes were assessed under white rust prevalent conditions. Out of 30 genotypes tested, none were found to be free of white rust disease infection and none were classified as resistant. However,11genotypes were registered as as moderately resistance, while, 19 genotypes fell under the were in the susceptible category. Promisingly, some genotypes exhibited resistance to white rust, offering potential for developing superior cultivars to effectively manage the disease in regions where mustard cultivation is prevalent. Aims: The study aimed to evaluate 30 rapeseed-mustard genotypes during the Rabi sessions of 2021-22 and 2022-23, focusing on their resistance to white rust. The primary objective was to identified genotypes with potential resistant traits, contributing to the development of superior cultivars for effective white rust management in regions where rapeseed-mustard cultivation is prominent. Study Design: Randomized Block Design. Place and Duration of Study: Experimental field of the Department of Plant Pathology, College of Agriculture, BUAT, Banda session 2021-22 and 2022-23. Results and Conclusion: None of the tested genotypes were found to be entirely free from white rust infection, and none of these achieved under resistance. However, the study identified 11 genotypes as moderately resistance and 19 genotypes fell into the susceptible category. Despite the challenges posed by white rust, sum genotypes demonstrated resistance, offering promising potential for the development of advanced cultivars. This finding holds significant for regions where rapeseed-mustard cultivation faces the threat of white rust, providing the basis for future efforts enhancing crop resilience and productivity.

Behavior of rust in new and old inner leaves in Conilon coffee

Coffee rust (Hemileia vastatrix) epidemics are studied in detail in Coffea arabica where a single lesion can cause defoliation, in contrast to the same disease in Coffea canephora, in which the infected leaves remain on the plant. The objective of this study was to compare the progress of coffee rust based on its incidence in young and old inner leaves in different genotypes of Conilon coffee. For this purpose, a field experiment was performed in Vila Valério, state of Espírito Santo. The incidence of rust disease was evaluated during twelve months in plant genotypes 143 (ENCAPA 8131), 02 (ENCAPA 8111), G35 (Verdebrás), and Verdinho HP grown in fields. With data on rust incidence collected during one year, it was possible to determine the disease progress curve and calculate the area under disease progress curve (AUDPC) for each genotype. The data were obtained from the young and old leaves and statistically compared. Rust was more prevalent in old inner coffee leaves. The Gompertz model gave the best adjustment to the disease progress curve. Genotype 143 was the most resistant. Infected leaves on the plants could be an important inoculum source to be considered in the management of rust in Conilon coffee.

The challenge of managing yellow rust (Puccinia striiformis f.sp. tritici) in winter wheat: how combined climate and pathogen stressors impact variability in genotype reactions

Despite the ongoing evolution of wheat pathogens due to the selection pressures of agro-ecological conditions, many studies have often overlooked the combined impact of both biotic and abiotic factors on disease occurrence. From 2016 to 2023, a comprehensive screening of obligate pathogens, including B. graminis f. sp. tritici, P. graminis f. sp. tritici, P. triticina, and P. striiformis f. sp. tritici, was carried out. This screening was conducted on a phenotyping platform encompassing 2715 winter wheat genotypes and their wild relatives, both with and without resistant genes (Lr, Yr, and Sr) for rust diseases. The data were analyzed using PCAmix, best subsets regression, and linear regression modeling. The findings from this study reveal that the plant reactions to leaf and yellow rust infections is far from straightforward. It is heavily influenced not only by prevalent rust races and climatic factors that impact pathogen life cycles but also by variations in the susceptibility reactions of wheat genotypes to the broader agro-ecological conditions. We also observed a tendency for leaf rust and yellow rust to coexist within the same host plant, even though yellow rust is typically considered more aggressive. We reported for the first time genes related to yellow rust resistance breakdown in Serbia in 2023. Lastly, we underscored the importance of investigating resistance responses to rust diseases not exclusively through the interrelation between resistance genes and pathogen virulence, but also by considering how plants respond to the combined stresses of abiotic and biotic factors. Consequently, our study sets the groundwork for further research into how plants respond to multiple stressors and contributes for further investigations related with effective integrated rust management.

Evaluation of newer fungicides for the management of wheat stem rust caused by (Puccinia graminis f. sp. tritici)

Evaluation of newer fungicides for the management of wheat stem rust caused by (Puccinia graminis f. sp. tritici)

Integrated approach for the management of common bean rust (Uromyces appendiculatus) under field conditions

A field experiment was conducted to test the efficacy of different management practices and fungicide application timings for common bean rust management in Chitwan, Nepal. It was conducted in a randomized complete block design (RCBD) with two factors: management practices (Azoxystrobin, Trichoderma viride, maize intercropping + Trichoderma viride, Neem + Garlic extracts, and inoculated and untreated controls) and fungicide application timings (8 days after inoculation and 3 days after inoculation), each with three replications. The minimum disease severity was found with azoxystrobin, which was at par with neem + garlic extract and maize intercropping + Trichoderma at 50 days after inoculation (DAI). The maximum number of rust pustules per cm2 was observed in the control plots (7.56), followed by Trichoderma (4.79) at 50 DAI. The maximum necrotic colonies (%) were observed with the control (36.88%), followed by Trichoderma (25.15%), while the effects of other treatments were at par at 40 DAI. Maize intercropping with Trichoderma resulted in a maximum plant height (201.56 cm), which was at par with azoxystrobin (197.81 cm). The plants treated with azoxystrobin showed maximum green pod yield at one picking (2411.35 g) which was at par with maize intercropping + Trichoderma and neem + garlic extracts. Rust was controlled more effectively when the fungicides were sprayed at 4 DAI than 8 DAI. The maximum disease control was observed with Azoxystrobin; however, as other treatments also had comparable effects, an integrated approach could be adopted for the sustainable management of common bean rust.

