scholarly journals Evaluasi Resistensi dan Daya Hasil Enam Klon Harapan Kentang Transgenik Terhadap Serangan Penyakit Hawar Daun (Evaluation of Resistance to Late Blight and Tuber Yield of Six Potential Potato Transgenic Clones)

2019 ◽  
Vol 28 (1) ◽  
pp. 41
Author(s):  
NFN Kusmana ◽  
Alberta Dinar Ambarwati
Keyword(s):  
Late Blight ◽  
Phytophthora Infestans ◽  
Tuber Yield ◽  
Potato Crop ◽  
Transgenic Potato ◽  
Yield Component ◽  
Experimental Unit ◽  
Plant Vigor ◽  
Main Plot ◽  
Rb Gene

<p>Penyakit hawar daun (Phytophthora infestans) merupakan salah satu penyakit utama pada tanaman kentang. Kerusakan yang berat akibat penyakit hawar daun dapat menyebabkan kehilangan hasil panen sampai 80%. Gen pembawa ketahanan terhadap penyakit hawar daun dikenal dengan nama gen RB dan telah berhasil dimasukkan ke dalam genom kentang dan menghasilkan kentang transgenik. Tujuan penelitian untuk menguji ketahanan enam klon kentang transgenik terhadap serangan penyakit hawar daun (P. infestans) dan daya hasil. Penelitian dilakukan di Lapangan Uji Terbatas Desa Citere, Kecamatan Pangalengan, Kabupaten Bandung, 1.400 m di atas permukaan laut. Rancangan percobaan menggunakan rancangan petak terpisah, dengan petak utama perlakuan tidak disemprot fungisida dan disemprot fungisida dua kali seminggu dan anak petak 10 genotipe kentang yang terdiri atas enam hibrida kentang transgenik, satu genotipe kentang transgenik Katahdin SP951 sebagai pembanding resisten dan tiga varietas pembanding rentan kentang nontransgenik Granola, Atlantic, dan Katahdin. Jumlah ulangan tiga kali dengan populasi tanaman terdiri atas 50 tanaman/plot. Pengamatan dilakukan terhadap vigor tanaman, insiden serangan hawar daun, dan komponen hasil. Hasil pengamatan menunjukkan bahwa untuk vigor tanaman tidak terjadi interaksi serta antarperlakuan tidak berbeda nyata. Genotipe yang resisten terhadap hawar daun adalah klon 20, 27, 65, dan 66 setara dengan kontrol positif Katahdin SP951 dan nyata lebih resisten dari varietas pembanding Granola, Atlantic, dan Katahdin. Klon yang resisten terhadap hawar daun menampilkan hasil yang tinggi pada plot tidak disemprot fungisida, sementara pada plot disemprot fungisida 20 kali semua genotipe menampilkan hasil optimalnya. Tingkat kehilangan hasil mencapai 18,8–84,4%. Genotipe dengan intensitas serangan hawar daun tinggi memiliki tingkat kehilangan hasil yang juga tinggi. Klon 20 dan 27 menampilkan daya hasil yang relatif tinggi dengan penundaan penggunaan fungisida 7 minggu setelah tanam.</p><p><strong>Keywords</strong></p><p>Genotipe; <em>P. infestans; Solanum tuberosum</em> L</p><p><strong>Abstract</strong></p><p>Late blight (Phytophthora infestans) is one of main potato diseases. Due to severe damage to late blight potato, crop will be cause lost of harvest up to 80%. Gene carriers of resistance to late blight known as the RB gene and have been incorporate into the genom of potato and produce transgenic potato. The objective of the research was to test six advanced transgenic potato clones for resistance to late blight (Phytophthora infestans). The research was conducted at Confined Field Trial at Citere Village, Pangalengan District Bandung (1,400 m above sea level). The experimental design was split plot. The main plot was spray with fungicides twice/week and was replicated three times. Subplot were 10 potato genotypes, consists of six transgenic potato hybrids, transgenic Katahdin SP951 as resistant check and three varieties of nontransgenic as susceptible check, i.e. Granola, Atlantic, and Katahdin.  An experimental unit consists of 50 plants/plot, every treatment with three replicates. Plant observed were plant vigor, intensity of late blight damage, tuber yield component, and lost of yield. The result showed that there were no interaction of plant vigor and also all the treatmens were not significantly different. Transgenic potato clones of 20, 27, 65, 66, and Katahdin SP951 were resistant to late blight compare to check varieties of Granola, Atlantic, and Katahdin. The highest yielding at none spraying of fungicides were obtained from the resistance clones. Whereas,  on the 20 sprayed fungicides all of  the clones were high yielding. Tuber yield lossed ranged from 18,8–84,4%, the susceptible genotypes were also showed high losses. Clones 20 and 27 showed reletive high yielding and can be delayed application fungicides for period of 7 weeks after planting. </p>

scholarly journals Pengujian Ketahanan Klon-klon Hasil Silangan Tanaman Kentang Transgenik dengan Nontransgenik terhadap Penyakit Hawar Daun Phytophthora infestans di Lapangan Uji Terbatas

