Root Rot Soil Research Articles

Вплив седаксану на ріст і стійкість сіянців сосни звичайної до інфекційного вилягання та ґрунтової посухи

Visn. Hark. nac. agrar. univ., Ser. Biol., 2019, Issue 2 (47), pp. 82-91 INFLUENCE OF SEDAXANE ON GROWTH AND RESISTANCE OF SEEDLINGS OF SCOTCH PINE TO ROOT ROT DISEASE AND SOIL DROUGHT Yu. V. Karpets, M. A. Shkliarevskyi Dokuchaev Kharkiv National Agrarian University (Kharkiv, Ukraine) Sedaxane

Research on bacteria microecology in root rot rhizosphere soil of Coptis chinensis produced in Shizhu city

Illumina Hiseq 2500 high-throughput sequencing platform was used to study the bacteria richness and diversity, the soil enzyme activities, nutrients in unplanted soil, root-rot and healthy rhizophere soil of Coptis chinensis for deeply discussing the mechanism of the root-rot of C. chinensis. The high-throughput sequencing result showed that the artificial cultivation effected the bacteria community richness and diversity. The bacteria community richness in healthy and diseased rhizosphere soil showed significant lower than that of in unplanted soil (P<0.05) and declined bacteria diversity. The bacteria community richness in root-rot rhizosphere soil increased significantly than that of health and unplanted soil and the diversity was lower significant than that of unplanted soil (P<0.05). The results of soil nutrients and enzyme activities detected that the pH value, available phosphorus and urease activity decreased and the sucrase activity increased significantly (P<0.05). The content of organic carbon and alkaline hydrolysis nitrogen the catalase and urease activity in root rot soil samples was significantly lower than that of healthy soil samples (P<0.05). However, the contents of available phosphorus and available potassium were significantly in root-rot sample higher than that of healthy soil samples (P<0.05). Comprehensive analysis showed that the artificial cultivation declined the bacteria community richness and diversity. The bacteria community richness decreased significantly and the decreased diversity may be the cause of the root-rot. Meanwhile, the decrease of carbon and the catalase activity may be another cause of the root-rot in C. chinensis produced in Shizhu city, Chongqing province.

Evaluation of the forma specialis concept in Aphanomyces euteiches

One hundred and fifty-seven isolates of Aphanomyces euteiches were collected for comparison of morphology and pathogenicity. Pea, alfalfa or snapbean were used as baits for 140 isolates, 17 were collected using other crop and weed species. Isolates were tested for pathogenicity to seedlings of pea, alfalfa, snapbean, red clover and sugarbeet, and disease severity was rated with the aid of a five-class scale (1–5). Half of the isolates caused disease severity A. cochlioides . Ninety-five per cent of the isolates caused disease severity > 2·5 on alfalfa. Five per cent of the isolates were weakly virulent to both pea and alfalfa, but were morphologically similar to A. euteiches . Only one isolate was observed in the collection which matched the description of A. euteiches f.sp. phaseoli , and two isolates were highly virulent to red clover. Somatic segregation for virulence was also observed among cultures recovered from single zoospores of a broad host-range isolate. Such cultures differed from the parent isolate in virulence to every host except alfalfa. A relationship was found between the cropping history of agricultural soils and host specialization of isolates baited from such soils. Only 20% of the isolates baited from alfalfa root-rot soils were virulent to both pea and alfalfa, whereas 80–100% of the isolates from pea root-rot soils, and pea/alfalfa root-rot soils were moderately to highly virulent to both hosts.

Effects of soil pasteurization on root rot, seedling survival and plant dry weight of subterranean clover inoculated with six fungal root pathogens

