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Dampak Penggunaan Fungisida Sintetik terhadap Kelimpahan Cendawan Endofit dan Perkembangan Penyakit Tanaman Padi
No full textAplikasi fungisida umum digunakan dalam pengendalian penyakit-penyakit
padi. Penggunaan fungisida dianggap memiliki pengaruh negatif terhadap
organisme non-target termasuk cendawan endofit. Cendawan endofit pada padi
telah berhasil diisolasi dan di antaranya mampu meningkatkan pertumbuhan serta
ketahanan tanaman inang dari cekaman biotik dan abiotik. Keberadaan cendawan
endofit di dalam jaringan tanaman tidak terlepas dari pengaruh keadaan lingkungan
sekitarnya, salah satunya adalah pengaruh penggunaan fungisida sintetik. Namun,
pengetahuan tentang dampak fungisida terhadap cendawan endofit belum banyak
diketahui. Tujuan penelitian ini adalah: (1) mendapatkan informasi mengenai
keanekaragaman dan kelimpahan cendawan endofit tanaman padi akibat
penggunaan fungisida sintetik; dan (2) mengetahui hubungan antara perubahan
keanekaragaman dan kelimpahan cendawan endofit dengan perkembangan
penyakit pada tanaman padi karena penggunaan fungisida.
Penelitian dilakukan dari bulan Juni 2018 hingga Maret 2019 di Balai Besar
Peramalan Organisme Pengganggu Tanaman Jatisari Karawang dan di
Laboratorium Mikologi Tumbuhan Departemen Proteksi Tanaman IPB. Tahapan
penelitian dimulai dari persiapan lahan, penanaman padi, isolasi cendawan endofit,
dan aplikasi fungisida. Percobaan di lapangan terdiri atas dua taraf faktor yaitu
fungisida kontak (mankozeb), fungisida sistemik (difenokonazol), dan kontrol
sebagai pembanding. Isolasi cendawan endofit dan aplikasi fungisida dilakukan
setiap minggu, dimulai saat tanaman berumur 3 hingga 10 minggu setelah tanam
(mst). Variabel yang diamati dan dihitung adalah total segmen daun dan batang padi
yang dikolonisasi cendawan endofit, jenis dan jumlah spesies cendawan endofit,
serta frekuensi kolonisasi cendawan endofit. Selanjutnya dihitung indeks
keanekaragaman Shanon-Wiener, indeks kemerataan, dan indeks kesamaan
Sorensen cendawan endofit dari setiap perlakuan. Lima isolat cendawan endofit
dengan frekuensi kolonisasi tertinggi diuji antagonis terhadap penyebab penyakit
busuk pelepah (Sarocladium oryzae) dan juga diuji patogenisitas terhadap benih
padi. Tingkat keparahan dan kejadian penyakit tanaman padi juga diamati dalam
uji coba lapangan. Hubungan antara cedawan endofit dan keparahan dan kejadian
penyakit tanaman padi dianalisis dengan korelasi Pearson.
Hasil penelitian menunjukkan bahwa ada peningkatan kolonisasi cendawan
endofit dengan pertambahan umur tanaman padi. Terdapat 37 morfospesies
cendawan endofit yang berhasil diisolasi dari daun dan batang tanaman padi.
Berdasarkan analisis indeks keanekaragaman Shanon-Wiener dan indeks
kemerataan, cendawan endofit pada batang lebih beragam daripada daun padi.
Berdasarkan analisis indeks kesamaan Sorensen, cendawan endofit antara berbagai
perlakuan memiliki kesamaan spesies yang tinggi. Genus dominan cendawan
endofit yang mengolonisasi daun dan batang padi yaitu Acremonium, Curvularia,
Fusarium, Helminthosporium, Nigrospora, Penicillium, dan Mucor.
