Rust-infected Plants Research Articles

Effects of Rust on Plant Growth and Stoichiometry of Leymuschinensis under Different Grazing Intensities in Hulunber Grassland

Grazing is the main utilization of native grassland, and forage fungal disease is one of the limiting factors of grassland productivity. The present research in the Hulunber meadow steppe grassland was conducted to investigate the responses of the dominant plant Leymus chinensis (Trin.) to beef cattle grazing, rust, and their interaction influence. Six grazing intensity treatments with three replicates were established. The response of L. chinensis to grazing and rust was systematically studied for two consecutive years. The main findings were that grazing and rust had significant effects (p < 0.05) on the growth and nutrient elements content of L. chinensis. Compared with the 0 cattle ha−1 treatment, the dry matter of L. chinensis in the 0.42, 0.63, and 1.67 cattle ha−1 treatments decreased by 42.2%, 90.5%, and 339.5%, respectively. Compared with non-infected plants, dry matter of rust-infected L. chinensis plants decreased by 45.6%. The N:C and P:C ratios of rust-infected plants were lower than in non-infected plants, and positively correlated with their relative growth rates. Therefore, we concluded that the growth rate hypothesis still applied in L. chinensis under the interactive effects of grazing and disease. Additionally, grazing can alleviate the loss of dry matter caused by disease.

Wheat yellow rust monitoring by learning from multispectral UAV aerial imagery

The use of a low-cost five-band multispectral camera (RedEdge, MicaSense, USA) and a low-altitude airborne platform is investigated for the detection of plant stress caused by yellow rust disease in winter wheat for sustainable agriculture. The research is mainly focused on: (i) determining whether or not healthy and yellow rust infected wheat plants can be discriminated; (ii) selecting spectral band and Spectral Vegetation Index (SVI) with a strong discriminating capability; (iii) developing a low-cost yellow rust monitoring system for use at farmland scales. An experiment was carefully designed by infecting winter wheat with different levels of yellow rust inoculum, where aerial multispectral images under different developmental stages of yellow rust were captured by an Unmanned Aerial Vehicle at an altitude of 16–24 m with a ground resolution of 1–1.5 cm/pixel. An automated yellow rust detection system is developed by learning (via random forest classifier) from labelled UAV aerial multispectral imagery. Experimental results indicate that: (i) good classification performance (with an average Precision, Recall and Accuracy of 89.2%, 89.4% and 89.3%) was achieved by the developed yellow rust monitoring at a diseased stage (45 days after inoculation); (ii) the top three SVIs for separating healthy and yellow rust infected wheat plants are RVI, NDVI and OSAVI; while the top two spectral bands are NIR and Red. The learnt system was also applied to the whole farmland of interest with a promising monitoring result. It is anticipated that this study by seamlessly integrating low-cost multispectral camera, low-altitude UAV platform and machine learning techniques paves the way for yellow rust monitoring at farmland scales.

Effect of silicon on the severity of brown rust of sugarcane in South Africa

Silicon (Si) has been identified as a key element in the management of a wide range of pests and diseases in plants. This study focused on the effect of Si on the severity of brown rust of sugarcane caused by Puccinia melanocephala H & P. Sydow. The trial, repeated twice, consisted of eight treatments which included two different forms of Si and a control to which no Si was added. Plants were naturally infected by spores from brown rust-infected plants within a polytunnel. From three weeks after planting, plants were rated weekly for disease severity and these data were used to calculate an area under disease progress curve (AUDPC). All treatments ≥400 mg Si l−1 had a significantly lower final disease severity rating and AUDPC than the untreated control. No significant difference in disease severity was noted between the 1600 and 2000 mg Si l−1 treatments. A once off application of calcium silicate at a concentration of 1016 mg Si l−1, applied at planting provided the same reduction in disease severity as K2SiO3 applied weekly at a Si concentration of 1200 mg Si l−1. There was a significant negative relationship between the concentration of Si added and disease severity. A similar relationship was noted for the disease severity index and Si accumulation and deposition in the leaf. Results from this study showed a reduction in brown rust severity with an increase in Si content in the plant.

