Dynamics of bacterial blight disease in resistant and susceptible rice varieties

Bacterial blight (X. oryzae pv. oryzae) is a serious disease in rice across the world. To better control the disease, it is important to understand its epidemiology and how key aspects of this (e.g. infection efficiency, and spatial spread) change according to environment (e.g. local site conditions and season), management, and in particular, variety resistance. To explore this, we analysed data on the disease progress on resistant and susceptible varieties of rice grown at four sites in the Philippines across five seasons using a combination of mechanistic modelling and statistical analysis. Disease incidence was generally lower in the resistant variety. However, we found no evidence that the primary infection efficiency was lower in resistant varieties, suggesting that differences were largely due to reduced secondary spread. Despite secondary spread being attributed to splash dispersal which is exacerbated by wind and rain, the wetter sites of Pila and Victoria in south Luzon tended to have lower infection rates than the drier sites in central Luzon. Likewise, we found spread in the dry season can be substantial and should therefore not be ignored. In fact, we found site to be a greater determinant of the number of infection attempts suggesting that other environmental and management factors had greater effect on the disease than climate. Primary infection was characterised by spatially-random observations of disease incidence. As the season progressed, we observed an emerging short-range (1.6 m–4 m) spatial structure suggesting secondary spread was predominantly short-range, particularly where the resistant variety was grown.

Study on the Role of Phytohormones in Resistance to Watermelon Fusarium Wilt

Fusarium wilt disease is one of the major diseases causing a decline in watermelon yield and quality. Researches have informed that phytohormones play essential roles in regulating plants growth, development, and stress defendants. However, the molecular mechanism of salicylic acid (SA), jasmonic acid (JA), and abscisic acid (ABA) in resistance to watermelon Fusarium wilt remains unknown. In this experiment, we established the SA, JA, and ABA determination system in watermelon roots, and analyzed their roles in against watermelon Fusarium wilt compared to the resistant and susceptible varieties using transcriptome sequencing and RT-qPCR. Our results revealed that the up-regulated expression of Cla97C09G174770, Cla97C05G089520, Cla97C05G081210, Cla97C04G071000, and Cla97C10G198890 genes in resistant variety were key factors against (Fusarium oxysporum f. sp. Niveum) FON infection at 7 dpi. Additionally, there might be crosstalk between SA, JA, and ABA, caused by those differentially expressed (non-pathogen-related) NPRs, (Jasmonate-resistant) JAR, and (Pyrabactin resistance 1-like) PYLs genes, to trigger the plant immune system against FON infection. Overall, our results provide a theoretical basis for watermelon resistance breeding, in which phytohormones participate.

Effect of weather parameters, host resistance and sowing date on disease severity and temporal dynamics of Fusarium wilt in chickpea (Cicer arietinum L.)

Fusarium wilt incited by Fusarium oxysporum f. sp. ciceris is an economically damaging disease of chickpea (Cicer arietinum L.). Field experiments on epidemiological studies revealed that sowing during second fortnight of November curtailed the disease severity index (22.50 and 20.83% during 2018-19 and 2019-20, respectively) whereas, sowing during first fortnight of October enhanced the disease severity index (34.86 and 30.41%). The area under disease progress curve was significantly higher in susceptible variety JG 62 and was the least in resistant variety HC 1. The correlation analysis exhibited positive correlation of disease severity index with maximum and minimum temperature while negative correlation with relative humidity morning and evening, irrespective of date of sowing. The principal component analysis depicted resistance index, sowing time and weather parameters as positional factors in determining Fusarium wilt progression. In susceptible variety, Gompertz model was the best fitted model for simulating the Fusarium wilt epidemic over time.

tRNA-derived fragments from wheat are potentially involved in susceptibility to Fusarium head blight

Background Fusarium head blight (FHB) caused by Fusarium graminearum is a devastating fungal disease of wheat. The mechanism underlying F. graminearum-wheat interaction remains largely unknown. tRNA-derived fragments (tRFs) are RNase-dependent small RNAs derived from tRNAs, and they have not been reported in wheat yet, and whether tRFs are involved in wheat-F. graminearum interactions remains unknown. Results Herein, small RNAs from the spikelets inoculated with F. graminearum and mock from an FHB-susceptible variety Chinese Spring (CS) and an FHB-resistant variety Sumai3 (SM) were sequenced respectively. A total of 1249 putative tRFs were identified, in which 15 tRFs was CS-specific and 12 SM-specific. Compared with mock inoculation, 39 tRFs were significantly up-regulated across both wheat varieties after F. graminearum challenge and only nine tRFs were significantly down-regulated. tRFGlu, tRFLys and tRFThr were dramatically induced by F. graminearum infection, with significantly higher fold changes in CS than those in SM. The expression patterns of the three highly induced tRFs were further validated by stem-loop qRT-PCR. The accumulation of tRFs were closely related to ribonucleases T2 family members, which were induced by F. graminearum challenge. The tRFs’ targets in host were predicted and were validated by RNA sequencing. Conclusion Integrative analysis of the differentially expressed tRFs and their candidate targets indicated that tRFGlu, tRFLys and tRFThr might negatively regulate wheat resistance to FHB. Our results unvealed the potential roles of tRFs in wheat-F. graminearum interactions.

