Ustilago Zeae Research Articles

BIOLOGICAL AND ECOLOGICAL STATE OF COMMON SMUT (USTILAGO ZEAE) IN CORN SILAGE FIELDS IN THE KYZYLORDA REGION AND MEASURES TO COMBAT IT

Corn, as one of the most important grain feed crops, is of great importance in increasing gross grain yields. Corn smut (Ustilago zeae) can also cause large economic losses in susceptible sweet corn hybrids. Protection against this pathogen is mainly based on prevention. To date, many corn smut control methods have been recommended or evaluated, including crop rotation, sanitation, seed treatments, fertility modification, and biological control. Despite these frequently cited control strategies, host resistance appears to be the only effective control method for common smut in areas where Ustilago zeae is common. The purpose of the study is to study the resistance to smut against a natural infectious background of samples from a collection of corn from breeding nurseries in Kazakhstan. Based on the results of a study of the resistance of a corn collection to bladder smut against a natural infectious background, varieties were identified on whose plants symptoms of the disease were not detected: Altay 250 MV, Budan 237 MV, Tatty-2012 and Tayelsizdik-20 SV. The identified samples also had high productivity and grain yield. A high level of heritability (Hb2 – 0.85) of the disease susceptibility index among the studied samples was revealed.

Evaluation of maize hybrids for resistance to major diseases and pests in the conditions of the southwestern Forest-Steppe of Ukraine

Topicality. The results of phytopathological evaluation of breeding material (the maize hybrids (Zea mays L.)) against the natural background of the main diseases fusarium (Fusarium (F. moniliforme J. Sheld), bacteriosis (Bacillus mesentericus-vulgatus Flugge), white rust (non-parasitic disease), boil smut (Ustilago zeae (Beskm.) Unger)) are given. The damage of corn hybrids by the European corn borer (Ostrinia nubilalis Hb) was determined. Purpose. Our research was aimed to conduct a comprehensive evaluation of new maize hybrids for resistance to major diseases and pests in the conditions of the southwestern Forest-Steppe of Ukraine. Methods. The studies was conducted on the fields of Bukovyna State Agricultural Experimental Station of Institute of Agriculture in Carpathian region NAAS in selective crop rotation of NAAS according to generally accepted methods of field experiments, methodical recommendations and handbooks. The resistance of 299 maize hybrids was evaluated, including 125 hybrids in the competitive variety trial and 174 in the preliminary variety trial. Pochayivskyi 190 MV and DB Lada hybrids were used as a standard for comparing early-ripening hybrids, and Orzhytsia 237 MV and DB Khotyn hybrids were used as a standard for comparing mid-early hybrids. Early-ripening hybrids are included in the FAO 180–199, and mid-early hybrids – in the FAO 200–299. Results. Sampling based on hybrids resistance to major diseases and damage by European corn borer will improve grain quality and productivity of newly developed maize hybrids. Highly resistant, resistant and medium resistant to diseases hybrids were identified, which can be recommended for state variety testing: to Fusarium pathogen – 52, 97 and 92 (80.5 %) hybrids, bacteriosis – 143, 106, 38 (95.9 %), white smut – 190, 59, 34 (94.8 %), boil smut – 279, 8, 10 (99.3 %), respectively, and to damage by European corn borer: highest resistant (damage 0–5 %) – 172, high resistant (6–15 %) – 75, and medium resistant (damage 16–25 %) – 35 (94.3 %) hybrids. Conclusion. As a result of multi-year research, a number of maize hybrids, which are characterized by resistance to major diseases and pests and high yielding properties (9.2 t/ha), were bred by the Bukovyna State Agricultural Experimental Station of the Institute of Agriculture in the Carpathian Region of NAAS in co-authorship with breeders of the Institute of Grain Crops of NAAS., Thus, 77 maize hybrids have high resistance to damage by European corn borer, 8 hybrids were distinguished by high resistance to the pathogen of boil smut. In addition, 97 maize hybrids were resistant to Fusarium pathogen. The implementation of these hybrids in production will significantly improve the maize yield in the southwestern Forest-Steppe of Ukraine. For the second year, the early ripe hybrid (FAO 180) DB Tyras, created in co-authorship with the State Institute of Grain Crops of NAAS, is undergoing state variety testing. The hybrid is characterized by high resistance to pathogens of Fusarium, boil smut, the potential yield of which is 13.5 t/ha. Key words: hybrid, maize, natural background, disease, pest, resistance, injury, damage

