Gibberellin (GA), auxin (IAA) and brassinosteroid (BR) are indispensable in the process of plant growth and development. Currently, research on the regulatory mechanism of phytohormones in banana dwarfism is mainly focused on GA, and few studies are focused on IAA and BR. In this study, we measured the contents of endogenous GA, IAA and BR and compared the transcriptomes of wild-type Williams banana and its dwarf mutant across five successive growth periods. We investigated the relationship between hormones and banana dwarfism and explored differential gene expression through transcriptome analysis, thus revealing the possible metabolic regulatory mechanism. We inferred a complex regulatory network of banana dwarfing. In terms of endogenous hormone levels, GA and IAA had significant effects on banana dwarfing, while BR had little effect. The key gene in GA biosynthesis of is GA2ox, and the key genes in IAA biosynthesis are TDC and YUCCA. The differential expression of these genes might be the main factor affecting hormone levels and plant height. In terms of hormone signal transduction, DELLA and AUX/IAA repressor proteins were the core regulators of GA and IAA, respectively. They inhibited the process of signal transduction and had feedback regulation on hormone levels. Finally, the transporter protein PIN, AUX1/LAX protein family and ABCB subfamily played supplementary roles in the transport of IAA. These results provide new insights into GA and IAA regulation of banana growth and a reliable foundation for the improvement of dwarf varieties.

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Pleurotus pulmonarius is a popular edible fungus and widely cultivated in many areas of China. In June 2018, yellow rot (more than 10% incidence) was found on the first crop of P. pulmonarius fruiting bodies in a mushroom factory in Nanning, Guangxi Province, China. At first, yellow water-soaked lesions appeared in the infected fruiting bodies. Lesions then spread and purulent tissues were formed. Severe rot induced production of deformed fruiting bodies and offensive odor. Internal sections of the diseased tissue (approximately 0.5 × 0.5 cm) were sterilized in 75% alcohol for 30 s, rinsed three times with sterilized and deionized water, crushed and suspended in sterilized and deionized water. The suspension was spread on the Luria-Bertani (LB) medium. After incubation at 30°C for 2 days, dominant bacterial colonies were oyster white, smooth, convex, and circular. Individual colonies were transferred two times to LB medium using the conventional streak plate techniques to obtain the pure cultures. The cells were gram-negative, short rods, motile, and no capsules or endospores were observed. Using a BoJian Gram-negative bacteria biochemical analysis kit (5 CARDS, Hopebio, Qingdao, China), data were obtained and analyzed, showing that the isolated strain belongs to the Cedecea genus (positive for β-galactosidase, citric acid, arginine, sucrose, mannitol, sorbitol, D-glucose, gelatin hydrolysis and VP test but negative for H2S, urease, oxidase, indole, rhamnose, melibiose, amygdalin, lysine, ornithine, lactose, inositol and arabinose). Amplified 16S rDNA gene sequences (1,424 bp, GenBank accession No. MT925570) of the isolate using the universal primers 27f and 1492r (Lane 1991) exhibited 99.86% identity with Cedecea neteri M006 (CP009458.1). Based on its morphological characteristics, 16S rDNA sequences, and biochemical test results, the strain was identified as C. neteri. Pathogenicity tests for this strain were performed with bacterial suspensions (approximately 1 × 108 CFU/ml) after growing for 24 h in LB medium at 30°C. Mycelia of P. pulmonarius were cultivated for 60 days in plastic bags. Then young fruiting bodies were formed after induced with low temperature stimulation to serve as a host source. The prepared bacterial suspensions were directly sprayed onto the surface of three bags of fruiting bodies; another three bags were sprayed with sterilized and deionized water as negative control. All inoculated fruiting bodies were then incubated at 20°C with 90 to 95% relative humidity. All experiments were repeated three times. After 2 days, all the fruiting bodies inoculated with the bacterial suspensions showed yellow water-soaked lesions, and the normal growth of the fruiting bodies was inhibited. An offensive odor then developed along with a severe soft rot that was similar to the disease symptoms observed under natural conditions. The fruiting bodies of negative control were growing healthily with no symptoms. Koch's postulates were fulfilled by isolating bacteria from lesions on artificially inoculated fruiting bodies that were identical to the original isolates based on morphological characteristics, 16S rDNA sequences and biochemical test results. C. neteri was formally reported as a pathogen to humans that could cause bacteremia (Farmer et al. 1982). Recently, it has also been reported causing soft rot disease on mushrooms of Pholiota nameko (Yan et al. 2018) and yellow sticky disease on mushrooms of Flammulina velutipes (Yan et al. 2019). However, to the best of our knowledge, this is the first report of C. neteri-induced yellow rot disease of P. pulmonarius in China.

