First Report of Rhizoctonia solani AG-4 HG-III Causing Sheath Blight on Foxtail Millet in China.

Foxtail millet (Setaria italica) is an important grain and forage crop. This crop is widely grown in Northern China (Yang et al.2020). In Aug 2021, foxtail millet variety of Jigu42 showing lodging were found in Baoding China with the incidence of 30% and irregular brown lesions were found in sheaths and leaves of infected plants. The center of the lesions was kraurotic and pale, and the edges were gray-brown or dark brown. Twelve samples with typical lesions were collected from the surveyed field to isolate the pathogen. The infected samples were cut into square pieces of about 3 to 5 mm and were immersed into NaOCl (1%) for 1 min followed by washing with sterile water for three times. Then all sterilized tissues were inoculated on potato dextrose agar (PDA) plates and incubated at 25℃. After 3 days, fresh mycelial tips grown from the tissues were transferred to new plates for purification and incubated in the dark at 25°C for 4-5 days until the hyphae covered the whole plates. The colonies of 15 isolates on PDA medium showed similar colonial characteristics, which were fluffy and white initially, gradually turned light brown, and no sclerotia was observed even at 20 days later. Micro-examination revealed that all isolates showed the identical morphological features as Rhizoctonia sp. (Sneh et al. 1991), which contained the septate and right-angled branching hyphae with slight constriction at the base of mycelial branches, and three to seven nuclei per cell (Yang et al. 2013). Total genomic DNA was extracted from 5-day-old cultures, and the internal transcribed spacer (ITS) region of rDNA was amplified with ITS1 and ITS4 as the primers (Garibaldi et al. 2019). The sequencing results showed that the nucleotide sequences of 15 amplicons were identical and shared 100% identity with the corresponding fragments of R. solani AG-4 HG-III from sugar beet (GenBank accession No. MH172666 and MH172663) in Blastn search. The sequencing size of ITS in this study was 3 bp shorter than that of sugar beet, with a length of 722, because the base 'T' in the beginning and 'GA' in the end of the sequences did not detected in our study. Phylogenetic tree of 16 isolates of different AG4 subgroups was created by the software MEGA 7.0 through the NJ method, and the showed that the isolates were clustered to the clade of AG-4 HG-III group. The sequences of three isolates were deposited in GenBank under the accession No. ON810364, ON810365 and ON810366. For pathogenicity test, 5 mm diameters plate of the 5-day-old fungus which cultured on PDA were inoculated to the sheath of 10 foxtail millet plants grown in pots at 5- or 6-leaf stage. Then, the inoculated plants were placed into a growth chamber, and the inoculated sheaths were covered with wet cotton ball for 2 days to keep humidity, while sterile water was inoculated as the control. All plants were cultivated at 26°C with 14 h light and 10 h dark for 14 days. The experiment was repeated for three times. As the result, the same lesions observed in the field appeared on the inoculated plants at 10-14 days post inoculation, whereas the mock was healthy. The pathogen was re-isolated from the infected samples. The morphological characteristics and the nucleotide sequences of ITSs were same as that of the original isolates. All in above, the pathogen cusing sheath blight on foxtail millet was identified as R. solani AG-4 HG-III. To our knowledge, this is the first report of R. solani AG-4 HG-III causing sheath blight on S. italica in China. This finding expands the host range known for R. solani AG-4 HG-III and will be helpful for developing effective control strategies of foxtail millet sheath blight.

Rapid impedance method for predicting the potential shelf life of packaged pasteurized milk.

The potential shelf life of packaged pasteurized milk was studied using a rapid impedance method. The results showed a high correlation between the shelf life of Fengxing and Xiang Man-lou pasteurized milks and between the detection time and the logarithm of colony-forming units per milliliter. The impedance detection time was measured after preliminary incubation at 30 degrees C for 6 h for 100 and 200 microL milk samples, or at 37 degrees C for 6 h for 100-400 microL milk samples for Fengxing pasteurized milk, and after 6 h preliminary incubation at 30 degrees C for 300 and 400 microL milk samples or 6 h at 37 degrees C for 100-400 microL milk samples for Xiang Man-lou pasteurized milk. Regressive equations were then constructed to predict the potential shelf life. Compared with the traditional method, the impedance method plus pre-incubation of milk at elevated temperatures (30 and 37 degrees C) was rapid, accurate, and convenient. The entire estimation process was completed within 11-14 and 14-20 h for Fengxing and Xiang Man-lou pasteurized milks, respectively.

The influence of prosthesis designs and loading conditions on the stress distribution of tooth-implant supported prostheses.

The aim of this study was to observe the influence of prosthesis design and loading condition on the stress distributions of tooth-implant supported prostheses. Six 2D finite element models, two reference models, and four experimental models were computed to simulate different prosthesis designs. Six different loading conditions were applied to investigate the stress distributions of tooth and implant, respectively. The stresses of reference models were considered as 100%; the stresses of experimental models at the same locations were compared with those of reference models. The stresses around implants were higher than those around teeth. When vertical loading was applied only on the implant, the stresses to both the implant and teeth were at their lowest. The highest stress to the tooth was in the model TTPF and the lowest in the model TPFF. The highest stress to the implant was in the model TPPF and the lowest in the model TPFF. These data indicated that the loading on the tooth-implant supported prosthesis was mainly supported by the implant. Minimizing the loading on the tooth decreased the stress to both the tooth and the implant. Adding fixtures as abutment was more effective in decreasing the stress than adding tooth as abutment in tooth-implant supported prosthesis.