2013 ◽  
Vol 22 (2) ◽  
pp. 187 ◽  
Author(s):  
Alberta Dinar Ambarwati ◽  
Muhamad Herman ◽  
Edi Lisanto ◽  
Euis Suryaningsih ◽  
Eri Sofiari
Keyword(s):  
Late Blight ◽  
Phytophthora Infestans ◽  
Field Trial ◽  
Durable Resistance ◽  
Transgenic Potato ◽  
Resistance Testing ◽  
Solanum Bulbocastanum ◽  
Phenotypic Resistance ◽  
Rb Gene ◽  
Confined Field Trial

STRAK. Tanaman kentang transgenik Katahdin event SP904 dan SP951 mengandung gen RB, yang diisolasi dari spesies liar kentang diploid Solanum bulbocastanum. Gen RB mempunyai ketahanan yang bersifat  durable dengan spektrum yang luas terhadap ras-ras Phytophthora  infestans di Amerika Serikat. Dalam perakitan tanaman kentang tahan penyakit hawar daun P. infestans di Indonesia, transgenik Katahdin dijadikan sebagai donor tahan dalam persilangan dengan varietas rentan Atlantik dan Granola. Klon-klon hasil silangan dianalisis secara molekuler mengandung gen RB. Penelitian dilakukan untuk menguji ketahanan klon-klon hasil silangan tanaman kentang transgenik dengan nontransgenik terhadap isolat P. infestans di lapangan uji terbatas (LUT) yang berlokasi di Balai Penelitian Tanaman Sayuran (Balitsa), Lembang dari bulan Oktober 2009 sampai dengan Maret 2010. Klon-klon yang diuji ialah 12 klon hasil silangan Atlantik x transgenik Katahdin SP904 (A); 15 klon hasil silangan Atlantik x transgenik Katahdin SP951 (B); 17 klon hasil silangan Granola x transgenik Katahdin SP904 (C); dan 20 klon hasil silangan Granola x transgenik Katahdin SP951 (D). Atlantik dan Granola digunakan sebagai kontrol rentan, sedangkan transgenik Katahdin sebagai kontrol tahan. Pengamatan dimulai ketika muncul gejala awal, yaitu pada 26, 32, 39, 46, dan 53 hari setelah tanam. Ketahanan tanaman semakin menurun dengan bertambahnya periode pengamatan, diikuti meningkatnya intensitas penyakit dan AUDPC. Semua klon yang diuji menunjukkan keragaman dalam ketahanan fenotipik terhadap hawar daun P. infestans. Klon-klon hasil silangan Atlantik x transgenik Katahdin SP951 mempunyai nilai AUDPC 697, yang hampir sama dengan transgenik Katahdin SP904 yaitu 698,5. Klon-klon Granola x transgenik Katahdin SP951 mempunyai nilai AUDPC  687,5 lebih kecil dibandingkan transgenik Katahdin SP904. Hasil penelitian ini juga menunjukkan bahwa klon-klon tersebut mempunyai ketahanan yang lebih tinggi dibandingkan transgenik Katahdin SP904. Pada pengamatan 46 hari setelah tanam atau 20 hari setelah infeksi diperoleh tiga klon tahan yaitu B49 (skor 7,5), C111 (skor 7,1), dan D26 (skor 7,3). Ketahanan ini lebih tinggi daripada transgenik Katahdin SP904 (skor 5,1) dan transgenik Katahdin SP951 (skor 6,4). <br /><br />ABSTRACT. Ambarwati, AD, Herman, M, Listanto, E, Suryaningsih, E and Sofiari, E 2012. Resistance Testing on Transgenic and Nontransgenic Potato Clones Against Late Blight Phytophthora  infestans in Confined Field Trial.  Transgenic potato Katahdin event SP904 and  SP951 containing RB gene, which were isolated from a wild diploid potato species, Solanum bulbocastanum. RB gene showed durable resistance with broad spectrum to all known races of  P. infestans in the USA. In development of  potato resistant to late blight P. infestans in Indonesia, Katahdin transgenic were used as a resistant donor and crossed with susceptible varieties i.e. Atlantic and Granola. Clones derived from the crossing were molecularly analyzed and had RB gene contain. Experiment was conducted to assess the resistance of the clones derived from crossing of Katahdin transgenic and nontransgenic to P. infestans in confined field trial (CFT), located at the Indonesian Vegetable Research Institute (IVEGRI), Lembang from October 2009 to March 2010. Several clones tested were 12 clones of Atlantic x Katahdin transgenic SP904 (A); 15 clones of Atlantic x Katahdin transgenic SP951 (B); 17 clones of Granola x Katahdin transgenic SP904 (C); and 20 clones of Granola x Katahdin transgenic SP951 (D). Atlantic and Granola were used as susceptible control whereas Katahdin transgenic as resistant control. Observation was started as late blight symptoms and detected at 26, 32, 39, 46, and 53 days after planting. Plant resistance decreases with increasing period of observation, followed by increasing disease intensity and AUDPC. All clones tested showed variation in phenotypic resistance to late blight P. infestans. Clones derived from crossing of Atlantic x Katahdin transgenic SP951 had AUDPC score 697 and almost similar to Katahdin transgenic SP904 (698.5). Clones derived from crossing of Granola x Katahdin transgenic SP951 had AUDPC score 687.5 and smaller than Katahdin transgenic SP904. The results also indicated that these clones had higher resistance than Katahdin transgenic SP904. Observation at 46 days after planting or 20 days after infection resulted three resistant clones i.e. B49 (score 7.5), C111 (score 7.1); and D26 (score 7.3).  This resistance was higher than Katahdin transgenic SP904 (score 5.1) and Katahdin transgenic SP951 (score 6.4). <br />

