Bean Rust Research Articles

Phenotypic and Genotypic Characterization of Uromyces appendiculatus from Phaseolus vulgaris in the Americas.

Populations of 90 Uromyces appendiculatus isolates were collected from throughout the Americas and evaluated for virulence on 19 standard bean rust differentials, and also on 12 landraces of Phaseolus vulgaris from South and Central America. The landrace differentials represented geographical centers of bean domestication. Three groups were observed. Two groups were isolates from centers of bean domestication and a third heterogeneous group comprised isolates from countries in South and Central America. Molecular analysis using random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) was also conducted on these isolates. Cluster analysis of the molecular profiles showed three groups that corresponded to those obtained by virulence tests. These results show a clear differentiation of the pathogen population along similar lines as its host and suggest parallel evolution in the bean rust pathosystem.

Secondary mould metabolites of Cladosporium tenuissimum, a hyperparasite of rust fungi

Investigation of the extracts of a culture of Cladosporium tenuissimum, a known hyperparasite of several rust fungi, gave rise to the isolation of cladosporols B–E ( 2– 5). Their structure and stereochemistry were elucidated on the basis of 1H and 13C NMR evidence and CD measures. Cladosporols 1– 5 were active in inhibiting the urediniospore germination of the bean rust agent Uromyces appendiculatus.

Histological studies on the mycoparasitism of Cladosporium tenuissimum on urediniospores of Uromyces appendiculatus

Interactions between the mycoparasite Cladosporium tenuissimum and the bean rust Uromyces appendiculatus were studied through light and electron microscopy in vitro at the host-parasite interface. Urediniospore germination decreased on contact with ungerminated C. tenuissimum conidia, possibly due to antibiosis mechanisms. C. tenuissimum grew towards the bean rust spores and coiled around their germ tubes. Penetration of the urediniospores occurred either enzymatically and/or mechanically, through appressorium or infection cushion structures, from which a thin penetrating hypha was generated. Enzyme production by the mycoparasite was suggested by the loosening of the matricial components of the spore wall, which sometimes left chitin fibrils visible. Mycoparasite hyphae grew within the host spore, emptied its content, and emerged profusely forming conidiophores and conidia. C. tenuissimum was able to grow on media containing laminarin, suggesting the ability of producing glucanases, but not when chitin was used as the sole carbon source. Conidia that had been grown on a sugar-rich medium, filtered, and extracted with organic solvents, were found to contain cladosporol and related compounds. Complete control of the bean rust disease was achieved by application of C. tenuissimum culture filtrates but not by conidial suspensions. This is the first report of parasitism by C. tenuissimum on U. appendiculatus. These investigations provide additional observations on a genus besides Melampsora and Cronartium from which this fungus has been isolated and tested to date. The possible role of environmental factors for the exploitation of this organism as a biocontrol agent is also mentioned.

Chemical Control Studies and Resistance to Bean Rust in Bean Germplasm

(2004). Chemical Control Studies and Resistance to Bean Rust in Bean Germplasm. East African Agricultural and Forestry Journal: Vol. 70, No. 1, pp. 29-33.

Sexual Stage Development of Uromyces appendiculatus and Its Potential Use for Disease Resistance Screening of Phaseolus vulgaris.

In June 1989, pycnia and aecia of the bean rust pathogen were observed in eastern Colorado on volunteer plants of pinto bean cvs. UI 114 and UI 126 that grew from seed that remained in the field after harvest the previous season. Harvested aeciospores were viable and produced typical reddish-brown uredinia on unifoliolate leaves of UI 114 seedlings in the greenhouse. Evidence of bean rust overwintering has been confirmed in 10 years from 1989 to 2002 in eastern Colorado and the surrounding region. Overwintering conditions were reproduced at Fort Collins, CO in fall 1992 and spring 1993. Debris treatments had significantly higher disease incidence on stems, total number of lesions on stems, disease incidence on leaves, and total number of lesions on leaves of plants of pinto cvs. UI 114 and Olathe than plants without debris. Bean leaves of both cultivars had significantly higher disease incidence than stems. There also was an increased incidence of aecial infection for UI 114 seedlings that germinated through leaf debris with rust compared with stem debris under greenhouse conditions with abundant moisture. Bean leaf debris smaller than 0.36 mm in diameter resulted in significantly more aecial lesions on UI 114 than larger leaf debris and stem debris. Additional greenhouse experiments demonstrated that diverse collections of naturally occurring, overwintered, rust-infested bean debris from eastern Colorado produced different levels of pycnial and aecial infection on pinto cvs. UI 114, Olathe, and Chase. Chase, currently resistant to the uredinial stage of the prevalent bean rust races in Colorado and surrounding states, had a low incidence of aecial lesions on seedling stems when exposed to pycnial and aecial stages in the greenhouse. These observations indicate that selection of bean rust resistance genes should rely on multiple sources of resistant germ plasm to counter the potential increase in new races that could derive from sexual recombination in bean-production regions.

