KARAKTERISASI DAN IDENTIFIKASI Colletotrichum spp. PENYEBAB ANTRAKNOSA MANGGA DI INDRAMAYU

GILANG VAZA BENATAR, Dr. Ir. Arif Wibowo, M.Agr.Sc.;Dr. Suryanti, S.P.,M.P.

2021 | Tesis | MAGISTER FITOPATOLOGI

Mangga merupakan salah satu komoditas hortikultura utama Indonesia. Indramayu, dikenal sebagai Kota Mangga, menjadi salah satu daerah sentra penghasil mangga. Budidaya mangga tidak terlepas dari berbagai hambatan, salah satunya hambatan biotik berupa infeksi patogen. Colletotrichum spp. adalah patogen penting pada mangga yang menyebabkan penyakit antraknosa. Kehilangan hasil akibat penyakit ini dapat mencapai 100%. Studi terkait antraknosa mangga di Indonesia sangat sulit ditemukan, terutama terkait karakteristik patogen penyebabnya. Penyebab antraknosa mangga di Indonesia teridentifikasi sebagai Gloeosporium mangiferaae pada awal abad 20 yang hingga kini diidentikkan sebagai C. gloeosporioides. Di sisi lain, telah teridentifikasi 18 spesies Colletotrichum spp. yang diasosiasikan sebagai penyebab antraknosa mangga di dunia. Diagnosis yang akurat terhadap patogen penyebab antraknosa mangga sangat penting dilakukan untuk merencanakan pengendalian yang efektif dan efisien. Dalam studi ini, gejala antraknosa yakni luka cekung melingkar berwarna cokelat kehitaman teramati pada kebun dan gudang simpan mangga di Indramayu. Insidensi dan intensitas penyakit mangga tercatat 28.4% dan 11.87% secara berturut-turut. Identifikasi dilakukan terhadap 14 isolat Colletotrichum spp. berdasarkan pendekatan morfologi dan analisis mulltigenik. Isolat Colletotrichum spp. dalam studi ini memiliki ciri morfologi berupa hifa bersepta dan hyaline; koloni aerial cottony, putih, putih-kehijauan, hingga putih-keabuan; koloni reverse didapati zonasi konsentrik putih, kuning, hingga oranye, dan di tengahnya berwarna hijau gelap; rerata pertumbuhan koloni 9,58 mm per hari; masa konidia salmon hingga oranye gelap dijumpai pada semua isolat kecuali isolat BR-HGL; konidia silindris dengan kedua ujung tumpul, tidak bersepta, hyaline, dan guttulate, panjang 12,86-17,88 mikro meter, dan lebar 3,45-5,01 mikro meter; apresoria cokelat, cokelat gelap atau cokelat kehitaman, dan ovoid hingga tidak beraturan; seta tegak lurus yang semakin meruncing ke puncak dan cokelat gelap nampak pada isolat BP-IMY, GL-JTY, GL-SKG, AP-SKG, dan DN-HGL. Semua isolat diketahui patogenik dalam uji patogenisitas. Gejala antraknosa terbentuk 1-4 hari setelah inokulasi dengan rerata diameter dan luas luka 24,57-470,07 mm2. Semua isolat erbagi ke dalam lima grup berdasarkan kategori morfologi dan uji patogenisitas. CKR-JTB, LJW-JTY, BR-HGL, AP-SKG, dan BP-IMY dipilih sebagai isolat representative untuk analisis multigenik menggunakan penanda ITS, Actin, dan GAPDH. Semua isolat terpilih teridentifikasi sebagai C. asianum dan didukung dengan kemiripan ciri morfologi. Studi ini merupakan laporan pertma C. asianum yang berasosiasi dengan antraknosa mangga di Indonesia.

Mango is one of Indonesia's main horticultural commodities. Indramayu, known as "The City of Mango", is one of the major mango-producing areas. Mango cultivation is inseparable from various obstacles. One of which is biotic stress caused by pathogen infection. Colletotrichum spp. is an important pathogen causing anthracnose disease. The yield loss due to this disease can reach 100%. Many anthracnose studies in Indonesia focus on control of the disease, but information related to its pathogens is extremely difficult to find. The mango anthracnose pathogen in Indonesia was identified as Gloeosporium mangiferaae in the early 20th century which until now known as C. gloeosporioides, while 18 species of Colletotrichum have been associated with the disease in the world. An accurate diagnosis is very important to underlie the development of more efficient control measures of the disease in this country. In this study, a field investigation was used to assess the occurrence of mango anthracnose in 5 subdistricts in Indramayu, and the disease was found in all the surveyed sites. Symptoms of dark-brown sunken spots to large chlorotic lesions that merged and formed a larger necrotic area were observed on mango fruit. The incidence and intensity of the disease were recorded to be 28.4% and 11.87% respectively. Identification was carried out on 14 Colletotrichum isolates based on a morphological approach and multigenic analysis. Furthermore, the isolates generally formed white, greenish-white, grayish-white, cottony, and sparse aerial hyphae. Also, dark orange conidial mass appeared on the aerial hyphae, while, reverse hyphae was white with concentric rings and dark green in the middle. Then, the mycelial growth rate was observed at 7.51-10.64 mm day-1 with an average of 9.58 mm day-1. The conidia of the isolated fungi were cylindrical with obtuse ends, smooth-walled, hyaline, and guttulate. The length and width of the conidia was 12.86-17.88 micrometer and 3.45-5.01 micrometer with an average of 16.81 micrometer and 4.57 micrometer respectively, while the length/width ratio was 3.55-4.19 with an average of 3.7. Appressoria were established from mycelia, which in most cases were dark brown, and ovoid to slightly irregular in shape. Seta perpendicular that tapered to the top and dark brown was seen in isolates of BP-IMY, GL-JTY, GL-SKG, AP-SKG, and DN-HGL. Generally, all the 14 isolates were pathogenic in the pathogenicity test. The anthracnose symptoms were formed 1-3 days after inoculation with the mean diameter and area of the lesion were 24.57 mm and 470.07 mm2 respectively. All of the isolates were divided into five groups based on morphological categories and pathogenicity test. Among all, CKR-JTB, LJW-JTY, BR-HGL, AP-SKG, and BP-IMY were chosen as representative isolates for multigenic analysis with ITS, Actin, and GAPDH marker pairs. All of the 5 chosen isolates belonged to C. asianum supported with morphological characteristics. This study is the first report of C. asianum associated with mango anthracnose in Indonesia.

Kata Kunci : mangga, antraknosa, Colletotrichum spp.