First report of leaf blight on pumpkin caused by Nigrospora sphaerica in China.

Pumpkin (Cucurbita moschata), which belongs to the gourd family (Cucurbitaceae), is widely planted throughout the world. In June 2023, many pumpkin plants (cv. Miben) displayed leaf blight and chlorosis in fields located in Suizhou (31.99°N, 113.02°E), Hubei Province, China. The disease incidence ranged from 30 to 40% in nine fields, 6.3 ha in total. The symptoms were irregularly shaped lesions that expanded along the mid-vein until the leaf turned brown and wilted. Fungal isolations were performed as described previously (Liu et al. 2023). Twenty pumpkin leaf samples with typical symptoms were collected and cut into 1 cm×1 cm pieces. The diseased tissue was surface-sterilized in 75% ethanol for 30 sec, plated on potato dextrose agar (PDA) medium and incubated at 25℃ for 3 days. Then, the emerging single fungal hyphal tip was transferred onto PDA plates to obtain purified isolates. A total of eighteen isolates on PDA plates were initially white and then developed to dark gray. The 5-day-old cultures growing on mung bean medium produced conidia that were black, single-celled, smooth, spherical or oblate, and ranged in size from 14.5 to 20.8 µm×13.3 to 20.5 µm (n=50). Therefore, the isolates were morphologically identified as Nigrospora sphaerica. Moreover, the genomic DNA of the isolates (HB-P1,HB-P2, and HB-P3) was extracted for amplification and sequencing of the regions of internal transcribed spacer (ITS) (White et al. 1990), nuclear large subunit rRNA (nLSU) (O'Donnell 1992; Rehner and Samuels 1994), and ß-tubulin (TUB2) (Glass and Donaldson 1995), with primers ITS1/ITS4, LROR/LR3, and Bt2a/Bt2b, respectively. Sequences were submitted to GenBank under accession numbers PP348112, PP348113, PP348114 (ITS), PP411414, PP411415, PP411416 (nLSU), and PP357438, PP357439, PP357440 (TUB2). BLASTn showed that the sequences ITS, nLSU, and TUB2 of HB-P1, HB-P2, and HB-P3 had >99% nucleotide identities ((ITS: 100%, 508/508 bp, MF996488.1; 99.8%, 506/507, ON326588.1; 100%, 500/500 ,MK748317.1), (nLSU: 99.83%, 573/574, KT462720.1; 99.83% , 574/575 bp, KT462720.1; 99.65%, 575/577, KT462720.1), and (TUB2: 100%, 388/388, MN719407.1; 99.74%, 387/388, MN719407.1; 100%, 387/387, MN719407.1)) with Nigrospora sphaerica, respectively. A multilocus (ITS, nLSU and TUB2) phylogenetic analysis indicated that the isolates were Nigrospora sphaerica. Pathogenicity of three isolates were tested on pumpkin plants (cv. Miben). Fifteen pumpkin plants were inoculated by spraying the leaves (1×106 spores/ml), respectively, and 10 pumpkin plants were treated with sterile water as a negative control. All plants were incubated in an artificial climate box (LongYue, ShangHai) at 25℃ for 12 days. The experiment was repeated three times. Twelve days later, the inoculated pumpkin plants developed symptoms of leaf blight, while the control plants remained healthy. Then, pathogens were re-isolated from the each leaf of inoculated pumpkin plants and not from the control plants. Nigrospora sphaerica has been previously reported to cause leaf spot on watermelon in Malaysia (Ismail and Abd Razak 2021). To our knowledge, this is the first report of N. sphaerica causing leaf blight on pumpkin in China. This new disease can cause leaf blight, which may affect pumpkin productivity.

Effect of entomopathogenic fungi on behavior and physiology of Solenopsis invicta (Hymenoptera, Formicidae).

