Fungal canker agents in apple production hubs of Iran

To identify apple canker casual agents and evaluate their pathogenicity and virulence in apple production hubs including West Azarbaijan, Isfahan and Tehran provinces; samples were collected from symptomatic apple trees. Pathogenic isolates on the detached branches were identified as Cytospora cincta, Diplodia bulgarica, Neoscytalidium dimidiatum and Eutypa cf. lata. E. cf. lata was reported as a potential apple canker causal agent in Iran for the first time based on the pathogenicity test on the detached branches, whereas it caused no canker symptoms in apple trees until 6 months after inoculation. Currently, E. cf. lata seems to be adapted to a single city. C. cincta, D. bulgarica and N. dimidiatum caused canker symptoms in apple trees. “C. cincta” and also “C. cincta and N. dimidiatum” were the most widespread and aggressive apple canker species, respectively, associated with apple canker in Iran. Therefore, they are considered to be the main threat to apple production in Iran and should be carefully monitored. Disease progress curve, area under the disease progress curve and optimum temperatures were determined for mentioned species. It is concluded that the establishment of each species occurs in appropriate areas and times in terms of the optimum temperature for their growth.

Analysis and simulation of plant disease progress curves in R: introducing the epifitter package

The analysis of the disease progress curves (DPCs) is central to understanding plant disease epidemiology. The shape of DPCs can vary significantly and epidemics can be better understood and compared with an appropriate depiction and analysis. This paper introduces epifitter, an open-source tool developed in R for aiding in the simulation and analysis of DPC data. User-level functions were developed and their use is demonstrated to the reader using actual disease progress curve data for facilitating the conduction of several tasks, including (a) simulation of synthetic DPCs using four population dynamics models (exponential, monomolecular, logistic, and Gompertz); (b) calculation of the areas under disease progress curve and stairs; (c) fitting and ranking the four above-mentioned models to single or multiple DPCs; and (d) generation and customization of graphs. The package requires the installation of R in any desktop computer and the scripted analysis can be fully documented, reproduced, and shared. The epifitter R package provides a flexible suite for temporal analysis of epidemics that is useful for both research and teaching purposes.

PENGGUNAAN FORMULA CAIR Trichoderma harzianum T10 BERBAHAN TEPUNG JAGUNG TERHADAP REBAH SEMAI (Pythium sp.) BIBIT MENTIMUN

Penelitian bertujuan untuk: 1) mengetahui konsentrasi tepung jagung yang tepat untuk medium cair Trichoderma harzianum T10, 2) mengetahui pengaruh aplikasi T. harzianum T10 dalam berbagai konsentrasi medium cair tepung jagung terhadap penekanan penyakit rebah semai dan pertumbuhan bibit mentimun. Penelitian dilaksanakan di Laboratorium Perlindungan Tanaman dan di lahan Fakultas Pertanian, Universitas Jenderal Soedirman pada bulan September 2017 sampai Januari 2018. Pengujian in vitro menggunakan Rancangan Acak Lengkap dengan lima perlakuan dan lima ulangan, meliputi perlakuan formula cair medium Potato Dextrose Broth (PDB), formula cair tepung jagung konsentrasi 5, 10, 15 dan 20 g/L. Pengujian in planta menggunakan Rancangan Acak Kelompok dengan 6 perlakuan dan 5 ulangan, membandingkan kontrol dengan tanaman yang diberi perlakuan T. harzianum T10 pada masing-masing formula cair konsentrasi tepung jagung. Variabel yang diamati meliputi kepadatan konidium, masa inkubasi, kejadian penyakit, area under disease progress curve (AUDPC), potensi tumbuh maksimum, daya kecambah, tinggi tanaman, panjang akar, bobot segar akar dan bobot segar tajuk. Hasil penelitian menunjukkan bahwa kepadatan konidium T. harzianum T10 tertinggi pada formula medium cair tepung jagung konsentrasi 20 g/L sebesar 3,67x106 konidium/mL, tetapi belum mampu menyamai medium PDB. Aplikasi T. harzianum T10 yang efektif menekan penyakit rebah semai adalah perlakuan T. harzianum T10 dalam formula cair tepung jagung konsentrasi 15 g/L, yaitu mampu menekan kejadian penyakit 71,43% dan menunda masa inkubasi 35,83%. Aplikasi T. harzianum T10 selain konsentrasi 15 g/L belum berpengaruh terhadap variabel yang diamati dan diukur.