Mapping of the Ur‐7 Gene for Specific Resistance to Rust in Common Bean

Bean rust, caused by Uromyces appendiculatus (Pers.: Pers.) Unger, is a major disease of common bean (Phaseolus vulgaris L.). A recommended strategy to obtain durable rust resistance is to use molecular markers linked to rust resistance genes for pyramiding monogenic resistance genes into a single bean cultivar. However, markers linked to the Ur‐7 gene for specific resistance (SR) to rust present in the cultivar Great Northern (GN) 1140 have not been reported. Our objectives were to identify random amplified polymorphic DNA (RAPD) markers linked to the Ur‐7 gene for SR to rust race 59 using bulked segregant analysis in an F2 population from the Middle American (MA) common bean cross ‘GN1140’ (resistant) × GN Nebr. #1 (susceptible) and to map the Ur‐7 gene on an existing RAPD marker‐based linkage map constructed by means of recombinant inbred lines (RILs) from the MA cross GN BelNeb‐RR‐1 × A 55. A single dominant gene controlling SR to race 59 was found in the F2 and confirmed in the F3 Six RAPD markers were detected in a coupling phase linkage with the Ur‐7 gene. Cosegregating coupling‐phase markers OAD12.550 and OAF17.900 were found. These were also present in pinto US‐5 from which the rust resistance of GN1140 was derived. Among the three repulsion‐phase markers, marker OAB18.650 was the most closely linked to the Ur‐7 gene at a distance of 7.6 centimorgans (cM). All linked markers detected in the F2 population also segregated in the RILs and were located on linkage group 11 of the existing linkage map. These markers linked to the Ur‐7 gene of MA origin identified here, along with other independent rust resistance genes from other germplasm, could be utilized to pyramid multiple genes into a bean cultivar for more durable rust resistance.

Effect of Commercial Adjuvants on Vegetable Crop Fungicide Coverage, Absorption, and Efficacy.

The addition of an appropriate adjuvant with foliar fungicide can significantly improve coverage, absorption, and efficacy. Laboratory and field studies evaluated coverage, absorption, and efficacy of commercial adjuvants with diverse chemistries on multiple host-pathogen systems. Organosilicone-based adjuvants improved coverage by 26 to 38% compared with a latex spreader-sticker and water. Significant crop by coverage interaction effects were also detected. The organosilicone/methylated seed oil-based adjuvant, Aero Dyne-Amic, significantly improved total [14C]azoxystrobin absorption on onion and potato by 30 and 21%, respectively, compared with water. The spreader-sticker, Bond, improved [14C]azoxystrobin absorption on onion and dry bean by 41 and 39%, respectively, compared with water. In experimental field plots, dry bean rust incidence was reduced by 52% when Kinetic or Latron AG-98 was added to maneb compared with maneb alone. The area under the potato early blight disease progress curve was reduced 29, 24, or 21% when Kinetic, Bond, or Latron AG-98 was added to maneb, respectively, compared with maneb applications alone.