СТІЙКІСТЬ СУЧАСНИХ ГІБРИДІВ КУКУРУДЗИ ДО САЖКОВИХ ХВОРОБ В УМОВАХ ПІВНІЧНОГО СТЕПУ УКРАЇНИ

The research results of the resistance determination of the maize hybrids (Zea mays L.) of different maturity groups to the affection by boil (Ustilago zeae (Beckm.) Unger) and kernel (Sphacelotheca reiliana (Ruhn) Clint) smuts in the Northern Steppe of Ukraine were provided. During 2016–2018, the experiments were conducted in the fields of the State Enterprise “Experimental Farm “Dnipro” of the State Enterprise Institute of Grain Crops of NAAS. The assessment scale of maize hybrids resistance to smut was given. Over the years of research, 52 samples were analyzed. It was found that the common boil smut was widely distributed in 2016, when the hybrids disease average was 2.7 %; only on plants of DN Burshtyn medium-ripe hybrid the infection was not detected. 2017 was unfavorable for the spread of the disease: only 23 % of maize hybrids of medium-ripe and medium-late ripening groups had smut tumor, the average disease degree was 0.4 %. In 2018, half of the studied samples showed no boil smut symptoms, the average degree of disease was 0.9 %, and DN Galateia middle-early hybrid had a maximum degree of disease – 6.7 %. The analysis of the received data testifies that for years of researches there were most resistant to affection by boil smut such hybrids as: DB Lada, DN Rubin, Dniprovskyi 181 SV, DN Adzhamka, DN Burshtyn, DN Veles, DN Astra, DN Sarmat, DN Bulat, DN Palanok and DN Dnipro, and they belonged to different maturity groups. According to the hybrids resistance scale to boil smut, all studied samples were highly resistant and resistant. The tumor was the most often found on the ears, less often on the stems and other parts of the plant. Regarding kernel smut, the survey results indicated a tendency to increase of the disease spread level in the Northern Steppe. In 2016 a 40 % of hybrid samples was affected by kernel smut with an average affection of 0.9 %; in 2017 these indicators were 71.0 and 3.7 %, and in 2018 – 86.0 and 5.9 %, respectively. Over the years of research, it was determined that the DN Astra middle-early hybrid is the most resistant to kernel smut compared to plants of DN Palanok, DN Vesta, DN Demetra, DN Bulat and Pochaivskyi 190 MV hybrids, which were affected annually. According to the hybrids resistance scale to kernel smut, it was found that in 2016 all samples were in the highly resistant group, and the disease degree did not exceed 10 %. In 2017, more than 10 % of plants of DN Adzhamka, DN Vesta, DN Hetera and DN Nazar hybrids were affected, so they were classified as resistant forms, other samples – as highly resistant. In 2018, only the DN Palanok hybrid was estimated as medium-resistant, 6 hybrids (DB Lada, Pochaiivskyi 190 MV, Nur, Korund, DN Galateia, DN Dnipro) belonged to the resistant group, the rest – to the highly resistant group. Regarding the affected hybrid plants, kernel smut was mainly detected on the ears and partly on the panicles (sometimes simultaneously). It was found that 2016 was favorable for the maize hybrids affection by boil smut, and 2018 – by kernel smut. It was found that the degree of plants affection by smut diseases did not depend on the maturity group of the hybrids. All tested samples are highly resistant and resistant to both types of smut. Key words: hybrids, maize, affection, kernel smut, boil smut.

