Anthracnose of Onion (Allium cepa L.): A Twister Disease

Abstract

The onion (Allium cepa L.) is a lucrative and high-value vegetable–spice crop in India, but it is sensitive to several of diseases caused by fungi, bacteria, viruses, and nematodes, of which a fungal disease, anthracnose, caused by Colletotrichum spp., is a major issue for both onion producers and researchers since it severely affects the bulb production. Twister disease is currently one of the most common problems in onion production, particularly in humid regions, and it reduces productivity while also lowering the value and profitability. Twister disease is visualised by white or pale-yellow water-soaked oval depressed lesions on leaf blades, which are the first symptoms. Lesions expand as the disease advances, and numerous black-coloured, slightly elevated structures/fruiting bodies appear in the middle area, arranged in concentric rings. Curling, twisting, chlorosis of the leaves, and aberrant extension of the neck or pseudo-stem occurs, followed by rotting of the bulb. In an unmanaged crop, an excess gibberellin production by Colletotrichum gloeosporioides and Gibberella moniliformis is suspected to induce twisting and aberrant neck elongation, which will ruin onion productivity. It is difficult and environmentally unfriendly to control these infections. Since, to the best of our knowledge, this is the first review on onion anthracnose, we tried to consolidate information. This review updates our knowledge of the pathogen, including the disease cycle, infection pathways, and disease management techniques. As a result, growers will be benefit from the application of cultural, biological, and chemical measures and the use of resistant varieties.

Possible Morphological and Chemical Resistance Mechanism of Shallots (Allium Cepa Var Ascalonicum) to Colletotrichum Gloeosporioides Penz

“…However, the study identified another alternative, Tajuk, which showed lower severity, compared with the other genotypes, up to five weeks after inoculation. As reports on Sumenep not producing a flower that might cause a problem in the utilization as a source of resistance for breeding (Dutta et al, 2022), the partial resistance found in Tajuk could be useful and noteworthy, in addition to fungicide application to control C. gloeosporioides.…”

“…Later, the infection moves to the neck region or above the basal plate. Further, the symptoms superficially will appear on bulbs, spread to inner tissue, causing deformation and rotting of the bulb, and in the worst case, continue to complete death of the plant (Dutta et al, 2022). Since the leaf infection could result in yield reduction and rotting of bulbs during and after storage, the resistance properties in the shallot leaves are most relevant, determining the success of shallot production.…”

“…Although several studies stated that the Sumenep variety was moderately resistant to anthracnose (Galvan et al, 1997;Hidayat and Sulastrini, 2016), more studies need pursuing indicated by the absence of newly developed resistant varieties with high yields in Indonesia. A cause of this may be the inability of the Sumenep variety to flower (Galvan et al, 1997;Dutta et al, 2022). Therefore, screening for resistance to C. gloeosporioides is highly required to find good resistance sources in shallot.…”

Inventarisasi Penyakit Bawang Merah (Allium ascalonicum L.) Varietas Lokananta Asal Biji (True Shallot Seed)

“…Jamur terutama menginfeksi pada daun atau bagian tanaman yang lemah, memproduksi berbagai macam struktur infeksi seperti konidia, acervulus, seta dan apresoria selama proses infeksi pada proses interaksi inang dan patogen (Gautam, 2014). Gejala awal dari penyakit ini adalah bercak berwarna hijau muda kekuningan atau berupa bercak kecil berwarna putih (Galvan et al, 1997;Dutta et al, 2022). Gejala khas yang nampak pada tanaman yaitu daun menguning, melengkung, berlekuk, klorosis dan malformasi pada leher daun.…”

“…Gejala khas yang nampak pada tanaman yaitu daun menguning, melengkung, berlekuk, klorosis dan malformasi pada leher daun. Gejala lanjut menyebabkan akar tanaman menjadi lebih sedikit dan lebih pendek dibanding pada tanaman sehat, kemudian tanaman akan mati (Dutta et al, 2022;Sarianti dan Subandar, 2022). Infeksi biasanya muncul pada daun yang lebih tua, serangan lanjut menyebabkan daun layu dan mati (Galvan et al, 1997).…”