Contributions of the Bean/Cowpea CRSP to cultivar and germplasm development in common bean

Disease and abiotic stress are important factors limiting bean production wherever beans are grown. The development of bean cultivars having resistance to these stresses is a cost-effective and sustainable means to address these constraints. During the past 20 years, the Bean/Cowpea Collaborative Research Support Project (B/C CRSP) has supported common bean cultivar development and germplasm improvement programs in the USA and developing countries. Plant breeders have developed and released in Central America and the Caribbean bean cultivars and germplasm with one or more of the following traits; resistance to bean golden yellow mosaic virus (BGYMV), bean common mosaic necrotic virus (BCMNV), rust, web blight and common bacterial blight (CBB) and greater tolerance to high temperatures. In the highlands of Mexico and Ecuador bean cultivars with resistance to anthracnose, rust, root rots and bean common mosaic virus (BCMV), greater biological nitrogen fixation and improved adaptation to intermittent drought have been released. The bean breeding programs in East Africa have developed and released bean cultivars and germplasm with resistance to BCMNV, rust and bruchid seed weevils. Participation in the B/C CRSP has permitted USA bean breeding programs to develop and release bean cultivars and germplasm with resistance to BGYMV, BCMNV, anthracnose, rust, CBB, architectural avoidance to white mold and greater yield potential. Numerous plant breeders, plant pathologists and agronomists from developing countries have received advanced degree training in the USA, which has enhanced the capacity to develop improved bean cultivars for Latin America and Africa. The lack of sustainable seed production and delivery systems continues to limit the impact of the release of improved bean cultivars in many parts of Latin America and East Africa.

Benzothiadiazole (BTH) Induces Cell‐Death Independent Resistance in Phaseolus vulgaris against Uromyces appendiculatus

AbstractBenzo‐(1,2,3)‐thiadiazole‐7‐carbothioic acid S‐methyl ester (BTH), trade name Bion®, was used to induce resistance in bean cultivars Borlotto Nano Lingua di Fuoco (BLF), Borlotto Taylor, Cannellino, Cannellino Montalbano, Saxa and Top Crop, against rust caused by Uromyces appendiculatus. A single 0.3 mm BTH spray 7 days before inoculation was sufficient to fully control the disease in all the examined cultivars. As regards the more susceptible BLF, either a single treatment 14 days before inoculation, or three applications on the third, fifth and seventh day before inoculation, were equally effective to prevent infection. Histochemical and cytochemical investigations showed that BTH causes hydrogen peroxide (H2O2) accumulation in the treated tissues. H2O2 deposits were localized in situ for the first time in the apoplast of the leaf epidermis. No cell death was detected at BTH concentrations below the phytotoxicity threshold, suggesting that acquired resistance against bean rust is mainly related to the enhanced activity of anionic peroxidases, promoted by H2O2 accumulation, thereby leading to cell wall strengthening. This hypothesis is also supported by the long induction phase required to establish complete resistance.

Mapeamento de genes de resistência do feijoeiro à ferrugem, antracnose e mancha-angular usando marcadores RAPD

A organização de diferentes genes de resistência da cultivar Ouro Negro de feijoeiro-comum (Phaseolus vulgaris) à ferrugem, antracnose e mancha-angular foi estudada com o auxílio de marcadores moleculares. Uma população de 154 linhas endogâmicas recombinantes (RIL's) obtidas do cruzamento entre as cultivares Ouro Negro e Rudá foram inoculadas com sete raças fisiológicas de Uromyces appendiculatus, três de Colletotrichum lindemuthianum, e quatro de Phaeoisariopsis griseola. Amostras de DNA de cada uma das RIL's foram amplificadas via PCR utilizando 70 diferentes primers. A análise da segregação da resistência à ferrugem, antracnose e mancha-angular na população de 154 RIL's revelou diferentes modos de herança para a resistência a cada uma das raças fisiológicas. A análise de ligação genética revelou que os diferentes genes de resistência à ferrugem e à antracnose estão no mesmo grupo de ligação. Os genes de resistência à mancha-angular também foram mapeados juntos, porém em outro grupo de ligação. Verificou-se neste trabalho que a utilidade dos marcadores RAPD, previamente identificados como ligados a genes de resistência do feijoeiro a doenças foi restrita. Apenas cinco dos 38 marcadores moleculares testados foram validados na população de RIL's como ligados aos genes de resistência à ferrugem e à antracnose. Três novos marcadores (OBA16(669) e OBA16(583) a 10,4 cM em acoplamento e OAD9(3210) a 13,9 cM em repulsão) ligados ao bloco gênico de resistência da cultivar Ouro Negro à mancha-angular foram identificados.