Subterranean clover was exposed to two levels of inoculum of millet seed colonized by Fusarium avenaceum, Fusarium oxysporum, Phoma medicaginis, Phytophthora clandestina, Pythium irregulare, or Rhizoctonia solani within pasteurized and unpasteurized field soil from sites with (root rot site) and without (virgin site) a history of subterranean clover root rot at Augusta, W.A., with the aim of establishing their pathogenicity in the presence of other soil organisms including resident pathogens. Introduction of F. avenaceum (2.5% w/w), P. clandestina (0.5 and 2.5%), P. irregulare (0.5 and 2.5%), or R. solani (0.2 and 1.0%) increased damage to tap and lateral roots of subterranean clover in pasteurized and unpasteurized root rot and virgin soils. All fungi tested, with the exception of P. medicaginis (2.0 and 10.0%) or P. medicaginis (2.0 and 10.0%) and F. oxysporum (0.5 and 2.50%), caused reduction of seedling survival in pasteurized root rot and virgin soils respectively. When the soil was unpasteurized, all fungi except F. oxysporum (2.5%) and P. medicaginis (2.0 and 10*0%) in virgin soil, but only P. irregulare (2.5%) or R. solani (0.2 and 1.0%) in root rot soil, reduced seedling survival. In unpasteurized soils plant dry weight was reduced by P. clandestina (2.5%), P. irregulare (0.5 and 2.5%), or R. solani (0.2 and 1.0%) in root rot and virgin soils, but F. oxysporum (0.5%) reduced plant size only in the root rot soil. Within pasteurized soil all fungi, with the exception of P. medicaginis (2.0 and 10.0%) in virgin soil and F. avenaceum (2.5%), P. irregulare (0.5 and 2.5%), or R. solani (0.2%) in root rot soil, caused reduction in plant size. P. clandestina, P. irregulare or R. solani, in particular, and to a lesser extent, P. avenaceum, are capable of causing serious damage to subterranean clover in natural soil.

Selected Chemical and Physical Properties of Soils Manifesting Cotton Root Rot1

AbstractSome soils that produce cotton (Gossypium spp.) that is free of Phymatotrichum omnivorum are physically adjacent to similar soils on which cotton annually succumbs to the fungus. This study evaluated relationships of soil properties to incidence of cotton root rot (CRR) at 26 sites. Complete pedon descriptions were made, and horizons were sampled and analyzed to determine selected physical and chemical soil properties. Means of soil analyses for non‐root rot (NRR) and root rot (RR) soil groups were compared by t‐test using the weighted averages for the surface horizons, upper 0.50‐m and 1.0‐m sections. Physical properties were not suitable indicators of disease incidence; however, extractable Mg2+ within land resource areas was found to be significantly greater in NRR‐affected rather than RR‐affected soils. Furthermore, the ratio of extractable Ca2+ to Mg2+ was found to be greater in RR soils than NRR soils. X‐ray analysis of the soil carbonates did not indicate that the differences were the result of differential Mg contents of the soil carbonates. In addition to Mg2+, mean extractable Fe2+, Zn2+, and Cu2+ were found to be greater in NRR soils in some cases. The soluble bicarbonate ion content of surface horizons was also found to be higher in RR soils than NRR soils. Results suggest that cotton grown in RR soil is more stressed than that grown in adjacent NRR soil.

Influence of P and K fertilization on Phytophthora root rot or excess soil water injury of alfalfa cultivars

Abstract Phytophthora root rot (PRR) is an important disease of alfalfa (Medicago sativa L.) in wet soils. Excess soil water (ESW) stress is required for the successful infection and development of PRR. The effects of P at 0, 40, and 80 μg.g‐1 soil and K at 0, 120, and 240 μg.g‐1 soil (in factorial combinations) on the severity of PRR or ESW stress was investigated on a PRR‐susceptible (Iroquois) and a resistant (Oneida) alfalfa cultivar in a greenhouse trial. P and K applications significantly increased the dry weight of tops prior to imposition of PRR or ESW stress. However, plants subjected to PRR or ESW stress did not respond significantly to P or K and there was no significant effect of P or K on the severity of PRR or ESW injury. The plants subjected to PRR or ESW stress had lower tissue P concentration than those under stress‐free conditions. Increasing P additions resulted in a significant increase in P concentration of Iroquois plants, while in Oneida the response was non‐significant. The respons...

Effect of 2-chloroethylphosphonic acid and gibberellic acid on survival of tall and dwarf peas grown in root rot soils

Seeds of peas, Pisum sativum L. varieties Alaska and Early June, were soaked for 3 hours in 2.3 × 10−3 M 2-chloroethylphosphonic acid (CEPA) or 3 × 10−5 M gibberellic acid (GA3), sown in steamed or root rot soils, and grown to flowering stage at controlled soil temperatures with 14 hours per day of 32 000 lumens per square meter. CEPA delayed emergence and decreased survival in var. Alaska, but increased survival in var. Early June between 14 C and 18 C. GA3 decreased survival in both varieties. Early emergence was followed by increased wilting. CEPA showed antigibberellin activity, in most instances counteracting the adverse effects of GA3.

