PEWARISAN SIFAT HERMAPRODIT DAN KONTRIBUSINYA TERHADAP DAYA HASIL PADA JARAK PAGAR (Jatropha curcas L.)

Abstract

ABSTRAK Kontribusi sifat hermaprodit terhadap daya hasil tanaman jarak pagar belum banyak diketahui. Tujuan penelitian adalah mengetahui peran bunga hermaprodit terhadap daya hasil dan mekanisme pewarisannya. Penelitian dilakukan terhadap 60 genotipe jarak pagar di Kebun Percobaan Balittri Sukabumi. Penelitian dilaksanakan mulai bulan Mei 2007 sampai dengan Juli 2010. Jarak tanam 2 m x 2 m, menggunakan 2,5 kg pupuk kandang + 20 g Urea + 20 g SP 36 + 10 g KCl per tanaman. Penelitian terdiri dari (1) evaluasi tipe bunga jarak pagar dan (2) pewarisan sifat hermaprodit dan kontribusinya terhadap daya hasil. Hasil evaluasi menunjukkan bahwa delapan dari 60 genotipe jarak pagar yang dievaluasi merupakan tanaman tri-monoecious yang menghasilkan bunga jantan, bunga betina, dan bunga hermaprodit, 52 lainnya merupakan tanaman monoecious yang hanya menghasilkan bunga jantan dan bunga betina. Karakter yang dimiliki oleh delapan genotipe tri-monoecious yang dievaluasi adalah lebih lambat berbunga (mulai berbunga pada umur 120- 274 hari) dan berdaya hasil rendah sampai sedang (jumlah buah 23-228 per tanaman pada tahun pertama). Kemunculan bunga hermaprodit tidak terjadi sepanjang tahun, tetapi lebih dominan pada tanaman berumur enam bulan. Persentase bunga hermaprodit berkisar 6,25-53% dari total bunga yang dihasilkan. Persentase fruitset pada tandan bunga hermaprodit lebih tinggi dibanding tandan bunga non-hermaprodit, dengan tingkat keberhasilan rata-rata 80% (kisaran 56-100%). Pada tandan bunga yang tidak menghasilkan bunga hermaprodit, buah jadi rata-rata sebesar 50% (kisaran 11-100%). Daya hasil tanaman jarak pagar ditentukan oleh genetik tetua. Bunga hermaprodit diwariskan oleh tetua betina maupun tetua jantan. Gen pengendali sifat hermaprodit diduga adalah gen sederhana yang bersifat dominan. Kata kunci: Jatropha  curcas,  monoecious,  tri-monoecious,  bunga hermaprodit, fruit set ABSTRACT Hermaphrodite character has been reported in physic nut, its role and contribution to production process especially to the yield has not been investigated. The objectives of this research were to evaluate hermaphrodite flowers contribution on yield and their mechanism inheritance. The evaluation was conducted at the Experimental Station of Balittri Sukabumi from May 2007 to July 2010. The spacing was 2 m x 2 m with 2,5 kg manure + 20 g Urea + 20 g SP 36 + 10 g KCl/plant. The experiment consisted of (1) evaluation of flower type of physic nut and (2) hermaphrodite inheritance and their contribution on yield. Results of the experiment indicated eight from 60 physic nut genotypes were tri- monoecious which were capable on producing male, female, and hermaphrodite flowers while as the rest (52 genotypes) were monoecious which produced only male and female flowers. The tri-monoecious were generally late flowering (120-274 days after planting) and low to medium yield (producing 23-228 fruits per plant in the first year). Hermaphrodite flowers generally occurred six months after planting at the amount ranged from 6,25-53% of total flowers. Fruit set of inflorescences having hermaphrodite flowers was higher, average of 80% (ranged from 56- 100%) than those with female and male flowers, average of 50% (ranged from 11-100%). Yield of physic nut was affected by the genetic potential of their parents rather than hermaphrodite character. Hermaphrodite flower character was inherited by both female and male parents and might be controlled by simple-dominant gene. Key words: Jatropha curcas, monoecious, tri-monoecious, hermaphrodite flower, fruit set