Selection of potato genotypes Solanum tuberosum group Andigena by their tolerance to Phytophthora infestans (Mont.) of Bary

Phytophthora infestans is the most limiting biotic problem of potato crop in Colombia and the world. It is a pathogen that threatens the sustainability of the crop. Therefore, it is necessary to evaluate work collections of potato to identify enotypes that show disease tolerance. The objective of this work was to select genotypes of Solanum tuberosum group Andigena by their tolerance to P. infestans. This study was carried out under conditions of Pasto, in the South of Colombia at 2,820 masl. A total of 76 introductions of guata potatoes were evaluated under natural inoculum, including Capiro as a susceptible control, Betina as moderately tolerant and Pastusa Suprema as highly tolerant. The number of stems and stolons per plant was registered. Disease severity assessments and traits related to the area under the disease progress curve were made. At harvest stage, yield values per plant and its components were recorded. Principal Component and Classification analyses discriminated tolerant introductions of susceptible. Significant positive correlations were found between the yield with the number of stolons, tubers per plant and tuber weight, and negative correlations with everity and area under the relative disease progress curve. The selected introductions showed high yield per plant and mostly minor severities to the population, indicating an agronomic potential that must be evaluated in different environments to determine its adaptability and stability. UdenarStGua53, UdenarStGua61, UdenarStGua68, UdenarStGua73, UdenarStGua75, UdenarStGua77 y UdenarStGua78, coming from the International Potato Center (CIP) are confirmed as a source of tolerance to P. infestans and can be considered as parental within species improvement programs.

Management of the Common Bacterial Blight of the Bean by Rhodotorula glutinis and Sporidiobolus johnsonii

Bean common bacterial blight reduces crop productivity and is difficult to control. However, biological control by yeast can be an efficient complementary measure in management. The objective was to evaluate the ability of Rhodotorula glutinis and Sporidiobolus johnsonii to reduce the severity of bean common bacterial blight. The cultivar used was IAPAR Tuiuiú. The first experiment was sown in March and repeated in October, in a 4 × 3 factorial scheme (zero, one, two and three applications and three treatments R. glutinis, S. johnsonii and Acibenzolar-S-Methyl (ASM)). For this purpose were evaluated the area under the disease progress curve (AACPD), number of pods per plant (NVP), number of grains per pod (NGV), thousand grain mass (MMG) and productivity. For the results of the March cultivation, due to the low temperature, the maximum severity of bean common bacterial blight was 8% and the applications of yeasts were not significant for AACPD. The isolate R. glutinis showed the highest average of productivity with two applications, being 1006.44 kg ha-1. For October cultivation, R. glutinis and S. johnsonii isolates reduced AACPD by 66.84 and 58.42%, respectively with three applications. For productivity, R. glutinis and S. johnsonii showed no difference between the number of applications. The ASM showed a productivity of 4418.56 kg ha-1 with three applications. The results indicate that the yeasts R. glutinis and S. johnsonii reduce the severity of bean common bacterial blight and the most appropriate number of applications are two for both isolates.

Model Selection in Describing Disease Progress Curve of Fusarium Wilt (Fusarium oxysporum F.SP. Sesami) Disease in Sesame Varieties

An epidemic of disease is the progress of the disease in time and space. The objectives of the present study are to understand and compare the four nonlinear models for disease progress curves of five sesame varieties. The regression parameters estimation, standard error, R-square, Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) were estimated. The lowest values of standard error and the highest values of R-square were calculated from the monomolecular model. Also, the result showed that; the disease progress curve better fitted within the monomolecular model for each varieties with the smallest AIC and BIC values. This model is appropriate for modelling epidemics where there is a monocycle within a growing season. The Monomolecular model allows the estimation of the disease progression rate and an area under the disease progress curve was carried out to know the level of reaction to the disease. The lowest rate of fusarium wilt disease was recorded from Hirhir followed by Setit-2. However, the highest value was recorded from Setit-3 followed by Setit-1. A highest value of area under disease progress curve (AUDPC) was calculated from Setit-3. However, the lowest was calculated from Hirhir. Varieties with low disease incidence could be useful in breeding programs aimed at developing varieties with higher resistance to Fusarium wilt disease.

