UJI AKTIVITAS ANTIFUNGAL EKSTRAK DAUN JOHAR (Cassia siamea Lamk) TERHADAP PERTUMBUHAN FUNGI Phytophthora palmivora

Phytophthora palmivora adalah fungi penyebab busuk buah pada tanaman kakao. Kerusakan yang diakibatkan oleh fungi ini adalah menurunya hasil panen hingga 90%. Penelitian ini bertujuan untuk mengetahui adanya pengaruh pemberian ekstrak daun tanaman johar (Cassia Siamea Lamk) terhadap pertumbuhan fungi Phytophthora palmivora. Jenis penelitian ini adalah eksperimental laboratoris dengan metode RAL dengan 3 kali ulangan dan 7 perlakuan. Hasil analisis data menunjukan adanya pengaruh antara konsentrasi ekstrak daun tanaman johar (Cassia Siamea Lamk) terhadap pertumbuhan fungi Phytopthora palmivora dengan berbeda signifikan pada tiap-tiap konsentrasinya. Konsentrasi ekstrak daun tanaman johar (Cassia Siamea Lamk) yang paling efektif adalah 50% dengan rata-rata diameter zona hambat sebesar 1.34 cm.

Daños y hábitos de la polilla Carmenta foraseminis Eichlin en frutos de Theobroma cacao en la zona de Satipo - Perú

La polilla Carmenta foraseminis es la plaga más importante del cultivo de cacao en toda región y su identificación ha sido reciente, por lo que no hay estudios de sus hábitos del insecto, dado a que fueron confundidos anteriormente con enfermedades fungosas; por ello el objetivo fue determinar daños y hábitos de la polilla Carmenta foraseminis Eichlin en frutos de cacao. Se hizo recolecciones en campo entre los meses de marzo a julio, época de mayor producción del cultivo; asimismo se hizo observaciones de los estadios en laboratorio. Los resultados arrojan nuevos comportamientos de la plaga que no han sido descritos por otros autores, sobre todo en cuanto a la larva en el epicarpio, mesocarpio y endocarpio del fruto, de igual modo su asociación con enfermedades fungosas sobre todo con el pseudo hongo Phytophthora palmivora. Se concluye que desde los frutos verdes ya se muestran signos de la presencia de la plaga con la expulsión de excrementos marrones hacia el exterior del fruto, en el penúltimo estadio larval barrena la placenta del fruto y raras veces logra alimentarse de semillas pregerminadas; en el último estadio larval se alimenta del mesocarpio y construye un túnel con una boca circular en el pericarpio cerrado por tejido seco. La prepupa construye un cocón con hilos de seda revestido con excretas marrones; el adulto emerge por la mañana y demora unos 15 minutos en estirar sus alas para emprender vuelo a saltos y luego un vuelo recto sin zumbido.

​Control Activity and Antibiotic Gene Detection of Endophytic Bacteria in Suppressing Cocoa Black Pod Disease (Phytophthora palmivora Butl.)

Background: Black pod rot disease of cocoa caused by (Phytophthora palmivora Butl.) is one of the major diseases on cocoa plantations worldwide. Many attempts have been made to prevent or reduce the infection of pathogens, but they have not provided optimum results. This study aims to detect antibiotic genes in endophytic bacteria that can suppress cocoa black pod disease. Methods: Eight endophytic bacteria were isolated from healthy cocoa pods and twigs that showed potentials in suppressing P. palmivora growth in vitro were used in suppressing of black pod rot disease in vivo tests. Antibiotic biosynthesis-related genes from eight endophytic bacterial isolates were confirmed by using PCR method, which includes phenazine-1-carboxylic (PCA), pyrrolnitrin (PRN), phenazine-1-carboxamide acid (PCN), pyoluteorin (PLT) and 2,4-diacetylphloroglucinol (DPAG/Phl). Result: The endophytic bacteria, 4RSI, 5BR B3 and 2RW B2 isolates showed the highest disease suppressing index to black pod rot disease in vivo, i.e., 70.27%, 70.08% and 56.64%. The isolates 5BR B3 and 2RW B2 DNA yielded PCR product by using PCA primers (1400 bp), PRN primers (700 bp) and DAPG primers (1600 bp), while the 5RSI isolate yield PCR product using PRN primers only. Endophytic bacterial isolates 5BRB3 and 2RW B2 provided partial disease suppression to pod rot disease by inhibit pathogen growth and antibiotic compounds production.

