ISOLASI DAN IDENTIFIKASI CENDAWAN TERBAWA BENIH KAKAO HIBRIDA

ABSTRAKBenih merupakan komponen dasar dalam menentukan produktivitastanaman kakao. Benih yang sehat dapat merupakan faktor penting dalammenentukan keberhasilan produktivitas kakao. Benih kakao mempunyaikadar air cukup tinggi sehingga berpotensi terinfeksi cendawan, yangdapat menurunkan mutu benih dan produksi kakao. Penelitian bertujuanuntuk mengisolasi dan mengidentifikasi beberapa cendawan terbawa benihpada kakao hibrida. Penelitian dilakukan di Kebun Induk Benih PusatPenelitian Kopi dan Kakao Indonesia, Jember, Laboratorium Mikro-biologi, Balai Penelitian Bioteknologi Perkebunan Indonesia, danLaboratorium Pengendalian Hayati IPB Bogor pada bulan Juni sampaiOktober 2008. Penelitian menggunakan benih kakao hibrida dari hasilpersilangan buatan antar TSH 858 dengan Sca 6, dan percobaan disusundengan rancangan acak lengkap dengan 3 ulangan. Benih ditumbuhkanpada 3 media, yaitu water agar (WA), potato dextrose agar (PDA), dankertas saring (KS). Tingkat infeksi pada benih diamati setiap hari dandianalisis dengan analisis sidik ragam dan dilanjutkan dengan uji selangberganda Duncan. Cendawan diisolasi, dibiakkan, dimurnikan, dandiidentifikasi dengan menggunakan buku kunci identifikasi. Tingkatinfeksi cendawan terbawa benih kakao hibrida tertinggi terdapat pada harikeempat (35,00%) dan kelima (51,67%) pada media PDA. Sebanyak 13spesies cendawan terbawa benih kakao hibrida berhasil diidentifikasidengan menggunakan media WA dan PDA, serta 8 spesies cendawandengan media KS. Ke-13 cendawan terbawa benih yang ditemukan sangatberpotensi menurunkan mutu fisiologis benih dan produktivitas kakao.Cendawan tersebut perlu diuji lebih lanjut karena masing-masing memilikisifat-sifat patogenik, saprofitik, atau antagonistis terhadap cendawan lainpada benih kakao. Cendawan terbawa benih kakao hibrida paling dominanadalah Aspergillus spp., Penicillium chrysogenium, Coletotrichumacutatum, Curvularia geniculata, dan Fusarium spp. Cendawan-cendawanyang diduga berbahaya adalah Aspergillus spp., Coletotrichum acutatum,Curvularia geniculata, Fusarium spp., Phoma glomerata, danMacrophoma sp., dan yang diduga bersifat patogenik adalah Aspergillusflavus, Aspergillus ochraceus, Cladosporium herbanum, Curvulariageniculata, Fusarium oxysporum, Phoma glomerata, dan Macrophoma sp.Kata kunci : Theobroma cacao, benih hibrida, infeksi cendawan, mediatanamIsolation and Identification of Fungi on Hybrid Cacao SeedsABSTRACTSeed is the basic component influencing the productivity of cacaoplantation. Healthy seed is the most important factor in determining thesuccess of cacao productivity. Moisture content of cacao seeds is quitehigh potentially to cause fungi infection, which can further reduce seedquality and cacao production. The research aimed at isolating andidentifying several seedborne fungi on hybrid cacao. The study wasconducted at main nursery of Indonesian Coffee and Cocoa ResearchInstitute Jember, Laboratory of Microbiology, Indonesian BiotechnologyResearch Institute for Estate Crops, and the Laboratory for BiologicalControl of IPB Bogor from June to October 2008. Research used hybridcacao seeds derived from crossing between TSH 858 x SCA 6, and theexperiment was arranged using completely randomized design with threereplicates. Cacao seeds were grown on three media, i.e. water agar (WA),potato dextrose agar (PDA), and filter paper (KS). Infection rates on theseedlings were observed every day and analyzed using ANOVA followedby Duncan's multiple regression test (DMRT). Fungi were isolated,cultured, purified, and identified using the identification keys. The highestrate of seedborn fungal infection occured on fourth (35.00%) and fifth(51.67%) days on PDA media. A total of 13 species of seedborn fungi onhybrid cocoa were identified by using WA and PDA media, as well as 8other species by using KS. The 13 seedborne fungi potentially reduce seedphysiological quality and cacao productivity. These fungi need to befurther tested because each has its own pathogenic, saprophytic, orantagonistic properties towards other fungi on cacao seeds. Predominantseedborn fungi on hybrid cacao were Aspergillus spp., Penicilliumchrysogenium, Coletotrichum acutatum, Curvularia geniculata, andFusarium spp. The fungi suspected harmful were Aspergillus spp.,Coletotrichum acutatum, Curvularia geniculata, Fusarium spp., Phomaglomerata, and Macrophoma sp., and those suspected pathogenic wereAspergillus flavus, Aspergillus ochraceus, Cladosporium herbanum,Curvularia geniculata, Fusarium oxysporum, Phoma glomerata, andMacrophoma sp.Key words : Theobroma cacao, fungi infection, hybrid seed, growingmedi