Influence of soil temperature on the development of pea root rot

Pisum sativum vars. Early June, Early Sweet, and Sweet were grown in five root-rot soils and a sterilized control soil maintained at 28°, 26°, 24°, 22°, 18°, 16°, 14°, and 10 °C. Light intensity, day length, and soil moisture were kept constant. Data were recorded from seeding to mature plant development on loss of seed weight, gain in plant weight and height, losses due to preemergence killing and postemergence wilting, lesioning on the subterranean part of the epicotyls, and the fungi and nematodes found associated with the diseased tissues. Results showed that soil temperature generally, with distinct exceptions, had a definite influence on the growth of the peas, according to varieties, in the root rot soils. One fungus predominated as the causal agent of root rot for each variety: Fusarium spp. for var. Early June, which was highly tolerant to root rot soil, and Rhizoctonia solani for Early Sweet and Sweet, which were later maturing varieties. Pythium spp. was also involved in the root rot. The number of seedlings lost as a result of preemergence killing showed greater variation in relation to pea variety and root-rot soil than soil temperature, but postemergence wilting was correlated more closely with soil temperature. The variety Early Sweet was so susceptible to root rot over a wide range of soil temperatures as to preclude its general use in pea-growing areas.

Fungistasis as a factor in the rhizosphere phenomenon.

IN the course of work in progress on soil inhibitory factors, it has been observed that the spores of certain fungi which are unable to germinate when introduced into fresh fertile soil on glass slides coated with 0.5 per cent peptone in 2.0 per cent agar, owing to the presence in the soil of a fungistatic factor, may germinate readily when seedling roots grow in their immediate vicinity, that is, within a distance of some 2 mm. This observation has been made with conidia of Gliocladium roseum and Paecilomyces marquandii on glass slides buried beneath germinating peas so that the seedling roots grew into contact with the slides; and also with Fusarium solani and two unidentified isolates of Fusarium in similar experiments using seedlings of pea, wheat and lettuce. Fusarium solani and one of the unidentified Fusaria show peculiar behaviour; in the presence of soil their conidia germinate normally, but usually produce terminal chlamydospores on short germ tubes and cease further development. Park1 has reported similar formation of chlamydospores by Fusarium roseum in response to an inhibitory factor produced by Bacillus macerans. In the presence of seedling roots the chlamydospores germinate and growth is resumed (Fig. 1). According to the abstract of a thesis by Burke2 on root rot of Phaseolus vulgaris, Fusarium solani f. phaseoli may exhibit the same type of behaviour in naturally infested root-rot soils. It has further been observed with Gliocladium roseum and with the Fusaria studied that the germ tubes show a strong tropic growth towards the roots, although those of Paecilomyces marquandii do not appear to show such directed growth.

ROW TREATMENT OF SOIL WITH TETRAMETHYLTHIURAM DISULPHIDE FOR CONTROL OF BLACKROOT OF SUGAR-BEET SEEDLINGS. I. GREENHOUSE TESTS

The prevention of blackroot of sugar-beet seedlings has been attempted in greenhouse experiments, by row applications of different proprietary compounds to naturally-infested field soils representing three distinct types and differing biologically with respect to associated pathogens.Segmented seed, var. U.S. 215 × 216, was used in all the tests as was also a standard, commercial fertilizer. In earlier trials, the chemical under test and the fertilizer were added separately to a measured volume of rootrot soil. In later trials, the chemical mixed with the fertilizer was incorporated with the soil by a method approaching more closely that employed in field practice. The two procedures, designated as the precision and the surface application method, respectively, are described in detail. Calculations for the requisite amounts of chemical and fertilizer were made on the basis of sugar-beet rows in the field being spaced 22 in. apart, i.e., 23,760 linear feet of row per acre.Tetramethylthiuram disulphide (50%, nonwettable), when applied as Arasan or D-419 at the rate of 3 to 4 lb. per acre, consistently proved to be by far the most effective of the chemicals tested, in reducing pre- and postemergence black-root. Arasan, which was investigated more intensively than any of the other chemicals, was found (a) to retain its fungicidal capability after being mixed for as long as 14 months with a commercial fertilizer, (b) to be effective in reducing the incidence of the disease in three quite different types of soil, and (c) to remain effective in the soil over relatively long periods of time. These beneficial effects are contingent, however, upon correct placement of the chemical, best results having been obtained when the seed germinated in, and the seedlings grew up through, soil impregnated with the Arasan–fertilizer mixture. Up to 21 °C., Arasan, at a rate as high as 4 lb. per acre, will, in a moderately wet soil, effectually control the disease without injury to the seedlings. At 27° to 29 °C., moderate injury to roots and lower hypocotyl resulted from a 3 lb. per acre application of the chemical and, following a 4 lb. application, root and hypocotyl injury was accentuated, typical foliar symptoms appeared, and mortality of seedlings was appreciable.Of the other chemicals tested, 2,4,5-trichlorophenyl acetate (Mycotox No. 1), 20% copper trichlorophenate (C-119), 50% 2,4,5-trichlorophenyl chloroacetate (F-800), and a product of undisclosed chemical composition (CCH-358 or 358A) showed encouraging possibilities.