Uromyces viciae-fabae haustorium formation in susceptible and resistant faba bean lines

Haustorium formation by the faba bean rust (Uromyces viciae-fabae) was studied on susceptible and resistant faba bean lines. The resistant lines showed incomplete resistance, based on late acting hypersensitivity or on non-hypersensitive resistance acting before haustorium formation. Histological observations on infected leaves showed that both the number of haustoria per infection unit and their developmental stage was reduced in both resistant lines. Isolation of haustoria confirmed that both the number and the size of haustoria were reduced in resistant lines, irrespective of whether the resistance was associated with hypersensitivity. Plant age had no detectable effect on both parameters.

Yield Loss Associated with Soya Bean Rust (Phakopsora pachyrhizi Syd.) in Uganda

AbstractStudies were conducted to quantify the yield loss attributable to soya bean rust, a relatively new disease in Uganda. This was carried out for three consecutive seasons in the central, eastern, northern and western parts of the country, using three commercial varieties (Nam 1, Nam 2 and Namsoy 3) and two elite varieties (UG‐5 and GC‐00138‐29). The commercial varieties recorded higher yield losses (26.9–36.3%) and higher rust severities >50%, whereas the elite varieties recorded lesser yield losses of <10% and rust severities of <30%. Yield losses were highest in the central region (22.9%), and lowest in the northern region (15.1%). Yield losses differed significantly between seasons and were associated with reduction in seed weight and filled pod per plant.

Developmentally regulated conversion of surface‐exposed chitin to chitosan in cell walls of plant pathogenic fungi

Summary Conversion of surface‐exposed chitin to chitosan in cell walls of in vitro ‐ and in vivo ‐differentiated infection structures of two rust fungi, the wheat stem rust fungus Puccinia graminis f. sp. tritici and the broad bean rust fungus Uromyces fabae , and of the causal agent of maize anthracnose, Colletotrichum graminicola , were studied. Epi‐fluorescence microscopy with the fluorescence‐labeled lectin wheat germ agglutinin (WGA) revealed that surfaces of infection structures formed on the plant cuticle expose chitin, whereas surfaces of structures formed after invading the host do not. To identify chitin modification by de‐ N ‐acetylation, we raised polyclonal antibodies specifically recognizing de‐ N ‐acetylated chitosan. These antibodies labeled only those infection structures that differentiate inside the plant, indicating that chitosan is exposed on cell wall surfaces post penetration. Surface modification of the fungal cell walls by chitin de‐ N ‐acetylation is discussed as a fungal strategy to protect cell walls of pathogenic hyphae from enzymatic hydrolysis by host chitinases, and to avoid generation of an auto‐catalytic defense response system in the invaded host tissue.

Histological Characterization of Resistance to Uromyces viciae-fabae in Faba Bean

ABSTRACT Components of resistance to the faba bean rust (Uromyces viciae-fabae) were studied at the histological level in seedlings and adult plants of nine faba bean (Vicia faba) lines differing in their level of resistance. Resistance of these lines was previously shown to be characterized macroscopically by an increased latent period, a decreased colony size, and a relatively decreased infection frequency. In some lines, the resistance also was associated with macroscopically visible necrosis. Histological investigations revealed few differences in spore germination and appressorium formation. Significant levels of aborted stomatal penetration by the rust fungus were found on all resistant lines. However, differences among lines were more evident once the stomata were penetrated by the infection structures. Resistance was mainly due to a restriction of haustorium formation with varying levels of early abortion of the colonies, a reduction in the number of haustoria per colony, and smaller colony size. In addition, necrosis of the host cells associated with infection hyphae was detectable in some lines from the beginning of colony development. This microscopically visible necrosis became stronger from 4 days after inoculation, resulting in a reduced growth of the colony. Differences in resistance levels were more marked in adult plants than in seedlings.