Productivity and resistance to infection by biotic factors of lines - parental components of mayz hybrids when using biopreparations under irrigation

Purpose and objectives. The purpose was to improve the existing technology of growing parents of innovative maize hybrids on irrigated lands by evaluating the impact of new biologicals on plant diseases, pest infestation and seed yield under irrigation in the Southern Steppe.Materials and methods. The study was conducted in the experimental field of the Institute of Irrigated Agriculture of NAAS in 2019–2020. Factor A – parental lines belonging to various ripening groups (DK 445, DK 411, DK 281, and DK 247) included in the pedigree of hybrids Stepovyi, Skadovskyi, Azov, Arabat, Chonhar, Vira, Oleshkivskyi, Hileia and others bred at the Institute of Irrigated Agriculture of NAAS and the Institute of Grain Crops of NAAS. Factor B - treatment of maize parents with innovative biologicals – Fluorescein BT, Trichopsin BT, Biospectrum BT. The methods were conventional for irrigation conditions and maize breeding studies.Results and discussion. The studied biologicals had positive effects on resistance to fungal diseases. The development of blister smut (Ustilago zeae Beckm.) on early-ripening line DK 281 was influenced by all the biologicals. Fluorescein BТ reduced the disease incidence by 1.9%; Trichopsin BG – by 3.0%; Biospectrum BT – by 3.2%. The incidence of Fusarium head blight was also decreased by biologicals. Biospectrum BT was the most effective agent. The incidence of Fusarium head blight in the lines decreased by 2.8–4.0%. The lowest incidence of Fusarium wilt was recorded in line DK 247 treated with Biospectrum BT – 8.9%. Corn borer infestation was reduced by Trichopsin BT and Biospectrum BT, which have both insecticide/fungicidal and growth-stimulating effects. The reduction in the incidence was 2.3–2.8%, depending on the genotype of the lines. Treatment with biologicals improved the cob structure of the studied lines. Trichopsin BT and Biospectrum BT had the greatest effects on the cob parameters. Due to Biospectrum BT, the cob length increased by 5.2–6.7%, the cob diameter – by 2.0–4.9%, and the cob grain weight – by 3.0–7.1%. The results of measurement of the yields from the parents (maize lines) showed that under irrigation the average performance of the studied maize lines ranged 3.75 to 6.11 t/ha, depending on the genotype of the lines (factor A) and the use of biologicals.Conclusions. It was found that biologicals Fluorescein BT, Trichopsin BT, and Biospectrum BT reduced the damage to maize lines induced by blister smut, Fusarium wilt, and corn borer by 0.9–4.2%. Treatment with Biospectrum BT ensured the highest grain yields from the maize parent, which averaged 4.63 t/ha, the gain in the yield was 0.44 t/ha or 10.5%. Treatment with Trichopsin BT had a positive effect on the yield, which averaged 4.54 t/ha, providing a gain in the yield of 0.35 t/ha or of 8.4%. Treatment with Fluorescein BT increased the yield by 0.14 t/ha or by 3.3%. Biospectrum BT was the most effective agent, which provided a significant reduction in the damage to the maize lines caused by fungal diseases and pests

FIELD ASSESSMENT OF ACCESSIONS FROM THE MAIZE COLLECTION FOR RESISTANCE TO BOIL SMUT

Background. The efficiency of heterotic breeding is determined by reasonable selection of the lines with the best combining abilities and important breeding traits. It is possible to use the variability potential of the majority of traits when the level of resistance to the main diseases and pests is quite high. The most harmful disease of maize is common or boil smut (caused by Ustilago zeae (Beckm.) Unger). The breeding of resistant lines and hybrids of maize is the most rational, cheap and ecologically safe way to fight the disease. The initial stage of breeding work is the identification of pathogen-resistant forms.Materials and methods. In 2017, 594 accessions of six main Zea mays L. subspecies were studied using a score scale against the natural infectious background at the Kuban Experiment Station of VIR. The weather conditions (downpours and abrupt daily temperature fluctuations) were favorable for severe infection of maize plants with the pathogen.Results and conclusion. No disease symptoms were found in 173 accessions; 162 genotypes were affected only slightly. The greatest number of accessions with resistance to boil smut belonged to subsp. indentata (Sturt.) Zhuk. (69.4% of the total studied accessions), subsp. everta (69.2%) and subsp. semidentata (Sturt.) Zhuk. (66.7%). Accessions of subsp. amylacea (Sturt.) Zhuk. were more susceptible to the pathogen than other maize subspecies. The Russian, European and North American local maize varieties and self-pollinated lines had a low infection rate, while the accessions that came to the VIR collection from Asia and South America showed higher rates. After two years of comprehensive studies, the selected forms can be recommended for the use in breeding for immunity.

