African Journal of
Biotechnology

  • Abbreviation: Afr. J. Biotechnol.
  • Language: English
  • ISSN: 1684-5315
  • DOI: 10.5897/AJB
  • Start Year: 2002
  • Published Articles: 12196

Full Length Research Paper

Extreme resistance to late blight disease by transferring 3 R genes from wild relatives into African farmer-preferred potato varieties

Ethel N. Webi
  • Ethel N. Webi
  • International Potato Center, Biosciences East and Central Africa (BecA-ILRI hub), P. O. Box 25171-00603 Nairobi, Kenya.
  • Google Scholar
Kariuki Daniel
  • Kariuki Daniel
  • Department of Biochemistry, Jomo Kenyatta University of Agriculture and Technology, P. O. Box 62000-00200 Nairobi, Kenya.
  • Google Scholar
Kinyua Johnson
  • Kinyua Johnson
  • Department of Biochemistry, Jomo Kenyatta University of Agriculture and Technology, P. O. Box 62000-00200 Nairobi, Kenya.
  • Google Scholar
Njoroge Anne
  • Njoroge Anne
  • International Potato Center, Biosciences East and Central Africa (BecA-ILRI hub), P. O. Box 25171-00603 Nairobi, Kenya.
  • Google Scholar
Ghislain Marc
  • Ghislain Marc
  • International Potato Center, Biosciences East and Central Africa (BecA-ILRI hub), P. O. Box 25171-00603 Nairobi, Kenya.
  • Google Scholar
Magembe Eric
  • Magembe Eric
  • International Potato Center, Biosciences East and Central Africa (BecA-ILRI hub), P. O. Box 25171-00603 Nairobi, Kenya.
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  •  Received: 13 May 2019
  •  Accepted: 29 August 2019
  •  Published: 30 September 2019

Abstract

Three late blight resistance (R) genes from wild potato species were transferred as a stack into the farmer-preferred varieties ‘Tigoni’ and ‘Shangi’. Transgenic events were tested by detached-leaf assays (DLA) and whole-plant assays (WPA) with isolates of Phytophthora infestans using 20,000 sporangia / mL inoculum. For the first DLA, 9 out of 13 ‘Tigoni’ and 10 out of 12 ‘Shangi’ transgenic events had scores below 3% of leaf affected area. 17 of the 19 transgenic events with low scores were subjected to a second DLA using two different P. infestans isolates. 8 of them exhibited extreme LB resistance while the remaining 9 transgenic events showed hypersensitive response (HR). 6 transgenic events (2 ‘Tigoni’ and 4 ‘Shangi’) with extreme resistance by DLA were subjected to WPA and they all exhibited extreme resistance to LB. Hence, this study demonstrates that a simple DLA predicts high level of resistance to late blight. R gene expression analysis in 18 transgenic events showed different transgenic events exhibiting different levels of expression in the three genes. However, that pathogen induction and / or high R gene expression are necessary for extreme resistance when transgenic events bear a stack of three R genes was not observed.

 

Key words: Detached-leaf assay, late blight, Phytophthora infestans, resistance.