scholarly journals UJI KETAHANAN GALUR-GALUR KENTANG TRANSGENIK HASIL TRANSFORMASI DENGAN GEN RB TERHADAP PENYAKIT HAWAR DAUN (PHYTOPHTHORA INFESTANS) DI KP PASIRSARONGGE, CIANJUR

2013 ◽  
Vol 13 (2) ◽  
pp. 141-150
Author(s):  
Edy Listanto ◽  
M. Herman ◽  
Eri Sofiari
Keyword(s):  
Late Blight ◽  
Phytophthora Infestans ◽  
First Generation ◽  
Block Design ◽  
Transgenic Potato ◽  
Resistant Plant ◽  
Randomized Complete Block Design ◽  
Transgenic Lines ◽  
Transgenic Potatoes ◽  
Rb Gene

Resistance test strains of transgenic potatoes transformed with RB gene to late blight (Phytophthora infestan) in KP Pasirsarongge, Cianjur.  Potato late blight caused by Phytophthora infestans (P. infestans) (Mönt.) de Barry continues to be one of the most important crop diseases of all time. Genetic engineering of potato using RB gene for resistant plant to this disease is the most effective and environmental friendly to prevent widespread of late blight. This research aims to perform resistance of transgenic potato lines containing RB gene to lateblight (P. infestans) in Pasirsarongge, Cianjur field trial station. The first generation of transgenic lines were planted on polybag containing soil:manures using randomized complete block design. Tested plant inoculation was done naturaly from inoculum source from border row (Granola) that has been planted at one month before. The symptom was observed at one month after planting and damage scoring was done every three days for five times. Twenty two transgenic lines of tested plant showed various resistance respond to late blight (P. infestans) attack. Three transgenic lines showed highly resistance to late blight (P. infestans) were lines 11, 24, and 25, one transgenic line has resistant level was line 6.

scholarly journals Efficacy of fungicide mixtures for the management of Phytophthora infestans (US-1) on potato

2010 ◽  
Vol 90 (1) ◽  
pp. 19-29 ◽  
Author(s):  
F.N. Muchiri ◽  
R.D. Narla ◽  
O.M. Olanya ◽  
R.O. Nyankanga ◽  
E.S. Ariga
Keyword(s):  
Late Blight ◽  
Phytophthora Infestans ◽  
Tuber Yield ◽  
Severe Disease ◽  
Resistance Management ◽  
Foliar Blight ◽  
Progress Curve ◽  
Fungicide Mixtures ◽  
Spray Regimes ◽  
Disease Pressure

