First record of Fusarium verticillioides causing sorghum wilt in south Sulawesi Indonesia: field incidence, severity, and molecular confirmation

Primeiro registro de Fusarium verticillioides causando murcha de sorgo em Sulawesi do Sul, Indonésia: incidência de campo, gravidade e confirmação molecular

Abstract

Sorghum (Sorghum bicolor (L.) Moench) is an important crop for food diversification and bioenergy programs in Indonesia due to its drought tolerance, adaptability to marginal lands, and high nutritional value. However, a previously unreported sorghum wilt disease in Indonesia is hindering its productivity. Morphological, molecular, and pathogenicity testing methods were used in this study to identify the cause of sorghum wilt in South Sulawesi. According to a field survey conducted in Maros Regency (2025), disease incidence ranged from 11 percent to 100 percent, and disease severity increased as the plants aged. The Super 1 variety showed a 27.72% incidence 21 days after planting (DAP), while Numbu showed 11.08%. At 56 days after planting (DAP), both varieties reached 100% incidence with severity reaching 91.7%. Pathogen isolation produced colonies with long-chained microconidia ranging in color from white to pale purple. Macroconidia are rarely septate (3–5), and no chlamydospores are present. Isolate FV-SR01 belongs to the Fusarium verticillioides clade, showing 99.8–100% similarity to reference strains, according to molecular analysis based on ITS and TEF1-α sequences. According to pathogenicity tests, seedlings exhibited wilting symptoms within ten to twelve days after inoculation; the disease severity index reached 3.6 (80–90% wilting), and the same isolate was successfully re-isolated, fulfilling Koch’s postulates. This study indicates that F. verticillioides is the primary cause of wilt disease in sorghum in South Sulawesi. This report is the first of its kind in Indonesia and will help strengthen the plant disease database and aid in the development of sustainable sorghum management strategies.

Keywords:
F. verticillioides; sorghum; Indonesia; disease incidence; severity; molecular identification; pathogenicity test

Resumo

O sorgo [Sorghum bicolor (L.) Moench] é uma cultura importante para a diversificação alimentar e os programas de bioenergia na Indonésia, devido a sua tolerância à seca, adaptabilidade a terras marginais e alto valor nutricional. No entanto, uma doença de murcha do sorgo, nunca antes relatada na Indonésia, prejudica sua produtividade. Métodos morfológicos e moleculares, e testes de patogenicidade foram utilizados nesta pesquisa para identificar a causa da murcha do sorgo no sul de Sulawesi. De acordo com um levantamento de campo realizado no município de Maros (2025), a incidência da doença variou entre 11% e 100%, e a gravidade da doença aumentou com o avanço da idade das plantas. A variedade Super 1 apresentou 27,72% de incidência aos 21 dias após o plantio (DAP), enquanto a Numbu apresentou 11,08%. Aos 56 dias após o plantio (DAP), ambas as variedades atingiram 100% de incidência, com gravidade de 91,7%. O isolamento do patógeno produziu colônias com microconídios em cadeias longas, de cor branca a roxo-claro. Os macroconídios raramente apresentavam 3-5 septos, e não foram observadas clamidósporas. O isolado FV-SR01 pertence ao clado F. verticillioides, com 99,8-100% de similaridade com a cepa de referência, de acordo com a análise molecular baseada nas sequências ITS e TEF1-α. De acordo com o teste de patogenicidade, as mudas apresentaram sintomas de murchamento aos 10 a 12 dias após a inoculação; o índice de gravidade da doença atingiu 3,6 (80 a 90% de murchamento) e o mesmo isolado foi isolado novamente com sucesso, cumprindo os postulados de Koch. Este estudo demonstra que F. verticillioides é a principal causa da murcha do sorgo no sul de Sulawesi. Este relatório é o primeiro na Indonésia e contribuirá para fortalecer o banco de dados de doenças de plantas, bem como ajudar a desenvolver estratégias de manejo sustentável do sorgo.