Prevention of leaf yellowing in Asian soybean rust infected plants is associated with green cotyledon color and the infection index

Because the six major known resistance genes to Asian soybean rust (ASR) are pathotype-specific, they rarely offer durable resistance to all ASR pathogens. Thus, other types of resistance such as field resistance or tolerance that confer broad-spectrum resistance to ASR pathogens are required for soybean breeding. The Chinese soybean variety Lu Pi Dou has a green cotyledon color (CC) and a no leaf yellowing (LY) phenotype was previously identified during ASR infection of this strain. This phenotype may reduce yield losses of soybean cultivars infected with ASR infections if it is independent of pathotype-specific major resistance genes and undesirable phenotypes. Thus, to identify associations of LY and CC and other color traits and loci that are linked to the six known ASR resistance genes, recombinant inbred lines (RILs) and backcross (BC) BC2F5 lines were derived from Lu Pi Dou and BRS184 plant strains. Comparisons of LY, CC, and genotypes of simple sequence repeat (SSR) markers revealed that the absence of LY is tightly associated with green CC in accordance with the expression of the genes d1 and d2. However, although variations of LY in RILs with yellow CC predominantly reflected the infection index (IFI), no associations were observed between LY and pubescence color, pod color, seed coat color, or flanking SSR markers for six known ASR resistance loci. An association of LY with CC and IFI was also shown in data from BC populations. Therefore, prevention of LY during ASR infection of Lu Pi Dou was primarily dependent on the double-recessive genotype d1d1d2d2 for CC and secondarily on low IFI.

Tracking down worldwide Puccinia psidiidispersal

Puccinia psidii causes rust disease on many host species in the Myrtaceae [1]. First reported in 1884 on guava in Southern Brazil [2], the rust has since been detected on several myrtaceous in South America, Central America, Caribbean, Mexico, USA: in Florida, California, and Hawaii. More recently, P. psidii was reported in Japan infecting M. polymorpha[3]. Of special note is that a rust was found infecting Myrtaceae species in Australia, where the fungus was reported as Uredo rangelii, based on the tonsure found on the urediniospores surface. However, DNA sequence data did not differentiate that rust from P. psidii[4], and the same tonsure patch, was also observed on rust urediniospores collected from several host species in Brazil [unpublished data].We have hypothesed that P. psidii was introduced into Hawaii through California by trade of rust infected myrtaceous plants, and that P. psidii populations from South America are distinct from the rust populations that became estabilished in California and Hawaii.

The Cytokinin-Activated Transcription Factor ARR2 Promotes Plant Immunity via TGA3/NPR1-Dependent Salicylic Acid Signaling in Arabidopsis

Cytokinins affect plant immunity to various pathogens; however, the mechanisms coupling plant-derived cytokinins to pathogen responses have been elusive. Here, we found that plant-derived cytokinins promote resistance of Arabidopsis to Pseudomonas syringae pv. tomato DC3000 (Pst). Modulated cytokinin levels or signaling activity in CKX- or IPT-overexpressing plants or in ahk2 ahk3 mutants correlated with altered resistance. In fact, the cytokinin-activated transcription factor ARR2 contributes specifically to Pst resistance. The salicylic acid (SA) response factor TGA3 binds ARR2, and mutation of TGA-binding cis-elements in the Pr1 promoter abolished cytokinin- and ARR2-dependent Pr1 activation. Cytokinin treatment did not increase pathogen resistance in tga3 plants, as the cytokinin-dependent induction of Pr1 was eliminated. Moreover, SA signaling enhanced binding of ARR2/TGA3 to the Pr1 promoter. Taken together, these results show that cytokinins modulate the SA signaling to augment resistance against Pst, a process in which the interaction between TGA3 and ARR2 is important.

