Antifungal Activities of Ageratum conyzoides L. Extract against Rice Pathogens Pyricularia oryzae Cavara and Rhizoctonia solani Kühn

Blast disease and sheath blight disease caused by infection with Pyricularia oryzae and Rhizoctonia solani, respectively, are serious fungal diseases in paddy fields. Although synthetic fungicides have been used to control these diseases, the development of ecologically friendly alternatives is required because fungicides can cause health problems and environmental pollution. Natural herbs possessing antifungal activities are among the candidates as alternatives. Ageratum conyzoides is known to contain antifungal compounds, such as precocene II and polymethoxyflavones. Here, we report the antifungal activities of five compounds isolated after ethanol extraction from Ageratum conyzoides against Pyricularia oryzae and Rhizoctonia solani in vitro. Further, we demonstrated the protective effect of the extract on rice from Pyricularia oryzae infection by field trial testing in a shaded net-house.

In Vitro Evaluation of Trichoderma asperellum Isolate UGM-LHAF against Rhizoctonia solani Causing Sheath Blight Disease of Rice

Trichoderma spp. is a fungus widely used to control soil-borne pathogens, such as Rhizoctonia solani which is plant pathogenic fungi in widely host range, especially on rice. This research aimed to evaluate the ability of Trichoderma asperellum isolate UGM-LHAF against R. solani causing sheath blight disease of rice in vitro condition. Trichoderma sp. used in this research was obtained from The Biological Laboratory of Pakem, Yogyakarta, Indonesia, and Rhizoctonia sp. was obtained through isolation of diseased rice obtained from rice fields in Yogyakarta. The two isolates were characterized base on morphology and molecular identification based on ITS rDNA. The pathogenicity test of Rhizoctonia sp. was evaluated by adding four sclerotia of Rhizoctonia sp. near rice roots at 6 days after sowing. The in vitro test used dual culture and antifungal activity (0%, 10%, 25%, 50% culture filtrate of Trichoderma sp.) with three replicates of each treatment. Two isolates were identified as T. asperellum and R. solani. Sheath blight symptoms appeared after 12 days inoculation. In the in vitro test, T. asperellum isolate UGM-LHAF was able to inhibit the mycelial growth of R. solani (64.23% on dual culture and 68.5% on antifungal activity). This study suggests that T. asperellum isolate UGM-LHAF able to inhibit the growth of R. solani and can be a further potential candidate as a biocontrol agent against R. solani causing sheath blight disease of rice.

The Relationship between Sheath Blight Disease Incidence, Disease Severity, and Rice Yield

Produksi padi dapat mengalami penurunan akibat gangguan oleh penyakit hawar pelepah yang disebabkan oleh Rhizoctonia solani. Penelitian bertujuan memperkirakan penurunan hasil padi akibat penyakit hawar pelepah berdasarkan keparahan penyakit yang terjadi pada stadium masak susu. Penelitian dilaksanakan di rumah kawat dan lahan percobaan Balai Besar Penelitian Tanaman Padi pada musim hujan 2019/2020. Penelitian di rumah kawat menggunakan tiga varietas padi yaitu “Ciherang”, “Inpari 32 HDB”, dan “Baroma”; sedangkan penelitian di lahan percobaan menggunakan “Ciherang”. Inokulasi R. solani dilakukan pada tanaman padi stadium anakan maksimum dengan menyisipkan tanaman terinfeksi sebagai sumber inokulum penyakit diantara rumpun padi pada tingkat insidensi antara 5%–50%. Tingkat keparahan penyakit pada tanaman di rumah kawat dan lahan percobaan terus berkembang selama periode pengamatan dan mencapai berturut-turut 60.09% dan 70.56%. Lebih lanjut, keparahan penyakit yang tinggi menyebabkan penurunan hasil yang tinggi pula. Pengetahuan tentang hubungan insidensi dan keparahan penyakit bermanfaat dalam menentukan prediksi hasil sehingga pengendalian penyakit dapat dilakukan sedini mungkin untuk menghindari kehilangan hasil yang tinggi.