Stability of self-pollinated corn lines to bubble head with artificial infection in Bukovina

An assessment of the resistance of self-pollinated corn lines to the action of the pathogen of bubble head in an infectious nursery with artificial infection of the onset.
 The result of the research was the isolation of the most tolerant to the damage of bubble head samples that will be used in breeding against resistance to this excitator (Ustilago zeae (Beckm.) Unger).

Influence of fertilizer PRP SOL application in maize on the occurrence of selected diseases and pestsWpływ stosowania nawozu PRP SOL w kukurydzy na występowanie wybranych chorób i szkodników

Summary The aim of this study was to evaluate the effect of fertilizer PRP SOL application on the occurrence of diseases and pests in maize crops grown for grain. The investigation were carried out in the years 2010–2011 at Zlotniki Experimental Station of the Poznan University of Life Sciences, as one-factorial experiment. The control variant were the maize plants conventionally fertilized at the doses: 80 kg P2O5/ha, 120 kg K2O/ha. As a second level factor distributed to the treatments with fertilizers by PRP SOL, applied before sowing plants at the dose 220 kg/ha. Nitrogen fertilization was applied to all variants at the dose 160 kg N/ha. The field observations did not prove a significant influence of applied fertilizer PRP SOL, on the occurrence of selected diseases and pests as compared to the control variant. A large variability in plants infection by common smut, was related to weather conditions. In wet year 2010 the average plants infection with Ustilago zeae Unger was 24.3%, while in the dry year 2011 only 0.3%. The weather conditions also influenced on the number of damaged plants by Ostrinia nubilalis Hbn., and the percentage values ranged from 1.4 to 4.0. In the variants with fertilizers by PRP SOL, noted a trend to lower infection by the fungi of Fusarium and the lower plants lodging.

Increased resistance to Ustilago zeae and Fusarium verticilliodes in maize inbred lines bred for Fusarium graminearum resistance

Preliminary field observations in our maize breeding nurseries indicated that breeding for improved resistance to gibberella ear rot (Fusarium graminearum) in maize may indirectly select for resistance to another ear disease, common smut (Ustilago zeae). To investigate this, we compared the disease severity ratings obtained on 189 maize inbreds, eight of which included our inbreds developed with selection for gibberella ear rot resistance after field inoculation and breeding for 8–10 years. No correlation was found between disease severities for the 189 inbreds but the eight gibberella-resistant lines were consistently more resistant to smut. To further examine this relationship and to determine if these eight inbreds would be useful for developing inbreds with either common smut or fusarium ear rot (F. verticilliodes) resistance, we conducted a Griffing’s diallel analysis on six inbreds of maize, four with high levels of gibberella ear rot resistance representing all of the pedigree groups in our eight gibberella lines, and two with very low levels. Our most gibberella ear rot resistant inbreds, CO433 and CO441, had the lowest disease ratings for all three diseases, the consistently largest general combining ability effects and several significant specific combining ability effects. It was concluded that some inbreds bred specifically for gibberella ear rot would also be useful in breeding for resistance to common smut and fusarium ear rot.

