J. Vraný

The effect of Foliar application of some readily metabolized substances, growth regulators and antibiotics on Rhizosphere microflora

SummaryThe effect of foliar application on the microflora of the wheat root surface grown in nutrient solutions was studied, particularly with respect to the effect of nutrients absorbed and metabolized by the plant (urea, phosphate), of growth regulators (2-methyl-4-chlorphenoxyacetic acid and 2,4-dichlorophenoxyacetic acid) and of antibiotics (chlortetracycline and chloramphenicol). The effect of these substances was more pronounced in influencing the growth of roots than the growth of overground parts. No relationship could be established between the effect on wheat growth and the microbial count on the roots. The bacterial count of the root surface was decreased on applying triiodobenzoic acid and especially on applying chloramphenicol. In the other cases an increase in the number of bacteria was observed, most marked after the application of urea. An indirect proportionality seems to exist between the effect on fungi and on bacteria. After the foliar application of triiodobenzoic acid and chloramphenicol the number of fungi on roots was strikingly higher, while after urea it decreased.Foliar application of triiodobenzoic acid and chloramphenicol was reflected in qualitative changes in the composition of the bacterial flora of the root surface with respect to the occurrence of morphological and nutritional groups and groups with different physiological properties. Quantitative changes in root excretion, particularly on applying chloramphenicol, were observed.The applicability of foliar treatment as a means of controlling rhizosphere microflora is discussed, together with problems bearing on the relationship between foliar application and the rhizosphere effect.Abstractлсследовалось действие на микроϕлору поверхности корней пшеницы, выращиваемой в питательных растворах, внекорневой подкормки следующими веществами: питательные вещества, абсорбируемые и метаболиэируемые растением (мочевина, ϕосϕат), регуляеоры роста (2-метил-4-хлорϕеноксиук сусная кислота и 2,4-дичлорϕеноксиуксус ная кислота) и антибиотики (хлортетрациклин и хлорамϕеникол). Действие этих веществ проявлялось более выраэительно на росте корней, чем на росте листьев. Не наблюдалось корреляции между действием на рост пшеницы и числом микроограниэмов на корнях.Число бактерий на корнях понижалось после применения трийодбенэойной кислоты, а в особенности -хлорамϕеникола. В остальных случаях наблюдалось повышение числа бактерий, наиболее эначительное после нанесения на листья мочевины. Обнаружепа обратная эависимость между действием этих веществ на бактерии и на грибки: после нанесения па лист трийодбенэойрой кислоты или хлорамϕеникола число грибков на корнях было гораэдо больше, после обработки листьев мочевиной ниже.Обработка листьев трийодбенэойной кислотой и хлорамϕениколом отражалась на качестиенных иэменениях состава бактерийной ϕлоры поверхрости корней, а именно на составе морϕологических и троϕических групп и групп с раэличными ϕиэиологическими особенностями. Равным обраэом, были отмечены количественные иэменения в корневых выделениях -в особенности после обработки хлорамϕениколом.Обсуждаются воэможности применения внекорневой подкормки как средства контроля микроϕлоры риэосϕеры, а также вопросы, свяэанные с действием этого мероприятия на эϕϕект риэосϕеры.

Control of microorganisms in the rhizosphere of wheat by inoculation of seeds withPseudomonas putida and by foliar application of urea

After inoculation of wheat seeds with various bacterial strains germination of plants was usually inhibited at first but growth was stimulated later. After inoculation withPseudomonas putida K 11 producing physiologically active compounds the total number of bacteria increased together with the bacteria: fungi ratio in the rhizosphere. These characteristic were further increased after foliar application of urea due to increased root exudation. Dry mass of upper wheat parts was about 15 — 80 % higher in green-house experiments, in which the plants were treated in the two above ways. More reliable results, were usually obtained by bacterization ofP. putida and foliar application of urea as compared with the situation when the seeds were inoculated without the foliar application or, on the contrary, after foliar application without inoculation of the seeds. Only when urea was applied early and in a soil contaminated with the fungusGaeumannomyces graminis var.tritici (causing “take-all” of the wheat) no favourable results could be detected. In these cases the foliar application without inoculation of the seeds was more successful. Symptoms of the disease of wheat roots caused byG. graminis were less frequently observed after the inoculation of the seeds with the strainP. putida K 11 and after the foliar application of urea.

Effect of foliar application of urea on the root microflora

The author studied the effect of the foliar application of urea on the microflora of the wheat root surface in relation to time. The effect of this treatment was manifested in the dry weight of the roots and in the parts above the ground seven days after application. The number of bacteria on the plants increased markedly on the first days after application, while the number of fungi showed a pronounced decrease. In time the differences were equalized. Bacteria requiring amino acids and growth factors predominated on the roots of treated plants, while the main fungi were members of the genusFusarium and in the control plants members of the genusPenicillium.AbstractИсследовалось действие внекорневой подкормки на микрофлору поверхности корней пшеницы мочевины. Подобная обработка растений проявлялась в сухом веществе корней и наземных частей 7 дней после обработки растений: в первые дни после начала опыта количество бактерий у растений выраженно повышалось, тогда как количество грибков значительно понижалось. С течением времени эта разница стиралась. На корнях обработанных мочевиной растений преобладали бактерии, нуждающиеся в аминокислотах и факторах роста, в то время как у грибов преобладали представители рода Fusarium, тогда как у контрольных растений—Penicillium.