Loose Plant Architecture 1-Interacting Kinesin-like Protein KLP Promotes Rice Resistance to Sheath Blight Disease

Background Sheath blight disease (ShB) is a destructive disease affecting rice production. Previously, we have reported that Loose Plant Architecture 1 (LPA1) promotes resistance to ShB. However, the mechanisms by which LPA1 confers resistance against this disease have not been extensively investigated. Notably, interactors that regulate LPA-1 activity remain elusive. Findings In this study, we identified the interaction of kinesin-like protein (KLP) with LPA1 in the nucleus of rice cells by yeast two-hybrid, bimolecular fluorescent complimentary (BiFC), and co-immunoprecipitation (co-IP) assays. To investigate the role of KLP in promoting resistance to ShB, wild-type, klp mutant, and KLP overexpressor (KLP OX) rice plants were inoculated with Rhizoctonia solani AG1-IA. The results indicated that, compared with the wild-type control, klp mutants were more susceptible while KLP OX plants were less susceptible to ShB. Since LPA1 transcriptionally activates PIN-FORMED 1a (PIN1a), we examined the expression of 8 related PIN genes. The results showed that only the expression of PIN1a and PIN3b coincided with KLP expression levels. In addition, a chromatin immunoprecipitation (ChIP) assay showed that KLP bound directly to the promoter region of PIN1a but not of PIN3b. Transient expression assays confirmed that LPA1 and KLP transcriptionally activate PIN1a, and that coexpression of KLP and LPA1 had an additive effect on the activation of PIN1a, suggesting that KLP enhances LPA1 transcriptional activation activity. Conclusions Taken together, our results show that KLP is a novel LPA1 interactor that promotes resistance of rice to ShB.

Biological Control of Rice Sheath Blight Disease (Rhizoctonia solani) Using Bio-pesticides and Bio-control Agents

A series of experiments were conducted in Plant Pathology Laboratory at Bangladesh Rice Research Institute (BRRI), Gazipur to know the efficacy of four bio-pesticides Recharge, Microtech1, Agroplus and Chitin and two bio-control agents (Trichoderma harzianum and Bacillus subtilis) on the major rice disease sheath blight (ShB) caused by Rhizoctonia solani in in-vitro and field condition. One fungicide Nativo (Tebuconazole 50% + Trifloxystrobin 25%) and one disease control (without any treatments) were also included as treatment for comparison. Radial mycelia growth of R. solani was mostly inhibited by a Bangladesh Trichoderma harzianum (BT1), Recharge and chemical fungicide Nativo 75 G at 48 hours of dual contact of R. solani and tested bio-pesticides or bio-control agents in in-vitro. The other bio-pesticides along with B. subtilis didn’t show any inhibition effect on the mycelia growth of R. solani which was similar to control (only water) treatment. Fungal inhibition 87.5% and 86.3% of Rhizoctonia solani was obtained by Recharge and Trichoderma harzianum (BT1), respectively which was nearly similar to the chemical treatment Nativo (96.3%) in in-vitro dual culture method compared to control treatment. In net house condition, 74% sheath blight disease was inhibited by soil application of Recharge (0.3 g/m2 with 50 ml water) for two times at the time of transplanting and 30 days after transplanting (DAT), whereas similar soil application of B. subtilis (OD600=0.3) was not found effective to control the ShB disease (< 30% disease reduction). The highest ShB disease was reduced by the chemical control Nativo 75 G (94.2%) followed by BT1 (89%), bio-pesticide Recharge (70.8%), Microtech1 (37.4%) and Chitin (61.3%) compared with the disease control when the tested materials were sprayed for two times (3 days before and 4 days after inoculation). Bangladesh Rice J. 24 (1): 47-58, 2020