Comparative Proteomics Reveals Differential Mechanism of Root Cold-resistance between Vitis. Riparia × V. Labrusca and Cabernet Sauvignon

Grapevines, containing large amounts of bioactive metabolites that offer health benefits, are widely cultivated around the world. The cold damage of growing outside with extreme low temperature during overwintering stage limits the expansion of production. Although the levels of morphological, biochemical and molecular in different Vitis species exposure to different temperatures have been investigated, differential expression of proteins in roots is still limited. Here, the roots of cold-resistant (Vitis. riparia × V. labrusca, T1) and cold-sensitive varieties (Cabernet Sauvignon, T3) at −4°C as well as of the former at −15°C (T2) were measured by iTRAQ-based proteomic analysis, expression levels of genes encoding candidate proteins were validated by qRT-PCR. The results showed that the root activity of cold-resistant variety was stronger than that of cold-sensitive variety, and it declined with the decrease of temperature. A total of 25 proteins were differentially co-expressed at T2 versus (vs) T1 and T1 vs T3, and these proteins were involved in stress response (e.g. DHN1, SHSPCP and USPCP), bio-signaling (e.g. PKCP, S/TPP and nsS/TP), metabolism (e.g. GluP, GluBE and PE), energy (e.g. AAC, AAACP and NADCP), and translation (e.g. rpL14, rpS21 and PPI). The relative expression levels of the candidate 13 genes were consistent with their fold-change values of proteins. The signature translation pattern for the roots at spatio-temporal treatments of varieties and temperatures provides insight into the differential mechanism of cold resistance of grapevines.

Plant Growth-promoting and Bio-control Activity of Micrococcus luteus Strain AKAD 3-5 Isolated from the Soybean (Glycine max (L.) Merr.) Rhizosphere

Background: Applications of bioinoculants for improving crop productivity may be an eco-friendly alternative to chemical fertilizers. Rhizosphere or soil-inhabiting beneficial microbes can enhance plant growth and productivity through direct and indirect mechanisms, i.e., phosphate solubilization, nutrient acquisition, phytohormone production, etc. Objective: This study is based on the hypothesis that diseases resistant plants can act as a source of potential microbes that can have good plant growth-promoting traits and bio-control potential. Methods: In this study, we have isolated the rhizobacterial strains (AKAD 2-1, AKAD 2-10, AKAD 3-5, AKAD 3-9) from the rhizosphere of a disease-resistant variety of soybean (JS-20-34) (Glycine max (L.) Merr.). These bacterial strains were further screened for various plant growth-promoting traits (phosphate solubilization, indole acetic acid (IAA), ammonia, biofilm, HCN, Exopolysaccharide (EPS), and enzyme production activity (catalase, cellulase, and chitinase)). Results: Among four, only bacterial strain AKAD 3-5 has shown plant-growth-promoting and biocontrol (98%) activity against Fusarium oxysporum. Morphological, biochemical, and molecular characterization (16S rRNA) revealed that this rhizobacterial isolate AKAD 3-5 closely resembles Micrococcus luteus (Gene bank accession: MH304279). Conclusion: Here, we conclude that this strain can be utilized to promote soybean growth under varied soil stress conditions.

Bacterial Coated Fertilizer Induced Resistance Against Wheat Stripe Rust

Wheat is the second largest consumed cereal by humans after Rice and its high yield and production is very critical for ever increasing global population. The wheat crop is grown all over Pakistan and threatened by several limiting factors. Stripe rust, caused by Puccinia striiformis, is the most destructive wheat pathogen and can reduce yield up to 70% in Pakistan. The present study aimed at exploring the role of Zabardast urea, a bacterial coated urea with zinc, in inducing resistance against wheat stripe rust. The study involved the collection and maintenance of stripe rust inoculum on Morroco cultivar which later used to inoculate seedlings of Akbar-2019 and Galaxy-2019 resistant and susceptible varieties with three different fertilizer levels viz. specialty fertilizer zabardast urea, plain urea with zinc and plain urea. The results demonstrated the positive role of bacterial coated urea with zinc and reduced the disease severity by 10% and 5% in susceptible and resistant cultivars, respectively, leaving resistant variety asymptomatic. The plain urea with zinc also decreased disease severity in susceptible variety Galaxy-2013 by 6% in comparison with plain urea treatment underlying the role of zinc in combating stripe rust. The study underlines the importance of specialty fertilizers in inducing resistance against stripe rust in wheat and needs further experimentation exploring the mechanisms involved in disease resistance under field conditions.