Palavras-chave:
F. verticillioides; sorgo; Indonésia; incidência da doença; gravidade; identificação molecular; teste de patogenicidade

1. Introduction

Sorghum (Sorghum bicolor (L.) Moench) is one of the most important cereal crops worldwide, ranking fifth after maize, rice, wheat, and barley. It serves as a multipurpose crop used for food, feed, and bioethanol production due to its high adaptability to a wide range of climatic and soil conditions, especially under drought and marginal environments (Reddy et al., 2020). In Indonesia, sorghum has gained increasing attention in recent years as part of the government’s national program for crop diversification and sustainable bioenergy development (Biba, 2016; Wirawan et al., 2026; BRIN, 2024). Several regions, including South Sulawesi, have been promoted for sorghum cultivation because of their favorable agroecological conditions and strategic role in supporting food and energy security. However, the expansion of sorghum cultivation has been challenged by the emergence of several diseases that threaten yield and quality. Among them, wilt disease has been reported as one of the most destructive diseases affecting sorghum production in many sorghum-growing regions of the world (Corallo et al., 2025). The disease is primarily caused by soil-borne fungi belonging to the genus Fusarium, these pathogens can cause yield losses ranging from 30% to over 60% under severe conditions.In addition to quantitative yield reduction, Fusarium infections often result in grain contamination with fumonisins and other mycotoxins, further exacerbating economic and food safety impacts (Diakite et al., 2022; Voss et al., 2007; Xu et al., 2020). These pathogens infect plant roots and vascular tissues, leading to vascular discoloration, leaf yellowing, stunting, and eventually plant death. Several Fusarium species have been associated with these symptoms, including F. verticillioides, F. proliferatum, F. thapsinum, and F. oxysporum (Voss et al., 2007; Michielse and Rep, 2009).

Among these species, F. verticillioides (Sacc.) Nirenberg is one of the most common cereal pathogens and is of high economic significance. This pathogen has been widely reported to cause stem rot, ear rot, and seedling damping-off in maize and other grasses (Ferrigo et al., 2023). F. verticillioides can survive in plant residues and soil as overwintering structures, or colonize seeds as a latent infection, ensuring long-term inoculum availability (Opoku et al., 2026). In sorghum, F. verticillioides has been associated with stem rot and wilt diseases in various countries, including India, Nigeria, and the United States, underscoring its global distribution and impact (Ferrigo et al., 2023). In addition to its pathogenicity, F. verticillioides is also a major producer of fumonisins, a group of mycotoxins that pose serious health risks to humans and animals, with genetic variability among strains contributing to differences in fumonisin contamination levels (Opoku et al., 2026)

In Indonesia, reports on Fusarium-related diseases of sorghum are extremely limited. Most previous studies have focused on F. verticillioides infections in maize, particularly in relation to ear rot and fumonisin contamination (Sumartini et al., 2019; Rahmawati et al., 2020). To the best of our knowledge, there is no specific literature describing F. verticillioides as the cause of wilt disease in Indonesian sorghum. This statement is based on the results of literature searches conducted in international databases (such as Scopus, Web of Science, and Google Scholar) and on currently available national publications before this paper was submitted, ensuring that the information presented reflects the most up-to-date findings accessible at the time of manuscript preparation. In South Sulawesi, which is among the main regions targeted for sorghum development, farmers have recently observed severe wilting symptoms in sorghum fields, leading to significant stand losses. The disease was characterized by leaf chlorosis and rolling, vascular discoloration, and root rot symptoms. Preliminary observations suggested the involvement of a Fusarium species, but the causal agent had not been confirmed.

Documenting new disease occurrences is crucial for plant health monitoring and for developing effective disease management strategies. The use of resistant varieties, crop rotation, and seed health management are key components of an integrated disease management program, as rapid and accurate pathogen identification is crucial. In this context, the objective of this study was to identify the causative agent associated with sorghum wilt symptoms through morphological and molecular analysis. Furthermore, by applying Koch’s postulates, this study also confirms the pathogenicity of F. verticillioides in sorghum. As a final objective, this study presents the first report on F. verticillioides as the causative agent of sorghum wilt in South Sulawesi, Indonesia. This will enhance the national plant disease database and aid future management strategies.