Fungicide application strategies (timing, frequency, rates and mixtures) are important for the control and resistance management of potato late blight caused by Phytophthora infestans. The efficacy of fungicide mixtures consisting of fenamidone + mancozeb and propamocarb HCL + mancozeb at various rates and in spray regimes containing metalaxyl and mancozeb was evaluated for late blight control (US-1) at four locations in Kenya. Propamocarb HCL + mancozeb significantly (P < 0.05) reduced foliar blight compared with mancozeb and the untreated control under moderate to severe disease pressure. Disease severity was significantly lower following application of propamocarb HCL + mancozeb at a rate of 4L ha-1 than at rates of 2L and 3L ha-1 in 1999 and 2000, but it was not significantly lower following applications at a rate of 3L ha-1 in 2000 and 2001. There were no significant differences in mean final late blight score among the three rates of 0.9, 1.0 and 1.1 kg ha-1 of fenamidone + mancozeb. All fungicide mixtures and application sequences significantly reduced the area under the disease progress curve and final late blight scores as compared with the unprotected control. Total and marketable tuber yield significantly (P < 0.05) increased in all fungicide-treated plots.

scholarly journals Infection of Potatoes by Oospores of Phytophthora infestans in Soil

Plant Disease ◽  
1999 ◽  
Vol 83 (9) ◽  
pp. 876-876 ◽  
Author(s):  
A. Strömberg ◽  
L. Persson ◽  
M. Wikström
Keyword(s):  
Late Blight ◽  
Phytophthora Infestans ◽  
Mating Type ◽  
Potato Crop ◽  
Selective Medium ◽  
Day Length ◽  
Talcum Powder ◽  
Soil P ◽  
Nodal Cuttings

Phytophthora infestans (Mont.) de Bary, causing late blight on potatoes and considered to be a typical airborne disease, was found to be infective also by oospores in the soil. P. infestans is heterothallic, and is known to reproduce asexually in Sweden since only one mating type, A1, was present until 1986. Since the 1970s, the other mating type, A2, of P. infestans has migrated to most parts of the world from its original location in central Mexico (2). When A1 and A2 meet, they may form oospores, which are thick-walled, resting structures, giving the pathogen a possibility to recombine as well as survive without its host, for instance in the soil. The soil stages of the pathogen are now therefore under intense investigation. Oospores of P. infestans were produced from two Scandinavian A1 and A2 isolates in Rye A broth mixed with talcum powder and dried for 7 weeks. The inoculum was mixed with sterile, standardized soil in concentrations of 10, 150, 250, and 400 oospores per ml of soil. Cv. Bintje plants cultivated in vitro from nodal cuttings on Murashige and Skoog medium were transplanted to the soil after rooting. Brown discolorations were obtained on the underground stems and tubers on potato plants grown in the two highest concentrations of oospores for 1 month at 15°C and 16-h day length. After 3 days of incubation on P. infestans-selective medium (3), sporangia covered the tissue from plants grown in 250 and 400 oospores per ml of soil and the pathogen was reisolated. This shows that germinating oospores of P. infestans can infect underground stems and tubers of potatoes in soil and further explains the early attack of late blight as observed in a potato crop in Sweden 1996 and 1997 (1). References: (1) B. Andersson et al. Potato Res. 41:305, 1998. (2) D. Andrivon. Phytopathology 85:1053, 1995. (3) G. W. Griffith et al. Mycologist 9:87, 1995.

Resistance to Phytophthora infestans Clonal Lineage US-23 in Potato Cultivars and Its Relationship with Early Blight Resistance and Tuber Yield

Plant Disease ◽  
2021 ◽  
Author(s):  
Weiya Xue ◽  
Kathleen G. Haynes ◽  
Xinshun Qu
Keyword(s):  
Late Blight ◽  
Phytophthora Infestans ◽  
Early Blight ◽  
Tuber Yield ◽  
Late Blight Resistance ◽  
Field Trials ◽  
Potato Cultivars ◽  
Blight Resistance ◽  
Clonal Lineage ◽  
Progress Curve

Resistance to late blight, caused by Phytophthora infestans clonal lineage US-23, in 217 old and modern potato cultivars was evaluated in field trials in 2016 and 2017 in Pennsylvania. Significant differences in resistance were found among these cultivars (P < 0.0001). Significant interaction between cultivars and environments was found (P < 0.0001). The values of relative area under the disease progress curve ranged from 0 to 0.5841 in 2016 and from 0 to 0.5469 in 2017. Broad-sense heritability of late blight resistance was estimated to be 0.91 with a 95% confidence interval of 0.88 to 0.93. Cluster analysis classified the cultivars into 5 groups: resistant, moderately resistant, intermediate, moderately susceptible, and susceptible. Thirty cultivars showing resistance and 32 cultivars showing moderate resistance were identified. The 217 cultivars were also evaluated for foliar maturity, tuber yield and resistance to early blight, caused by Alternaria solani. A few cultivars with late blight resistance independent of late maturity were found. Late blight resistance and early blight resistance were positively correlated, and 17 cultivars possessed resistance to both diseases. Yield tradeoff associated with late blight resistance was not observed among the cultivars in the absence of disease pressure.

