What type of study is this?

This is a Observational study (also classified as: Molecular Study).

September 10, 2025

First Report of Pyracantha fortuneana Fruit Rot Caused by Alternaria alternata in Yunnan Province, China

Key Points

A. alternata caused fruit rot in P. fortuneana, resulting in 10.4% disease incidence across 500 fruits.
Morphological and molecular analyses confirmed A. alternata with 95-100% genetic homology to reference strains.
Pathogenicity tests showed lesions developed on inoculated fruits, while negative controls remained symptom-free.
These findings highlight the need for monitoring and control strategies for fruit rot in P. fortuneana.

Abstract

Pyracantha fortuneana (H. L. Li, Rosaceae), valued for ornamental and ecological uses, is widely distributed in southern/southwestern China. Its polysaccharides exhibit antioxidant and anticancer potential, driving commercial juice development (Yao et al. 2020). On 10 October 2024, fruit rot symptoms were observed on P. fortuneana at Qujing Normal University, Yunnan, China (25.52°N, 103.75°E). Symptomatic fruits displayed circular to subcircular black lesions; internal tissues were necrotic and brown. Disease incidence averaged 10.4% ± 2.07% (SD) across 500 fruits from five replicates (100 fruits each). Pathogen isolation utilized four replicate 9-cm PDA plates. Three lesion-margin fragments (0.2 × 0.5 cm) per replicate were surface-sterilized (75% ethanol, 4 min), triple-rinsed in sterile water, and incubated at 28 °C in darkness. Hyphal tips from emerging white mycelia were transferred to PDA medium plate after 24 h. Colonies developed gray-green centers with regular white margins within 3 days, covering plates fully by day 9. Nine morphologically similar strains were isolated; a representative (BHB) was characterized morphologically and molecularly. After 14 days, colonies produced solitary or catenate conidia (5.28–13.52 μm × 8.90–28.38 μm; mean 8.66 × 15.50 μm, n=50). Conidia were pyriform to elliptical, with 1–6 transverse and 0–1 longitudinal septa, exhibiting slight septal constrictions, consistent with Alternaria spp. (Simmons 2007). For molecular identification, genomic DNA was extracted, and eight loci were amplified/sequenced: SSU (NS1/NS4), LSU (LSU1Fd/LR5), ITS (ITS1/ITS4), TEF1 (EF1-728F/EF1-986R), Alt a 1 (Alt-for/Alt-rev), EndoPG (PG3/PG2b), OPA10-2 (OPA10-2R/OPA10-2L), H3 (H3-1a/H3-1b) (Zhang et al. 2023; Zheng et al. 2015). Sequences (SSU: PQ895780; LSU: PQ895777; ITS: PQ895770; TEF1: PV082022; Alt a 1: PV082020; EndoPG: PV092677; OPA10-2: PV092678; H3: PV082021) showed 95–100% homology to Alternaria alternata reference strains (GenBank accessions: PP190241 1,010/1,010 bp, PP190242 858/858 bp, PP189927 544/544 bp, PP196558 251/252 bp, PP196559 462/481 bp, PP196560 439/439 bp, PP196561 670/702 bp, ON375577 407/407 bp). Maximum-likelihood and Bayesian phylogenetic analyses (PhyloSuite v1.2.3) using concatenated loci placed BHB within the A. alternata clade. Combined morphology and multigene phylogeny identified BHB as A. alternata. Pathogenicity was confirmed by inoculating needle-wounded fruits with mycelial plugs and conidial suspensions (1×10⁶ conidia/ml). Unwounded fruits inoculated with suspensions/plugs served as positive controls; needle-wounded fruits treated with sterile water were negative controls. After 7 days, lesions matching field symptoms developed on all plug-inoculated fruits (wounded/unwounded), but only on wounded suspension-inoculated fruits. Negative controls remained symptom-free. Reisolation from lesions yielded cultures morphologically and molecularly identical to A. alternata. To our knowledge, this is the first report of A. alternata causing P. fortuneana fruit rot in China. These findings provide critical insights for monitoring disease spread and developing control strategies.

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