Pengaruh fungisida terhadap cendawan endofit daun dan batang padi tidak
menunjukkan perbedaan yang nyata. Namun, pada batang, frekuensi kolonisasi
cendawan endofit menurun selama fase pertumbuhan muda tanaman dengan
perlakuan mankozeb dan difenokonazol. Frekuensi kolonisasi genus Nigrospora
dan Fusarium juga menurun pada batang dengan perlakuan difenokonazol selama
fase pertumbuhan muda tanaman.
Mankozeb dan difenokonazol berpengaruh secara nyata mengurangi
keparahan penyakit bercak cokelat sempit (Cercospora oryzae) pada 9 dan 10 mst,
tetapi tidak memengaruhi keparahan penyakit hawar daun bakteri (Xanthomonas
oryzae pv oryzae). Sementara itu, mankozeb dan difenokonazol meningkatkan
kejadian penyakit busuk pelepah pada 8 mst. Berdasarkan analisis korelasi Pearson,
hubungan antara indeks keanekaragaman cendawan endofit (H’) dengan tingkat
keparahan dan kejadian penyakit tidak konsisten di setiap minggu. Dengan
perlakuan difenokonazol, indeks keanekaragaman (H’) cendawan endofit pada
batang konsisten berkorelasi positif terhadap keparahan penyakit bercak cokelat
sempit setiap minggu. Analisis korelasi Pearson antara frekuensi kolonisasi genus
dominan cendawan endofit dengan keparahan penyakit bercak cokelat sempit juga
tidak konsisten setiap minggu. Beberapa genus cendawan endofit secara nyata
berkorelasi negatif atau bahkan positif terhadap keparahan dan kejadian penyakit
padi pada minggu tertentu.
Berdasarkan hasil uji antagonis diperoleh bahwa isolat cendawan endofit
yang terpilih memiliki kemampuan menghambat pertumbuhan penyebab penyakit
busuk pelepah (S. oryzae) dengan tingkat penghambatan berkisar antara 30% - 80%.
Mekanisme penghambatan tersebut berupa kompetisi. Berdasarkan uji
patogenesitas, Curvularia sp., Nigrospora sp., dan Penicillium 7 bersifat non
patogen terhadap benih padi.
Hasil penelitian ini dapat menjadi acuan mengenai dampak pengendalian
penyakit tanaman dengan menggunakan fungisida terhadap keanekaragaman dan
kelimpahan cendawan endofit pada tanaman padi dan kaitannya dengan
perkembangan penyakit padi
Dampak Penggunaan Fungisida Sintetik pada Kelimpahan Cendawan Endofit Tanaman Padi
Full text linkApplication of fungicides to control rice diseases potentially have adverse effect on non target organisms including endophytic fungi. Unfortunately, information of fungicide effect on endophytic fungi on rice is still limited. The purpose of this research was to study the diversity and abundance of endophytic fungi on rice plant because of application of synthetic fungicides. There were two treatments in this study: non systemic fungicide (mankozeb) and systemic fungicide (difenoconazole) which were compared to control (without fungicide). Isolation of endophytic fungi and application of fungicides were conducted every week started at aged of 3 to 10 weeks after planting. Variables observed were total segment of rice colonized by endophytic fungi, colonization frequency of endophytic fungi, continued by identification and analysis of the diversity of endophytic fungi. This study showed that there was an increase in colonization of endophytic fungi with an increase of plant ages. The diversity of endophytic fungi was higher in stems than in leaves with the value of H\u27 is 0.00-1.35 and 0.00-0.98 respectively. The most common types of endophytic fungi appear in each isolation of rice segments were Acremonium, Curvularia, Fusarium, Helminthosporium, Nigrospora, Penicillium, and Mucor. Both fungicides do not significantly affect the percentage of colonization and diversity of endophytic fungi. At the beginning of planting (4-6 MST) there was a decrease in the percentage of endophytic fungal colonization in the stem. From the percentage of colonization of each genus of fungi, Nigrospora and Fusarium decreased significantly with difenoconazole on the stem during the vegetative phase.
Keywords: colonization, community, difenoconazole, diversity, mancoze
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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