scholarly journals POPULATION STRUCTURE OF PHYTOPHTHORA INFESTANS ON WORLDWIDE SCALE: A REVIEW

2017 ◽  
Vol 29 (2) ◽  
pp. 281
Author(s):  
Khalid Naveed ◽  
Nasir A. Rajputt ◽  
Sajid A. Khan ◽  
Arbab Ahmad
Keyword(s):  
Population Structure ◽  
Late Blight ◽  
Phytophthora Infestans ◽  
Potato Cultivar ◽  
R Genes ◽  
Solanum Bulbocastanum ◽  
Tuber Resistance ◽  
Commercial Potato ◽  
Rb Gene ◽  
Late Blight Of Potato

Phytophthora infestans is a destructive pathogen that causes late blight of potato worldwide. Several sexually and asexually reproducing lineages of the pathogen have been identified and new lineages are more virulent as compared to their parental lineages. A new highly aggressive clonal lineage EU13_A2 has spread into potato fields of Europe, Africa and Asia in place of the older lineages. In North America, 24 clonal lineages US1to US24 have been identified. Despite of sexual reproduction, the overall population of P. infestans in potato and tomato fields is dominated by asexual lineages. Breeding has been done to transfer 'R' genes into commercial potato cultivars through classical breeding and by pyramiding of genes. Defender is the only potato cultivar that has foliar and tuber resistance to late blight. Genetically modified potato with RB gene from Solanum bulbocastanum has been developed but it lacks tuber resistance to disease. This review discusses population structure of P. infestans worldwide and breeding efforts to produce late blight resistant potato.

scholarly journals Genotype reaction of Solanum tuberosum, andigena and phureja groups to late blight (Phytophthora infestans Mont. De Bary)

2019 ◽  
Vol 36 (E) ◽  
pp. 138-157
Author(s):  
Jennyfer Moncayo ◽  
Roberth Delgado ◽  
Carlos Marcillo ◽  
Claudia Salazar ◽  
Carlos Betancourth
Keyword(s):  
Solanum Tuberosum ◽  
Late Blight ◽  
Phytophthora Infestans ◽  
Potato Crop ◽  
Block Design ◽  
Food Product ◽  
Randomized Complete Block Design ◽  
Late Blight Disease ◽  
Disease Effect ◽  
Blight Disease

Potato crop is the fourth main food product in the world, but is affected by Phytophthora infestans, the late blight disease causal agent. This research was carried out in a town of Pasto high plateau, South of Colombia. In order to evaluate the reaction of different genotypes of creole potato (Solanum tuberosum groups Phureja and Andigena) with regard the disease. A Randomized Complete Block design was established with three repetitions, where 30 genotypes were distributed and three plants were evaluated per repetition during two crop cycles in natural exposure to the pathogen. To assess the disease effect on production, the same genotypes were maintained with chemical control in an adjacent batch. Genotypes classified as tolerant are Chaucha Manzana, Cachuda, Criolla Colombia, Malvaseña, Andina and Criolla, during the first cycle with performance values ​​between 23 to 26t.ha-1 and during the second to Calavera Negra, Chaucha Paisa, Ratona, Criolla Galeras, Ratona Roja, Tornilla Roja and Aguacata with performance values ​​between 23 to 28t.ha-1. The graphic severity scale allowed genotypes to be categorized as susceptible and highly susceptible. The results indicate that for the prevalent pathogen race in this study area, there are no resistance sources within the studied collection. However, genotypes such as Criolla Colombia and Andina showed a better performance in terms of yield.

scholarly journals GENETIC STABILITY ANALYSIS OF RB GENE IN GENETICALLY MODIFIED POTATO LINES TOLERANT TO Phytophthora infestans