Control of Bean Rust using Antibiotics Produced by Bacillus and Streptomyces species - Translocation and Persistence in Snap Beans

Antibiotic culture filtrates produced by Bacillus (CA5) and Streptomyces spp. were tested for translocation and persistence when applied on snap beans inoculated with rust (Uromyces appendiculatus) in greenhouse pot experiments. The antibiotics were applied on the first trifoliate leaves and translocation was assessed as the number of rust pustules on non-treated leaflets or trifoliates while persistence was assessed as the number of rust pustules on rust infected plants at different times after antibiotic treatment. The treatments were replicated three times, each replicate consisting of a pot containing three plants. Antibiotics from both Bacillus and Streptomyceswere found to have up to 100% trans-lamina and leaflet-to-leaflet translocation but no significant trifoliate-totrifoliatetranslocation. The antibiotic culture filtrates also retained significant rust control for up to 10 days after application on the bean plant. However, no significant rust control was found on the plants after 16 days of treatment. The study indicated that the antibiotics produced by antagonistic Bacillus and Streptomyces species possess systemicactivity that can persist within the plant for over one week. These metabolites are potential bean rust control products that could be incorporated in integrated disease management programs

Teliospore-inducing activity for wheat leaf rust in the extracts of various host plant leaves infected with telia of rust fungi

MeOH and water extracts were obtained from 16 species of infected leaves with rust fungi belonging to 18 species in 6 families: Pucciniaceae, Melampsoraceae, Coleosporiaceae, Pileolariaceae, Phragmidiaceae, and Phakopsoraceae. All the extracts of rust-infected plants with telia showed the teliospore-inducing activity for wheat leaf rust (Puccinia recondita f. sp. tritici).

Distinguishing nitrogen deficiency and fungal infection of winter wheat by laser-induced fluorescence

One of the most important tasks in precision farming is the site-specific application of fertilisers and pesticides in heterogeneous large-area fields. For such site-specific crop management, effective remote sensing methods for the detection of crop diseases and nutrient deficiencies are required. The aim of the present work was to compare laser-induced fluorescence (LIF) parameters from nitrogen-deficient and pathogen (rust and mildew)-infected winter wheat (Triticum aestivum L.) plants and to assess the potential of LIF to detect and discriminate between these types of stress. Both long term nitrogen deficiency and pathogen infection resulted in an increase of the ratio of fluorescence at 686 and 740 nm (F686/F740) accompanied by a reduction of leaf chlorophyll content to approximately 35 μg cm−2. A linear negative correlation between chlorophyll content and F686/F740 ratio (r2 = 0.78) was found for leaves with chlorophyll content ranging between 17 and 52 μg cm−2. Since chlorophyll breakdown appeared an unspecific symptom to both nitrogen deficiency and pathogen infection, it was not possible to discriminate between these types of stress only by means of the F686/F740 ratio. Specific for the pathogen-infected leaves was a large heterogeneity in the records of their spectral parameters caused by inhomogeneous, discrete lesions of fungi infection. Nitrogen-deficient plants with homogeneous reduction in chlorophyll content showed, in contrast, more uniform readings of the spectral parameters. Thus, mildew- and rust-infected plants, grown under sufficient nitrogen fertilisation could be distinguished from those grown under reduced nitrogen supply by the higher variance of their spectral readings. The simultaneous scanning multipoint mode measurements of LIF and laser light reflection characteristics with parallel estimation of their heterogeneity is proposed for the discrimination between nitrogen deficiency and pathogen infection under field conditions.

The effect of surfactants and some herbicides on teliospore viability in Puccinia thlaspeos (Schub.)

Puccinia thlaspeos is being studied as a potential biocontrol agent for Isatis tinctoria. The goal of the work reported here was to gather information pertinent to the integrated use of herbicides and P. thlaspeos. The effect of three herbicides currently used to control I. tinctoria on viability of teliospores from inoculum was studied along with common surfactants. Neither chlorsulfuron nor metsulfuron-methyl had a significant impact on teliospore germination when used alone but the 2,4-D formulation used in these studies decreased teliospore viability. The surfactants Sylgard and IFA-S90 reduced spore germination while Regulaid had little effect. However, when rust-infected plants were sprayed with different combinations of herbicides and surfactants, the viability of teliospores produced on those plants was not decreased.

Fungi Associated with the Stalk Rot Complex of Pearl Millet.