THE MICROBIOLOGICAL BALANCE OF STRAWBERRY ROOT ROT SOIL AS RELATED TO THE RHIZOSPHERE AND DECOMPOSITION EFFECTS OF CERTAIN COVER CROPS

Soybean and red clover, grown as cover crops and incorporated into strawberry root rot soil, showed a marked difference in ability to control the disease on variety Premier. Soybean caused a striking reduction in the incidence of root rot and a drastic shift in the bacterial equilibrium of the soil. Red clover had little effect on the severity of the disease or the general microflora of the soil.A study of "rhizosphere effects" reveals that the characteristic differences between the resultant bacterial equilibrium of the soils in which the two leguminous plants were grown, could not be attributed to influences exerted by the latter in the living state. However, the bacterial types favoured during decomposition in experimental cultures of tissues of red clover and of soybean, each inoculated with root rot soil, were identical with those isolated from root rot soil with which red clover and soybean, respectively, had been incorporated. In contrast to the putrefactive decomposition of red clover, soybeans apparently underwent a carbohydrate breakdown that could be reproduced essentially in culture by the substitution of glucose for soybean tissues. Beneficial changes in the bacteriology of actual root rot soils could be induced by the decomposition of pure carbohydrate in place of soybean. The favourable alteration in the bacterial equilibrium was accompanied by a corresponding modification of the fungous flora such that potentially pathogenic forms were replaced by presumably innocuous ones. These carbohydrate treated soils were capable of producing strawberry plants with well developed healthy root systems. The ability of soybean to control strawberry root rot therefore seems to depend primarily on a carbohydrate type of breakdown in diseased soil, causing a highly favourable shift in the microbiological equilibrium. The decomposition of red clover, on the other hand, did not under the same conditions induce these salutary effects.

STRAWBERRY ROOT ROT IN RELATION TO MICROBIOLOGICAL CHANGES INDUCED IN ROOT ROT SOIL BY THE INCORPORATION OF CERTAIN COVER CROPS

Strawberry plants, variety Premier, were grown in naturally-infected root rot soil in which consecutive "crops" of several agricultural plants had been turned under, and in other lots of the same soil that had been steam sterilized or fertilized with barnyard manure. On examination of their roots it was found that the incidence and severity of root rot were closely correlated with soil treatment. Plants grown in sterilized soil remained free from disease as did those of the soybean series until the third season when they were slightly affected. Plants in the manure, corn, red clover, timothy, and untreated soil series all became diseased, the severity of attack increasing in the respective series in the order named.Although roots of the various cover crops were found to contain representatives of several different genera of fungi, a specific fungus was dominant in each as was the nematode, Pratylenchus pratensis, in timothy and clover. This build-up of specific organisms appeared to be correlated with the incidence and severity of the disease in the roots of the strawberry plants that followed in the respective series.However, in strawberry plants grown in the variously treated soils, fungal infection was negligible and, on the whole, not related to that of the preceding cover crop. An exception to this was the heavy infection by the mycorrhizal fungus (Rhizophagus sp.?), following timothy and corn, but a lack of correlation, in many cases, between the presence of the fungus and discoloured and necrotic tissue indicated that other agencies might be responsible for the injury. In timothy and red clover treated soils, nematodes, particularly Pratylenchus pratensis, might have been an important factor.Fewer bacteria were found adjacent to roots of healthy plants than to those of diseased ones. Qualitative differentiation on the basis of nutritional requirements indicated a striking relationship between the incidence of certain groups of bacterial isolates and the severity of disease attack. The equilibrium between presumably "harmful" bacteria and the innocuous, normally occurring rhizosphere types is designated the Bacterial Balance Index. There are marked differences in the microbiological equilibria of the different soil series; increased severity of root rot is associated with a fall in the Bacterial Balance Index.