Isolation and Identification Rust Pathogens and the Study of Antioxidant Enzyme Activity and Gene Expression under Rust Infection in Zoysia japonica

The goal of this study was to identify the zoysiagrass rust pathogens and to analyze the differences in rust-resistant and rust-susceptible Zoysia japonica germplasm upon inoculation. Based on the assessment of spore morphology and 18S ribosomal DNA (rDNA) molecular identification, the zoysiagrass rust pathogen was identified as Puccinia zoysiae Diet. The development of mycelium, the rate of spreading, and the timing of spore production were more delayed in the rust-resistant (RR) genotype than the rust-susceptible (RS) genotype. After inoculation, the activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) initially decreased, then increased in both the RR and RS genotypes, but the increased enzyme activities were faster in the RR than in the RS genotype. Rust resistance was positively correlated with antioxidant enzyme activity. The observed changes in CAT, POD and APX activity corresponded to their gene expression levels. The results of this study may be utilized in accurately evaluating the damage of rust disease and rust-resistance in zoysiagrass germplasm aimed at breeding the rust-resistant zoysiagrass varieties and improving disease management of zoysiagrass turf.

Forewarning of stripe rust (Puccinia striiformis) of wheat in central zone of Punjab

Wheat crop is attacked by number of diseases some of which cause yield losses and deteriorates quality. Rust pathogens are most important pathogens of wheat which can cause considerable economic losses if uncontrolled. Stripe rust, caused by Puccinia striiformis f. sp. tritici, is an important wheat disease common in wheat growing areas experiencing cold and humid weather conditions during the crop season. Different meteorological parameters influence occurrence and development of stripe rust in northern India including Punjab. Based on investigations on relationship of stripe rust with weather parameters, weather based prediction model for stripe rust was developed using disease severity and weather data (2007-08 to 2018-19) recorded at Ludhiana. The data of 2009-10 and 2019-20 was used for validation of model. Regression model based on maximum and minimum temperature, morning relative humidity and sunshine hours gave good results. Validation of model indicated that relationship between observed values of disease and predicted values was very close.

Genome-wide survey of the F-box/Kelch (FBK) members and molecular identification of a novel FBK gene TaAFR in wheat

F-box proteins play critical roles in plant responses to biotic/abiotic stresses. In the present study, a total of 68 wheat F-box/Kelch (TaFBK) genes, unevenly distributed across 21 chromosomes and encoding 74 proteins, were identified in EnsemblPlants. Protein sequences were compared with those of Arabidopsis and three cereal species by phylogenetic and domain analyses, where the wheat sequences were resolved into 6 clades. In silico analysis of a digital PCR dataset revealed that TaFBKs were expressed at multiple developmental stages and tissues, and in response to drought and/or heat stresses. The TaFBK19 gene, a homolog of the Attenuated Far-Red Response (AFR) genes in other plant species, and hence named TaAFR, was selected for further analysis. Reverse-transcription quantitative real-time PCR (RT-qPCR) was carried out to determine tissue-specific, hormone and stress (abiotic/biotic) responsive expression patterns. Of interest, TaAFR was expressed most abundantly in the leaves, and its expression in response to leaf rust variants suggests a potential role in compatible vs incompatible rust responses. The protein was predicted to localize in cytosol, but it was shown experimentally to localize in both the cytosol and the nucleus of tobacco. A series of protein interaction studies, starting with a yeast-2-hybrid (Y2H) library screen (wheat leaf infected with incompatible leaf rust pathogens), led to the identification of three TaAFR interacting proteins. Skp1/ASK1-like protein (Skp1) was found to interact with the F-box domain of TaAFR, while ADP-ribosylation factor 2-like isoform X1 (ARL2) and phenylalanine ammonia-lyase (PAL) were shown to interact with its Kelch domain. The data presented herein provides a solid foundation from which the function and metabolic network of TaAFR and other wheat FBKs can be further explored.