Stalk rot is frequently observed in maturing, rust-infected pearl millet (Pennisetum glaucum). Fungi were isolated from internal stalk tissue, and their association with node discoloration and rust infection at different stages of plant maturity was determined to gain a greater understanding of stalk rot etiology. In 1995, stalk rot was observed in a breeding population of pearl millet. Stalks of 10 rust-infected plants were collected on each of three dates during grain fill. Frequency of symptomatic, discolored nodes was higher in the later sampling dates. Stalk sections from 119 discolored nodes were surface sterilized and plated onto agar media. Fungi most frequently isolated from symptomatic nodes were Bipolaris setariae (isolated from 47% of discolored nodes), Fusarium semitectum (28.6%), and F. moniliforme sensu lato (23.5%). Isolation frequency of these fungi differed (P < 0.05) with sampling date. In 1996 and 1997, the hybrid HGM 100 was evaluated at two dates of planting in each year. Ten stalks were sampled at each of four growth stages: panicle emergence, stigma emergence, milk, and hard dough. A total of 140 stalks was assessed for rust severity and for internal stalk discoloration at the nodes. The frequency of discolored nodes increased with plant maturation and was correlated (P < 0.01) with severity of rust infection. All nodes were plated on an agar medium, and a total of 1,512 isolates from 30 fungal genera or species were isolated from the 1,540 nodes of the sampled stalks. F. moniliforme was isolated most frequently (isolated from 23.5% of all nodes). Frequency of isolation of F. moniliforme from nodes within stalks increased with advancing maturity in the earlier dates of planting, but was not correlated with rust infection. B. setariae (isolated from 9.2% of all nodes) was more frequently isolated from plants at the dough stage in three plantings, and was correlated (P < 0.01) with rust severity. Trends in the frequency of isolation of other fungi were inconsistent between planting dates or among growth stages. Frequency of isolation of F. semitectum (isolated from 11.0% of all nodes) and Alternaria spp. (6.9% of all nodes) was correlated (P < 0.05) with rust severity. Frequency of isolation of Curvularia spp. (isolated from 7.0% of all nodes) was negatively correlated (P < 0.05) with rust severity. Isolation of Alternaria spp. and B. setariae was more frequently associated with node discoloration than was isolation of the other fungi. Stalk rot of pearl millet is the result of a complex of several fungi whose incidence was influenced by rust infection, plant maturation, and environmental factors associated with differences among years and dates of planting.

Glyphosate Absorption and Translocation in Rust-Infected Quackgrass (Elytrigia repens)

Puccinia coronatainfection increased absorption of14C-glyphosate in quackgrass 3 days after inoculation (DAI) when compared to 0,6,9, or 12 DAI. Days after inoculation had no effect on glyphosate translocation out of treated leaves until 9 to 12 DAI when 89% of the absorbed14C-glyphosate was retained within the infected leaf. In contrast, only 43% was retained in leaves treated at 0 DAI. In other studies,14C-glyphosate absorption increased linearly from 21 to 35% 12 to 96h after treatment (HAT). Differences between control and rust-infected plants were not significant. Sixty-three percent of absorbed14C-glyphosate translocated out of control leaves by 96 HAT, while only 10% translocated out of rust-infected leaves. Additionally, 28 and 4% of the14C absorbed was recovered from the rhizomes of control and rust-infected plants, respectively.

Analysis of the spatial distribution of rust-infected leek plants with the Black-White join-count statistic

Leek rust, caused byPuccinia allii Rudolphi, is an important disease of leek (Allium porrum L.) in the Netherlands. For the development of a practical sampling method for early detection of leek rust in commercial fields, information on the spatial distribution of the disease is necessary. In this study, the spatial distribution of diseased plants during three naturally occurring epidemics of leek rust was observed. The observations were analysed with the Black-White join-count statistic. The spatial distribution of rust-infected leek plants was different for each of the three epidemics, ranging from random to highly clustered. These results show, that in the development of a practical sampling method for detection of leek rust, it is necessary to take into consideration a possibly clustered distribution of diseased plants.

