Peningkatan mutu benih dan bibit kakao hibrida (Theobrma cacao L.) dengan pendekatan fisiologi dan biologi

Abstract

Low quality seed and pathogenic infection have made the cacao production in Indonesia still below the national average 2 tons/ha/year. The major problems of cacao seeds are that they are recalcitrant, should be harvested at the right time, carry pathogens, and deteriorate rapidly. This study consisted of five experiments: (1) biological and physiological changes as the indicators of physiological maturity of cacao hybrid seeds, (2) isolation and identification of fungi on hybrid cacao seeds, (3) pathogenicity of some seed-born fungi isolated from cacao hybrid seeds, (4) the influence of seed storage and treatment on vigor of hybrid cacao seeds and seedlings, and (5) effectiveness of seed treatment and planting medium to promote vigor of hybrid cacao seedlings. The research results showed that during the development of the hybrid cacao seeds TSH 858 x Sca 6 and ICS 60 x Sca 6, there was a decrease in the total content of chlorophyll in seed and fruit to a minimum level when seeds were physiologically matured, and no change occurred afterwards. The changes of carotenoid and anthocyanin content in seed and fruit, viability and vigor of seeds were parabolic and showed an increase to a maximum level and then a decrease happened. The carotenoid and anthocyanin content in seed and fruit at the time of physiological maturity reached the maximum. The development of hybrid cacao seeds consist of three periods: before reaching physiological maturity (T1), physiological maturity (T2), and after the physiological maturity (T3). During seed development, each type of hybrid cacao had a different length of period (T1).

Revitalisasi program pengembangan tanaman kakao pada tahun 2009/2010 membutuhkan 168.000.000 benih. Keberhasilan program ini tergantung pada ketersediaan benih yang berkualitas, khususnya benih yang vigor dan sehat. Benih bervigor tinggi diperoleh dari pohon induk yang vigor dan sehat serta dipanen pada saat masak fisiologis. Distribusi benih bervigor rendah dan terinfeksi penyakit (seedborne diseases) mengakibatkan kerugian yang sangat besar dan berjangka panjang dalam mengurangi produktivitas tanaman kakao. Permasalahan utama benih kakao yaitu bersifat rekalsitran; berkadar air tinggi, mudah terinfeksi patogen, dan memiliki periode konservasi yang relatif lebih singkat, sehingga penurunan mutu fisiologis benih dapat terjadi lebih cepat. Oleh karena itu perlu dilakukan teknik invigorasi yang tepat dengan perlakuan matriconditioning plus Trichoderma spp. dan penggunaan medium campuran tanah, pasir, kompos (2:1:1) plus agens hayati. Kedua perlakuan ini merupakan strategi penting untuk memperbaiki dan meningkatkan mutu benih atau bibit kakao yang sehat serta ramah lingkungan.