Epidemiological Criteria to Support Breeding Tactics Against the Emerging, High-Consequence Wheat Blast Disease

Plant disease epidemiology can make a significant contribution for cultivar selection by elucidating the principles of an epidemic under different levels of resistance. For emerging diseases as wheat blast (WB), epidemiological parameters can provide support for better selection of genetic resources. Field experiments were conducted at two locations in Bolivia in 2018–2019 to characterize the temporal dynamics of the disease on 10 cultivars with different levels of reaction to WB. Logistic models best (R2 = 0.70–0.96) fit the disease progress curve in all cultivars followed by Gompertz (R2 = 0.64–0.94), providing additional evidence of a polycyclic disease. Total area under disease progress curve (tAUDPC), final disease severity (Ymax), and logistic apparent infection rates (rL*) were shown to be appropriate epidemiological parameters for describing resistance and cultivar selection. Cultivars that showed a high spike AUDPC (sAUDPC) showed a high leaf AUDPC (lAUDPC). tAUPDC, Ymax, and rL* were positively correlated among them (P < 0.01) and all were negatively correlated with grain weight (P < 0.01). Based on the epidemiological parameters used, cultivars that showed resistance to WB were Urubó, San Pablo, and AN-120, which were previously reported to have effective resistance against the disease under field conditions. The information generated could help breeding programs to make technical decisions about relevant epidemiological parameters to consider prior to cultivar release.

Genotype by environment interaction for area under the disease-progress curve (AUDPC) value in spring barley using additive main effects and multiplicative interaction model

The objective of this study was to assess genotype by environment interaction for area under disease progress curve values in spring barley grown in South-West Poland by the additive main effects and multiplicative interaction model. The study comprised of 25 spring barley genotypes (five cultivars: Basza, Blask, Antek, Skarb and Rubinek as well as all possible 10 two-way mixtures and 10 three-way mixtures combinations), evaluated at two locations in 4 years (eight environments) in a randomized complete block design, with four replicates. Area under disease progress curve (AUDPC) value of the tested genotypes ranged from 75.3 to 614.3, with an average of 175.3. In the AMMI analyses, 13.43% of the AUDPC value variation was explained by environment, 37.85% by differences between genotypes, and 18.20% by genotype by environment interaction. The mixture Basza/Skarb is recommended for further inclusion in the breeding program due to its low average AUDPC value (98.8) and is stable (AMMI stability value = 6.65).

Potensi Kolonisasi Mikoriza Arbuskular dan Cendawan Endofit untuk Pengendalian Layu Fusarium pada Bawang Merah

Layu Fusarium merupakan penyakit penting pada bawang merah (Allium cepa var. aggregatum) yang disebabkan oleh Fusarium oxysporum f.sp. cepae. Pada penelitian ini, isolat biokontrol potensial cendawan endofit dan mikoriza diuji kemampuan kolonisasinya secara tunggal dan kombinasi untuk menekan perkembangan penyakit layu Fusarium. Percobaan dilakukan menggunakan rancangan acak lengkap dengan 8 perlakuan dan 5 ulangan. Kemampuan menekan patogen diamati dari persentase kolonisasi agens biokontrol, periode laten penyakit, insidensi penyakit, laju infeksi, dan area under the disease progress curve (AUDPC). Agens biokontrol yang diujikan berhasil bersimbiosis dengan akar tanaman bawang merah. Aplikasi tunggal mikoriza arbuskular paling baik dalam memengaruhi pertumbuhan tanaman dan menekan perkembangan penyakit layu fusarium pada bawang merah dengan periode laten penyakit terpanjang 21 hari dan menurunkan insidensi penyakit hingga 40%.