Chemical characters of disease suppressive and conducive soil of Moler on shallot in Brebes Central Java

In the latest years, a disease epidemy of Moler caused by Fusarium oxysporum f.sp. cepae have just occurred in Brebes Central Java. The disease intensity, however, varies between the shallot production lands. Some lands show suppressive with disease intensity lower than 5%, and others are conducive to disease intensity over 50%. It is interesting that in Brebes occur suppressive and conducive soil to moler disease. The suppressiveness may be determined by environmental conditions, including chemical soil characters. This paper reports the chemical character of suppressive and conducive soil to moler disease in Brebes. The evidence shows that the suppressive soil is more fertile than that conducive one. The suppressive soil is chemically characterized by significantly higher organic mineral, C-organic, P-available, K-exchangeable, and Cation Exchange Capacity than that conducive one.

Phenolic Acid-Degrading Consortia Increase Fusarium Wilt Disease Resistance of Chrysanthemum

Soil microbial community changes imposed by the cumulative effects of root-secreted phenolic acids (PAs) promote soil-borne pathogen establishment and invasion under monoculture systems, but the disease-suppressive soil often exhibits less soil-borne pathogens compared with the conducive soil. So far, it remains poorly understood whether soil disease suppressiveness is associated with the alleviated negative effects of PAs, involving microbial degradation. Here, the long-term monoculture particularly shaped the rhizosphere microbial community, for example by the enrichment of beneficial Pseudomonas species in the suppressive soil and thus enhanced disease-suppressive capacity, however this was not observed for the conducive soil. In vitro PA-degradation assays revealed that the antagonistic Pseudomonas species, together with the Xanthomonas and Rhizobium species, significantly increased the efficiency of PA degradation compared to single species, at least partially explaining how the suppressive soil accumulated lower PA levels than the conducive soil. Pot experiments further showed that this consortium harboring the antagonistic Pseudomonas species can not only lower PA accumulation in the 15-year conducive soils, but also confer stronger Fusarium wilt disease suppression compared with a single inoculum with the antagonistic bacteria. Our findings demonstrated that understanding microbial community functions, beyond the single direct antagonism, facilitated the construction of active consortia for preventing soil-borne pathogens under intensive monoculture.

Tillage and rice mill wastes mulch and their effects on soil properties and yield of cassava (Manihot spp.) on a Typic psamment at Abakaliliki, Southeastern Nigeria

The experiment was undertaken using cassava (Manihot spp) to evaluate effects of different tillage practices and mulching (raised mulched bed, raised not mulched bed, flat mulched bed, flat not mulched bed, untilled mulched bed and untilled not mulched bed) on soil properties and cassava sprouting and yield in 2016 and 2017 planting seasons on a Typic psamment in Ikwo, Ebonyi State, Southeastern Nigeria. The experimental study is made up of six treatments, arranged in randomized complete block design and replicated four times. The results indicated significantly (P<0.05) higher (28.18 – 27.16%) GMC in beds mulched than corresponding values (17.10 – 15.26% and 16.20 – 15.10%) obtained in untilled mulched and untilled not mulched beds for both seasons. Results showed that available P, N, Ca and Mg were respectively higher (P<0.05) in mulched raised beds when compared to those of untilled mulched or untilled not mulched beds by 31 – 28%, 32 – 71%, 50 – 33%, 50 – 30%, 89 – 67% and 49 – 26%, 91–71%. At 28 DAP for 2016 and 2017 planting seasons results showed that 90–78% of the planted cassava cuttings sprouted between 14 – 17 days earlier in both tilled mulched beds and tilled not mulched beds compared to untilled mulched or untilled not mulched beds (5 – 48%). These were (P<0.05) 40 – 50% and 47–37% significantly higher in tilled mulched and tilled not mulched beds when compared to untilled mulched and untilled not mulched beds. At harvest (300 DAP), highest cassava tuber yield (7.5–7.3t ha-1 ) were obtained in raised mulched beds for 2016 and 2017. Cassava yields were (p<0.05) higher in raised mulched beds by 60 and 59% compared to their counterparts in untilled not mulched beds for the seasons. These findings imply that rice mill wastes mulch provide a good and conducive soil condition for cassava than unmulched or untilled environment and raised mulched beds provide more robust condition for cassava production relative to other treatments tested in this study

Analysis of the structure of bacterial and fungal communities in disease suppressive and disease conducive tobacco-planting soils in China

To clarify the differences between microbial communities resident in disease suppressive soil (DSS) and disease conducive soil (DCS) in tobacco cultivation, representative soil samples were collected from tobacco plantations in Shengjiaba, China, and the structure and diversity of the resident bacterial and fungal communities were analysed using high-throughput sequencing technology. Our results showed a greater number of operational taxonomic units associated with bacteria and fungi in DSS than in DCS. At the phylum level, abundances of Chloroflexi, Saccharibacteria, Firmicutes, and Planctomycetes in DSS were lower than in DCS, but abundance of Gemmatimonadetes was significantly higher. Abundances of Zygomycota and Chytridiomycota were higher in DSS than DCS, but abundance of Rozellomycota was significantly lower. At the genus level, abundances of 18 bacterial and nine fungal genera varied significantly between DSS and DCS. Relative abundances of Acidothermus, Microbacterium, Curtobacterium, and Colletotrichum were higher in DCS than DSS. The Shannon and Chao1 indices of DSS microbial communities were higher than those of DCS communities. High microbial diversity reduces the incidence of soil-borne diseases in tobacco plantations and promotes the formation of DSSs.

