Reaction of Sweet Cassava Genotypes to Xanthomonas phaseoli pv. manihotis From Three Regions of Brazil

Xanthomonas phaseoli pv. manihotis (Xpm) is the causal agent of Cassava Bacterial Blight (CBB), one of the most important cassava diseases. The aim of this study was to evaluate the susceptibility of sweet cassava genotypes to strains of Xpm from three different geographic regions of Brazil in greenhouse conditions. The inoculation of 14 genotypes of cassava was made by cutting leaflets using scissors previously soaked in a bacterial suspension with 1 × 108 UFC ml-1 and also by inserting a soaked toothpick into the bud of the oldest leaf. The results showed significant differences when the cassava genotypes were individually evaluated in relation to the Xpm strains used; however, the relationship between cassava genotypes and Xpm strains was significant for wilt symptom. The UnB 1111 strain was more aggressive than the UnB 1386 strain based on the average value of the reaction grade, showing the variation that exists between the bacterial isolates from different regions. Considering the reaction of cassava germplasm’s resistance to the three strains used in the study, the BGMC 434 genotype was the only one classified as resistant based on the average reaction grade. The genotypes BGMC 753, BGMC 1289, BGMC 982 and the elite clones BRS 396, BRS 397, BRS 398, 259/08 and BRS 399 were classified as moderately resistant, which indicates the possibility of recommending them for disease favorable regions.

A horizontally acquired expansin gene increases virulence of the emerging plant pathogen Erwinia tracheiphila

Erwinia tracheiphila is a bacterial plant pathogen that causes a fatal wilt infection in some cucurbit crop plants. Wilt symptoms are thought to be caused by systemic bacterial colonization through xylem that impedes sap flow. However, the genetic determinants of within-plant movement are unknown for this pathogen species. Here, we find that E. tracheiphila has horizontally acquired an operon with a microbial expansin (exlx) gene adjacent to a glycoside hydrolase family 5 (gh5) gene. Plant inoculation experiments with deletion mutants in the individual genes (Δexlx and Δgh5) and the full operon (Δexlx–gh5) resulted in decreased severity of wilt symptoms, decreased mortality rate, and impaired systemic colonization compared to the Wt strain. Co-inoculation experiments with Wt and Δexlx–gh5 rescued the movement defect of the mutant strain, suggesting that expansin and GH5 function extracellularly. Together, these results show that expansin–GH5 contributes to systemic movement through xylem, leading to rapid wilt symptom development and higher rates of plant death. The presence of expansin genes in diverse species of bacterial and fungal wilt-inducing pathogens suggests that microbial expansin proteins may be an under-appreciated virulence factor for many pathogen species.

Interaction of Physiology Character - Secondary Metabolic of Fusarium oxysporum on Tomatoes of Fusarium Wilt Symptom

Fusarium oxysporum (F. oxysporum) is the pathogen that caused fusarium wilt diseases on the tomatoes. The rise of the symptom was caused by secondary metabolic produced by F. oxysporum. The associated with the level of secondary metabolic pathogenesis that cause symptoms of wilt on tomatoes, but secondary metabolic excreted by F. oxysporum was not necessarily wilt in a plant. The phenomenon caused F. oxysporum producing secondary metabolic in the different concentration, either its quantity or quality. The nature of physiology being tested, observed by growing 4 isolates using a medium PDA on the temperature of 10, 15, 20, 25, 30, and 35 °C. The content of secondary metabolic measured on the four isolates using the Notz et al., (2002) and analyzed by using High-Performance Liquid Chromatography (HPLC). The results of the analysis of the nature of the physiological (colour colonies) were that every isolate planted for 8 days shows the variation of white, white redness, white yellowness until purpleness. Based on Methuen Handbook of Colour (Kornerup & Wanscher, 1978), generally isolates tested shows a bright colour, signaled with A letter at every code. Analysis HPLC on the results of secondary metabolic, either quantity or quality, sequentially were: isolates BAR (3; 1,997 ppm); ENR (3; 5,105 ppm); SID (4; 2,135 ppm) and MAL (5; 2,065 rpm). If it was seen by the relationship between the colour of colonies with the production of the secondary metabolic compound, it seemed that the older or darker colonies’ colour the more secondary compounds formed, but dark or old colonies’ colour does not determine a high quality of acid fusaric produced. Keywords: Colonies colour, F. oxysporum, secondary metabolic .

INCIDENCE DYNAMIC OF POD ROT DISEASE OF COCOA CLONES IN LAMPUNG, INDONESIA

Incidence dynamic of pod rot disease of cocoa clones in Lampung, Indonesia. The declining of production and productivity of cocoa in Indonesia might due to pests and diseases attacks and planting unselected clones. Dynamic of pod rot incidence was important to plan pest controlling. To study dynamic incidence of some cocoa clones, a research was conducting in Pesawaran District, a centre of cocoa production in Lampung. A farmer cocoa plot under agro-forestry system was selected which had been upgrading in 2014 by pruning and side-grafting with national clones including Sul 1, MCC 1, MCC 2, ICCRI 7 and selected local clone named T1, T2, and T3. The results showed that pod rot incidence occurred along the year of observation. For immature pod, pod rot incidence was dynamic and varied among months and clones. There was high pod rot incidence every months for particular clone. National clone Sul1 and local clone T3 exhibited more tolerant to pod rot disease than other clones. Clones Sul1 and T3 also produced more pod than others. High incidence of pod rot occurred on fruit stage of cherelle (incidence 38.7%) and small pod (incidence 18.8%) that well known as cherelle wilt symptom.

