RingkasanSeleksi ketahanan kakao terhadap penyakit pembuluh kayu (vascular-streak dieback, VSD) telah mendapatkan sejumlah klon tahan VSD. Di antara klon tahan tersebut terdapat klon Sca 6 dan DRC 15 yang menunjukkan keunggulan dayahasil. Tulisan ini melaporkan hasil pengujian dayahasil klon Sca 6 dan DRC 15 yang dilaksanakan secara terpisah. Pengujian klon Sca 6 dilaksanakaan di Kebun Kottablater (tipe iklim kering, ketinggian tempat ± 25 m dpl.), dan pengujian klon DRC 15 di Kebun Mumbulsari (tipe iklim kering, ketinggian tempat ± 45 m dpl.) keduanya di Jember, Jawa Timur. Percobaan dirancang dalam susunan rancangan acak kelompok lengkap dengan 4 blok. Evaluasi keragaan dayahasil dilakukan selama 6 tahun dan analisis stabilitas berdasarkan indeks tahun melalui pendekatan regresi. Hasil percobaan menunjukkan bahwa keragaan dayahasil kedua klon tersebut relatif sama yaitu 1,4 kg/ph dan bersifat stabil antartahun pengamatan serta menunjukkan adaptabilitas yang baik pada kondisi klimatologis lokasi pengujian. Dayahasil tersebut masih lebih rendah dibandingkan klon-klon unggul lain namun penanaman klon Sca 6 dan DRC 15 di daerah terserang berat VSD perlu dipertimbangkan dibandingkan penanaman klon unggul yang rentan. Klon Sca 6 memiliki berat biji kering relatif kecil, yaitu berkisar 0,65-0,86 g (mutu C) namun keragaan yang lebih besar dapat dijumpai pada daerah yang bertipe iklim basah, sedangkan klon DRC 15 menghasilkan berat biji kering 1,16 g (mutu AA). Analisis kadar lemak biji menunjukkan bahwa klon Sca 6 menghasilkan kadar lemak biji yang lebih tinggi di daerah basah sebesar 58,2% dibandingkan di daerah kering sebesar 49,6%. Klon DRC 15 dilaporkan menghasilkan kadar lemak biji sebesar 50,4%. SummarySelection on cocoa resistance to vascular-streak dieback (VSD) has identified some resistant clones for breeding purposes. Of the resistant clones, it was selected Sca 6 and DRC 15 which performing good potential for yield. This paper reports results on testing yield potential of the clones in separate trials. Sca 6 was tested in Kottablater Estate (dry climate in the altitude of ± 25 m Diterima (Recieved) : 13 Maret (March) 2009.

Phytophthora seedling blight disease is one of the important diseases in cocoa. The disease is caused by the fungus of Phytophthora palmivora belongs to class Oomycetes. The aim of this research was to determine the effectiveness of the use of row covers and copper oxide fungicide applications to control seedling blight Phytophthora. Covering treatment was to place cocoa seedlings inside bamboo frame covered by transparent plastic in order to avoid from rainfall effect. The research was conducted in the Kaliwining Experimental Station at Indonesian Coffee and Cocoa Research Institute (ICCRI). Experiments were carried out four treatments and repeated 6 times. Each treatment consists of 100 seedlings planted in polybags and placed in the nursery area with a protective paranet. The treatment consisted of (1) row covers, (2) spraying of copper oxide 0.2%, (3) a combination of row covers and copper oxide 0.2% and (4) control (no covers and spray). Observations made 7 days after treatment with an interval of 7 days for 10 weeks. The results showed that row covers able to prolong the incubation period of the disease for 14 days, while the application of row covers + copper oxide 0.2% was able to save cocoa seedlings by 96.2%.

The characteristics of pod related to cocoa pod borer resistance (CPB, Conopomorpha cramerella Snell.) had been identified in a series study. This research has objective to evaluate performance of the characteristics using more diverse of genetic background to select criteria for selection. Genetic materials for this study were 25 cocoa clones which be planted in Central Sulawesi for resistant evaluation. Field evaluation of the resistance were assessed using the variable of the percentage of unextractable bean, number of entry and exit hole larvae by which the clones were grouped into 5 groups of resistance. A laboratory works were carried out to assess pod characteristics based on the number of trichome, granule of tannin and thickness the lignified-tissue of sclerotic layer using micro-technique method at the different level of pod maturity (3.0; 3.5; 4.0 months). Correlation between groups of those variables was analyzed using Canonical Correlation. The analysis performed a positive association between the thickness of sclerotic layer at the secondary furrow with the number of entry holes and the number of entry holes through sclerotic layer. The thickness performed a higher value of the coefficient in association with the variables of canonical for pod characteristics (0.59; 0.55; 0.43) and the variables of canonical for CPB resistance (0.54; 0.51; 0.39) that would presenting the characteristics of pod related to CPB resistance. Lignification at sclerotic layer was considered as genotypic expressions due to the thickness at the secondary furrow at 3.0, 3.5 and 4.0 months of pod maturity performed high value of broad-sense heritability i.e. 0.75, 0.89 and 0.92 respectively. A qualitative assessment of the lignification clearly differentiate the resistant clones (ARDACIAR 10) with the susceptible clones (ICCRI 04, KW 516 and KW 564).Key words : cocoa pod borer, Theobroma cacao L., pod characteristics, resistance

Canopy  replacement  with  vascular  streak dieback  (VSD) resistant  clones is  expected  to  reduce  VSD  infestation  by  reducing  space  of  Oncobasidiumtheobromae infection,  and  to  increase  cocoa  yield.  This  experiment  was carried  out  in  endemic  areas  of  VSD  in  Kaliwining  Experimental  Station  of ICCRI  and  Kendenglembu  estate.  Canopy  replacement  technique  in  Kendenglembu  was  done  by  side  cleft  grafting  on  primary  branches  and  top  grafting on  plagiotropic  branches  of  primary  branches.  Number  of  grafted  shoots per  plant,  i.e.  1,  2,  3,  4,  5  and  6  was  used  as  treatments  using  Sca  6  and Sulawesi  1.  The  12  treatments  were  arranged  in  randomized  complate  block design,  each  treatment  replicated  6  times  and  10  plants  per  treatment.  Growth of  shoot,  canopy  coverage  and  development  of  VSD  incidence  were  the  main variables.  In  Kaliwining,  side  cleft  grafting  was  applied  at  1.5  m  above  soilsurface  using  Sulawesi  1  and  Sca  6  clones  as  the  scion  and  TSH  858  and ICS  60  clones  as  rootstocks.  VSD  intensity  was  observed  by  scoring  method. Cocoa  yield  was  the  main  variable.  The  result  showed  that  both  techniques caused  similar  growth  rate  of  the  shoots.  The  rate  of  canopy  covering  by resistant  clones  reduced  VSD  infestation  following  Y  =  -0.7848X  +  69.324 (R²  =  0.995)  equation.  Three  resistant  shoots  per  tree  was  effective  in  reducing  VSD  infestation.  Four  years  after  grafting  were  bean  yield  by  using Sulawesi  1  was  434%  over  control  while  360%  yield  for  Sca  6  compared  to average  control  of  ungrafted  plants  of  ICS  60  and  TSH  858.  Polyphenol content of both resistant clones was higher than that on susceptible ones, however transfer  mechanism  of  that  substance  to  the  susceptible  stocks  is  still  unknown. It  is  concluded  that  canopy  replacement  using  productive  and  resistant  clones is  considered  to  be  an  effective  method  to  overcome  VSD  problem  and  to improve  cocoa  yield. Key words:Theobroma cacao, vascular streak dieback, canopy replacement, yield.