Studi karakteristik sifat ketahanan tanaman kakao (Theobroma cacao L.) terhadap hama penggerek buah kakao(Conopomorpha cramerella Snell.)

SUSILO, Agung Wahyu, Promotor Prof. (Emer). Dr. Ir. Woerjono Mangoendidjojo, M.Sc

2010 | Disertasi | S3 Ilmu Pertanian

Studi karakteristik tanaman kakao tahan hama penggerek buah kakao (PBK, Conopomorpha cramerella Snell.) dilakukan untuk menentukan kriteria seleksi. Studi diawali dengan karakterisasi sifat-sifat buah yang terkait dengan ketahanan PBK terhadap kepadatan trikoma, frekuensi granula tanin, dan lignifikasi lapisan sklerotik secara mikroskopik. Klon KW 514 yang bersifat tahan dan KW 411 yang bersifat agak tahan, memiliki kepadatan trikoma dan frekuensi granula tanin lebih tinggi dibandingkan RCC 72 yang bersifat rentan. Klon-klon tahan, ARDACIAR 10 dan KW 514, menunjukkan lignifikasi lapisan sklerotik lebih intensif dan struktur jaringan lebih kompak dibandingkan KW 411 dan RCC 72. Trikoma diduga berperan dalam mekanisme antixenosis, sedangkan tanin dan lignifikasi lapisan sklerotik berperan dalam mekanisme antibiosis. Sifat-sifat tersebut terekspresi secara maksimal saat umur buah 3,0 – 4,0 bulan. Studi dilanjutkan dengan evaluasi hubungan karakteristik buah tersebut dengan respons ketahanan PBK di lapangan berdasarkan keragaan 25 klon kakao. Respons tanaman terhadap infestasi PBK dievaluasi selama 14 bulan. Ketebalan lapisan sklerotik di antara alur primer umur buah 3,0; 3,5; dan 4,0 bulan menunjukkan nilai koefisien kanonikal yang tertinggi sehingga lignifikasi lapisan sklerotik merepresentasikan karakteristik ketahanan PBK. Klon-klon tahan secara konsisten menunjukkan lignifikasi lapisan sklerotik lebih intensif dan struktur jaringan lebih kompak dibandingkan klon-klon rentan. Lignifikasi tersebut merupakan ekspresi genotipik tanaman sebab ketebalan lapisan sklerotik memiliki nilai dayawaris arti luas yang tergolong tinggi. Hasil analisis sidik jari DNA menunjukkan bahwa klon-klon tahan PBK merupakan genotipe yang berbeda, klon-klon tersebut termasuk dalam kelompok Trinitario dan Forastero. Berdasarkan jarak genetik dan nilai heterozigositas genetik dapat disusun kombinasi persilangan sesuai tujuan pemuliaan ketahanan PBK

Study on pod characteristics related to cocoa pod borer (CPB, Conopomorpha cramerella Snell.) resistance was carried out to identify criteria for selection. Initial study was performed to characterize physical and chemical compound of the cocoa pod which correspond to CPB resistance by observing the performance of trichome, granule of tannin and lignification at sclerotic layer by microscopic analysis. Resistant clone of KW 514 and moderately resistant clone of KW 411 showed higher values of trichome density and frequency of tannin granule than that of susceptible clone of RCC 72. Resistant clones of ARDACIAR 10 and KW 514 qualitatively showed more lignin at the sclerotic layer than KW 411 and RCC 72. The trichome might play its role on antixenosis mechanism, while tannin and lignin play their role on an antibiosis mechanism. These characterististics were expressed maximally during 3.0 – 4.0 months of pod age. The further study for evaluating relationship between the pod characteristics with variables of resistance were performed by using 25 clones. The plant’s responses to CPB infestation were evaluated during 14 months. The thickness of sclerotic layer between primary furrow at 3.0, 3.5 and 4.0 months of pod age showed higher value of canonical coefficient than that of other ages that lignification process can be assumed to represent as part of the resistant characteristics. The resistant clones consistently performed more intensive and more compact lignified tissues than that of the susceptible clones. Lignification at sclerotic layer was considered as genotypic expressions due to the thickness of the layer performed high value of broad sense heritability. The selected resistant clones are genetically different based on DNA fingerprinting analysis, they are belonged to Trinitario and Forastero groups. By using the information of genetic distance and heterozygosity level among the tested clones it can be arranged a better crossing plan on breeding program for CPB resistance.

Kata Kunci : Pod characteristics,Theobroma cacao L,Cocoa pod borer,Plant resistance, karakteristik buah, penggerek buah kakao, ketahanan tanaman