Growth and yield of potato plants inoculated with rhizosphere bacteria

Pot and field experiments on small plots were carried out to study the effect of isolates ofPseudomonas fluorescens-putida bacteria, applied to potato tubers, on the growth response of potato plants. Inoculation of tuber pieces with the isolates in pot experiments caused a better growth of young potato plant (111 % increase). The effect depended on the viable count in the bacterial suspension and on growth conditions of the plants. Inoculation of potato seed pieces before planting in field experiments caused a 4 –30 % improvement in plant growth and tuber yield. The complex action of inoculation with rhizobacteria apparently caused changes in the microflora colonizing the roots and stolons, which in turn brought about a better growth and yield.

The effect of foliar application of urea on the root fungi of wheat growing in soil artificially contaminated withFusarium spp.

Repeated treatment of overground parts of wheat with a solution of urea was reflected in an increased count of bacteria and a decreased count of fungi on the roots of plants grown in soil contaminated with the fungusFusarium spp., which is known to be noxious to plants. The occurrence of some fungal genera on the roots of plants growing in contaminated and uncontaminated soil after foliar application of urea was also changed. The roots of treated planted were found to contain more bacteria with a lytic effect and retarding the growth of the fungus used for the contamination. The favourable effect of foliar application of urea on wheat was reflected in an increased dry weight of plants even if growing in a soil contaminated withFusarium.

Rhizosphere mycoflora of wheat after foliar application of chlorocholine chloride, urea and 4-chloro-2-methylphenoxyacetic acid

A single-step spraying of wheat during shooting under field conditions with solutions of CCC (chlorocholine chloride), CCC and urea, CCC and Aminex (ammonium salt of 4-chloro-2-methylphenoxyacetic acid), or CCC, urea and Aminex caused changes both in numbers and composition of the rhizosphere mycoflora. The numbers both in the rhizosphere of differently treated plants and in the free soil decreased during vegetation. A more pronounced effect in the number of fungi was demonstrated in plants treated only with CCC. The difference was more considerable during first 10 days after the spray. As far as the relative occurrence of individual genera in the rhizosphere soil is concerned, fungi of the generaPenicillium Link ex Fr.,Fusarium Link ex Fr.,Verticillium Nees andTrichoderma Pers were most influenced after the treatment with the used agents.

Inoculation of potatoes with microorganisms under field conditions

The effect of inoculation of potatoes with isolates ofPseudomonas putida andTrichoderma sp. suspension and in preparations with kaolin and peat carriers on growth of potatoes, yields and physiological proporties of tubers was investigated on seven locations of the potato-rye and sugar-beet regions. In 57.5% of experiments increased yields could be detected. More favorable results were obtained in the sugar-beet region and on commercially utilized fields when using suspensions of the isolates. Variability of the results can be partially explained by soil-climatic factors affecting colonization of the rhizosphere by the microorganisms and their effect on the environment. Physiological properties and the quality of the harvested tubers were comparable with those of the control. The results are discussed from the point of view of a possible inoculation of potatoes with rhizobacteria and, in the presence ofTrichoderma sp., improvement of their growth and yields.

Changes of microflora of wheat roots after foliar application of urea

Upper parts of wheat grown in containers with brown soil were four-times repeatedly treated with a solution of urea. The foliar application of urea resulted in a considerable increase of the number of bacteria in the roots and a decrease of the number of fungi. Seventeen and 13 genera of fungi could be detected in the rhizosphere of the treated plants, 3 and 5 weeks, respectively, after the application, whereas 23 and 16 genera could be identified in the rhizoplane of the treated plants. Fungi of the generaFusarium andPenicillium predominated in the root region. The foliar application of urea resulted in an increased relative occurrence of the genusFusarium and decreased relative representation of the genusPenicillium. Changes in the relative occurrence of other 18 genera of fungi present in small quantities on wheat roots could also be observed. The foliar application of urea affected not only numbers of fungi determined by the dilution plate method but also the occurrence of active hyphae.

Rhizosphere microflora and colonization of wheat roots by Gaeumannomyces graminis var. tritici after foliar application of urea and benomyl.

The effect of foliar application of 2% urea and 0.6% benomyl on changes in colonization of the rhizosphere by microorganisms and of roots by the fungusGaeumannomyces graminis (Sacc.)Arx etOlivier var.triticiWalker was followed in vegetation glass-house experiments. Treatment with a urea solution resulted in increased counts of bacteria (82 %),Pseudomonas fluorescens (46 %),Agrobacterium sp. (31 %) and antagonistic bacteria with respect to the used fungus isolate and in a decreased occurrence of micromycetes (63 %). Treatment of wheat with a benomyl solution resulted in an increased count of bacteria (43 %) and a decreased occurrence ofP. fluorescens (16 %),Agrobacterium sp. (50 %) and fungi (67 %). After treatment with both compounds the infection of roots byG. graminis considerably decreased as compared with untreated plants. The results are discussed from the point of view of the effect of application of the studied compounds to upper parts of wheat on the microflora colonizing its roots.

Microbial changes in clover rhizosphere after foliar and soil application of cobalt

Application of cobalt(II) nitrate to the leaves of red clover (Trifolium pratense L.) resulted in a pronounced increase of dry weight and the number of root nodules. Counts of bacteria in the rhizosphere, content of ammonia and production of carbon dioxide m rhizosphere soil were also higher, whereas the content of nitrates decreased Differences m the counts of bacteria, aotmomycetes, Azotobaoter, anaerobic bacteria and cellulose decomposing bacteria m the rhizosphere of control and treated plants were not directly related to the way of application of cobalt. GeneraPenicillium, Fusarium andTrichoderma predominated among fungi. The relative occurrence of pemcillia was higher after the application of cobalt, the incidence of fusaria was lower. The effects of foliar and soil application of cobalt on rhizosphere microflora were not identical.