In an ant colony, a large number of nestmates with a similar gene pool coexist, making them more vulnerable to pathogenic attacks. These pathogens influence the behavior and physiology of the fire ant Solenopsis invicta Buren. Here, we evaluated the impact of entomopathogenic fungi (EPF) Metarhizium anisopliae on the behavior (locomotion and foraging) and physiology (biological molecules, anti-fungal activity, and survival) of S. invicta. Distance traveled and velocity significantly decreased, while turn angle and angular velocity significantly increased in ants exposed to a higher concentration of M. anisopliae compared to ants exposed to control after 36 h, which showed disturbed locomotion. Fungus infection significantly affected the foraging behavior of ants. Fungus-exposed ants spent significantly less time in the food zone (area with food) than in the inner zone (area without food). The activities of 4 enzymes, peroxidase, glutathione-S-transferase, hydrogen peroxide (H2O2), and carboxylesterase were significantly decreased. In contrast, catalase and anti-fungal activities were increased after fungal exposure compared to the control. The activity of acetylcholinesterase, which hydrolyses the important neurotransmitter acetylcholine, also decreased after fungal application compared to the control. Survival of ants was also significantly reduced after fungus infection compared to the control. Our findings help to understand the influence of M. anisopliae on the behavior and physiology of S. invicta, which will help in the management of S. invicta using the EPF M. anisopliae.

A two-stage fine-tuning method for low-resource cross-lingual summarization.

Cross-lingual summarization (CLS) is the task of condensing lengthy source language text into a concise summary in a target language. This presents a dual challenge, demanding both cross-language semantic understanding (i.e., semantic alignment) and effective information compression capabilities. Traditionally, researchers have tackled these challenges using two types of methods: pipeline methods (e.g., translate-then-summarize) and end-to-end methods. The former is intuitive but prone to error propagation, particularly for low-resource languages. The later has shown an impressive performance, due to multilingual pre-trained models (mPTMs). However, mPTMs (e.g., mBART) are primarily trained on resource-rich languages, thereby limiting their semantic alignment capabilities for low-resource languages. To address these issues, this paper integrates the intuitiveness of pipeline methods and the effectiveness of mPTMs, and then proposes a two-stage fine-tuning method for low-resource cross-lingual summarization (TFLCLS). In the first stage, by recognizing the deficiency in the semantic alignment for low-resource languages in mPTMs, a semantic alignment fine-tuning method is employed to enhance the mPTMs' understanding of such languages. In the second stage, while considering that mPTMs are not originally tailored for information compression and CLS demands the model to simultaneously align and compress, an adaptive joint fine-tuning method is introduced. This method further enhances the semantic alignment and information compression abilities of mPTMs that were trained in the first stage. To evaluate the performance of TFLCLS, a low-resource CLS dataset, named Vi2ZhLow, is constructed from scratch; moreover, two additional low-resource CLS datasets, En2ZhLow and Zh2EnLow, are synthesized from widely used large-scale CLS datasets. Experimental results show that TFCLS outperforms state-of-the-art methods by 18.88%, 12.71% and 16.91% in ROUGE-2 on the three datasets, respectively, even when limited with only 5,000 training samples.

Insecticide resistance monitoring and correlation analysis of insecticides in field populations of the brown planthopper Nilaparvata lugens (stål) in China 2012-2014.

The brown planthopper is a serious rice pest in China. Chemical insecticides have been considered a satisfactory means of controlling the brown planthopper. In the present study, we determined the susceptibility of twenty-one populations of Nilaparvata lugens to eleven insecticides by a rice-stem dipping method from 2012 to 2014 in eight provinces of China. These field-collected populations of N. lugens had developed high levels of resistance to imidacloprid (resistant ratio, RR=233.3-2029-fold) and buprofezin (RR=147.0-1222). Furthermore, N. lugens showed moderate to high levels of resistance to thiamethoxam (RR=25.9-159.2) and low to moderate levels of resistance to dinotefuran (RR=6.4-29.1), clothianidin (RR=6.1-33.6), ethiprole (RR=11.5-71.8), isoprocarb (RR=17.1-70.2), and chlorpyrifos (RR=7.4-30.7). In contrast, the susceptibility of N. lugens to etofenprox (RR=1.1-4.9), thiacloprid (RR=2.9-8.2) and acetamiprid (RR=2.7-26.2) remained susceptible to moderate levels of resistance. Significant correlations were detected between the LC50 values of imidacloprid and thiamethoxam, dinotefuran, buprofezin, and etofenprox, as well as between clothianidin and thiamethoxam, dinotefuran, ethiprole, acetamiprid, and thiacloprid. Similarly, significant correlations were observed between chlorpyrifos and etofenprox, acetamiprid and thiacloprid. Additionally, the activity of the detoxification enzymes of N. lugens showed a significant correlation with the log LC50 values of imidacloprid, dinotefuran and ethiprole. These results will be beneficial for effective insecticide resistance management strategies to prevent or delay the development of insecticide resistance.