Reaction of spring soft wheat to drought in the forest-steppe of the Trans-Urals

The purpose of the research is the reaction of spring soft wheat varieties to dry phenomena during the growing season in the forest-steppe zone of the Trans-Urals. Methods. The material was 24 varieties of various biotypes for maturation from the nursery of the competitive variety testing of the Kurgan Research Institute of Agricultural Sciences. Results. The negative effect of the drought reduced the yield in the experiments by 11.9 c/ha, the weight of 1000 grains by 5.7 g, and the nature by 19.7 g/l. The influence of grain size on the yield both in favorable years and in years of drought was noted (r = 0.63…0.98). In arid conditions, vitreous is correlated with yield, 1000 grain weight, in kind, to a lesser extent with gluten content, bread volume, and “flour strength”. The lack of moisture during the grain filling period increased the gluten content by 3.4 %, the quality by 15.1 e. p. IDC, the flour strength by 102.7 e. a., the volume of bread by 106 g/l. In favorable years, the weight of 1000 grains and the vitreous content of the grain correlate with gluten (r = 0.44; r = 0.24–0.84). Indicators of productivity and physical properties of grain increase when sowing at the optimal time, with a certain decrease in the gluten content (by 1.2 %), flour strength (by 5.3 e. a.), bread volume (by 73.2 e. p.). In the early sowing period, moisture deficiency reduces the indicators for all varieties Under these conditions, early-maturing varieties form a larger grain both when sowing at an early time (29.0 g) and when sowing at the optimal (31.3 g). In a drought, the role of the variety is especially high. High drought resistance was shown by the Zauralochka variety of the Kurgan Research Institute of Agriculture, which successfully passed the test in the dry years (2012, 2020) in the GSI system and in the environmental test (KASIB). The yield of the drought-resistant variety Zauralochka on average for the HSU was 20.2 c/ha, exceeding the standard Hercules by 2.2 c/ha. Scientific novelty. The features of the influence of dry phenomena on the yield and the main indicators of the quality of varieties are revealed, the correlation between them is determined. According to drought resistance, a variety of spring soft wheat Zauralochka was selected.

Efficient Transformation of Catalpa bungei Shows Crystal Genes Conferring Resistance to the Shoot Borer Omphisa plagialis

Although Catalpa bungei is a forest plant with considerable economic and ornamental value in China, its wood and decorative qualities are constrained by insect pests such as the shoot borer Omphisa plagialis (Lepidoptera). Overexpressing insect resistance genes such as crystal genes to develop an insect-resistant variety of C. bungei is an environmental and ecological approach. However, genotype limitations and low regeneration rates of embryogenic calli (EC) inhibit the development of transformation and the insect-resistant gene expression system in C. bungei. Here, we first established embryogenic callus induction and regeneration systems of five genotypes using mature seed and stem segment explants; the highest induction and regeneration rates of EC were 39.89 and 100%, respectively. Next, an efficient and stable Agrobacterium-mediated genetic transformation system was developed from EC and its positive frequency was up to 92.31%. Finally, using the transformation system, 15 and 22 transgenic C. bungei lines that expressed Cry2A and Cry9Aa-like were generated, respectively. These transgenic lines that exhibited significantly higher resistance to O. plagialis in the laboratory and field have great promise for meeting the challenge of future pest management under changing climatic conditions. Additionally, this efficient, fast, and stable transformation system could be a potential tool for gene function analysis and forest tree genetic improvement.

Comparative Transcriptome Analysis of Rice Cultivars Resistant and Susceptible to Rhizoctonia Solani AG1-IA

Background: Rice sheath blight, which is caused by Rhizoctonia solani, is the most destructive disease affecting rice production, but the resistance mechanism to this pathogen has not been fully elucidated. Results: In this study, we selected two rice cultivars based on their resistance to the pathogen and analyzed and compared the transcriptomic profiles of two cultivars, the moderately resistant variety Gangyuan8 and the highly susceptible variety Yanfeng47, at different time points after inoculation. The comparative transcriptome profiling showed that the expression of related genes gradually increased after pathogen inoculation. The number of differentially expressed genes (DEGs) in Yanfeng47 was higher than that in Gangyuan8, and this result revealed that Yanfeng47 was more susceptible to fungal attack. At the early stage (24 and 48 h), the accumulation of resistance genes and a resistance metabolism occurred earlier in Ganguan8 than in Yanfeng47, and the resistance enrichment entries were more abundant in Ganguan8 than in Yanfeng47. Conclusions: Based on the GO and KEGG enrichment analyses at five infection stages, we concluded that phenylalanine metabolism and the jasmonic acid pathway play a crucial role in the resistance of rice to sheath blight. Through a comparative transcriptome analysis, we preliminarily analyzed the molecular mechanism responsible for resistance to sheath blight in rice, and the results lay the foundation for the development of gene mining and functional research on rice resistance to sheath blight.