2. Materials and Methods

2.1. Study location and duration

The study was conducted in sorghum fields located in Maros Regency, South Sulawesi, Indonesia, from May 2025 to September 2025. Laboratory analyses were carried out at the Plant Pathology Laboratory and the Molecular Biotechnology Laboratory for DNA identification at Board for the Assembly and Modernization of Agriculture, Ministry of Agriculture, Republic of Indonesia.

2.2. Field survey and symptom observation

The initial stage of the study involved a field survey conducted during the vegetative growth phase through the early generative phase of sorghum plants. The wilting symptoms observed included leaf curling, marginal chlorosis, necrosis, discoloration of vascular tissue in the stem, and partial root rot accompanied by reduced lateral root development. Disease incidence was calculated as the percentage of symptomatic plants relative to the total number of plants observed. Disease severity was assessed using a 0–4 ordinal scale as described by Willocquet et al. (2023), where 0 indicates no symptoms, 1 indicates very mild symptoms, 2 indicates moderate symptoms, 3 indicates severe symptoms, and 4 indicates very severe or total tissue damage.

To improve reliability, the severity levels were categorized by two observers independently. The observation results were then compared, and if there were discrepancies, discussions were held until a consensus was reached. The frequency of plants in each severity category was recorded, and the Disease Severity Index (DSI) was calculated using a standard Formula 1:

$DSI\left(\text{\%}\right)=\frac{\sum \left(n_i\cdot v_i\right)}{N\cdot V}\times 100$ (1)

where $n_i$is the number of plants in category $i$, $v_i$is the severity score of category $i$(0–4) (Table 1), $N$is the total number of plants assessed, and $V$is the maximum score on the scale (4). This approach provides a quantitative measure of disease severity across treatments and allows for statistical comparison among genotypes. As emphasized by Willocquet et al. (2023), the use of ordinal scales and derived indices such as DSI is a widely accepted method in plant pathology for summarizing disease intensity in epidemiological studies.

Table 1
Disease severity scales (0–4) based on the DSI (Disease Severity Index) method as described by Willocquet et al. (2023).

Category (i)	Severity Score (Vi)	Symptom Description
0	0	No symptoms, plant is healthy
1	1	Very mild symptoms, small spots or slight wilting (<10% tissue affected)
2	2	Mild symptoms, visible lesions but limited (10–25% tissue affected)
3	3	Moderate symptoms, considerable damage (26–50% tissue affected)
4	4	Severe symptoms, extensive damage or plant death (>50% tissue affected)

In this study, ten plants were assessed per replication, with six replications conducted for each treatment. Each variety (Numbu and Super 1) was planted in four plots, and within each replication, five observation points were selected systematically to represent field variability. This design ensured adequate sampling intensity and statistical robustness for evaluating disease incidence and severity

The Formula 2 used for disease incidence was:

$$\text{Incidence}(\text{\%})=\frac{\text{Number of diseased plants}}{\text{Total number of plants observed}}\times 100$$ (2)

2.3. Pathogen isolation and purification

Pathogen isolation was performed by excising discolored vascular tissues, which had been surface-sterilized with 1% sodium hypochlorite (NaOCl) for one minute, rinsed with sterile distilled water, and dried on sterile filter paper. The tissue segments were then placed on PDA medium and incubated at 28 ± 2 °C for 5–7 days. Emerging fungal colonies were subsequently purified using the single-spore isolation technique to obtain pure cultures.

2.4. Morphological characterization

Morphological characterization was conducted by culturing pure isolates on PDA and CLA media. Colony color, texture, and pigmentation were recorded, while microconidia were examined for shape, size, cell number, and chain formation patterns. Macroconidia were assessed for septation, size, and morphology, and the presence or absence of chlamydospores was noted. Morphological data were compared with the standard descriptions of F. verticillioides provided by Leslie and Summerell (2006).