Ustilago maydis, model system for analysis of the molecular basis of fungal pathogenicity

SUMMARY Ustilago maydis, a facultative biotrophic basidiomycete fungus, causes smut disease in maize. A hallmark of this disease is the induction of large plant tumours that are filled with masses of black-pigmented teliospores. During the last 15 years U. maydis has become an important model system to unravel molecular mechanisms of fungal phytopathogenicity. This review highlights recent insights into molecular mechanisms of complex signalling pathways that are involved in the transition from budding to filamentous growth and operate during the pathogenic growth phase. In addition, we describe recent progress in understanding the structural basis of morphogenesis and polar growth in different stages of U. maydis development. Finally, we present an overview of recently identified genes related to pathogenic development and summarize novel molecular and genomic approaches that are powerful tools to explore the genetic base of pathogenicity. Ustilago maydis (DC) Corda (synonymous with Ustilago zeae Ung.)-Kingdom Eukaryota, Phylum Fungi, Order Basidiomycota, Family Ustilaginomycetes, Genus Ustilago. Infects aerial parts of corn plants (Zea mays) and its progenitor teosinte (Zea mays ssp. parviglumis). Maize smut is distributed throughout the world. Disease symptoms: U. maydis causes chlorotic lesions in infected areas, the formation of anthocyanin pigments, necrosis, hyperplasia and hypertrophy of infected organs. Infection by U. maydis can inhibit development and lead to stunting of infected plants. A few days after infection plant tumours develop in which massive fungal proliferation and the formation of the black-pigmented, diploid teliospores occurs. Under natural conditions tumours predominantly develop on sexual organs (tassels and ears), stems and nodal shoots. Tumours may vary in size from minute pustules to several centimetres in diameter and contain up to 200 billion spores. Useful web site: http://www-genome.wi.mit.edu/annotation/fungi/ustilago_maydis/

Spatial and Temporal Variability of Corn Growth and Grain Yield

Effects of factors influencing spatial and temporal variability of crop yields are usually expressed in crop growth patterns. Consequently, monitoring crop growth can form the basis for managing site-specific farming (SSF). This experiment was conducted to determine whether crop growth patterns forecast grain yields. Effects of irrigation rates (50 and 80% evapotranspiration, ET), elevation, soil texture, soil NO3-N, arthropods, and diseases on corn (Zea mays L.) growth and grain yield were evaluated at Halfway, TX, in 1998 and 1999. Data on plant height, leaf area index, leaf dry matter, stem dry matter, and ear dry matter were collected from geo-referenced locations (DGPS). These data were used to derive total dry matter, crop growth rate, and net assimilation rate (NAR). Grain yields at DGPS locations were classified into four distinct clusters. In 1998, a dry season, clusters were strongly influenced by elevation and soil texture. Grain yields were higher at high elevations where water use was high and soil texture was heavy compared with low elevations. Grain yields at low elevations also were reduced by common smut [Ustilago zeae (Beckm.) Unger] that preferred dry conditions. In 1999, a relatively wet season, clusters included areas with different elevation and soil texture combinations. Measured parameters forecast grain yields better in 1998 than in 1999. Differences in NAR were evident before the 12-leaf stage, making NAR a potentially useful measurement for early in-season management decisions. Biomass measurements, for which differences were observed after the 12-leaf stage, also may be used to formulate decisions for both in-season and the following season's management.

Prevalence and Transmission of Seed-Borne Fungi of Maize Grown in a Farm of Korea

Seed-borne fungi of some maize cultivars/lines grown during the months from May to September of 2001, collected from Dongguk University farm, Go Young City, IL Sang Gu, Korea were detected by blotter method. In all six fungi namely Alternaria alternata (Fr.) Keissler, Aspergillus niger Van Tiegh, Fusarium moniliforme Sheldon, Fusarium sp., Penicillium sp. and Ustilago zeae Unger, were found to associated with maize seeds. Prevalence of seed-borne fungi also varied. The highest percentages of seed-borne fungi were recorded with Fusarium moniliforme and the lowest in Penicillium sp. Transmission of all seed-borne pathogens from seeds to seedlings were also detected by test tube seedling symptom test. Among the seed- borne fungi, Alternaria alternata, Fusarium moniliforme and Fusarium sp. produced distinct seed rot and seedling infection symptoms. All the transmitted seed-borne fungi might be caused primary source of infection to the maize crop.

Spatial and temporal variability of corn grain yield: site-specific relationships of biotic and abiotic factors.