Gas Exchange and Emission of Chlorophyll Fluorescence during the Monocycle of Rust, Angular Leaf Spot and Anthracnose on Bean Leaves as a Function of their Trophic Characteristics

Measurements related to gas exchange and chlorophyll fluorescence emission were taken from healthy and diseased bean leaves with rust, angular leaf spot, and anthracnose during lesion development for each disease. The experiments were performed at different temperatures of plant incubation, and using two bean cultivars. The main effect of temperature of plant incubation was in disease development. There was no significant difference between cultivars in relation to disease development and in magnitude of physiological alterations when disease severity was the same for each cultivar. These diseases reduced the net photosynthetic rate and increased the dark respiration of infected leaves after the appearance of visible symptoms and the differences between healthy and diseased leaves increased with disease development. The transpiration rate and stomatal conductance were stable during the monocycle of rust, however, these two variables decreased in leaves with angular leaf spot and anthracnose beginning with symptom appearance and continuing until lesion development was complete. Carboxylation resistance was probably the main factor related to reduction of photosynthetic rate of the apparently healthy area of leaves with rust and angular leaf spot. Reduction of the intercellular concentration of CO2, due to higher stomatal resistance, was probably the main factor for leaves with anthracnose. Chlorophyll fluorescence assessments suggested that there was no change in electron transport capacity and generation of ATP and NADPH in apparently healthy areas of diseased leaves, but decreases in chlorophyll fluorescence emission occurred on visibly lesioned areas for all diseases. Minimal fluorescence was remarkably reduced in leaves with angular leaf spot. Maximal fluorescence and optimal quantum yield of photosystem II of leaves were reduced for all three diseases. Bean rust, caused by a biotrophic pathogen, induced less damage to the regulation mechanisms of the physiological processes of the remaining green area of diseased leaves than did bean angular leaf spot or anthracnose, caused by hemibiotrophic pathogens. The magnitude of photosynthesis reduction can be related to the host–pathogen trophic relationships.

Broadening the Genetic Base of Common Bean Cultivars

Knowledge, access, and use of diversity available in cultivated and wild relatives are essential for broadening the genetic base of cultivars to sustain improvement. My objectives are to review briefly the origin, domestication, and organization of genetic diversity in Phaseolus beans, highlight production problems and traits deficient in the common bean (P. vulgaris L.) cultivars, cite sources of useful gemplasm, and review progress achieved in broadening the genetic base of cultivars. Phaseolus beans originated in the Americas. Only five species, P. acutifolius A. Gray, P. coccineus L., P. lunatus L., P. polyanthus Greenman, and P. vulgaris L. were domesticated. The interspecies diversity in relation to common bean is organized in primary, secondary, tertiary, and quaternary gene pools. Intraspecies diversity in common bean is separated into two major gene pools (Andean and Middle American). Cultivars are further divided into races, each with their distinguishing characteristics. Also, cultivars of dry seed and snap bean exist. Abiotic and biotic stresses limit common bean production. The genetic base of cultivars within market classes is narrow and inadequate level of resistance to common bacterial blight [caused by Xanthomonas campestris pv. phaseoli (Smith) Dye] and white mold [caused by Sclerotinia sclerotiorum (Lib) de Bary] exist in cultivars. High levels of resistance to these and other desirable traits exist in the relatives and gene pools of P. vulgaris Early maturity, adaptation to higher latitude, upright plant type, high pod quality and seed yield, and resistance to Bean common mosaic virus (a potyvirus) and/or rust [caused by Uromyces appendiculatus (Pers.:Pers.) Unger] have been bred into cultivars. However, most of the genetic variability available in the common bean races, gene pools, and wild relatives remains to be utilized. To maximize and sustain bean production, high yielding, high quality cultivars that are less dependent on water, fertilizer, pesticides, and manual labor should be developed. This need warrants sustained, comprehensive, and integrated genetic improvement, in which favorable alleles from cultivated and wild relatives are accumulated in superior cultivars. A three‐tiered breeding approach involving: (i) gene introgression from alien germplasm, (ii) pyramiding favorable alleles from different sources, and (iii) simultaneous improvement of multiple traits for common bean cultivars would be the most appropriate strategies to meet theses needs.

