Wheat (Triticum aestivumL.) is a herbaceous plant of the Poaceae family, native to the Near East [1] and cultivated in several regions of the world, mainly in temperate zones [2] for its seeds rich in carbohydrates, proteins, minerals, vitamins, and fiber, which facilitate intestinal transit [3]. It is one of the most widely consumed cereals in the world [4] and ranks third after maize and rice [5]. Wheat grains are one of the main raw materials in the baking industry, and the starch extracted from these grains is used as a raw material in the manufacture of several non-food compounds such as ethanol, bioplastic, adhesive, paper, and cosmetics. This crop is also used as animal feed [6].

In 2023, global wheat production was estimated at 799 million tons. China, India, and Russia were the three leading global producers, with outputs of 136.6, 110.6, and 91.5 million tons, respectively. Cameroon, with an average production of around 599.67 tons, is not among the world’s leading wheat producers [7]. With such low wheat production, Cameroon therefore relies on imports to meet its wheat consumption. Hence, it is dependent on external sources for its wheat supply and imported approximately 859,000 tons, worth 154.27 billion CFA francs, in 2023 [8]. Consequently, the Cameroonian government has, since the Russian-Ukrainian war, been facing difficulties in importing wheat. To address these difficulties, the State of Cameroon has launched initiatives aimed at improving its wheat production. This revival of wheat production is being achieved through the distribution of improved seeds, fertilizers, pesticides, and agricultural tools to farmers, as well as through the organization of training sessions and the implementation of financial support programs.

As with any crop, the success of wheat cultivation depends on the use of good quality seeds, free from seed-borne fungi, and the application of good farming practices [9]. Despite these initiatives by the Cameroonian government, wheat production remains low and does not meet national demand. This low production is due to biotic and abiotic constraints. Among the biotic constraints, seed-borne fungi of wheat are the most feared. They are responsible for numerous fungal diseases transmitted to plants through seeds. These fungal diseases cause yield losses of up to 43% [10]. To support this evidence, several studies have reported numerous fungal species that cause diseases transmitted to plants through seeds. Thus, research conducted in Iran by [11] reported that fungi of the genera Penicillium, Bipolaris, Tilletia, Aspergillus and Fusarium were associated with wheat seeds. Similarly, work by [12] demonstrated that fungal species such as Alternariaalternata, Fusariummoniliforme, Aspergillus flavus and Bipolarissorokiniana were associated with wheat seeds cultivated in Pakistan. Those by [13], conducted in Egypt, showed that wheat seeds harbour 44 fungal species belonging to 20 genera, the most frequent of which were Alternariaalternata, Cladosporium sp., Epicoccumpurpurascens, Fusarium verticillioides, Penicillium sp., Stemphylium sp., and Tilletiatritici. These seed-borne fungi of wheat are responsible for numerous diseases, such as damping-off, which causes low germination rates [13]. Helminthosporiosis caused by Bipolarissorokiniana is a disease transmitted to plants through seeds, characterised by brown to black spots on the leaves and blackening of the grains [12].

In Cameroon, information on fungal diseases transmitted to plants by fungi associated with wheat seeds is virtually non-existent. The objective of this work was to carry out a study on the fungi associated with wheat seeds in order to demonstrate their existence and develop a means of controlling these wheat pathogens.

All the seeds tested were found to be infected by fungi, but at different levels. Overall, 4785 isolates belonging to 21 fungal species were identified from the different varieties of wheat seeds, including 2402 isolates for 21 species through the PDA culture medium method and 2383 isolates for 11 species using the rolled blotting paper method (Table 1). Among these different fungal species, the most frequent were species of Fusariumgenus, followed by Colletotrichum and Curvularia. Penicillium was the least frequent species. With the agar plate method, five fungal species were in the genus Fusarium and two species in the genera Aspergillus and Colletotrichumwere detected. The same observation (with the exception of the Fusarium genus) was made by the rolled blotting paper method, where four fungal species were identified.

The frequency of F. graminearum, C. graminicola, and Curvularialunata was 14.17, 9.89, and 9% respectively for the agar plate method, and 23.84, 14.55, and 11.05% respectively for the rolled blotting paper method. The frequency of Penicilliumsp. (the least frequent species) was 1.83 and 3.28% for the agar plate method and the rolled blotting paper method, respectively.

Table 1. Frequency (%) of different seed-borne fungi associated with wheat seeds.

*The numbers in brackets represent the number of occurrences of the fungal species, and/means that the fungal species was not observed.

Using the agar plate method, Fusariumgraminearum was the most frequent on all wheat seed varieties except for variety 20 HTWYT, where Curvularialunata was the most frequent (12.38%) (Table 2). On the IRAD 2 variety, F.graminearum (14.72%), Colletotrichumgraminicola (13.56%), and Curvularialunata (9.68%) were the most frequent, and Penicilliumsp. (1.16%) was the least frequent. With variety 20 HTWYT, C. lunata (12.38%) was the most frequent, followed by F. graminearum (10.99%) and Zymoseptoriatritici (10.31%). Mucor sp. was the least frequent (1.71%). C. graminicola and C. lunata had a frequency of 7.85% on variety 11 SATYNDR. On this same variety, species like Aspergillus, Nigrospora, and Acremoniumwere not detected. Similarly, Cladosporiumherbarum was not observed in varieties 12 HZWYT and 16 STEMRRSN.

