Pomegranate heart rot (black heart) was observed in several pomegranate-growing areas of Algeria. From 2022 to 2025, surveys were conducted across 15 provinces (20 localities), and a total of 85 fruits (symptomatic and asymptomatic) were collected. Fruits were cut transversely to assess internal symptoms, ranging from early aril browning to dry black rot. Thirty Alternaria isolates were obtained and grouped into four morphotypes based on colony and conidial morphological traits. A subset of 18 isolates was analysed by multilocus phylogeny (ITS, EF-1α, GAPDH and OPA10-2); all analysed isolates clustered within the Alternaria alternata species complex, in the clade including the ex-type strain CBS 916.96. Fruit pathogenicity tests with Algerian isolate GA reproduced typical internal heart rot symptoms, and the pathogen was consistently re-isolated from symptomatic tissues. In fruit inoculations with isolate GA, cultivars differed in susceptibility, with mean disease severities of 94%, 62% and 9.5% in ‘Taferrante’, ‘Ikhessène’ and ‘Kares’, respectively, expressed as the percentage of the fruit section presenting rot symptoms. Detached leaf assays indicated isolate-dependent differences in aggressiveness, and ‘Kares’ showed the lowest susceptibility. Overall, the results confirm that A. alternata is the causal agent of pomegranate heart rot in Algeria and provide baseline information for disease diagnosis and management.

Fire blight poses severe economic risks for production from economically important crops. This study assessed in vitro and in vivo antibacterial activity against Erwinia amylovora of non-volatile organic and aqueous extracts (from fruit peels or leaves) from pomegranate (Punica granatum), onion (Allium cepa), eucalyptus (Eucalyptus globulus), and garlic (Allium sativum). The ethanolic extract from pomegranate peel exhibited the greatest and most consistent antimicrobial activity in three in vitro assays (reverse agar plugs, wells, and disc diffusion). This extract also reduced disease severity during in vivo bioassays with immature pear fruits or detached leaves. Chemical characterization using Nuclear Magnetic Resonance spectroscopy indicated that this bioactivity was associated with the presence of compounds identified as the ellagitannins α- and β-punicalagin. These results highlight the potential of pomegranate peel extract as a potential biocontrol agent for fire blight management.