First Report of Soybean Seedling Disease caused by Rhizoctonia solani AG-7 in Taiwan

From August to November 2020, reduced emergence and damping-off of soybean seedlings were observed in two fields (Benzhou and Wandan) in Taiwan. Disease incidence was approximately 40% in Benzhou by field scouting. The roots of damping-off seedlings were brown. Affected seedlings could be easily pulled out from the soil and the lesions on the roots/stem were generally dry and sunken. These symptoms suggested the possibility of Rhizoctonia infection. Soil surrounding symptomatic seedlings were collected to bait the potential pathogen and symptomatic plants were used for pathogen isolation. The diseased tissues were washed with tap water and surface-disinfected with 1% bleach before placing on the Dexon selection medium at 26°C for 2 days (Ko and Hora 1971). Hyphae were transferred to potato dextrose agar (PDA), and a brown colony with brown and irregular-shaped sclerotia grew from 90 out of 99 isolates. The hyphae exhibited typical characteristics of Rhizoctonia solani, including a constriction and a septum near the end of branching hyphae (Ajayi-Oyetunde and Bradely, 2018). Two isolates from Benzhou and two isolates from Wandan were tested for their pathogenicity, and eight surface-disinfected seeds were distributed evenly on the water agar plates covered by 2-day-old mycelia at 25°C in dark for 7 days. All isolates caused cotyledon rot and reduced germination. To verify their pathogenicity in pots, double-sterilized sorghum seeds were inoculated with two strains and incubated at 25°C for 2 weeks to be used as fungal inoculum (Ajayi-Oyetunde and Bradely, 2017). A layer of 15 ml of fungal inoculum was placed 5 cm beneath the soil surface in pots. Four soybean seeds were planted approximately 3 cm above the inoculum in each pot. After two weeks, reddish lesions on the hypocotyls or taproots of all seedlings in the inoculated pots were observed, while seedlings in the control pots inoculated with sterile sorghum seeds remained healthy. The pathogen was re-isolated from lesions and had identical morphology to the original isolates. To characterize the fungal identity, the internal transcribed spacer (ITS) was sequenced using the primers ITS1/ITS4 (Sharon et al., 2006). Using BLASTN in the NCBI database, the sequence (GenBank no. MW410857 and MW410858) showed 100% (639/639 bp) similarity to KF907734 and 99.83% (635/636 bp) similarity to AF354099, both belong to R. solani anastomosis group 7 (AG-7) (Hua et al. 2014; Gonzalez et al. 2001). Phylogenetic analysis comparing sequences with different AGs (Ajayi-Oyetunde and Bradely, 2017) grouped our isolates within the AG-7 clade with a 100% bootstrap confidence. In the anastomosis test, an incompatible zonation and unequal mycelial growth rates were observed when AG-7 isolates were paired with an AG-1 IA isolate. On the other hand, the compatible tuft reaction was observed when two AG-7 isolates were paired, and the compatible merge reaction was observed in the self-pairing tests (Macnish et al. 1997). Accordingly, the molecular and morphological characterizations confirmed the causal pathogen as R. solani AG-7. R. solani AG-7 was first reported on radishes in Japan (Homma et al., 1983), first found on carnation in Taiwan (Lo et al., 1990), and in field soils of various crops but not soybean (Chuang, 1997). It was suggested that Rhizoctonia diseases of soybean may be present in Taiwan, but molecular confirmation was lacking (Anonymus, 1979). As R. solani AG-7 causes diseases of soybean in the US and Japan (Baird et al., 1996), the importance of AG-7 as an endemic pathogen of soybean in Taiwan should be recognized and its prevalence determined as a first step to managing this disease.

PERTUMBUHAN BAWANG MERAH (Allium cepa L.) YANG DIBERI PUPUK KOMPOS CAIR DAN JAMUR MIKORIZA ARBUSKULAR

The application of liquid compost and of beneficial soil microorganism such as arbsucular mycorrhizal fungi can be used to replace chemical fertilizer application. The aim of this study was to investigate the growth of red onion (Allium cepa L.) plant fertilized by liquid compost and inoculated by arbuscular mycorrhizal fungi. This study was conducted based on a completely randomized design with two factors. The first factor was an addition of liquid compost dosages (0, 50, 100 and 200 ml/polybag). The second factor was an addition of AM fungal inoculum (with and without addition). The results showed that the growth of red onion plant was not significantly affected by the addition of liquid compost and AM fungal inoculum. However, the red onion plant fertilized by 200 ml liquid compost per polybag had the lowest shoot dry weight. The addition of AM fungal inoculum was not increasing plant growth because the quality of used inoculum was not good.

Effect of fungal inoculum application on changes in organic matter of leaf litter composting

<p>The decomposition of organic matter on leaf litter substrat runs very slowly in nature resulting in the accumulation of litter in the ecosystem and has even become an organic waste that creates many problems. The research was dealt with the use of lignocellulolytic fungi inoculum consisting of 3 isolates: <em>Aspergillus fumigatus</em> (cellulolytic), <em>A. tubingensis</em> (xylanolytic) and <em>Geotrichium</em> sp (ligninolytic) as starter of leaf litter composting. The purpose of the study is to understand the pattern of humic-fulvat acid and C/N ratio on the process of composting of leaf litter with the addition of inoculum. Observations were made to the chemical changes of compost for 3, 6 and 9 weeks of composting and the data were analyzed in RM-anova (Repeated Measures of anova). The result shows the best pattern of humic acid and fulvic change from the initial to final composting occurs at the <em>Geotrichum</em> sp inoculum of 0.60 or 105.2% and for fulvic are of 0.55 or 56.1% of baseline. The highest ratio value of CHA/CFA at the end of observation was by consortium of <em>A. fumigatus</em> and <em>A. tubingensis</em> inoculums that was 2.94 and the lowest value was at commercial inoculum that was 0.80; and the sharpest change value also occurred in the consortium <em>A. fumigatus</em> and <em>A. tubingensis</em> inoculums of 2.20 or 297.3%. Therefore the consortium isolates were capable of causing the maturity of the compost most rapidly compared to other isolates.<em></em></p>

Perkecambahan dan Perbanyakan Gaharu secara In Vitro

<p class="p1">Agarwood (<em>Aquilaria malaccensis </em>Lank) is one of the forest wood that are continously exploited. Currently, the Indonesian export of agarwood is decreasing because its population is endangered by excessive logging. Agarwood propagations need technology for reproduction of agarwood seedlings and their fungal inoculum. <em>In vitro </em>technique for germination of recalsitrant seeds and micropropagation are technologies that can be used for propagation of agarwood seedlings. An experiment was done to develop techniques for <em>in vitro </em>germination and micropropagation of agarwood. The <em>in vitro </em>germination was done using two different techniques. Firstly, sterile seeds were germinated on an MS medium + 50 mg/l PVP, 50 mg/l GA, and 1 mg/l BA or kinetin. Secondly, sterile seeds were germinated on basal medium of MS, 1/2 MS medium, MS medium without vitamins, as well as on MS medium without pyridoxine, nicotinic acid and WPM. Shoot initiations and multiplications were done on MS and 1/2 MS media containing 1, 3, or 5 mg/l BA. The explants used were cotyledone nodes, terminal shoots, single node with leaf, and sinle node without leaf. The results showed that the seed germination rate on the different media ranged from 7,14 to 50%. The seed germination rate on the MS medium without vitamis was the highest. The best explants for shoot induction and multiplication was single node with leaf which was cultured on MS + 1 mg/l BA.</p>