Puccinia Arachidis Research Articles

Differential Accumulation of Phytoalexins in Leaves of Susceptible and Resistant Genotypes of Groundnut (Arachis hypogaea L.) Inoculated with Puccinia arachidis Speg.

AbstractThe accumulation of phytoalexins in a rust‐susceptible (KH 241‐D) and a rust‐resistant (PI 259747) genotype of groundnut 2,6, 15 and 25 days after inoculation with the rust pathogen, Puccinia arachidis Speg. was investigated. Within 2 days of inoculation of the resistant genotype, total phytoalexins reached 35 μg/g fresh weight, remained close to this level for a further 13 days but reached 104μg/g at 25 days after inoculation. In contrast, the susceptible genotype accumulated only 4μg/g fresh weight 2 days after inoculation and this increased gradually to 13, 23 and 52 μg/g fresh weight at 6, 15 and 25 days, respectively. Extracts from uninoculated leaves of both genotypes showed the presence of an antifungal compound which appeared as a diffuse spot in the Thin Layer Chromatography (TLC) bioassay, but this was essentially absent in inoculated leaves and did not correspond to any peak detected on High Performance Liquid Chromatography (HPLC). Compounds with UV spectra corresponding to isoflavanones were the major component of the phytoalexin response whereas other phytoalexins, formononetin, daidzein, and medicarpin comprised a minor component. A further compound with a retention time of 23.0 min on HPLC and a λ max of 280 nm only accumulated in inoculated leaves of the resistant genotype.

Accumulation of isoflavonoid phytoalexins in leaves of Arachis hypogaea differing in reaction to rust (Puccinia arachidis) and early leafspot (Cercospora arachidicola)

Groundnut leaves, naturally infected in the field with Cercospora arachidicola or artificially infected in the greenhouse with C. arachidicola or Puccinia arachidis, accumulated isoflavonoid phytoalexins. Major compounds included medicarpin, formononetin, demethylmedicarpin, three isoflavanones and the isoflavone, daidzein. In both greenhouse and field experiments cv. Egret was less susceptible than cv. P84/5/244 to both pathogens, and accumulated phytoalexin (medicarpin) concentrations which were up to three times greater. Higher concentrations and greater variation of phytoalexins were detected when both cultivars were infected with C. arachidicola than when they were infected with P. arachidis.

Resistance in groundnut toSclerotium rolfsii‐causedstem and pod rot†

Abstract Eight hundred and fifty‐nine groundnut germplasm accessions and breeding lines were screened in field trials for resistance to stem and pod rot caused by Sclerotium rolfsiiduring the 1985–88 post‐rainy seasons at the ICRISAT Asia Center, Patancheru, India. Unes that showed low susceptibility to stem and pod rot (< 10%) were further evaluated at the Marathwada Agricultural University farm, Parbhani, India, during 1987–91 in the rainy and summer seasons. Of the 20 selected genotypes seven interspecific hybrid derivatives (326, 988, 1019, 1024, 1065, 1267, and 1364) consistently exhibited stable resistance to both stem and pod rot. Nine breeding lines (ICGV 86034, 86124, 86252, 86388, 86590, 86606, 86635, 87160, and 87359) showed low susceptibility to stem and/or pod rot. Effective screening for stem and pod rot resistance was possible in the post‐rainy and summer seasons. Several lines with low susceptibility to 5. rolfsii also possess resistance to rust (Puccinia arachidis) and moderate resistance...

Effect of Temperature on Urediniospore Production and Germinability in Puccinia arachidis1

Abstract Effect of temperature on urediniospore production in Puccinia arachidis was investigated under monocyclic infection using detached leaves of the susceptible peanut (Arachis hypogaea L.) cultivar TMV 2. Urediniospores produced at different temperatures were also examined for their germinability in vitro. The optimal temperature for urediniospore production was at about 20 and 25 C. Temperatures below 20 C or above 30 C were highly detrimental to urediniospore production. There were also marked differences in the percent germination of urediniospores produced at different temperatures. Urediniospores produced at 20 and 25 C showed the highest germination percentages. The interaction of temperature with urediniospore production and germinability is important in understanding the development of peanut rust epidemics.

Partial purification and properties of extracellular chitinase produced by Acremonium obclavatum, an antagonist to the groundnut rust, Puccinia arachidis

An extracellular chitinase of Acremonium obclavatum was partially purified. It had an M r of 45 kDa on SDS-PAGE, and was optimally active at pH 3 to 4 and 50°C. Hg and Mn (10 mM) inhibited activity. The chitinase hydrolysed colloidal chitin more rapidly than crude chitin or isolated A. obclavatum cell walls. The partially-purified enzyme inhibited uredospore germination and germ-tube growth of Puccinia arachidis.