Bean rust biological control using bacterial agents

Over 120 bacterial strains were evaluated in a greenhouse for control of bean rust caused by Uromyces appendiculatus. The strains, found previously to be antagonistic to some fungal pathogens, were isolated from dry edible bean ( Phaseolus vulgaris) and other hosts. Only Pantoea agglomerans B1, from a bean blossom, and Stenotrophomonas maltophilia C3, a chitinolytic strain from a Kentucky bluegrass leaf, were effective in multiple experiments in reducing bean rust severity. The addition of colloidal chitin to C3 cell suspensions and treatment with chitin broth cultures of C3 were evaluated as methods to improve biocontrol efficacy of C3. While chitin amendments increased rust control in the greenhouse as compared to C3 cells in buffer, chitin broth cultures gave the highest- and longest-lasting level of control. In four field experiments, treatments with C3 suspended in buffer, with and without chitin amendment, reduced rust severity in only one experiment. Strain B1 was not effective. In three other field experiments, C3 chitin broth cultures were comparable to multiple applications of thiophanate methyl or thiophanate methyl combined with manganese ethylenebisdithiocarbamate (maneb) in reducing bean rust severity.

The evolutionary significance of variation in infection behavior in two species of rust fungi on their hosts and related nonhost plant species

We explored the association between the phylogeny of 14 species of beans in the genera Phaseolus and Vigna (subtribe Phaseolinae) and the progress of infections in them caused by two pathogenic rust fungi, Uromyces appendiculatus (Pers.) Unger and Uromyces vignae Barclay. The analyses involved construction of phenograms, ordinations, and cladograms derived from the infection characteristics and their comparison to a composite of three previously published DNA phylogenies. The patterns of infection by U. vignae showed no relationship to the phylogeny of the infected plants. The course of infection by U. appendiculatus, however, displayed a significant phylogenetic component, although the defense responses of the infected plants themselves did not. These differences in phylogenetic signal between infections caused by the two fungi may reflect distinct evolutionary histories with members of the Phaseolinae, a long association for U. appendiculatus but a much more recent one for the more host-specific U. vignae.Key words: bean rust, cowpea rust, evolution, infection characteristics, Phaseolus, Vigna.

Overwinter Survival of Bean Rust Urediniospores in North Dakota.

Bean rust (Uromyces appendiculatus) reached epidemic proportions in North Dakota and Minnesota from 1993 to 1996. Although U. appendiculatus is a macrocyclic autoecious rust, neither pycnia nor aecia have been observed in commercial dry bean (Phaseolus vulgaris) in North Dakota fields. The source of initial inoculum is not clearly understood. This study determined the potential for urediniospore survival overwinter. Uredia-bearing bean leaves from artificially inoculated greenhouse-grown plants were kept outside near a field from November to May from 1990 to 1996. Based on bioassays urediniospores survived overwinter, but viability declined over time. Overwinter survival indicates urediniospores may function as initial inoculum.

Association of bean rust and common bacterial blight epidemics with cropping systems in Hararghe highlands, eastern Ethiopia

Surveys of common bean rust and common bacterial blight (CBB) diseases were conducted in the Habro, Chercher and Wobera areas of the Hararghe highlands, Ethiopia during the 1998 and 1999 cropping seasons in four different bean cropping systems. Intercropping constituted 91% of the cropping systems. Bean proportions in intercropping ranged from 13 to 55%. In intercropping, the mean rust incidence and severity was reduced by 25 and 16%, respectively, compared with sole cropping. Similarly CBB incidence was reduced by 29% while severity was reduced by 20%. Single and multiple variable logistic regression analyses were used to determine the association of rust and CBB diseases with cropping systems and practices, geographical areas, cropping years and altitude. The analyses indicated that cropping system, geographical area and cropping year were important variables and affected both rust incidence and severity. In Habro during 1998 there was a high probability of rust incidence and severity greater than 25%. The probability of rust incidence and severity exceeding 25% inHabro was about 11 and4 times greater than in Chercher and Wobera areas, respectively. Less than 50% bean proportions in intercropping were significantly associated with low (<25%) rust severity. Similarly geographical area, altitude and cropping system affected CBB incidence and severity. In Habro and at lower altitudes there was a high probability ofgreater than 25% CBB incidence and severity. Bean plants at podding and or maturity were closely associated with high rust and CBB severity. Intercropping systems were more associated with lower CBB and rust intensity than sole cropping.