Inadequate information on factors affecting crop yield variability has contributed to the slow adoption of site-specific farming (SSF). This study was conducted to determine the effects of biotic and abiotic factors on the spatial and temporal variability of irrigated corn grain yields and to derive information useful for SSF. The effects of water (80% evapotranspiration (ET) and 50% ET), hybrid (drought-tolerant and -susceptible), elevation, soil index (SI)(texture), soil NO3–N, arthropods, and diseases on corn grain yield were investigated at Halfway, TX on geo-referenced locations. Grain yields were influenced by interrelationships among biotic and abiotic factors. Grain yields were consistently high under high water treatment, at higher elevations, and on soils with high SI (high clay and silt). Soil NO3–N increased grain yields when water was adequate. Management zones for variable rate fertilizer and water application should, therefore, be based on information on elevation, SI, and soil NO3–N. The effects of arthropods, diseases, and crop stress (due to drought and N) on corn grain yield were unpredictable. Spider mite (Oligonychus pratensis) and common smut (Ustilago zeae) damage occurred under hot and dry conditions in 1998. Spider mite infestations were high in areas with high soil NO3–N. Moderate air temperatures and high relative humidity in 1999 favored southwestern corn borer (Diatraea grandiosella) and common rust (Puccinia maydis) incidences. Knowledge of conditions that favor arthropods and diseases outbreak and crop stress can improve the efficiency of scouting and in-season management of SSF. Management of SSF can be improved when effects of biotic and abiotic factors on grain yield are integrated and evaluated as a system.

The risk to Australia from Tilletia indica, the cause of Karnal bunt of wheat

In Australia, weather conditions at anthesis are suitable for the infection of susceptible wheat crops by Tilletia indica and Karnal bunt could develop at many locations in Australia. Should the pathogen become established in all suitable locations, and if current world prices were applied to wheat grown in infested areas, the loss to Australia would be about M91M per year. If there were no price discount for uninfested wheat from areas infested with I: indica, the potential loss would reduce to about $295M per year. Thus Kamal bunt is a disease that would cause considerable damage to Australia’s economy through loss of domestic and international markets for our wheat. Current quarantine regulations should minimise the risk of T: indica entering Australia. If T indica becomes established in Australia, eradication is unlikely, based on a comparison of the Australian experience following separate introductions of Ustilago zeae, the cause of boil smut of maize. There is a possibility that T. indica could be contained if it is confined to one or a few regions. Disease management strategies could reduce losses. These would involve the segregation of grain obtained from infested areas from that harvested in disease-free areas, longer rotation between wheat crops in infested areas, and the development of resistant cultivars.

Basidiomycosis: a review of the literature.

The basidiomycosis, fungal infections provoked by basidiomycetes or agaric fungi have been recorded at growing frequencies in the medical literature, especially after the advent of AIDS in 1991. The basidiospores of these fungi, scattered in the atmosphere and transported by winds or air currents, reach the maxillary sinuses through the nasal route, most of the times causing signs and symptoms of chronic sinusitis. Basidiomycetes have also been isolated from sputum, especially Schizophyllum commune. Lesions of the buccal mucosa, brain abscesses, onychomycosis and endocarditis have been described, with a growing interest in this type of deep mycosis on the part of mycologists and infectologists. The present paper reports descriptions of mycetism as well as infectious processes caused by basidiomycetes, such as Schizophyllum commune, Ustilago maydis (= Ustilago zeae) and Coprinus cinereus.

