Durable Late Blight Resistance in Potato Through Dynamic Varieties Obtained by Cisgenesis: Scientific and Societal Advances in the DuRPh Project

Abstract

From 2006 through 2015, a research project on Durable Resistance in potato against Phytophthora (DuRPh) was carried out at Wageningen University and Research Centre. Its objective was to develop a proof of principle for durable resistance against late blight by cisgenesis. This public-funded project aimed at stimulating research on genetic modification and public debate on innovative genetic techniques. It was decided to clone and transfer late blight resistance (R) genes of crossable wild potato species (cisgenes) by Agrobacterium tumefaciens-mediated transformation without non-potato genes. A stack of multiple R genes were planned to be inserted into established varieties, thereby creating a dynamic variety in which the composition of the stacks may vary over space and time. Cisgenic plants were selected based on the expression of all inserted R genes and trueness-to-type. Within the project, 13 R genes from wild potato species were genetically mapped and three of them were cloned. Four varieties were transformed with one to three R genes. This was initially done using kanamycin resistance provided by a selectable marker gene of synthetic origin in order to quickly test the performance and stability of the introduced R genes and stacked R gene combinations. Once the functioning thereof was confirmed, marker-free transformations were conducted; thus, true cisgenic events were selected. The results about the different R genes, their chromosomal location, their specificity, the background dependence, the maximum size of a stack, its regeneration time and associated somaclonal variation frequency and its stability were studied. After selection and characterisation in the laboratory, the best cisgenic events were assessed in field trials for late blight resistance. This showed that inserted R genes were capable of turning a susceptible variety into a resistant one. Maximising longevity of the resistance was assured through resistance management research. It was shown that stacking of multiple R genes and monitoring how to deploy these stacks spatially and temporally could reduce fungicide use by over 80%. Communications through media and field demonstrations were manifold to allow public and policymakers to decide if cisgenesis is an acceptable tool to make potato farming more sustainable. Future deployment of the DuRPh strategy will depend largely on its status as a genetically modified crop or its exemption thereof. Worldwide near eradication of late blight would increase global annual potato production by close to 80 million tons, thereby contributing considerably to the needed additional global future food supply.

Molecular Screening of Potato Varieties Bred in the Northwestern Zone of the Russian Federаtion

“…Известно большое число генетических факторов, вовле-ченных в контроль устойчивости растений картофеля к фитофторозу (Simko et al, 2007;Tiwari et al, 2013;Ramakrishnan et al, 2015;Haverkort et al, 2016). В нашей работе использованы маркеры лишь нескольких генов (см.…”

“…У 26 из 39 образцов был выявлен D-тип цитоплазмы, харак-терный для вида S. demissum. Как известно, этот тип был интрогрессирован в селекционные сорта от S. demissum вместе с R-генами расоспецифической устойчивости к фитофторозу R1-R11 (Ross, 1986;Sanetomo, Hosaka, 2013;Tiwari et al, 2013;Haverkort et al, 2016).…”

Effect of Organic Potato Farming on Human and Environmental Health and Benefits from New Plant Breeding Techniques. Is It Only a Matter of Public Acceptance?

“…Big efforts to obtain durable resistance in potato against late blight disease were done through cisgenesis (DuRPh project, [47]), by combining multiple resistance genes. The sustainable control of this pathogen can be achieved only through genetic modification.…”

“…The sustainable control of this pathogen can be achieved only through genetic modification. Different late blight resistance genes were cloned from wild relatives (Solanum stoloniferum, S. bulbocastanum, S. demissum, and S. venturii) and introduced in several potato cisgenic lines [32,33,47,48] using a marker-free transformation approach [32,34]. Stacking of multiple R genes maximized durability of resistance and a correct spatial and temporal management where different improved lines may subsequently be introduced in a cultivation rotation scheme, supporting disease management and reducing fungicide use by over 80%.…”

I Have a Dream: Organic Movements Include Gene Manipulation to Improve Sustainable Farming

“…Since traits conferring resistance to P. infestans infection are present in the potato gene pool, in principle resistance can be introduced by conventional plant breeding techniques. However, it took almost half a century to establish the resistant varieties Bionica and Toluca containing a single resistance gene [15]. Gheysen and Custers stress [5] that these breeding strategies involved the use of the chemical colchicine to double the number of chromosomes.…”