Pleurotus giganteus (Berk.) Karunarathna & K.D. Hyde 2011 is one of the largest edible mushrooms integrating medicinal value and edible value. The complete mitochondrial genome of the edible fungus P. giganteus was published in this paper. It was determined using Pacbio and Illumina sequencing. The circular molecule is 102,950 bp in length, consisting of 30 protein-coding genes (PCGs), two ribosomal RNA (rRNA) genes, and 24 transfer RNA (tRNA) genes. The base composition of the whole mitogenome is A (37.3%), T (37.7%), G (12.2%), and C (12.8%). The phylogenetic tree shows P. giganteus was the basal taxon in Pleurotus and closely related to Pleurotus citrinopileatus Singer 1990.

Ginger (Zingiber officinale Rosc.) is an herbal crop widely grown in China for its medicinal and savory qualities of rhizomes. In August 2018, leaf spot symptoms were observed on ginger plants grown in a field in Nanning, Guangxi Province (E108°3'54", N23°14'48"). Disease incidence was above 50%, and in a Nanning field, rhizome yield loss was almost 30%. Early symptoms appeared as circular, necrotic areas that later developed into circular or irregular spots. The centers of the lesions were white and often surrounded by chlorotic halos (Figure S1A). In severe infections, the spots frequently coalesced, causing the entire leaf to become withered and curved. Small pieces (3 to 4 mm2) from the margin of infected lesions were surface sterilized in 75% ethanol for 40 s followed by 1% NaOCl for 90 s, placed on potato dextrose agar (PDA) and incubated at 28°C in the dark for 4 days. Hyphal tips from the leading edge of colonies were transferred to fresh PDA plates to obtain pure cultures. Fungal colonies were initially white, then turned black/grayish brown when maintained in the dark at 28°C after 5 days (Figure S1B). Conidia were single-celled, brown, or black, smooth, spherical, or subspherical with diameters varying from 9.5 to 15 μm (mean = 13.5 ± 0.72 µm, n = 50) (Figure S1C). Based on these morphological characteristics, the isolates were provisionally identified as Nigrospora oryzae (Ellis 1971; Hudson 1963). Genomic DNA was extracted from a representative isolate Sjb-2. The internal transcribed spacer (ITS) region, beta-tubulin (TUB2), and the translation elongation factor 1-alpha (TEF1-α) were amplified using primer pairs including ITS1/ITS4 (White et al. 1990), Bt-2a/Bt-2b (Glass and Donaldson 1995), and EF1-728F/EF1-986R (Carbone et al. 1999), respectively. The obtained ITS sequence (GenBank accession no. MW555242), TUB2 sequence (MZ048644), and TEF1-α sequence (MZ048645) showed >99% similarity with several GenBank sequences of N. oryzae (KF516962 for ITS; MK550707 for TUB2; and KY019425 for TEF1-α, respectively). Based on the combined sequences of ITS, TUB2 and TEF1-α sequences, a phylogenetic tree was constructed using the maximum likelihood method and confirmed that the isolates were N. oryzae (Figure S2). Pathogenicity of the isolate was confirmed by fulfilling Koch’s postulates. Agar blocks (3 mm diameter) containing a fungal mycelium were placed on detached healthy leaves of ginger. The leaves were then wrapped with sterile polyethylene and incubated in a greenhouse at 25°C with 60% RH. Within 7 days, symptoms appeared on inoculated leaves similar to spots observed in the field, whereas controls remained symptomless. The same pathogen was reisolated from the spots. Pathogenicity tests were performed twice with three replications, indicating that N. oryzae is responsible for leaf spot disease on ginger. The disease in ginger caused by N. oryzae had been reported in Southern Africa (Grech et al. 1989). To our knowledge, this is the first report of N. oryzae causing leaf spot of ginger in China. In the field, this pathogen can substantially affect ginger's health and rhizome yield if no effective control measures are implemented. Therefore, management of the disease should be further investigated to avoid major economic losses.