Laboratory and Field Resistance to the European Corn Borer in Maize Germplasm

There is a continuing need to screen maize (Zea mays L.) germplasm for sources of resistance to the European corn borer, Ostrinia nubilalis (Hübner). This study was conducted to determine the resistance characteristics to a univoltine strain of the European corn borer of six groups of maize germplasm and to examine the relationship among resistance characteristics. The groups of germplasm consisted of (i) a latitudinal series of inbred lines; (ii) a set of the indigenous landraces of Mexico; (iii) two Argentina landraces; (iv) two inbred lines used as controls. In addition, a multiple borer resistance population was studied. All germplasm was evaluated for seedling DIMBOA [2,4‐dihydroxy‐7‐methoxy(2H)‐1,4‐benzoxazin‐3(4H)‐one] content, susceptibility to leaf‐feeding (both laboratory and field) and to stalk tunneling by the European corn borer, susceptibility to Gibberella zeae (Schwein.) Petch (stalk rot) and Ustilago zeae (Beckm.) Unger (corn smut), and their ability to mature in the climatic conditions prevailing at Ottawa, ON. The inbred lines were characterized by high resistance to leaf feeding, but susceptibility to stalk tunneling, whereas the indigenous Mexican land races found among the various parameters, including validation of the relation of seedling DIMBOA levels and laboratory leaf‐feeding test with the field resistance to European corn borer. This study confirms the importance of examining broad groups of germplasm when searching for sources of resistance to the European corn borer.

Production of Cuitlacoche [Ustilago maydis (DS) Corda] on Sweet Corn

In parts of central Mexico, galls of common smut, caused by Ustilago maydis (Syn = Ustilago zeae Ung.), on ears of corn (Zea mays L.) are an edible delicacy known as cuitlacoche. Preliminary studies were done to identify methods to increase formation of ear galls on sweet corn. Of 370 sweet corn hybrids evaluated in disease nurseries, 38 hybrids were identified for which incidence of ear galls exceeded 40% in 1987 or 1988 or exceeded 12% in 1990. Inoculation techniques for inducing ear galls were: 1) spraying sporidial suspensions between leaf sheaths and stalks at the sixth to eighth nodes; 2) injecting sporidial suspensions into the sixth to eighth internodes; 3) wounding leaf sheaths at the sixth to eighth nodes with sand, followed by spraying a sporidial suspension into wounds; and 4) wounding leaf sheaths at the sixth to eighth nodes with sand in which teliospores were mixed. Only the sporidial injection technique substantially increased the incidence of smut, but it increased the incidence of stalk, tassel, and leaf galls more than ear galls. Thus, additional research is needed to determine when and how to inoculate with U. maydis to induce the formation of ear galls necessary to commercially produce cuitlacoche and to screen for disease resistance.

Field reactions of maize varieties commonly grown in Australia to boil smut caused by Ustilago zeae

The reactions of 62 hybrid maize varieties and 24 inbred lines to infection by boil smut (Ustilago zeae) were studied in the field in the 1982-83 and 1983-84 seasons. Plants were artificially inoculated and the incidence of disease (DI) was assessed on the plant as a whole and at particular loci (ears, axillary buds above and below the ears, tassels and leaves). A disease severity rating (DSR) was developed based on the mass of galls at various loci relative to plant mass. Of the 86 hybrids and inbreds tested, inbred 25, with a high DI overall and severe disease at all infection loci, was the only variety found highly susceptible to disease. Nevertheless, significant (P < 0.05) differences in susceptibility were detected among other hybrids and inbreds. Thirty-six of the major hybrid varieties were classified by cluster analysis into those with low overall DI (20 hybrids averaging 1.4%), moderate DI (12 hybrids, 5.0%) or high DI (4 hybrids, 9.8%). Hybrids with high DI included GH128, GH390, QK694 and Hycorn 1. Two DSR classes were apparent, high (11.0) and low (6.1). No hybrid had both high DI and high DSR. The hybrids General and PX75 had moderate DI and high DSR, while 9 hybrids had high DSR with low DI. Insufficient data were available for a similar classification of the remaining 26 hybrids. Hybrid E368 had a high DI. Among 13 inbred lines, 12 occurred in a low DI class (average 2.3%) and one in a high DI class (A691N, 14.6%). Only one low DSR class was apparent. Insufficient data were available for a similar classification of the remaining I I inbreds, but GN7, HBc and 25 had high DI, while Y 1 had virtually no disease. Disease incidences at most of the infection loci were highly correlated within varieties, except between ear and tassel or leaf incidences, and leaf and tassel incidences, for which no correlation was apparent. No positive correlation could be found between husk cover of mature ears and boil smut incidence in the ears. Except for the locally selected inbred 25, hybrids and inbreds developed in Australia from old open pollinated varieties had about the same disease incidence and severity as material introduced from the U.S.A. over the last 20 years. An evaluation of screening methods indicated that whorl inoculation increased DI on average only from 0.8 to 2.2%. Disease incidence decreased progressively as sowing date was delayed from November to February.