Table 2. Frequency (%) of different seed-borne fungi associated with wheat seeds by the agar plate method.

*The numbers in brackets represent the number of occurrences of the fungal species, and/means that the fungal species was not observed.

With the rolled blotting paper method, the frequency of seed-borne fungi of wheat was present depending on the variety and fungal species involved (Table 3). Fusariumgraminearum was the most frequent on all wheat seed varieties except for variety 42 ESWYT, where Colletotrichumgraminicola was the most frequent (24.3%). For variety 20 HTWYT, Curvularialunata, F. graminearum, and F.avenaceum were the most frequent with respective frequencies of 19.73, 18.06, and 13.04%. Species such as Aspergillus flavus and Penicillim sp., with frequencies of 4.34% each, were the least frequent. C. graminicola (24.3%), F. graminearum (23.95%), and F. avenaceum (14.58%) were the most frequent in the 42 ESWYT variety. A. flavus and F. solani were the least frequent (5.55% each). Trichoderma hamatum was not observed in this wheat variety. In variety 12 HZWYT, F. graminearum was the most frequent (28.66%), followed by C. lunata (17.66%), and F. solani was the least common (2.66%). C. graminicola was not among the species identified on this wheat variety.

Table 3. Frequency (%) of different seed-borne fungi associated with wheat seeds by the rolled blotting paper method.

*The numbers in brackets represent the number of occurrences of the fungal species, and/means that the fungal species was not observed.

Twenty-one fungal species were detected in all varieties of wheat seeds. Their presence could be explained by the fact that wheat provides a favorable substrate for their development. The number of fungal species identified depended on the study method used. On PDA culture medium, 21 fungal species were sampled, while with the rolled blotting paper method, 11 fungal species were sampled. The presence of a greater number of fungal species on PDA culture medium is thought to be due to the fact that it is a favorable medium for the development of fungi, as it provides the nutrients necessary for their growth, whereas blotting paper is not a culture medium as it does not provide any nutrients. These results corroborate those of [12][23], who showed that PDA culture medium yielded a greater number of fungi compared to blotting paper.

The species such as: Alternariatriticina, Aspergillus flavus, A. niger, Bipolarissorokiniana, Epicoccumpurpurascens, Colletotrichumgraminicola, Colletotrichumsp., Curvularialunata, Fusariumculmorum, F. graminearum, F. oxysporum, F. avenaceum, F. solani, Mucorsp., Penicilliumsp., and Zymoseptoriatritici isolated in this study have been reported in the works of [24]-[26].

The work of [13] carried out in Egypt reported that wheat seeds harbour 44 fungal species, whereas the present study reported 21 fungal species. The low diversity of seed-borne fungi of wheat observed in this study could be explained by the quality of the seeds used. Indeed, these seeds came from IRAD and are considered to be of good quality. IRAD implements rigorous practices during the harvesting, processing, and storage of seeds, which greatly limits fungal contamination and helps maintain healthy seeds. In addition, agroclimatic conditions, duration, and storage conditions strongly influence the appearance of certain fungal species [12][27].

F. graminearum, C. graminicola, and C. lunata were the most common species, reflecting their pathogenic nature and ability to colonize wheat seeds. These fungal species, therefore, pose a threat to seed germination, the growth and development of wheat plants, and yield [28]. Furthermore, their predominance could also be due to environmental conditions favorable to their development, such as moderate to warm temperature and high humidity, which promote spore germination and infection of seeds [29].

Among the most frequent wereF.graminearum and C.lunata species. These results align with those of [11][25], whose studies show that F. graminearum was less frequent on wheat seeds grown in Canada. The higher frequency observed in our study could be related to local environmental conditions, including warm temperatures and prolonged humidity periods, which favor the proliferation of F. graminearum. Other factors, such as differences in working or storage conditions for wheat seeds. Penicilliumsp. was the least frequent. This low frequency of Penicillium could be explained by the fact that it is an opportunistic fungal species. In addition, the disinfection of wheat seeds in a sodium hypochlorite solution may have contributed to the destruction of all Penicilliumsp. associated with wheat seeds.

The work of [30] has shown that F. graminearum causes significant yield losses and secretes mycotoxins that are harmful to human and animal health. Colletotrichumgraminicola negatively affects seed viability and wheat plant vigour [31]. Curvularialunata causes leaf necrosis in wheat plants [32].

This study highlighted the diversity of seed-borne fungi of wheat cultivated in Cameroon. These results suggest the development of an effective strategy to combat these fungi in order to improve wheat production. In this regard, the findings highlight the need to screen wheat varieties for resistance, evaluate targeted seed treatment options, and strengthen routine seed health monitoring programs.

The authors are grateful to Research Unit of Applied Botany (URBOA) of the University of Dschang, Cameroon, and Life Science Laboratory of the University of Buea, Cameroon for laboratory facilities, and the Institute of Agricultural Research for Development (IRAD), Nkolbisson, Yaoundé center for the provision of wheat seeds.

N.N.N. and S.S.G. manipulated and drafted the main text of the manuscript. E.K.K., I.N. and G.T.N. coordinated the manipulations and also approved the final version of the manuscript. All authors carefully proofread the manuscript.