Bacterial, archaeal and micro-eukaryotic communities characterize a disease-suppressive or conducive soil and a cultivar resistant or susceptible to common scab

Control of common scab disease can be reached by resistant cultivars or suppressive soils. Both mechanisms are likely to translate into particular potato microbiome profiles, but the relative importance of each is not known. Here, microbiomes of bulk and tuberosphere soil and of potato periderm were studied in one resistant and one susceptible cultivar grown in a conducive and a suppressive field. Disease severity was suppressed similarly by both means yet, the copy numbers of txtB gene (coding for a pathogenicity determinant) were similar in both soils but higher in periderms of the susceptible cultivar from conducive soil. Illumina sequencing of 16S rRNA genes for bacteria (completed by 16S rRNA microarray approach) and archaea, and of 18S rRNA genes for micro-eukarytes showed that in bacteria, the more important was the effect of cultivar and diversity decreased from resistant cultivar to bulk soil to susceptible cultivar. The major changes occurred in proportions of Actinobacteria, Chloroflexi, and Proteobacteria. In archaea and micro-eukaryotes, differences were primarily due to the suppressive and conducive soil. The effect of soil suppressiveness × cultivar resistance depended on the microbial community considered, but differed also with respect to soil and plant nutrient contents particularly in N, S and Fe.

The effect of susceptible and resistant potato cultivars on bacterial communities in the tuberosphere of potato in soil suppressive or conducive to common scab disease

ABSTRACTConnections between the structure of bacterial communities in suppressive soils and potato resistance to common scab (CS) are not well understood. In this study, one resistant and one susceptible cultivar were grown in a conducive and suppressive field to assess cultivar resistance × soil suppressiveness interactions. The resistant cultivar had a higher Mg content in periderm compare to susceptible cultivar, while suppressive soil had lower pH (5.3 vs 5.9), N, C, P, Ca contents but higher Fe and S compared with the conducive soil. Bacteria and actinobacteria numbers were higher in the conducive soil. Copy numbers oftxtBgene (coding for a pathogenicity determinant) were similar in both soils but were higher in the conducive soil (for periderm samples) and in the susceptible cultivar (for conducive soil samples). Taxonomic microarray analysis and Illumina sequencing of 16S rRNA genes amplicon showed that bacterial community differed between resistant vs susceptible cultivar and to a lesser extend between suppressive vs conducive soil. Bacteria participating in soil suppression belonged toPseudomonadaceae, Bradyrhizobiaceae, AcetobacteraceaeandPaenibacillaceae, while resistant cultivars selected a bacterial community resembling that of the suppressive soil, which was enriched inNitrospiraeandAcidobacteria. Thus, the analysis of soil suppressiveness×cultivar resistance interactions enabled to gain new insight to CS control in the field.IMPORTANCEIt was demonstrated that potato cultivars susceptible and resistant to common scab select differing bacterial community and above that this trait is further modified in suppressive and conducive soil. Common scab severity was diminished by either resistant cultivar or suppressive soil but without additive effect between them. Out of the two factors, potato cultivar had a more significant influence on tuberosphere bacterial community composition than soil. Results highlighted the usefulness of both cultivar resistance and soil suppressiveness traits in understanding and managing disease control of crops.

KERAGAMAN MIKOFLORA TANAH SUPRESIF DALAM MENGENDALIKAN PENYAKIT AKAR GADA PADA TANAMAN KUBIS (BRASSICA OLERACEA L.)

DIVERSITY OF SUPRESSIVE LAND MICROFLORA IN CONTROL OF PALLDER DISEASE IN CUBES PLANT (BRASSICA OLERACEA L.)Cabbage (Brassica oleracea L.) was a vegetable crops cultivated in the highlands to meet the needs of the community vegetable. The main obstacle was the cultivation of cabbage root disease outbreak mace (clubroot), which until now have not found an effective control techniques. Clubroot disease caused by organisms that resemble fungi: Plasmodiophora brassicae Wor. which was the soil inhibitant and soil borne pathogen. Therefore, there must be a way to control environmentally friendly by using suppressive soil, find microbes antagonists related to the cabbage plant habitat in the soil. The results showed that the index of diversity both on suppressive and conducive soil of 1.2304 and 1.2811 respectively, and the index of dominance on the suppressive and conducive soil were 0.6677 and 0.6838. Prevalence micoflora of the suppressive soil amounted to 44.22 % and 43.06 % conducive soil all dominated by Fusarium spp. Microbial antagonist as a potential control of P. brassicae was Trichoderma sp. Based on the analysis in the suppressive soil as much as 171 x 103 cfu /g soil, higher than on the conducive soil to 90 x 103 cfu /g soil.