Photosynthesis in stem rust-infected, resistant and susceptible near-isogenic wheat leaves

Secondary leaves of three near-isogenic lines of the wheat (Triticum aestivum) cultivar Prelude, differing in their degree of resistance to the wheat stem rust fungus (Puccinia graminis f.sp. tritici) race 32, were inoculated with uredospores of the fungus 12 days after germination. Photosynthetic O2 evolution, chlorophyll content, 3-phosphoglycerate content, and the gel electrophoretic pattern of thylakoid membrane proteins were investigated in rust-infected and healthy plants of the fully susceptible isoline Prelude, the moderately resistant isoline Prelude-Sr24, and the highly resistant isoline Prelude-Sr5. The rate of net photosynthesis, expressed per unit leaf area, was not significantly changed in any of the three near-isogenic lines during the early stages of infection, then increased slightly in the highly resistant line, while decreasing in the moderately resistant and fully susceptible lines. In the moderately resistant plants, this decrease continued linearly until 8 days after inoculation when no photosynthetic activity was detectable. In the susceptible line, the decrease gradually slowed down around 4–6 days after inoculation and photosynthetic activity remained constant thereafter. The chlorophyll content decreased only slightly during infection in highly resistant plants, but chlorophyll eventually disappeared completely from the infected, moderately resistant plants. The initially similarly strong decrease in chlorophyll content in the susceptible plants gradually came to a halt during the later stages of infection. Expressed per unit chlorophyll, photosynthetic O2 evolution increased slightly in highly resistant plants, remained unchanged in moderately resistant plants, and decreased to a stable level in the susceptible plants. The infection-induced changes in the 3-phosphoglycerate content closely resembled the changes in O2 evolution. No infection-induced changes were observed in the thylakoid membrane proteins from leaves of all three isolines. The results are discussed in relation to previously described changes in the primary metabolism of the three near-isogenic wheat lines after inoculation with the stem rust fungus, namely polyamine content, fructose-2,6-bisphosphate content, respiratory activity, invertase activity, and assimilate contents. Key words: Triticum aestivum, Puccinia graminis f.sp. tritici, O2 evolution, chlorophyll, 3-phosphoglycerate, thylakoid membrane proteins.

Attraction of Twospotted Spider Mite to Bean Rust Uredinia

Adults of the twospotted spider mite, Tetranychus urticae, were two- to sixfold greater on bean leaves, Phaseolus vulgaris, containing multiple uredinia of the rust fungus, Uromyces appendiculatus, than on rust-free bean leaves. On rust-free plants, freshly released mites went to the young trifoliolate leaves; but on rust-infected plants, they initially migrated to uredinia on older leaves. Mites became covered with echinulate urediniospores and vectored them to rust-free plants. The smooth-walled teliospores seldom adhered to the mites

Rust-Infected Quackgrass (Elytrigia repens) Growth and Rhizome Bud Death after Glyphosate Application

Photosynthesis decreased 32% in quackgrass infected with rust. Photoassimilate transport in rust-infected quackgrass, assessed by autoradiography, was less than that of control (no rust) leaves 35 min after exposure to14CO2. Greenhouse-grown quackgrass height, foliar and rhizome dry weights, rhizome length, and bud numbers decreased 11, 25, 28, 19, and 21% in rust-infected plants, respectively, compared to control plants. Foliar and rhizome biomass decreased 31 and 39%, respectively, in field-grown rust-infected plants. Rhizome bud death 48 h after treatment (HAT) in both control and rust-infected plants increased as glyphosate rate increased from 0.13 to 1 kg ae ha−1; however, control plant bud death was significantly greater than that of rust-infected plants.

The hydraulic conductivity of roots of rust-infected barley seedlings

The influence of Puccinia hordei (rust) infection on the root hydraulic conductivity ( Lp ) of excised roots of Hordeum distichum cv. Maris Mink (barley) was investigated using the Scholander pressure chamber technique. The solute potential of the root exudate was also measured to determine the contribution of the osmotic component to the total driving force for water flow across the roots. The root Lp of infected plants was significantly lower than control plants on days 5, 6 and 7 after infection. On days 4 and 8 after infection, Lp did not differ significantly. Root Lp increased with time for both control and infected plants from days 5 to 8 after infection. Root Lp varied between 1·4 and 3·6 × 10 −5 cm s −1 MPa −1 for roots of infected plants, and between 2·3 and 4·0 × 10 −5 cm s −1 MPa −1 for control plants. The solute potential of root xylem sap exudate was significantly higher (less negative) than that of control sap on days 6, 7 and 8 after infection, reflecting a decrease in the transport of solutes into the root xylem of roots of diseased plants. In control and infected plants, as the applied pressure increased, solute potential root exudate increased. These results are discussed in relation to the known susceptibility of rust infected plants to drought and the mechanisms by which rust infection increases such susceptibility.