Estimation of airborne fungal flora by the Andersen sampler versus the gravity settling culture plate: I. Isolation frequency and numbers of colonies

The gravity settling culture (GSC) plate and the sequential impaction cascade sieve volumetric air (SICSVA) sampler devised by Andersen were critically compared in the estimation of airborne fungal flora. One hundred twenty-seven side-by-side simultaneous 15 minute samples were obtained on Mehrlich's medium in Northern California. The SICSVA sampler collected 25 fungal types totaling 14,300 colonies, and the adjacent GSC plates displayed 18 genera in 1,091 colonies. Statistically significant differences in total colonies and frequency of isolation were noted for Penicillium, Alternaria, Aspergillus, Gliocladium, Pullularia, Rhizopus, Saccharomyces, Stemphilium, Ustilago zeae, and other (unidentified) fungi. The capability of the SICSVA sampler to isolate volumetrically in a reproducible fashion numbers of airborne fungal spores was demonstrated. It is suggested that these colonies can be logically grouped into a fraction that generally would lodge in the upper respiratory tract and another fraction which, because of the small spore sizes, would largely be capable of lung penetrance. Both methods demonstrated a capacity to produce falsely negative data, but this was especially true for the GSC plate. The GSC plate method cannot be endorsed for the quantitative evaluation of airborne fungal spores.

Synthesis of enzymes during the germination of fungus spores.

THE hypothesis that the development of an organism is mediated by alterations in its enzyme systems is generally accepted. Illustrative data, however, are scarce, though some changes in rat liver enzymes have been reported1,2. In the fungi, the development from the resting spore to an active growing mycelium is a very dramatic phenomenon. Usually, under proper conditions, the spore swells, produces a germ tube which elongates, branches, and forms a mature mycelium. If any marked changes in the enzyme content of the fungus occurs, one would expect such alterations at some period during germination, before the germ tube was fully formed. A change of this kind was thought to occur during the activation of ascospores of Neurospora crassa by heat3, but this effect could not later be confirmed4. Indirect evidence that the enzymes of a spore can be different from those of mature mycelium can be deduced from the catabolism by Tilletia caries of glucose variously labelled with carbon-14. The spores utilized glucose through the Entner Douderoff pathway, while the mycelium catabolized the sugar through the Embden, Meyerhof, Parnas system and hexose monophosphate shunt5. Results presented here show that in one fungus, Ustilago zeae, specific qualitative and quantitative changes in enzymes content occur during the germination of a spore.

The nature of the widespread soil fungistasis.

SUMMARY: Fungistasis of Conover loam, muck, and hardwood forest soils to conidia of Glomerella cingulata, Fusarium oxysporum f. lycopersici, and Penicillium frequentans was demonstrated by indirect methods such as agar disks, double agar layer plates, and cellophan folds, as well as by direct placement of spores on or in soils. All attempts to extract toxic substances from soil with water or organic solvents failed. Fungistatic volatile substances could not be demonstrated in soil. Redox, pH, and osmotic conditions were not responsible for soil fungistasis. Various lines of evidence led to the conclusion that the so-called widespread soil fungistasis as observed by indirect methods is the result of production of antibiotics by soil microbes growing on the surface of the assay media, and is not due to a reserve of toxic substances in soils. The possibility is suggested that individual fungus spores serve as nutrient microsubstrates in soil and stimulate the rapid growth of soil microbes on their surface or in their immediate vicinity, and that this results in the production of sufficient fungistatic substances to prevent spore germination. Preliminary evidence in support of this suggestion are results with concentrated 50% ethanol washings from teliospores of Ustilago zeae which markedly stimulated growth of mixed soil microbes and of pure cultures of Streptomyces sp. and Pseudomonas sp., known antibiotic producers, in agar media.