Caracterización de un jardín clonal de cacao (Theobroma cacao L.) en la amazonía peruana

La variabilidad genética de clones de cacao (<em>Theobroma cacao</em> L.), que existe en el jardín clonal de la Estación Experimental Pichanaqui, de procedencia nacional e internacional, plantea la necesidad de realizar una caracterización morfológica a nivel de frutos, con descriptores morfológicos y escalas para cada tipo de tejido colectado, que usaron como auxiliares las siglas, los colores y formas que permitieron diferenciar las características de cada individuo. Las variables evaluadas fueron número de frutos por planta, peso de mazorcas maduras, numero de granos por mazorca, peso de almendras seca por mazorca, peso de 10 semillas secas, presencia de plagas como la Moniliasis (<em>Moniliophthora roreri</em>), Escoba de bruja (<em>Moniliophthora perniciosa</em>), Mancha parda (<em>Phytophthora palmivora</em>), Perforador (<em>Carmenta foraseminis</em>), Chinche amarillo (<em>Monalonium dissimulatum</em>) y calidad organoléptica en pulpa fresca. Además, se evaluaron variables económicas como el ingreso neto del clon por hectárea. Los resultados indicaron que los mejores clones por su productividad, tolerancia media a plagas y enfermedades, rentabilidad y sabor fueron: ICS 1, ICS 60, SCA 6, ICS 39, y TSH 565. En conclusión, se debería fomentar la siembra de estos clones en los productores de la zona a fin de mejorar su competitividad en el mercado local y nacional.

Metalaxyl Resistance of Phytophthora palmivora Causing Durian Diseases in Thailand

Thailand is the leading producer and exporter of durians worldwide. Serious diseases in durians include root rot, stem rot, and fruit rot, which are caused by Phytophthora palmivora, P. nicotianae, and Pythium cucurbitacearum, respectively. Thai farmers have applied fungicides for more than 20 years to control rot, but it remains difficult to control. Thus, the monitoring of fungicide-resistance development in pathogens is important for disease management. Pathogens were isolated from naturally infected durians between 2016 and 2017 in southern Thailand. The sequences of the internal transcribed spacer (ITS) and 5.8S regions of rDNA were used for the identification of their species. Seventeen out of twenty isolates were confirmed to be P. palmivora. All the isolates were tested for mycelium-growth sensitivity to metalaxyl, azoxystrobin, and dimethomorph. The results showed that nine isolates were resistant to metalaxyl with the 50% effective concentration (EC50) higher than 100 mg L−1. By contrast, all the isolates were sensitive to both azoxystrobin and dimethomorph, with EC50 < 1 mg L−1. Metalaxyl-resistant isolates were not controlled (−25.6% to 22.2%) by the treatment of the detached leaves of ‘Monthong’ durian with 100 mg L−1 metalaxyl prior to inoculation, but all the metalaxyl-sensitive and moderately metalaxyl-resistant isolates were better controlled (33.0% to 62.6%). These results clearly indicate that metalaxyl-resistant strains are present in the populations of P. palmivora in Thailand.