2016 ◽  
Vol 16 (2) ◽  
pp. 51
Author(s):  
Edy Listanto ◽  
Eny Ida Riyanti ◽  
Tri Joko Santoso ◽  
Toto Hadiarto ◽  
A. Dinar Ambarwati
Keyword(s):  
Stability Analysis ◽  
Late Blight ◽  
Blot Analysis ◽  
Copy Number ◽  
Southern Blot Analysis ◽  
Transgenic Potato ◽  
Plant Genome ◽  
Late Blight Disease ◽  
Rb Gene ◽  
Blight Disease

Development of potato cultivars with high levels of broad spectrum resistance is a key long-term management strategy against late blight disease caused by Phytophthora infestans. Six progeny lines of hybridization between transgenic potato Katahdin SP951 with non-transgenic Granola and Atlantic were selected based on agronomical characteristics and resistance to late blight disease. The study aimed to analyze the number of insertions and stability of inserted RB gene in the transgenic potato lines. The research was carried out through plant DNA extraction, southern blot analysis and polymerase chain reaction (PCR). Southern blot analysis was used to detect the number of inserts integrated into potato genome, while PCR analysis was used to detect stability of RB gene from generation to generation. The results showed that the progenies obtained from hybridization between Atlantic and transgenic Katahdin SP951 (lines No. 20 and 27) and between Granola and transgenic Katahdin SP951 (line No. 69) contained one copy number of RB gene, according to the probing of nptII. The result is similar to that of inserted RB gene found in the parental transgenic Katahdin SP951. The presence of RB gene in four different generations (G0, G1, G2 and G3) showed stable integration of the gene into the plant genome. The single copy number of RB gene will repress the occurrence of silencing gene expression. The stability analysis of RB gene can determine that the gene is still present in plant genome after several generations.

scholarly journals RESISTANCE EVALUATION ON POPULATIONS OF CROSSES BETWEEN TRANSGENIC POTATO KATAHDIN RB AND NON-TRANSGENIC ATLANTIC AND GRANOLA TO LATE BLIGHT (Phytophthora infestans) IN CONFINED FIELD TRIAL

2011 ◽  
Vol 12 (1) ◽  
pp. 33 ◽  
Author(s):  
Alberta Dinar Ambarwati ◽  
Muhammad Herman ◽  
Agus Purwito ◽  
Sientje Mandang Sumaraw ◽  
Hajrial Aswidinnoor
Keyword(s):  
Late Blight ◽  
Phytophthora Infestans ◽  
Resistance Gene ◽  
Field Trial ◽  
Transgenic Potato ◽  
Solanum Bulbocastanum ◽  
Resistance Level ◽  
Progress Curve ◽  
Resistance Score ◽  
Confined Field Trial

Late blight resistance gene (RB gene) isolated from Solanum bulbocastanum, is a broad resistance gene against all races of Phytophthora infestans. The gene was transformed into Katah-din event SP904 and SP951 using Agrobacterium tumefaciens and these transgenic plants have been crossed with susceptible potato cultivars Atlantic and Granola. Populations of the crosses have been molecularly characterized for the integration of the RB transgene. The study aimed to evaluate the resistance of the populations of crosses between transgenic Katahdin RB  and susceptible non-transgenic parents (Atlantic and Granola) to late blight in a confined field trial at Pasir Sarongge, Cianjur, West Java. A total of 84 clones originated from four popula-tions were evaluated for resistance to late blight. These included 22 clones of Atlantic x transgenic Katahdin SP904, 16 clones of Atlantic x transgenic Katahdin SP951, 19 clones of Granola x transgenic Katahdin SP904, and 27 clones of Granola x transgenic Katahdin SP951. Observations of the late blight infection were conducted when late blight symptoms were detected, i.e. at 56, 60, 63, 70, and 77 days after planting (DAP). The result showed there were high variations in the resistance level of all the 84 clones tested. Clones of crosses between susceptible parents (Atlantic or Granola) and resistant parents (transgenic Katahdin SP904 or Katahdin SP951) showed a similar pattern based on the area under disease progress curve (AUDPC) value, i.e. 377.2 greater than the AUDPC of the resistant parents (180.1), but smaller than that of the susceptible parents (670.7). Observation at 77 DAP resulted four resistant potato clones having resistance score of 7.0-7.6, higher than the transgenic parents Katahdin SP904 (4.6) and Katahdin SP951 (6.8), i.e. clone B8 (Atlantic x transgenic Katahdin SP951) with resistance score of 7.6 and clones B26 (Atlantic x transgenic Katahdin SP951), C183 (Granola x transgenic Katahdin SP904), and D89 (Granola x transgenic Katahdin SP951) with resistance score of 7. These four transgenic potato resistant clones need to be further developed as promising potato clones to late blight.<br /><br />

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