Resistance against Dickeya solani in potato with the help of a susceptibility gene

Potato (Solanum tuberosum) is a staple crop across Europe, including Sweden. Among the reasons why it is so ubiquitous is its fairly easy cultivation, good adaptability to various climates, and high nutritional value. Today’s potato production is based on disease-free seed tubers. However, this technology often proves to be insufficient. Seed tubers serve as a target for accumulation of pests and pathogens, and one such pathogen is the necrotrophic bacterium Dickeya solani, which causes blackleg and soft rot. Due to its ability to macerate plant tissue and cause severe damages in the field, it is responsible for substantial yield losses across Europe. Consequentially, D. solani is treated as a quarantine organism in some countries. More importantly for this study, its presence has been reported in Sweden. In the present study, a new approach to potentially offer a durable and broad-spectrum disease resistance towards D. solani and some other pathogens is explored. Susceptibility genes encode products that are required for the pathogen’s survival or proliferation, thus making a plant more susceptible to disease development. By silencing the homologs of the susceptibility gene Downy Mildew Resistant 6 (DMR6) in diploid DM1- 3516 R44 and tetraploid Desirée background using RNA interference, an enhanced resistance was anticipated. Pleiotropic growth effects of DMR6 silencing were investigated and greenhouse-based infection assays were carried out. Two silenced RNAi silenced Desirée lines were tested, however, only one (dmr6-6) showed promising results as it repeatedly had smaller blackleg symptoms, high constitutive PR-1 expression, and showed no developmental and growth impairments compared to the corresponding wild type. Four diploid DM1-3516 R44 DMR6 silenced lines exhibited no growth impairments. This study indicates a potential of DMR6 for the further research in potato as an interesting target in potato breeding programs

Modelling illustrates that genomic selection provides new opportunities for intercrop breeding

Intercrop breeding programs using genomic selection can produce faster genetic gain than intercrop breeding programs using phenotypic selection. Intercropping is an agricultural practice in which two or more component crops are grown together. It can lead to enhanced soil structure and fertility, improved weed suppression, and better control of pests and diseases. Especially in subsistence agriculture, intercropping has great potential to optimize farming and increase profitability. However, breeding for intercrop varieties is complex as it requires simultaneous improvement of two or more component crops that combine well in the field. We hypothesize that genomic selection can significantly simplify and accelerate the process of breeding crops for intercropping. Therefore, we used stochastic simulation to compare four different intercrop breeding programs implementing genomic selection and an intercrop breeding program entirely based on phenotypic selection. We assumed three different levels of genetic correlation between monocrop grain yield and intercrop grain yield to investigate how the different breeding strategies are impacted by this factor. We found that all four simulated breeding programs using genomic selection produced significantly more intercrop genetic gain than the phenotypic selection program regardless of the genetic correlation with monocrop yield.We suggest a genomic selection strategy which combines monocrop and intercrop trait information to predict general intercropping ability to increase selection accuracy in the early stages of a breeding program and to minimize the generation interval