State embeddedness and public-private dynamics in central American coffee leaf rust management

This paper examines how differences in state's ‘embedded autonomy’ (i.e., the historical relationship between farmers and the state, public institutions, and state capacity) in El Salvador, Honduras, and Nicaragua shaped the management of the 2012 coffee leaf rust (CLR) epidemic, resulting in differential responses. We conducted 80 interviews with key coffee-sector actors and six focus groups representing 20 farmer organizations and 19 technical assistance providers to understand these divergent responses. We first examined the dynamic, historical, and relational contexts of contradictions, contestation, and negotiation in agri-food networks influencing each response. We then explored how the role of the state and agrarian structures in each country affected farmers' performance and access to different support systems for renovating and rehabilitating coffee plantations in response to the CLR epidemic. In El Salvador and Nicaragua, oligarchic control, weak state relationships with small coffee farmers and fragmented bureaucracies hindered effective CLR crisis response and recovery. Although farmers' organizations, NGOs, and the private sector attempt to fill the gap using market or ‘user pay’ mechanisms for CLR management, they cannot fully compensate for the state's shortcomings. In contrast, Honduras, which is closest to a ‘developmental state’ in the coffee sector, performed better. This is attributed to its more pro-smallholder development path since the 1970s, which bolstered state institutional structures and fostered social ties and dynamism within smallholder organizations in the coffee sector. However, decentralization and clientelist relations limited the country's ability to propose long-term CLR management strategies. We argue that a state's ‘embedded autonomy’ is critical in determining its approach and effectiveness in managing CLR crises and collaborating with and supporting coffee farmers. Finally, we highlight the importance of considering both conjunctural factors (such as meteorological and economic conditions) and the state's historical capacity and embeddedness in analyzing CLR outbreaks and their effects across different countries.

Virulence and genetic analysis of Puccinia graminis tritici in the Indian sub-continent from 2016 to 2022 and evaluation of wheat varieties for stem rust resistance.

Wheat stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), has re-emerged as one of the major concerns for global wheat production since the evolution of Ug99 and other virulent pathotypes of Pgt from East Africa, Europe, Central Asia, and other regions. Host resistance is the most effective, economic, and eco-friendly approach for managing stem rust. Understanding the virulence nature, genetic diversity, origin, distribution, and evolutionary pattern of Pgt pathotypes over time and space is a prerequisite for effectively managing newly emerging Pgt isolates through host resistance. In the present study, we monitored the occurrence of stem rust of wheat in India and neighboring countries from 2016 to 2022, collected 620 single-pustule isolates of Pgt from six states of India and Nepal, analyzed them on Indian stem rust differentials, and determined their virulence phenotypes and molecular genotypes. The Ug99 type of pathotypes did not occur in India. Pathotypes 11 and 40A were most predominant during these years. Virulence phenotyping of these isolates identified 14 Pgt pathotypes, which were genotyped using 37 Puccinia spp.-specific polymorphic microsatellites, followed by additional phylogenetic analyses using DARwin. These analyses identified three major molecular groups, demonstrating fewer lineages, clonality, and long-distance migration of Pgt isolates in India. Fourteen of the 40 recently released Indian wheat varieties exhibited complete resistance to all 23 Pgt pathotypes at the seedling stage. Twelve Sr genes were postulated in 39 varieties based on their seedling response to Pgt pathotypes. The values of slow rusting parameters i.e. coefficient of infection, area under disease progress curve, and infection rates, assessed at adult plant stage at five geographically different locations during two crop seasons, indicated the slow rusting behavior of several varieties. Six Sr genes (Sr2, Sr57, Sr58, Sr24, Sr31, and Sr38) were identified in 24 wheat varieties using molecular markers closely linked to these genes. These findings will guide future breeding programs toward more effective management of wheat stem rust.

Unraveling the diversity and functions of sugar transporters for sustainable management of wheat rust.

Plant diseases threaten global food security by reducing the production and quality of produce. Identification of disease resistance sources and their utilization in crop improvement is of paramount significance. However, constant evolution and occurrence of new, more aggressive and highly virulent pathotypes disintegrates the resistance of cultivars and hence demanding the steady stream of disease resistance cultivars as the most sustainable way of disease management. In this context, molecular tools and technologies facilitate an efficient and rational engineering of crops to develop cultivars having resistance to multiple pathogens and pathotypes. Puccinia spp. is biotrophic fungi that interrupt crucial junctions for causing infection, thus risking nutrient access of wheat plants and their subsequent growth. Sugar is a major carbon source taken from host cells by pathogens. Sugar transporters (STPs) are key players during wheat-rust interactions that regulate the transport, exchange, and allocation of sugar at plant-pathogen interfaces. Intense competition for accessing sugars decides fate of incompatibility or compatibility between host and the pathogen. The mechanism of transport, allocation, and signaling of sugar molecules and role of STPs and their regulatory switches in determining resistance/susceptibility to rusts in wheat is poorly understood. This review discusses the molecular mechanisms involving STPs in distribution of sugar molecules for determination of rust resistance/susceptibility in wheat. We also present perspective on how detailed insights on the STP's role in wheat-rust interaction will be helpful in devising efficient strategies for wheat rust management.