Biocontrol potential of rust of groundnut by Acremonium obclavatum

Acremonium obclavatum was frequently found associated with pustules of the rust fungus Puccinia arachidis on groundnut in Madras, India. Inoculation of A. obclavatum before, with, or after inoculation with P. arachidis reduced the number and size of uredosori both on intact and detached leaves of groundnut plants. Treatments with A. obclavatum resulted in reductions in number of pustules and uredospores, delay in maturity and opening of uredosori, and reduced viability of uredospores. The application of culture filtrates of A. obclavatum also reduced the number and size of pustules on intact and detached groundnut leaves. The potential use of A. obclavatum in biological control of groundnut rust is discussed. Key words: groundnut, Arachis hypogaea, groundnut rust, Puccinia arachidis, Acremonium obclavatum, biological control.

Registration of ‘ICGV 87160’ Peanut

fastigiata var. vulgaris) cultivar (Reg. no. CV-47, PI 478787) was released in 1990 by the Central Sub-Committee on Crop Standards, Notification, and Release of Varieties, Department of Agriculture and Cooperation, Ministry of Agriculture, Government of India, for rainy-season cultivation in peninsular India where rust (Puccinia arachidis Speg.) and late leafspot [Phaeoisariopsispersonata (Berk. & H.A. Curtis) Arx] are serious problems. ICGV 87160 was tested extensively in India under the designation ICG(FDRS) 10. It has produced an average of 53% higher pod yield than the control 'JL 24', based on 22 trials conducted at 15 locations during 1983 to 1986 in India. The average pod yield of ICGV 87160 in these trials was 2600 kg ha-1. It has also outyielded other popular Indian cultivars such as TMV 2 by 36%, J 11 by 22%, and Kadiri 3 by 9%. It also showed pod yield superiority over local cultivars in Bangladesh (69% over Dacca 1), Myanmar (20% over Japanese Small), Sri Lanka (100% over Local), Thailand (19% over Tainan 9), the Philippines (67% over BPI Pn-9), and Niger

Economic benefits of spraying fungicides to control groundnut foliar diseases in Zambia

The commonly cultivated groundnut varieties in the country are susceptible to early leaf spot (Cercospora arichidicola Hori), late leaf spot (Phaeoisariopsis personata Berk. & Curt. v. Arx.), and rust (Puccinia arachidis Speg.). Since the development of agronomically suitable disease resistant varieties will take considerable time, fungicidal control is the short term remedy to this problem

GENETICS OF RUST (PUCCINIA ARACHIDIS SPEG.) IN GROUNDNUT

Rust (Puccinia arachidis Speg.) resistant groundnut genotype NC Ac 17090 was crossed with susceptible genotype VG5 and their segregating populations of F1, F2 and B; and B2 were studied for the reaction to the disease. The additive component (d) was significant, while the dominance (h) was not significant. The epistatic interactions, additive x dominance () and dominance x dominance (1) were not significant.

Ultrastructure of the early stages of infection of peanut leaves by the rust fungus Puccinia arachidis

Peanut rust disease proved to be an excellent system for ultrastructural study of development of infection structures by the fungus Puccinia arachidis. Fungal structures were clearly visible by light microscopy in fixed and embedded samples and could be located either on leaf surfaces or within the large substomatal chambers of peanut leaves. Samples could easily be oriented for thin sectioning. The infection process was a highly orchestrated process involving precisely timed events and highly specialized structures. Infection pegs developed from appressoria over stomata and entered the leaf by growing into the openings between guard cells. Once past the rim formed by the guard cell walls, the infection peg expanded to form a substomatal vesicle in which a synchronous mitotic division of the four nuclei occurred. A primary infection hypha then developed from the vesicle and grew into the mesophyll of the leaf until its tip or side contacted a host cell. A septum then delimited a binucleate or trinucleate terminal haustorial mother cell from the remainder of the infection hypha. The wall of the haustorial mother cell became closely appressed to that of the host cell. Following differentiation of the haustorial mother cell, a penetration peg arose from it and penetrated the host cell wall. The peg invaginated the host cell plasma membrane as it elongated and then expanded at its tip to form the haustorium body into which most of the contents of the haustorial mother cell moved. Meanwhile, the primary infection hypha formed secondary hyphae that gave rise to additional haustorial mother cells and haustoria. Key words: Puccinia arachidis, peanut rust, infection process, ultrastructure.

