Development of a high-resolution melting marker for selecting Fusarium crown and root rot resistance in tomato.

Fusarium crown and root rot is a severe fungal disease of tomato caused by Fusarium oxysporum f. sp. radicis-lycopersici (FORL). In this study, the genomic location of the FORL-resistance locus was determined using a set of molecular markers on chromosome 9 and an F2 population derived from FORL-resistant inbred 'AV107-4' (Solanum lycopersicum) × susceptible 'L3708' (Solanum pimpinellifolium). Bioassay performed using Korean FORL strain KACC 40031 showed single dominant inheritance of FORL resistance in the F2 population. In all, 13 polymerase chain reaction-based markers encompassing approximately 3.6-72.0 Mb of chromosome 9 were developed based on the Tomato-EXPEN 2000 map and SolCAP Tomato single nucleotide polymorphism array analysis. These markers were genotyped on 345 F2 plants, and the FORL-resistance locus was found to be present on a pericentromeric region of suppressed chromosomal recombination in chromosome 9. The location of the FORL-resistance locus was further confirmed by testing these markers against diverse commercial tomato and stock cultivars resistant to FORL. A restriction fragment length polymorphism marker, PNU-D4, located at approximately 6.1 Mb of chromosome 9 showed the highest match with the resistance locus and was used for conducting high-resolution melting analysis for marker-assisted selection of FORL resistance.

Evaluation of maximum potential gene flow from herbicide resistant Brassica napus to its male sterile relatives under open and wind pollination conditions.

Pollen-mediated gene flow (PMGF) from genetically modified (GM) Brassica napus to its wild relatives by wind and insects is a major ecological concern in agricultural ecosystems. This study conducted is to estimate maximum potential gene flow and differentiate between wind- and bee-mediated gene flows from herbicide resistant (HR) B. napus to its closely-related male sterile (MS) relatives, B. napus, B. juncea and Raphanus sativus. Various markers, including pods formation in MS plants, herbicide resistance, and SSR markers, were used to identify the hybrids. Our results revealed the following: 1) maximum potential gene flow (a maximum % of the progeny of pollen recipient confirmed hybrid) to MS B. napus ranged from 32.48 to 0.30% and from 14.69 to 0.26% at 2-128 m from HR B. napus under open and wind pollination conditions, respectively, and to MS B. juncea ranged from 21.95 to 0.24% and from 6.16 to 0.16%, respectively; 2) estimates of honeybee-mediated gene flow decreased with increasing distance from HR B. napus and ranged from 17.78 to 0.03% at 2-128 m for MS B. napus and from 15.33 to 0.08% for MS B. juncea; 3) a small-scale donor plots would strongly favour insect over wind pollination; 4) no gene flow occurred from HR B. napus to MS R. sativus. Our approach and findings are helpful in understanding the relative contribution of wind and bees to gene flow and useful for estimating maximum potential gene flow and managing environmental risks associated with gene flow.