Respon Beberapa Genotipe Kacang Tanah terhadap Penyakit Layu Bakteri (Ralstonia solanacearum) di Rumah Kaca

<p>The objective of the study was to evaluate resistance response of groundnut genotypes against bacterial wilt (Ralstonia solanacearum) in the green house of Biochemistry Department, ICABIOGRAD, Bogor. Ralstonia solanacearum isolate was obtained from groundnut plant showing wilt symptom, collected from Karadenan village (Cibinong). Preparation of bacterial RS inoculum was done using SP (sucrose peptone) medium. Groundnut plants were inoculated by RS isolate using inoculum capacity of 107 cfu/ml. The experiment was arranged in randomized complete block design (RCBD) consisted of seven treatments with four replications, whilst Tupai and Kelinci genotypes were used as resistant and susceptible control check, respectively. The result indicated that groundnut genotypes i.e. ICGV 88262, Local Sindangbarang, PI 203395, ICG 10067, and ICG 3400, showed resistant response against bacterial wilt causing wilt damage of &lt;20%. Bacterial wilt disease could affect reductions of some groundnut phenotypic character. The plant height of resistant groundnut showed relatively tall than that of Kelinci. In addition, it showed the lowest healthy pod yield among the genotypes tested.</p><p> </p><p><strong>Abstrak</strong></p><p>Penelitian bertujuan untuk mempelajari tingkat ketahanan genotipe kacang tanah terhadap penyakit layu bakteri (Ralstonia solanacearum) di rumah kaca Kelompok Peneliti Biokimia BB-Biogen. Isolat R. solanacearum diperoleh dari tanaman kacang tanah yang menunjukkan gejala layu dari Desa Karadenan (Cibinong). Penyiapan dan penyediaan inokulum bakteri R. solanacearum menggunakan media SP (sukrose pepton). Tanaman kacang tanah diinokulasi dengan isolat R. solanacearum dengan kerapatan koloni 107 cfu/ml. Penelitian disusun menggunakan rancangan acak kelompok dengan tujuh perlakuan dan empat ulangan. Untuk pembanding tahan dan rentan masing-masing digunakan genotipe Tupai dan Kelinci. Hasil penelitian menunjukkan bahwa genotipe ICGV 88262, lokal Sindangbarang, PI 203395, ICG 10067, dan ICG 3400 tahan terhadap penyakit layu bakteri dengan nilai kerusakan &lt;20%. Penyakit layu bakteri berpengaruh terhadap penurunan beberapa karakter fenotipik kacang tanah, di mana tanaman genotipe kacang tanah tahan PLB relatif lebih tinggi dibandingkan dengan genotipe Kelinci. Polong bernas Kelinci paling sedikit di antara semua genotipe uji.</p>

Development, Detection, and Elimination of Verticillium dahliae in Mint Shoot Cultures

Roots of greenhouse-grown mint plants and in-vitro-grown shoot cultures were inoculated with Verticillium dahliae Kleb. conidial suspensions to study wilt symptom development and detection and elimination of the fungus. There were significant differences in the symptom expression between control and infected shoot cultures at all conidia concentrations for the four mints tested. Disease-symptom ratings were proportional to the V. dahliae inoculum density. Infected shoot cultures were stunted when inoculated with ≥ 103 conidia/mL. Verticillium dahliae was re-isolated from infected shoot cultures at all levels of inoculum, but not from any control cultures. Verticillium infections were easily detected by plating mint stems on potato dextrose agar. Shoot tips (0.5 to 15 mm) from infected in-vitro- and greenhouse-grown plants were isolated and screened for fungus. The most effective shoot length for fungus elimination was 3-5 mm. Shoot tips isolated from in vitro spearmint cultivars infected at 102 and 103 conidia/mL were 100% Verticillium free, but only 42% of `Black Mitcham' and 54% of `Todd's Mitcham' peppermints were free of the disease. Shoot tips from infected greenhouse plants produced Verticillium-free cultures from 79% of `Black Mitcham' and 90% of `Todd's Mitcham' plants. These results indicate the utility of testing for Verticillium and the safety of micropropagated mint shoots for certified planting stock programs.

Delayed Symptom Development in ein2-1, an Arabidopsis Ethylene-Insensitive Mutant, in Response to Bacterial Wilt Caused by Ralstonia solanacearum

Wilt disease caused by the phytopathogenic bacterium Ralstonia solanacearum is poorly understood at the molecular level. The possible roles of salicylic acid, jasmonic acid, and ethylene, compounds commonly associated with the plant response to pathogens, in wilt symptom development were investigated using various Arabidopsis thaliana mutants in a Col-0 background, an ecotype that develops wilt symptoms in response to the virulent GMI1000 strain. Following root inoculation, wilt symptoms were delayed in ein2-1, an ethylene-insensitive mutant, in response to several virulent strains of the pathogen. In ein2-1, bacteria invade the plant and multiply, reaching concentrations slightly lower than those detected in susceptible plants but 1 to 2 logs higher than in Nd-1, an A. thaliana ecotype resistant to strain GMI1000. This delay in disease symptom development of ein2-1 plants suggests that ethylene signaling plays a critical role in wilt disease development. Furthermore, a strong accumulation of transcripts corresponding to PR-3 and PR-4, two ethylene-responsive genes, was observed in susceptible Col-0 plants, but not in ein2-1 and Nd-1 plants, providing additional evidence for a role of ethylene in wilt symptom production. However, this hormone is probably not involved in the establishment of resistance to R. solanacearum, because homozygous ein2-1 plants in a resistant background remain fully resistant to strain GMI1000.