Evaluation of yielding capacity of the sweet potato promising clones to drought stress condition

English. Severity of drought is considered as one of the limiting factor contributed to the low yield of sweetpotato. To obtain the maximum yield, sweetpotato clones which are tolerant to the drought condition are needed. The field experiment was carried out at Muneng during the dry season 1995. The soil type is Mediteran Orthic at the altitude 10 m above sea level. Split plot design in two replications was used in this experiment. The main plot was two levels of irrigation, and the sub plot was 50 clones of sweetpotato. Drought stress significantly reduced the yield of sweetpotato. Due to drought the unmarketable tuber as well as tuber damage caused by weevil increased of 6.11 percent and 20.27 percent respectively. Yield losses due to drought was 33.55 percent under the stress index 0.3354. The variation of yield losses were 2.52-58.55 percent. Tuber yield under normal condition were 10.10-40.21 t/ha, while under drought stress were 4.46-27.45 t/ha. Selection of sweetpotato based on the yield above 25 t/ha obtained 17 clones, based on yield losses below 20 percent obtained 8 clones, and based on the tolerance index above 0.75 obtained 5 clones. Among these clones, MLG 12659-OP93-4 was always selected under various criteria, and under drought condition yielded 26.699 t/ha. It meant that this clone is a promising component which can be developed in the dry land at dry climate

unknown. Deraan kekeringan dapat menurunkan produksi umbi ubijalar. Untuk memperoleh klon ubijalar yang toleran terhadap deraan kekeringan, dilakukan penelitian di lapang pada MK 1995 di jenis tanah Mediteran Orthic ketinggian 10 m di atas permukaan laut (dpl). Rancangan yang digunakan Petak Terbagi, diulang dua kali. Petak utama adalah pengairan, terdiri atas dua taraf dan Anak Petak adalah 50 klon harapan ubijalar. Hasil penelitian menunjukkan bahwa deraan kekeringan berpengaruh terhadap berat umbi sehat dan produksi akhir umbi. Selain itu terjadi peningkatan jumlah umbi tidak layak jual sebesar 6.11 persen dan jumlah umbi terserang boleng 20.27 persen, walaupun secara statistik peningkatan tersebut tidak berbeda nyata. Diperoleh nilai intensitas cekaman sebesar 0,34. Kisaran kehilangan hasil akibat deraan kekeringan antara 25,3-58,55 persen, rata-rata mencapai 32,42 persen. Sedangkan kisaran hasil pada kondisi normal antara 10,101-40,205 t/ha, dan pada kondisi terdera kekeringan antara 4,460-27,445 t/ha. Pemilihan klon dengan tolok ukur hasil pada kondisi kekeringan di atas 25 t/ha diperoleh 4 klon dengan rata-rata hasil sebesar 26,316 t/ha, sedangkan dengan tolok ukur kehilangan hasil kurang dari 20 persen diperoleh 8 klon, dan apabila dengan tolok ukur indeks toleransi di atas 0,75 diperoleh 5 klon. Dari sejumlah klon yang diuji klon MLG 12659-OP93-4 selalu terpilih dalam berbagai tolok ukur, dan dalam kondisi kering mampu berproduksi 26,699 t/ha. Ini berarti bahwa klon tersebut merupakan klon harapan yang dapat dikembangkan di lahan kering, walau perlu diuji lebih lanjut