2.5. Molecular identification

Molecular identification was carried out through genomic DNA extraction using a commercial kit following the manufacturer’s protocol. PCR amplification targeted the ITS and TEF1-α regions using primers ITS1/ITS4 (White et al., 1990) and EF1/EF2 (O’Donnell et al., 1998). PCR conditions consisted of an initial denaturation at 95 °C for 5 minutes, followed by 35 cycles of denaturation at 95 °C for 30 seconds, annealing at 55 °C for 30 seconds, and extension at 72 °C for 1 minute, with a final extension at 72 °C for 10 minutes. PCR products were visualized by electrophoresis on 1.5% agarose gels, and fragments of approximately 550 bp (ITS) and 700 bp (TEF1-α) were submitted for sequencing. Sequence data were analyzed using BLAST (Altschul et al., 1990) and against the GenBank database, and phylogenetic analysis was performed using the Maximum Likelihood method in MEGA 11 software with the Kimura 2-parameter model and 1000 bootstrap replications. Isolate FV-SR01 was compared with Fusarium isolates from various countries, with Trichoderma ITS used as an outgroup (Tamura et al., 2021).

2.6. Pathogenicity test

Healthy sorghum seeds were planted in petri dishes containing sterile agar medium that had been sterilized to test for pathogenicity. Over a 14-day period, a conidial suspension of isolate FV-SR01 at a concentration of 10^(−6) conidia/mL was inoculated at the base of the seedlings, while the negative control received only sterile water. Each treatment was repeated six times (6 replicates), with 10 plants per replicate, resulting in a total of 60 plants per treatment. The experiment was conducted in a greenhouse with environmental conditions controlled according to research standards: temperature 25–28 °C, relative humidity 70–80%, and natural lighting adjusted to field conditions. Watering was performed regularly to maintain soil moisture, but not excessively to prevent the emergence of symptoms.

Disease symptoms were recorded for twenty-one days following inoculation, with observations conducted weekly (at 21, 28, 35, 42, 49 and 56 days). As described by Willocquet et al. (2023), disease severity was assessed using an ordinal scale of 0–4. After two observers independently classified the severity levels, the results were compared and verified through discussion to reach a consensus, ensuring data integrity. Each plant severity category was recorded, and a Disease Severity Index (DSI) was calculated using a standard formula.

To confirm the pathogen’s identity and satisfy Koch’s postulates, re-isolations were performed from symptomatic plant tissues. The resulting colonies were then identified morphologically (through microscopic observation of the shape of conidia, hyphae, and reproductive structures) and confirmed molecularly using PCR with primers specific to F..verticillioides. To confirm the identity of the isolate, the sequencing results were compared with the GenBank database. The role of isolate FV-SR01 in causing wilt disease in sorghum was confirmed through this procedure.

2.7. Data analysis

Data on disease incidence and severity were analyzed using analysis of variance (ANOVA), and differences between sorghum varieties were further evaluated using Duncan’s Multiple Range Test (DMRT) at a 5% significance level. Morphological and molecular data were analyzed descriptively and comparatively against reference descriptions. All experimental procedures were conducted under biosafety level 2 standards for handling plant pathogens. Validation of results was ensured by repeating isolation, identification, and pathogenicity testing three times to confirm data consistency.

3. Results and Discussion

3.1. Field symptoms and disease incidence

Typical wilt symptoms were observed in sorghum fields at Maros Regency during the vegetative to early reproductive stages.

Affected plants initially exhibited slight leaf rolling and marginal chlorosis, which gradually progressed to complete wilting and necrosis within 7–10 days. In severe cases, plants were stunted with dry lower leaves and poor panicle development. Longitudinal sections of the stems revealed brown to dark discoloration of the vascular bundles, and root systems were partially decayed with reduced lateral roots (Figure 1). The incidence of diseased plants in surveyed fields ranged from 11% to 100%, depending on soil moisture and previous crop history. These symptoms were consistent with descriptions of Fusarium wilt or stalk rot of sorghum reported in other countries (Thakur et al., 2013; Corallo et al., 2025). The pattern of field distribution and the occurrence in patches suggested a soil-borne nature of the pathogen.

Figure 1
Symptoms of Fusarium Infection in Sorghum Plants in South Sulawesi, Indonesia.

