PATOGENISITAS BEBERAPA ISOLAT CENDAWAN TERBAWA BENIH KAKAO HIBRIDA

BAHARUDIN BAHARUDIN, A. PURWANTARA, S. ILYAS, M.R. SUHARTANTO

Abstract


ABSTRAK
Benih kakao hibrida diketahui dapat membawa beberapa mikroba
yang bersifat patogenik dan menurunkan mutu benih. Penelitian bertujuan
untuk mengetahui pengaruh beberapa isolat cendawan terbawa benih
terhadap penurunan viabilitas benih dan vigor bibit kakao hibrida.
Penelitian dilakukan di Kebun Benih Pusat Penelitian Kopi dan Kakao
Indonesia, Jember, Laboratorium Mikrobiologi dan rumah kaca Balai
Penelitian Bioteknologi Perkebunan Indonesia, Bogor, pada bulan Juli
sampai November 2008. Penelitian menggunakan 13 cendawan terbawa
benih kakao hibrida. Benih diperoleh dari persilangan buatan antara kakao
TSH 858 dengan Sca 6. Penelitian menggunakan model Rancangan Acak
Lengkap dengan 4 ulangan. Inokulasi patogen pada benih kakao dilakukan
dengan cara merendam benih di dalam suspensi patogen dengan kerapatan
10 6 spora/ml selama 30 menit. Selanjutnya benih ditanam pada media pasir
steril dalam boks plastik ukuran 30 x 30 cm, menurut rancangannya.
Setiap perlakuan diulang 4 kali. Parameter yang diamati adalah daya
berkecambah, indeks vigor, kecepatan tumbuh relatif, kecepatan
berkecambah T 50 , laju pertumbuhan kecambah, jumlah daun, tinggi bibit,
panjang akar, jumlah akar dan kematian benih. Data dianalisis dengan
ANOVA dan dilanjutkan dengan uji Jarak Berganda Duncan. Hasil
penelitian menunjukkan bahwa ke-13 spesies cendawan bersifat patogenik
pada benih kakao hibrida. Cendawan patogen terbawa benih yang bersifat
patogenik adalah Aspergillus flavus, A. ochraceus, Cladosporium
herbanum,  Curvularia  geniculata,  Fusarium  oxysporum,  Phoma
glomerata dan Macrophoma sp. Cendawan patogen tersebut dapat
menurunkan daya berkecambah 20-40%, indeks vigor 30-47%, kecepatan
tumbuh relatif 13-45%, dan meningkatkan kecepatan perkecambahan
(T 50 menurun) dari 0,62-7,36 hari. Ke-13 isolat patogen dapat
menyebabkan kematian benih 29-52% dibanding kontrol. Ke-13 isolat
patogen juga menginfeksi bagian tanaman seperti kotiledon, daun, batang
dan akar bibit kakao, namun hanya Phoma glomerata dan Macrophoma
sp. yang menurunkan tinggi bibit, jumlah daun, jumlah dan panjang akar
secara nyata. Tujuh dari 13 isolat cendawan patogen terbawa benih tidak
hanya menurunkan viabilitas dan vigor benih kakao hibrida tetapi juga
dapat berkembang pada bibit sehingga perlu penanganan benih secara dini.
Kata kunci: benih hibrida, patogen terbawa benih, viabilitas, vigor benih,
Theobroma cacao

ABSTRACT
In 2009 revitalization of cacao plantations in Indonesia required 168
million seeds. Distribution of low quality and infected seeds leads to huge
losses and in a long term will destruct cultivation of cacao. Seed-borne
pathogens of infected cacao hybrid seeds are dangerous because they may
reduce physiological qualities of the seeds. The study aimed at
determining the effect of several isolates of seed borne fungi on the
viability and vigor of hybrid cacao seeds as well as growth of the
seedlings. The study was conducted at the Seed Garden Indonesian Coffee
and Cacao Research Center in Jember, Microbiology Laboratory and glass
house of Biotechnology Research Institute for Estate Crops of Indonesia,
Bogor, from July to November 2008. The study used 13 seed-borne fungi
in hybrid cacao. The cacao seeds were obtained from hand pollinated
crossing between TSH 858 with Sca 6. The experiment was arranged using
Completely Randomized Design with four replicates. Cacao seeds were
inoculated by immersing them for 30 minutes in the spore suspension of
13 isolates of seed-borne fungi CTB at a density of 10 6 spores/ml. After
inoculation, the seeds were planted on sterile sand in a plastic box (30 x 30
cm). Parameters observed were germination rate, vigor index, KCT-R T 50
rate of seedling growth, leaf number, seedling height, root length, root
number, and level of pathogenicity. Data were analyzed by ANOVA
followed with Duncan's Multiple Test. The results showed that the 13
species of seed-borne pathogens were in hybrid cacao seeds with varying
pathogenicity. The most pathogenic fungi were Aspergillus flavus,
Aspergillus ochraceus, Cladosporium herbanum, Curvularia geniculata,
Fusarium oxysporum, Phoma glomerata, and Macrophoma sp. Seed borne
pathogenic fungi had the ability to reduce seed germination of 20-40%,
vigor index of 30-47%, relative growth rate of 13-45%, and delayed
germination speed (T 50 decreases) from 0.62 to 7.36 days. Seed borne
pathogens caused (29-52%) death seed compared to control. All that 13
isolates of seed-borne pathogens infected plant tissues such as cotyledons,
leaves, stems, and roots of cacao seedlings, but only isolates of Phoma
glomerata and Macrophoma sp. which lowered the height of seedlings,
leaf number, root number and length. The study indicated that infection of
seed-borne pathogens on cacao seed hybrid can cause seed death.
Therefore, seeds should be handled properly.
Key words: hybrid seeds, seed borne pathogens, viability, seed vigor,
Theobroma cacao


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DOI: http://dx.doi.org/10.21082/jlittri.v19n1.2013.8-14

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