CSGR-1: A Computer Simulator of Groundnut Rust1

Abstract A computer simulator of groundnut rust (Puccinia arachidis Speg.), CSGR-1, was constructed based on four mathematical submodels describing environmental effects on (1) the increase rate of disease severity and daily multiplication factor of diseased leaflets, (2) the relationship between host growth and the effective accumulated temperatures, and (3) the relationships between infectious tissue and disease severity. The simulator was validated using independent data sets. With CSGR-1, disease development of groundnut rust can be predicted eleven days in advance given appropriate climatic data.

A Scale of Reaction Types of Groundnut to Puccinia arachidis Speg.

AbstractA scale of reaction types of groundnut to Puccinia arachidis Speg. is proposed based on observations of infected leaves taken from the field. A variety of reaction types was described and ranked in two ways, according to ontogenic development and to host susceptibility. The reaction types thus described were grouped into few classes, and the resulting scale was compared with the widely‐used scales of cereal rusts. The application of the proposed typological scale for a quick, qualitative assessment of groundnut varieties for rust resistance is discussed.ZusammenfassungEine Reaktionstypskala für Erdnüsse gegen Puccimia arachidis Speg.Vorgeschlagen wird eine Reaktionstypskala für Erdnüsse gegen Puccinia arachidis Speg., die sich auf Beobachtungen von feldgesammelten, infizierten Blättern stützt. Eine Vielfalt von Reaktionstypen wurde beschrieben und nach zwei Gesichtspunkten eingeordnet, nach der ontogenischen Entwicklung und der Wirtsanfälligkeit. Die so beschriebene Reaktionstypen wurden in einigen Klassen zusammengestellt und die daraus gebildete Skala mit der breitangewandten Getreiderostskala verglichen. Diskutiert wird die Anwendung dieser vorgeschlagenen typologischen Skala für eine schnelle, qualitative Beurteilung der Rostresistenz von Erdnußsorten.

Detection and Measurement of Plant Disease Gradients in Peanut with a Multispectral Radiometer

Percent reflectance values, when used as the independent variable, explained 94.6-96.5% of the variation in peanut rust disease severity along rust gradients. Reflectance of sunlight from peanut canopies at 800 nm provided a rapid and objective measurement of disease intensity and the amount of green leaf area contributing to pod yield. Recording percent reflectance offers a means to quantify the benefits obtained from disease control tactics aimed at protecting and maintaining healthy green leaf area from the effects of plant pathogens

Peanut Rust in West Africa: A New Component in a Multiple Pathosystem

Observations de cultures en Cote d'Ivoire, evaluation de pertes de recolte, etudes epidemiologiques experimentales, caracteres epidemiologiques, analyse en composante de l'interaction hote-pathogene, evolution du pathosysteme en intensification agricole

Decrease by plant development and leaf age of susceptibility of groundnut to rust (Puccinia arachidis) in a susceptible cultivar

The effects of plant development and leaf age on the infection efficiency (IE), the latency period (LP) and the sporulation intensity (SP) of groundnut rust were studied using detached and attached leaflets of a highly susceptible groundnut cultivar. The results indicate a decrease ofIE with increasing leaf age and an increase ofLP with increasing leaf age and development stage. A significant effect of detachment onIE was found. However, experiments on both detached and non-detached leaflets resulted in the same, general conclusions. The observed reduction ofIE and lengthening ofLP suggest that further studies would profitably distinguish epidemiologically different layers in the host canopy.

Rain-induced dispersal in Puccinia arachidis, studied by means of a rainfall simulator

A rainfall simulator was used on groundnut (Arachis hypogaea) plots artificially infected withPuccinia arachidis in order to study urediniospore dispersal caused by various amounts of rainfall. Several trapping method were used to compare dry, splash and drip dispersal caused by rain. The spore liberation mechanisms activated by rain and the flows of spores which they generate can be studied at the infected canopy or at the sporulating lesion scales. Two systems referring to these scales were considered to discuss the results. Dry dispersal seemed preponderant. The spore content of the lesions in the canopy was strongly reduced by rain. The results indicated that light rain showers may promote disease dispersal, whereas it may be hampered by heavy showers. Een regensimulator, een krachtig beregeningsapparaat, werd ingezet boven een aantal aardnoot-(Arachis hypogaea) veldjes geinoculeerd met de aardnootroest (Puccinia arachidis) om de uredosporenverspreiding te bestuderen bij verschillende hoeveelheden regenval. Diverse vangtechnieken werden toegepast om droge verspreiding, spatverspreiding en druipverspreiding ten gevolge van regen te vergelijken. De sporeninhoud van de sporenhoopjes op het gewas werd door regen sterk verminderd. De resultaten, verkregen in twee verschillende, maar elkaar aanvullende analyses, geven aan dat lichte regenbuien de ziekteverspreiding bevorderen, terwijl zware buien deze zouden afremmen.