AN OVERVIEW OF COMPARISON BETWEEN WHEAT RUSTS MYCOFLORA IN INDIA WITH GLOBAL SCENARIO

Wheat rusts are the oldest plant disease known to human and caused by Puccinia species. Puccinia species are the main constraints in wheat production wherever wheat is grown. Early literatures mention these devastating diseases and their ability to destroy entire wheat crops. These wheat rust pathogens are highly transmissible through air current in both cases, primary and secondary infections. Primary infection occur through alternate host developing spore (Aeciospores) and secondary infection caused by wheat (primary host) developing spore (Uredospores). Secondary infection results epidemics, several time as globally occurrence. Ecologically, the persistence of rusts as a significant disease in wheat can be attributed to specific characteristics of the rust mycoflora. Their ability to spread aerially over the large distance, production of urediospores in enormous number and evolving new pathotypes, makes the management of wheat rusts a very daunting task. These characteristics include a capacity to produce a large number of spores which can be wind disseminated over long distances and infect wheat under favorable environmental conditions and the ability to change genetically, thereby producing new races with increased aggressiveness on resistant wheat cultivars. KEY WORDS: Wheat Rust, Puccinia, Rust Mycoflora, Stem Rust, Leaf Rust, Stripe Rust

Characterizing the genetic architecture of nonhost resistance in barley using pathogenically diverse Puccinia isolates

Barley is an intermediate or near-nonhost to many cereal rust pathogens that infect grasses, making it a highly suitable model to understand the evolution and genetic basis of nonhost resistance (NHR) in plants. To characterise the genetic architecture of NHR in barley, we used the Oregon Wolfe Barley doubled haploid (DH) and Morex x SusPtrit RIL mapping populations. To elicit a wide array of NHR responses, we tested 492 barley accessions and both mapping populations with pathogenically diverse cereal rust isolates representing distinct formae speciales adapted to Avena, Hordeum, Triticum and Lolium spp.: P. coronata f. sp. avenae (Pca; oat crown rust pathogen) and f. sp. lolii (Pcl; ryegrass crown rust pathogen); P. graminis f. sp. avenae (Pga; oat stem rust pathogen) and f. sp. lolii (Pgl; the ryegrass stem rust pathogen); and P. striiformis f. sp. tritici (Pst; wheat stripe rust pathogen) and f. sp. pseudo-hordei (Psph; barley grass stripe rust pathogen). With the exception of Pcl and Pca, susceptibility and segregation for NHR was observed in the barley accessions and both mapping populations. QTLs for NHR were mapped on all seven chromosomes. NHR in barley to the heterologous rusts tested was due to a combination of QTLs with either or both overlapping and distinct specificities. Across both mapping populations, broadly effective NHR loci were also identified that likely play a role in host specialisation.

TERMS OF WINTER WHEAT TREATMENT BY FUNGICIDES TO CONTROL DEVELOPMENT OF BROWN RUST PATHOGEN

The terms of winter wheat treatment against brown rust pathogens (PucciniareconditeRob. exDesmf. sp. tritici) can greatly differ depending on climatic conditions and applied materials. The question is not studied enough for the Tambov region. In the production brown rust control fungicides are often used at the early periods of plant development (tillering, stem-extension stage). It makes the second treatment necessary as the preparation effect finishes at the maximum manifestation of disease (plant development phase-milky ripeness of kernels). In the Tambov region, the first pustules of brown rust appear on winter wheat plants in the beginning of the earing phase. This period occurs at the end of May/beginning of June. It is logical to assume that the maximum suppression of the disease on wheat will be achieved by spraying precisely at these times. To test this assumption, the field trials were conducted using the preparations ‘Reks duo’ and ‘Abakus’. They were used in the stem-extension stage and earing phase of winter wheat. Biological efficiency of fungicide spraying in earing phase of wheat was significantly larger (98.2–98.8%). Application of fungicides spraying in stem-extension stage was 85.6-86.5%. The amount of the saved yield was 0.60–0.81 t/ha (14.2–19.1%). Maximum values of winter wheat productivity (5.05 t/ha) was obtained when the preparation ‘Abakus’ was applied in earing phase. Wheat treatment by the preparations ‘Reks duo’ and ‘Abakus’ in earing phase was found more economically profitable, and the level of profitability was 130.9 and 55.0%, in stem-extension stage it was 109.2 and 35.4% respectively. The results of the trials showed that fungicides spraying in earing phase is the most optimal.