As the observation period after planting progressed, the incidence and severity of Fusarium wilt in the Numbu and Super 1 varieties increased, as shown in Figure 2. Regarding disease incidence, both varieties showed a significant increase from 21 to 56 days after planting (DAP). At the start of the observation period (21 DAP), the incidence of the Super 1 variety (27.72%) was significantly higher than that of Numbu (11.08%), but in subsequent observations (28–56 DAS), there was no significant difference between the two varieties, and the incidence rate continued to rise, reaching 100% at the end of the observation period (56 DAS). However, both varieties showed a progressive increase over time in disease severity. At the early stage (21 DAP), there was no significant difference between Numbu (13.05%) and Super 1 (14.22%). However, from 28 to 42 DAP, the Super 1 variety tended to exhibit more severe disease compared to Numbu, although this difference varied significantly. At 49 DAP, the Super 1 variety exhibited higher disease severity (91.66%) compared to Numbu (85.56%) with a significant difference. At the end of the observation period (56 DAP), both varieties Overall, these findings indicate that, although there were initial differences in disease progression between the two varieties, in the late stages of infection, both the incidence and severity of the disease tended to be relatively uniform and high. This suggests that, under the test conditions, the two varieties exhibited a relatively similar level of susceptibility to Fusarium wilt.

Figure 2
Mean Incidence and Severity of Fusarium Wilt Disease in Numbu and Super 1 Varieties. For each variable, numbers followed by the different letters in the same column are significantly different.

3.2. Morphological characteristics of the isolates

Fungal colonies consistently emerged from discolored vascular tissues within 3–5 days on PDA. The colonies were initially white and floccose, becoming pale violet (Figure 3A) with age and producing abundant aerial mycelia and light pink pigmentation on the reverse side. On carnation leaf agar (CLA), microconidia were abundant, single-celled, oval to cylindrical, and produced in long chains on monophialides. Macroconidia were relatively scarce, slightly curved, 3–5 septate, and measured 28–45 × 3–5 µm (mean 36 × 4 µm). Chlamydospores were absent (Figure 3B).

Figure 3
F. verticiliodes on PDA (A) and Conidia of F. verticiliodes under a microscope (400x) (B).

These morphological characteristics corresponded well with descriptions of F. verticillioides (Leslie and Summerell, 2006), distinguishing it from closely related species such as F. proliferatum and F. thapsinum by its production of long chains of microconidia and lack of chlamydospores. Based on these features, the isolate was provisionally identified as F. verticillioides and designated as FV-SR01.

3.3. Molecular identification

PCR amplification of the ITS and TEF1-α regions yielded fragments approximately 550 bp and 700 bp in length (Figure 4). BLASTn analysis of the ITS sequence from isolate FV-SR01 showed 99.8% similarity to the reference strain F. verticillioides NRRL 22172 (GenBank accession no. MN046896). Similarly, the TEF1-α sequence showed 100% similarity with the F. verticillioides isolate CBS 117825 (GenBank accession no. KF466382). Phylogenetic analysis using the Maximum Likelihood method placed FV-SR01 within the F. verticillioides clade with high bootstrap support (Firuge 5). These molecular data, together with the morphological characterization of conidia and hyphal structures, strongly support the identification of the isolate as F. verticillioides (Sacc.) Nirenberg, although the use of additional markers such as β-tubulin or calmodulin could further strengthen the confirmation of the pathogen’s identity.

Figure 4
Results of molecular identification as observed on agarose gel electrophoresis.

The phylogenetic tree constructed from ITS DNA sequences reveals genetic relationships among the tested Fusarium isolates (Figure 5). Some isolates cluster within the F. verticillioides complex, indicating genetic proximity to the reference strain, while other isolates form Separate clades corresponding to different Fusarium species. The branching pattern highlights the presence of considerable genetic diversity within this genus, with bootstrap values providing strong support for the major nodes. However, it should be noted that the ITS marker has resolution limitations and is not always capable of accurately distinguishing species within the F. fujikuroi complex. Therefore, these results only support the indication of the isolates’ affiliation with the F. verticillioides lineage, and further confirmation using additional markers such as TEF1-α, β-tubulin, or calmodulin is required to definitively determine species identity. These findings suggest that isolates from sorghum in South Sulawesi are largely associated with the F. verticillioides complex, although the presence of a separate clade indicates the involvement of several taxa in the wilt disease complex.