An Integrated Disease Management of Oil Palms Affected by Bud Rot Results in Shorter Recovery Times

Bud rot is a limiting disease that affects most oil palm crops destroying thousands of hectares in Latin America. Bud rot (BR) is caused by the oomycete Phytophthora palmivora (Butler). Integrated disease management (IDM) technology has been used to control the disease, which slows down the progress of the disease, allowing palm recovery. However, the effect of this technology on the recovery speed of treated palms is not well known. We studied the time taken for palm recovery from BR under the integrated management approach. The study was carried out on 21 oil palm commercial cultivars dura × pisifera (D × P) and O × G hybrids affected by BR in the Colombian oil palm Central Zone. The analysis included different recovery times (RT), the severity degree, time of the year (wet or dry season), number of reinfections, and cultivar. The RT of bud rot-affected palms ranges from 103 to 315 days, with an average of 202.8 days when an IDM is used. RT was lower than that reported in the diseased palms without IDM (540 days). According to the severity degree, the RT lasted 202 days for severity degree 1, 198 days for severity degree 2, and 222 with severity degree 3 and 4. In comparison, there was no significant difference between dry and rainy seasons in RT. Differences between cultivars were found; however, under IDM, all cultivars showed low RT. The IDM has a positive impact in reducing the RT to BR. Low RT has indirect effects minimizing potential yield losses, improving the number of successfully recovered palms, and reducing the risk of disease dissemination.

Karakterisik Morfologi Enam Isolat Lokal Trichoderma spp. dan Antagonismenya secara In Vitro terhadap Phytophthora palmivora

Penelitian tentang isolat lokal Trichoderma spp. bertujuan untuk menemukan karakteristik morfologi enam isolat lokal Trichoderma dan mengkaji daya antagonismenya terhadap Phytohpthora palmivora sebagai patogen busuk buah dan kanker batang kakao. Karakterisitik enam isolat lokal Trichoderma spp. asal rizosfer tanaman memiliki karakteristik yang agak berbeda, baik bentuk dan warna koloninya, tetapi juga pertumbuhannya, serta karakteristik morfologinya yang dibedakan berdasarkan ukuran panjang konidiofor, panjang fialid dan diameter konidia. Lima isolat Trichoderma spp. memiliki daya antagonisme terhadap P. palmivora. Enam isolat memiliki daya antagonis terhadap patogen P. palmivora yakni TrichoRKT1, TrichoRKlT2, TrichoRPBS2, TrichoRKlS1, TrichoRKA2 dan TrichoRPKl2. Presentase antagonisme terbesar juga terjadi pada isolat TRichoRKT1 (78,98%) dan TrichoRPKT1 (77,67%), keduanya tergolong antagonis kelas 2 atau aktifitas antagonis tinggi. Trichoderma spp. ditemukan memiliki mekanisme antagonisme kompetisi terhadap P. palmivora.

A Jacalin-like lectin-domain-containing protein of Sclerospora graminicola act as an apoplastic virulence effector in plant–oomycete interactions

SUMMARYThe plant extracellular space, including the apoplast and plasma membrane, is the initial site of plant– pathogen interactions. Pathogens deliver numerous secreted proteins, called effectors, into this region to suppress plant immunity and establish infection. Downy mildew caused by the oomycete pathogen Sclerospora graminicola (Sg) is an economically important disease of Poaceae crops including foxtail millet (Setaria italica). We previously reported the genome sequence of Sg and showed that the Jacalin-related lectin (JRL) gene family has significantly expanded in this lineage. However, the biological functions of JRL proteins remained unknown. Here, we show that JRL from S. graminicola (SgJRL) functions as an apoplastic virulence effector. We identified eight SgJRLs via protein mass spectrometry analysis of extracellular fluid from S. graminicola-inoculated foxtail millet leaves. SgJRLs consist of a Jacalin-like lectin domain and an N-terminal putative secretion signal, and SgJRL expression is induced by Sg infection. Heterologous expression of three SgJRLs with N-terminal secretion signal peptides in Nicotiana benthamiana enhanced the virulence of the pathogen Phytophthora palmivora inoculated onto the same leaves. Of the three SgJRLs, SG06536 fused with GFP localized to the apoplastic space in N. benthamiana leaves. INF1-mediated induction of defense-related genes was suppressed by co-expression of SG06536-GFP. These findings suggest that JRLs are novel apoplastic effectors that contribute to pathogenicity by suppressing plant defense responses.