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Saccharum officinarum L. is an octoploid with 80 chromosomes and a basic chromosome number of x = 10. It has high stem sucrose and contributes 80% of the chromosomes to the interspecific sugarcane cultivars that are grown commercially for sucrose. A genetic linkage map was developed for S. officinarum (clone IJ76-514) using a segregating population generated from a cross between Q165 (a commercial sugarcane cultivar) and IJ76-514. In total, 40 AFLP and 72 SSR primer pairs were screened across the population, revealing 595 polymorphic bands inherited from IJ76-514. These 595 markers displayed a frequency distribution different from all other sugarcane genetic maps produced, with only 40% being simplex markers (segregated 1:1). Of these 240 simplex markers, 178 were distributed on 47 linkage groups (LGs) and 62 remained unlinked. With the addition of 234 duplex markers and 80 biparental simplex markers (segregating 3:1), 534 markers formed 123 LGs. Using the multi-allelic SSR markers, repulsion phase linkage, and alignment with the Q165 linkage map, 105 of the 123 LGs could be grouped into 10 homology groups (HGs). These 10 HGs were further assigned to the 8 HGs observed in cultivated sugarcane and S. spontaneum. Analysis of repulsion phase linkage indicated that IJ76-514 is neither a complete autopolyploid nor an allopolyploid. Detection of 28 repulsion linkages that occurred between 6 pairs of LGs located in 4 HGs suggested the occurrence of limited preferential chromosome pairing in this species. Le Saccharum officinarum L. est un octoploïde à 80 chromosomes et un nombre chromosomique de base x = 10. Sa tige a une forte teneur en saccharose et contribue 80 % des chromosomes dans les cultivars interspécifiques de canne à sucre qui sont cultivés commercialement pour le saccharose. Une carte génétique a été produite pour le S. officinarum (IJ76-514) à l’aide d’une population en ségrégation issue d’un croisement entre Q165 (une variété commerciale) et IJ76-514. Au total, 40 paires d’amorces AFLP et 72 amorces SSR ont été criblées sur l’ensemble de la collection, révélant ainsi 595 bandes polymorphes héritées d’IJ76-514. Ces 595 marqueurs présentaient une fréquence de distribution différente de toutes les autres cartes génétiques produites, avec seulement 40 % de marqueurs simplex (ségrégation 1:1). Ces 240 marqueurs simplex étaient distribués sur 47 groupes de liaison et 62 marqueurs sont restés non-assignés. Avec l’addition de 234 marqueurs duplex et 80 marqueurs simplex biparentaux (ségrégation 3:1), 534 marqueurs formaient 123 groupes de liaison. Avec les marqueurs SSR multialléliques, la liaison en répulsion et l’alignement avec la carte de Q165, 105 des 123 groupes de liaison ont été assignés à 10 groupes d’homéologie (« HG ). Ces 10 HG ont ensuite été assignés aux 8 HG observés chez la canne à sucre cultivée et chez le S. spontaneum. Une analyse de la liaison en répulsion a révélé que le génotype IJ76-514 n’est ni complètement autopolyploïde ni complètement allopolyploïde. La détection de 28 liaisons en répulsion observées chez 6 paires de groupes de liaison situés dans quatre HG suggère un appariement chromosomique préférentiel limité chez cette espèce. [ABSTRACT FROM AUTHOR]

A major locus conferring resistance to the causal organism of powdery mildew, Erysiphe polygoni DC, in mungbean (Vigna radiata L. Wilczek) was identified using QTL analysis with a population of 147 recombinant inbred individuals. The population was derived from a cross between 'Berken', a highly susceptible variety, and ATF 3640, a highly resistant line. To test for response to powdery mildew, F7 and F8 lines were inoculated by dispersing decaying mungbean leaves with residual conidia of E. polygoni amongst the young plants to create an artificial epidemic and assayed in a glasshouse facility. To generate a linkage map, 322 RFLP clones were tested against the two parents and 51 of these were selected to screen the mapping population. The 51 probes generated 52 mapped loci, which were used to construct a linkage map spanning 350 cM of the mungbean genome over 10 linkage groups. Using these markers, a single locus was identified that explained up to a maximum of 86% of the total variation in the resistance response to the pathogen. [ABSTRACT FROM AUTHOR]

A major locus conferring resistance to the causal organism of powdery mildew, Erysiphe polygoni DC, in mungbean (Vigna radiata L. Wilczek) was identified using QTL analysis with a population of 147 recombinant inbred individuals. The population was derived from a cross between 'Berken', a highly susceptible variety, and ATF 3640, a highly resistant line. To test for response to powdery mildew, F7 and F8 lines were inoculated by dispersing decaying mungbean leaves with residual conidia of E. polygoni amongst the young plants to create an artificial epidemic and assayed in a glasshouse facility. To generate a linkage map, 322 RFLP clones were tested against the two parents and 51 of these were selected to screen the mapping population. The 51 probes generated 52 mapped loci, which were used to construct a linkage map spanning 350 cM of the mungbean genome over 10 linkage groups. Using these markers, a single locus was identified that explained up to a maximum of 86% of the total variation in the resistance response to the pathogen.