Figure 5
Phylogenetic Tree Based on ITS (Internal Transcribed Spacer) DNA Sequences of Various Fusarium Isolates.

Fusarium isolates from sorghum in South Sulawesi show a very high degree of similarity to F. verticillioides isolates from various countries, according to sequence homology analysis. Isolates from China (MT180471, PP892743) and Egypt (OR856080) have a homology percentage of 99.5–99.8% (Table 2). This near-100% similarity clearly indicates that the local isolates belong to the species F. verticillioides. The molecular results also support the previous morphological identification.

Table 2
Nucleotide Homology of Fusarium Isolates from Sorghum Originating in Makassar, South Sulawesi, Compared with Eight Fusarium Isolates from Different Countries Using the Kimura 2-Parameter Model in MEGA Fusarium 11. HW816241 Trichoderma ITS Was Used as an Outgroup Comparator.

No	Sequence	1	2	3	4	5	6	7	8	9
1	HW816241.1_JP_2015027308-A/7:_Trichoderma_ITS	ID
2	PQ152255.1_Fusarium_pseudoanthophilum_isolate_Linzhi_soil_Tibet	-16,7	ID
3	HQ995667.1_Gibberella_Fujikuroi_Var._moniliformis_Rice_India	-16,7	99,3	ID
4	MK020694_F._proliferatum_Maize_Nigeria	-16,7	98,4	99,2	ID
5	KT996046.1_Fungal_sp._isolate_E2709B_Piper_ostii_Ecuador	-16,7	98,1	98,9	99,3	ID
6	PV035054_Fusarium_oxysporum_f._sp._ciceris_India	-16,7	97,3	97,8	98,1	99,2	ID
7	OR856080.1_F._verticillioides_strain_RS1_Soil_Egypt_1	16,7	97,2	97,5	97,9	98,3	98,7	ID
8	MT180471.1_F._verticillioides_isolate_HYS_Rice_China_1	-16,7	97,2	97,5	97,9	98,3	98,7	99,2	ID
9	PP892743_F._verticillioides_breed_Maize_China_1	-16,7	97,2	97,5	97,9	98,3	98,7	99,2	99,6	ID
10	Fusarium_Shorgum_Mks_South_Sulawesi_Indonesia	-16,7	97,2	97,5	97,9	98,2	98,6	99,1	99,5	99,8

From various countries, according to sequence homology analysis. Isolates from China (MT180471, PP892743) and Egypt (OR856080) share 99.5–99.8% homology. This near-100% similarity clearly indicates that the local isolates belong to the species F. verticillioides. Molecular results also support the previous morphological identification. Furthermore, a lower similarity rate, around 97–98%, was found when compared to other species, such as F. proliferatum (Nigeria) and F. oxysporum (India), indicating that the South Sulawesi isolates are closer to F. verticillioides than to being part of those species. This is particularly important because several F.fujikuroi species exhibit similar morphology, making molecular confirmation essential for identifying the pathogen.

Overall, sequence homology data support the conclusion that the FV-SR01 isolate from sorghum in South Sulawesi belongs to the F. verticillioides clade. The high degree of similarity with isolates from various countries indicates strong genetic conservation within this species and suggests that F. verticillioides is the primary pathogen causing sorghum wilt at the study site. These results indicate that F. verticillioides is the cause of sorghum wilt in Indonesia, supported by solid molecular evidence.

3.4. Pathogenicity test

Wilt symptoms appeared on inoculated sorghum seedlings 10–12 days after inoculation (Figure 6). Infected plants exhibited yellowing of the lower leaves, followed by wilting and vascular discoloration identical to those observed in the field. No symptoms were observed on control plants inoculated with sterile water. The disease severity index reached 3.6 on the 0–4 scale, corresponding to 80–90% leaf wilting after 21 days.

Figure 6
(A) Healthy Sorghum Seedlings; (B) Sorghum Seedlings Exhibiting Wilt Symptoms.

The same fungus was consistently re-isolated from symptomatic seedlings, showing identical colony morphology and microscopic characteristics to the original isolate FV-SR01. Recovered isolates were also confirmed as F. verticillioides through ITS sequence analysis, thereby satisfying Koch’s postulates and confirming the pathogenic role of the isolate in causing sorghum wilt in South Sulawesi.