Effect of intercellular washing fluids on the interactions between bean plants and fungi nonpathogenic on beans

Intercellular washing fluids from various compatible plant–parasite interactions were tested for their ability to reduce silica deposition on plant walls and to increase haustorium production in bean leaves following inoculation with the normally incompatible cowpea rust fungus. Only fluids from bean, wheat, and sunflower plants infected with their respective compatible rust fungi exhibited such activity, and no fluid had any similar effect on the nonhost interaction between bean leaves and other rust fungi. Fluids from rusted bean leaves did not increase the intercellular growth of a saprophytic fungus or other fungal parasites nonpathogenic on beans, nor did they affect silica deposition induced by these fungi. These data suggest that some feature of silica induction in bean by the cowpea rust fungus is unique and is affected by components in the intercellular washing fluids from only certain rust-infected plants. Fluids from uninoculated healthy wheat or sunflower plants and a Driselase solution that induces haustoria in vitro all increased haustorium formation by the cowpea rust fungus, but to a lesser extent than fluids from infected plants; silica deposition was not affected in these cases, suggesting that fluids from uninoculated plants may promote haustorium formation rather than prevent silica deposition.

Shoot: root interrelationships in leeks infected with the rust, Puccinia allii Rud.: Growth and nutrient relations.

Growth and nutrient relations were examined in healthy leeks and in leeks inoculated with the rust, Puccinia allii, to give three different intensities of infection (i.e. 10, 20 and 30%). Experiments were conducted over an 8-week experimental period, although only data from 5 weeks after inoculation are shown. The dry weights of rust-infected plants were substantially reduced compared with controls over the entire experimental period. Although shoot: root (S: R) ratios were increased in rusted plants 2 weeks after inoculation, the trend was reversed thereafter and for the remainder of the experiment S:R ratio was reduced in comparison with healthy controls. The contents of nitrogen, phosphate, potassium and calcium were reduced in rusted plants compared to controls. On the other hand, with few exceptions, the concentrations and specific absorption rates of these minerals increased in rusted plants compared with healthy controls. The ability of infected plants to maintain a functional S:R equilibrium with respect to nutrient uptake was examined using an analysis based on comparing changes in incremental plant dry weight with incremental nutrient weight. Calculated values of functional equilibrium for control and rusted plants showed that rust infection altered functional equilibrium with respect to uptake of the four nutrients. The possible mechanisms underlying these changes in physiology and the analysis of such changes are discussed.

A single glycoprotein from Puccinia graminis f. sp. tritici cell walls elicits the hypersensitive lignification response in wheat

Con A-binding glycoproteins were detected in germ tube walls of Puccinia graminis f. sp. tritici and appeared to be potent inducers of the hypersensitive lignification response. This response, which is typical of the large resistance reaction in wheat leaves, was preceded by a increase in extractable phenylalanine ammonia-lyase (PAL) activity, a key enzyme of the phenylpropanoid pathway. Germ tube glycoproteins were isolated from homogenized fungal cell walls by differential centrifugation and affinity chromatography on a Con A-Sepharose column. The most active glycoprotein was purified on a Mono Q anion-exchange column. The relative molecular mass of the molecule was determined in SDS-polyacrylamide gels to be 67 kD. The carbohydrate portion consists mainly of mannose (50%) and galactose (47%) and contains the active part of the glycoprotein as demonstrated by the inability of pronase and trypsin digestion to influence activity. An elicitor-active glycoprotein with identical molecular mass and Con A-binding properties was isolated from intercellular fluids of rust-infected plants of the susceptible wheat cultivar Little Club indicating that the elicitor is released from fungal cell walls during infection. We discuss the role of Con A-binding proteins as inducers of non-host resistance in cereals.