The Choice of Groundnut (Arachis hypogaea) Varieties by Smallholders in South-east Tanzania. I. Observations on Different Varieties

SUMMARYSmallholders in south-east Tanzania grow the groundnut Red Mwitunde (Arachis hypogaea ssp. hypogaea), a long-season variety with seed dormancy, although earlier maturing varieties with no seed dormancy (ssp. hypogaea and fastigiata) usually yielded better in trials, particularly when late sown. Small-seeded, short-season varieties established better in the field than Red Mwitunde and other large-seeded varieties, especially under moisture stress. Trials with selective fungicides to estimate yield losses from leafspots (mainly Cercosporidium personatum) and rust (Puccinia arachidis), jointly and separately, showed no consistent varietal differences.

Mode of action of sodium sulfanilate for control of groundnut rust ( Puccinia arachidis S.) and its toxicity to the host plant ( Arachis hypogaea L.)

Protection of groundnut plants against leaf rust by sodium sulfanilate is reversed by both p-aminobenzoic acid and folic acid, indicating an antifungal action based on interference with folic acid biosynthesis. Folic acid is required for growth of the pathogen. However, protection may also be associated with induced disease resistence because amino acids, particularly aspartic acid and glycine, accumulated in the host plant while there was a reduction in content of threonine and proline. These conditions are possibly unfavorable for growth of the rust fungus and susceptibility of the host plant. Sodium sulfanilate causes phytotoxicity at high concentrations by reducing chlorophyll content. This phytotoxicity is reversed by addition of p-aminobenzoic acid.

Fungicidal control of groundnut leaf spot and rust in Nigeria

Four systemic fungicide formulations (tridemorph, tridemorph plus maneb, carbendazim and benomyl) and three non-systemic fungicides (captafol, mancozeb and copper oxychloride) were evaluated in field trials at two locations in Nigeria in 1981 and 1982 for control of early leaf spot ( Mycosphaerella arachidis Deighton, stat: conid: Cercospora arachidicola Hori), late leaf spot ( Mycosphaerella berkleyi W. A. Jenkins, stat: conid: Cercosporidium personatum (Berk. & Curt.) Deighton) and rust ( Puccinia arachidis Speg.) of groundnut ( Arachis hypogaea L.). Plots receiving mancozeb and tridemorph plus maneb showed best overall disease control and highest yields, followed by copper oxychloride. Benomyl and carbendazim controlled leaf spots predominantly while tridemorph controlled only rust. Captafol gave little overall disease control with yields only slightly better than untreated controls. Further tests are planned for tridemorph plus maneb and copper oxychloride using different concentrations and spray schedules.

Recent Invasions of Australia and New Zealand by Pathogenic Fungi and Counter Measures1

Despite the relative isolation of Australia and New Zealand and the strict quarantine regulations long imposed, many plant diseases have been introduced in recent years. The article analyzes 26 cases since 1960 which seem certain to be new arrivals, and have some economic significance. Wind‐borne introduction from the islands to the north seems likely in several cases (Cochliobolus heterostrophus, Peronosclerospora maydis, Puccinia arachidis, Mycosphaerella fijiensis var. difformis) and air currents are certainly responsible for many arrivals in New Zealand from Australia (acacia rusts, Puccinia menthae, P. helianthi. Puccinia melanocephal (sugar cane rust) is one case of possible intercontinental movement west to east on prevailing air currents (from Africa to India and the Far East, then Australia and Central America). However, accidental introduction by air travellers, or illegally introduced planting material, seems most likely to explain the recent appearance in Australia of Puccinia striiformis and Melampsora spp. on poplar, even if these have since spread naturally to New Zealand. Dothistroma septospora, causing a needle blight of Pinus radiata, is unusual in that it apparently moved from New Zealand to Australia (around 1975). Internal restrictions can limit further spread in some cases. Otherwise, the « cost » of these introductions has mainly arisen from the need for fungicide treatments and from the abondonment of valuable, but susceptible, cultivars. Introduced fungi may not behave as expected on the basis of earlier biological studies. Thus, P. striiformis survives the harsh Australian summers while D. septospora which necessitates costly fungicide treatments in New Zealand, has remained isolated and unimportant in Australia.