4. Discussion

In South Sulawesi, changes in the incidence and severity of wilt disease in the sorghum varieties Numbu and Super 1 reveal a complex relationship between tropical environmental factors, pathogen epidemiology, and the genetic susceptibility of the varieties. In the early stages of infection (21 DAS), the incidence was still relatively low, but it increased sharply within a short period of time, reaching nearly 100% at 42–56 DAS. This pattern indicates that F. verticillioides has a high infective capacity and can rapidly invade tissues following the initial phase of infection.

High temperatures (25–32 °C), fluctuations in relative humidity, and frequent dry spells followed by rainfall characterize the tropical environment of South Sulawesi, as reported by the Indonesian Meteorological, Climatological, and Geophysical Agency (BMKG, 2026). These factors are known to accelerate conidial germination and pathogen penetration into plant tissues, as well as induce physiological stress in plants, thereby increasing susceptibility to infection (Corallo et al., 2025). Additionally, the combination of high temperatures and suitable humidity also accelerates the development of wilt symptoms, as observed in Fusarium epidemics in other tropical regions (Zeng et al., 2021).

Phylogenetic analysis based on ITS sequences indicates that isolate FV-SR01 from sorghum in South Sulawesi clusters closely with F. verticillioides isolates from several countries, including China (MT180471, PP892743) and Egypt (OR856080), with nucleotide homology levels of 99.5–99.8%. Although ITS supports affiliation with F. verticillioides, the limited resolution of this marker within the F. fujikuroi complex should be noted; therefore, the use of additional markers such as TEF1-α, β-tubulin, or calmodulin would further strengthen the confirmation of species identity. The branching pattern with high bootstrap support indicates consistent genetic relationships among isolates, consistent with recent reports confirming high genetic conservation within this species (Ferrigo et al., 2023; Tsehaye et al., 2017)

Since this is the first report of F. verticillioides infecting sorghum in South Sulawesi, possible causes of disease emergence in sorghum should be considered. These may include pathogen spillover from maize, which is a more common host, environmental conditions favoring cross-infection, and the use of contaminated seeds.

From a methodological perspective, morphological analysis remains important for initial identification, as it provides direct evidence of colony characteristics and spore morphology. However, molecular testing is required to achieve higher resolution and confirm species identity, especially within complexes such as F. fujikuroi. Morphological methods alone may be limited by overlapping traits among species, while molecular methods alone may miss phenotypic variability. Therefore, the combined use of morphological and molecular approaches provides complementary strengths, ensuring more accurate identification.

From an epidemiological perspective, F. verticillioides is of particular concern due to its ability to produce fumonisins, a group of mycotoxins harmful to human and animal health. Fumonisin production in cereals can lead to health issues such as leukoencephalomalacia in horses, esophageal cancer in humans, and toxic effects in livestock (Opoku et al., 2026; Tsehaye et al., 2017). Tropical conditions characterized by high temperatures and recurring drought periods can exacerbate disease development and increase fumonisin accumulation in sorghum seeds, as described in a recent study (Corallo et al., 2025). These findings underscore the importance of implementing integrated disease management strategies, including the use of pathogen-free seeds, crop rotation with non-host species, crop residue management, and the development of sorghum varieties that are more resistant to Fusarium infection and fumonisin accumulatio.

Acknowledgements

The authors gratefully acknowledge the Indonesia Endowment Fund for Education (Lembaga Pengelola Dana Pendidikan Republik Indonesia – LPDP RI) for providing full financial support through LPDP Doctoral Scholarship Program (SK. No. LOG-716/LPDP.3/2024). This support was essential for the successful implementation of the experiments and analyses conducted in this study.

Data Availability Statement

Data supporting the findings of this study are available from the corresponding author upon reasonable request

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• Editor
  Takako Matsumura Tundisi

Publication Dates

• Publication in this collection
  20 July 2026
• Date of issue
  2026

History

• Received
  21 Dec 2025
• Accepted
  30 Apr 2026