Gynogenesis is an asexual mode of reproduction common to animals and plants, in which stimuli from the sperm cell trigger the development of the unfertilized egg cell into a haploid embryo. Fine mapping restricted a major maize QTL (quantitative trait locus) responsible for the aptitude of inducer lines to trigger gynogenesis to a zone containing a single gene () coding for a patatin-like phospholipase A. In all surveyed inducer lines, carries a 4-bp insertion leading to a predicted truncated protein. This frameshift mutation is responsible for haploid induction because complementation with wild-type abolishes the haploid induction capacity. Activity of the promoter is restricted to mature pollen and pollen tube. The translational NLD::citrine fusion protein likely localizes to the sperm cell plasma membrane. In roots, the truncated protein is no longer localized to the plasma membrane, contrary to the wild-type NLD protein. In conclusion, an intact pollen-specific phospholipase is required for successful sexual reproduction and its targeted disruption may allow establishing powerful haploid breeding tools in numerous crops.

Blackleg, caused by Leptosphaeria maculans (Desm.) Ces. et de Not., is a major disease of oilseed rape (Brassica napus L.) worldwide. Molecular markers would be useful tools to assist breeding for blackleg resistance. The objective of this study was (i) to map and characterize quantitative trait loci (QTL) for field blackleg resistance in doubled haploid (DH) and F2:3 populations from the cross ‘Darmor’ (resistant) × ‘Samourai’ (susceptible) and (ii) to compare QTL with those previously identified in the cross ‘Darmor‐bzh’ × ‘Yudal’. A total of 134 DH lines and 185 F2:3 families were genotyped with random amplified polymorphic DNA (RAPD) and restriction fragment length polymorphism (RFLP) markers and assessed for a disease index of resistance in 1998 and/or 1999 in one location. Genetic maps derived from the two populations included a total of 257 and 81 markers, respectively. Up to 30% of these markers were common to the Darmor‐bzh × Yudal map previously used. A total of six and four genomic regions were associated with resistance in the DH and F2:3 populations, respectively. They collectively explained 36 to 42% of the variation within each year and population. Three of them were consistent across the two populations derived from Darmor × Samourai cross and expressed dominant or overdominant effects. Four favorable alleles were derived from the susceptible parent. A total of 16 genomic regions were revealed for blackleg resistance in the two crosses Darmor‐bzh × Yudal and Darmor × Samourai studied. Four of them were consistent over the two crosses. The inconsistencies observed between populations and crosses can be explained by different genetic backgrounds and disease infestation levels. For marker‐assisted selection, these results suggest that QTL mapping must be carried out separately for each population.

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