Uji Resistensi Beberapa Klon Kentang Terhadap Penyakit Hawar Daun (Phythopthora infestans)

One of the important disease on potato late blight disease is caused by a fungus Phythopthora infestans (Mont.) de Bery. Damage by leaf blight disease can lead to decrease in the yield between 10-100%. The purpose of this study is to get 27 new varieties of potato clone accession numbers from crosses that have resistance to leaf blight disease Phythopthora infestans (Mont.) de Bery. Design Randomized trial method using group, treatment consisted of 27 clones of potato varieties from crosses with three comparators are Granola, Atlantic and Jasper. Was repeated twice. The results showed that the magnitude of the intensity of the attack on the last observation is converted to the level of resistance is known from 27 potato clones from crosses that were tested, there were six resistant clones that include the PT-04, AP-03, PT-03, AP-04, AP-07 and PT-02 with disease incidence between 9.70 to 18.33%, the four clones is somewhat resistant clone PT-01, PT-06, AP-08 and AP-02 with disease incidence between 20.48 to 37.50 %, while the other clones is somewhat fragile and susceptible to disease Phythopthora infestans (Mont.) de Bery.Salah satu penyakit penting pada kentang adalah penyakit hawar daun yang disebabkan oleh jamur Phythopthora infestans (Mont.) de Bery. Kerusakan oleh penyakit hawar daun ini dapat mengakibatkan penurunan hasil antara 10-100%. Tujuan penelitian ini adalah mendapatkan varietas baru dari 27 nomor aksesi klon kentang hasil persilangan yang memiliki ketahanan terhadap penyakit hawar daun Phythopthora infestans (Mont.) de Bery. Metode percobaan menggunakan Rancangan Acak Kelompok (RAK), perlakuan terdiri dari 27 klon kentang hasil persilangan dengan tiga varietas pembanding yaitu Granola, Atlantik dan Jasper. Diulang sebanyak dua kali. Hasil penelitian menunjukkan bahwa dari besarnya intensitas serangan pada pengamatan terakhir yang dikonversikan ketingkat ketahanan diketahui dari 27 klon kentang hasil persilangan yang diuji, terdapat enam klon yang termasuk resisten yaitu PT-04, AP-03, PT-03, AP-04, AP-07 dan PT-02 dengan kejadian penyakit antara 9,70-18,33 %, empat klon agak resisten yaitu klon PT- 01, PT-06, AP-08 dan AP-02 dengan kejadian penyakit antara 20,48-37,50 %, sedangkan klon lainnya agak rentan dan rentan terhadap penyakit Phythopthora infestans (Mont.) de Bery.Keywords: resistance, Phythopthora infestans (Mont.) de Bery, potato clone.

Generation and Screening of a BAC Library from a Diploid Potato Clone to Unravel Durable Late Blight Resistance on Linkage Group IV

We describe the construction and screening of a large insert genomic library from the diploid potato clone HB171(13) that has been shown to express durable quantitative field resistance to Phytophthora infestans, the causal agent of potato late blight disease. Integrated genetic mapping of the field resistance quantitative trait locus with markers developed from populations segregating for Rpi-blb3, Rpi-abpt, R2, and R2-like resistance, all located on linkage group IV, has positioned the field resistance QTL within the proximity of this R gene cluster. The library has been successfully screened with resistance gene analogues (RGA) potentially linked to the R gene cluster. Over 30 positive BAC clones were identified and confirmed by PCR and Southern hybridisations to harbour RGA-like sequences. In addition, BAC end sequencing of positive clones has corroborated two BAC clones with a very high level of nucleotide similarity to the RGA probes utilised.

Analysis of Anther-derived Potato by RAPDs and SSRs

RAPD and SSR analyses were used to characterize the genetic composition of anther-derived plants of a diploid potato clone, CP2 (S. chacoense 80-1 × S. phureja 1-3). The ploidy of anther-derived plants was first determined by flow cytometry. A total of 44 decamer primers was screened for polymorphism. The loci that segregated were selected and scored. The monoploids had only half as many loci carrying RAPD markers compared to the anther donor. Among the 13 anther-derived diploids, four were identified as homozygous by marker frequency similar to monoploids and nine as heterozygous. Five of seven SSRs obtained from published potato sequences were polymorphic in CP2. CP2 was found to be heterozygous with two alleles at four SSR loci (TC/TA, AAG, AGA, CTT), and three alleles at an ACTC locus. Primer pairs flanking each of the five polymorphic SSRs revealed that monoploids had only the allele contributed by chc 80-1. Homozygous diploids had only one band per SSR locus, whereas heterozygous diploids displayed more than one allele for at least one SSR locus. Results of the SSR analysis supported the findings based on RAPD markers; the same diploid clones were characterized as homozygous by both SSR and RAPD markers.

THE EFFECT OF FLOWER REMOVAL ON POTATO TUBER YIELD

Relationships between fruit and vegetative growth may influence tuber yield. In 1987, flower removal significantly increased yield at irrigated and dryland sites for the potato clone ND860-2. In 1988, flower removal did not significantly increase yield in Norchip, ND2008-2 or ND860-2 planted under dryland conditions. Response to flower removal appears to be dependent on environmental conditions.Key words: Solarium tuberosum, tuber yield, flower removal, potato, ND860-2, partitioning