全球范围内,辣椒(CapsicumannuumL.)是经济上最重要且种植最广泛的作物之一,具有营养和营养潜力,并增强食物的味道和香气(Ayob等人。,2022年;Kiran等人。,2020)。炭疽病被认为是辣椒生产的主要制约因素,导致热带和亚热带国家的巨大损失。2022年9月,辣椒水果展示沉没,从Flacq获得了皱缩和深色的黑色病变,表面上有丰富的小囊,毛里求斯。从有症状的组织中,切除了小块患病组织,使用1%次氯酸钠进行表面消毒,用无菌蒸馏水冲洗两次,风干并镀在PDA上。在室温下孵育7天后,回收了白色至灰色白色菌落和密集的白棉气生菌丝体。在两个分离物中,CHF和CH10,后者被认为是形态和分子表征。观察到的分生孢子(n=30)是单细胞的,直,圆柱形,两端呈圆形,中心附近有轻微收缩,平均长度和宽度为20.5µm和6µm,分别。对于隔离物的生长速率测量,从菌落的生长边缘取两个5×5毫米的真菌琼脂塞,接种在单个PDA平板的中心,并在室温下以自然光/黑暗循环孵育。垂直测量培养物的直径持续7天的时间,并将生长速率计算为每日生长的7天平均值(mm天-1)。在PDA上,真菌分离株(CH10)的生长速率为13.5mmday-1。根据形态特征,该分离物被分类在C.gloeosporioides物种复合物中。为了精确识别分离物,使用传统的DNA分离方法(Ranghoo和Hyde,2000),然后使用引物对ITS4/ITS5进行PCR扩增和DNA测序(White等人。,1990),GDF/GDR和T1/Bt2b(Gan等人,2016),分别。ITS基因序列(600bp)证实该分离株为炭疽菌,与KR704204相似99.83%,而GADPH(277bp),TUB2(733bp)和ApMat(801bp)基因序列与GenBank参考序列显示出99.64%至100%的相似性。分别为KT372374、KU221378和MG674932。分离物CH10的基因序列以以下登录号OR681557(ITS)保存在GenBank数据库中,OR233734(GADPH),OR475575(TUB2)和PP622748(ApMat)。通过用从7天大的分离株CH10菌落中制备的10μL分生孢子悬浮液(1×106孢子/ml)喷洒无病辣椒植物来证实Koch的假设。用无菌蒸馏水接种的健康辣椒植物用作阴性对照实验。这些植物在25℃的潮湿室内的盆中生长。接种后5天,试验植物出现炭疽病症状,而对照植物则无症状。从试验果实中成功回收原始分离物,从而实现了科赫的假设。该实验重复三次,并显示出相同的结果。据我们所知,这是毛里求斯的第一个记录,也是第一次报道由这种真菌引起的辣椒炭疽病。先前在欧洲曾报道过昆士兰炭疽病,墨西哥,US,波多黎各,澳大利亚,斐济,巴西,印度尼西亚和中国。此外,后者与木瓜有关,鳄梨,腰果,咖啡,波斯石灰,Licaniatomentosa,白色红树林,荔枝,芒果,肾标,橄榄,西番莲,柬埔寨龙血树和西海树(卡马拉和维埃拉,2022年;Shidiq等人。,2024;Wang等人。,2022年)。这项研究将使当地农民的培训和推广设施,以提高农民对这种致病因子的认识,并使他们能够采取必要措施,在毛里求斯建立辣椒作物对这种新出现的病原体的抵御能力。
Globally, chilli (Capsicum annuum L.) is one of the most economically important and widely cultivated crop which elicits ethnomedicinal and nutritional potential as well as enhancing the taste and aroma of foods (Ayob et al., 2022; Kiran et al., 2020). Anthracnose disease is regarded as a prime constraint in chilli production, leading to enormous losses in tropical and subtropical countries. In September 2022, chilli fruit displaying sunken, shriveled and dark bown to black lesion with abundant acervuli on the surface was obtained from Flacq,
Mauritius. From the symptomatic tissue, small pieces of the diseased tissue were excised, surface-disinfected using 1% sodium hypochlorite, twice rinsed using sterilized distilled water, air-dried and plated on PDA. After 7 days of incubation at room temperature, white to greyish white colony with dense white cottony aerial mycelium was recovered. Out of two isolates, CHF and CH10, the latter was considered for morphological and molecular characterization. The observed conidia (n=30) were unicellular, straight, cylindrical with rounded ends and slight constriction near the centre and had average length and width of 20.5 µm and 6 µm, respectively. For growth rate measurement of the isolate, two 5×5 mm of fungal agar plugs were taken from growing edge of colony, inoculated at centre of individual PDA plate and incubated at room temperature with a natural light/dark cycle. The diameter of the cultures were measured perpendicularly for a period of 7 days and the growth rate was calculated as 7-day average of daily growth (mm day-1). The growth rate of the fungal isolate (CH10) was 13.5 mm day-1 on PDA. Based on the morphological characters, the isolate was classified within the C. gloeosporioides species complex. For precise identification of the isolate, DNA was extracted from fungal mycelium using traditional DNA isolation methods (Ranghoo and Hyde, 2000), followed by PCR amplification and DNA sequencing using primer pairs ITS4/ITS5 (White et al., 1990), GDF/GDR and T1/Bt2b (Gan et al., 2016), respectively. ITS gene sequence (600 bp) confirmed that the isolate was Colletotrichum, with 99.83% similarity to KR704204 while GADPH (277 bp), TUB2 (733 bp) and ApMat (801 bp) gene sequences showed 99.64 to 100% similarity to C. queenslandicum with GenBank reference sequences, KT372374, KU221378 and MG674932 respectively. The gene sequences of isolate CH10 were deposited in GenBank database under the following accession numbers OR681557 (ITS), OR233734 (GADPH), OR475575 (TUB2) and PP622748 (ApMat). Koch\'s postulates were confirmed by spraying disease-free chilli plants with 10µL of conidial suspension (1 × 106 spores/ml) prepared from 7 days old colony of isolate CH10. Healthy chilli plants inoculated with sterile distilled water served as a negative control experiment. The plants were grown in pots in a moist chamber at 25˚C. After 5 days post-inoculation, anthracnose symptoms were developed on test plants while the control plant remained asymptomatic. The original isolate was successfully recovered from the test fruits, thus fulfilling Koch\'s postulates. The experiment was repeated thrice and revealed the same results. To the best of our knowledge, this is the first record of C. queenslandicum in
Mauritius and is the first time to report anthracnose of chilli caused by this fungus. Colletotrichum queenslandicum has previously been reported in Europe, Mexico, US, Puerto Rico, Australia, Fiji, Brazil, Indonesia and China. Furthermore, the latter was associated with papaya, avocado, cashew, coffee, Persian lime, Licania tomentosa, white mangrove, lychee, mango, Nephelium lappaceum, olive, passionfruit, Dracaena cambodiana and Syzygium australe (Câmara and Vieira, 2022; Shidiq et al., 2024; Wang et al., 2022). This study will allow local farmers training and extension facilities to increase awareness among farmers about this disease-causing agent and allow them to take necessary measures for building up chilli crops resilience against this new and emerging pathogen in
Mauritius.