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Fusarium wilt, caused by Fusarium oxysporum f. sp. ricini, is the most destructive disease in castor. Host plant resistance is the best strategy for the management of wilt. Identification of molecular markers linked to wilt resistance will enhance the efficiency and effectiveness of breeding for wilt resistance. In the present study, genomic regions linked to wilt resistance were mapped using a bi-parental population of 185 [F.sub.6]-RILs and a genetically diverse panel of 300 germplasm accessions. Quantitative trait loci (QTL) analysis performed using a linkage map consisting of 1090 SNP markers identified a major QTL on chromosome 7 with an LOD score of 18.7, which explained 44% of the phenotypic variance. The association mapping performed using genotypic data from 3465 SNP loci revealed 69 significant associations (p < 1 x [10.sup.-4]) for wilt resistance. The phenotypic variance explained by the individual SNPs ranged from 0.063 to 0.210. The QTL detected in the bi-parental mapping population was not identified in the association analysis. Thus, the results of this study indicate the possibility of vast gene diversity for Fusarium wilt resistance in castor. Key words: Fusarium oxysporum f. sp. ricini, Ricinus communis L., genome-wide association study, QTL mapping, SNP markers. La flétrissure fusarienne causée par le Fusarium oxysporum f. sp. ricini est la maladie la plus importante chez le ricin. La résistance de l'hôte est la meilleure stratégie pour lutter contre la flétrissure. L'identification de marqueurs moléculaires liés à la résistance à la flétrissure permettra d'augmenter l'efficience et l'efficacité de la sélection pour la résistance à la flétrissure. Dans le présent travail, les auteurs ont tenté d'identifier des régions génomiques liées à la résistance à la flétrissure au sein d'une population biparentale composée de 185 [F.sub.6] - RIL ainsi qu'au sein d'une collection de 300 accessions. L'analyse QTL a été réalisée au moyen d'une carte génétique comprenant 1090 marqueurs SNP et a permis d'identifier un QTL majeur sur le chromosome 7 qui présentait un score LOD de 18,7 et qui expliquait 44% de la variance phénotypique. L'analyse d'association a été réalisée à l'aide des données génotypiques pour 3465 SNP et a révélé 69 associations significatives (p < 1 x [10.sup.-4]) avec la résistance à la flétrissure. La variance phénotypique expliquée par les SNP variait entre 0,063 et 0,210. Le QTL détecté au sein de la population de cartographie biparentale n'a pas été identifié dans l'analyse d'association. Ainsi, les résultats de ce travail suggèrent une grande diversité génique pour la résistance à la flétrissure fusarienne chez le ricin. [Traduit par la Rédaction] Mots-clés : Fusarium oxysporum f. sp. ricini, Ricinus communis L., analyse d'association pangénomique, cartographie QTL, marqueurs SNP., Introduction Castor (Ricinus communis L.) is an important oilseed crop grown in arid and semi-arid regions of the world. Its oil is an important raw material for several industrial products [...]

To understand the castor wax layer's multifaceted contribution to Amphobotrys ricini pathogenesis, the hydrophobic components of cuticular wax were analysed from waxy and non‐waxy castor genotypes. Gas chromatography–mass spectrometry (GC–MS) technology enabled the stable detection and quantitative determination of various fatty acids and terpenoids. The investigation revealed a significant presence of triterpenoid compound 'lupeol', accounting for approximately 53.6% of the wax composition in the waxy genotype (DCH‐519), which was absent in non‐waxy genotype (ICS‐324). On exposure to lupeol, about 93.3% of conidia germinated leading to rapid mycelium growth and sporulation of A. ricini. SEM analysis of waxy and non‐waxy genotypes infected with A. ricini confirmed faster germination and production of longer germ tubes on waxy genotype compared with non‐waxy genotype, which may likely due to early recognition of the suitable host in the presence of lupeol, ultimately aiding in speedy germination and growth of the pathogen setting pace for pathogenesis. [ABSTRACT FROM AUTHOR]

Abstract Background Pearl millet [Pennisetum glaucum (L.) R. Br.] is a staple food and fodder crop of marginal agricultural lands of sub-Saharan Africa and the Indian subcontinent. It is also a summer forage crop in the southern USA, Australia and Latin America, and is the preferred mulch in Brazilian no-till soybean production systems. Use of molecular marker technology for pearl millet genetic improvement has been limited. Progress is hampered by insufficient numbers of PCR-compatible co-dominant markers that can be used readily in applied breeding programmes. Therefore, we sought to develop additional SSR markers for the pearl millet research community. Results A set of new pearl millet SSR markers were developed using available sequence information from 3520 expressed sequence tags (ESTs). After clustering, unigene sequences (2175 singlets and 317 contigs) were searched for the presence of SSRs. We detected 164 sequences containing SSRs (at least 14 bases in length), with a density of one per 1.75 kb of EST sequence. Di-nucleotide repeats were the most abundant followed by tri-nucleotide repeats. Ninety primer pairs were designed and tested for their ability to detect polymorphism across a panel of 11 pairs of pearl millet mapping population parental lines. Clear amplification products were obtained for 58 primer pairs. Of these, 15 were monomorphic across the panel. A subset of 21 polymorphic EST-SSRs and 6 recently developed genomic SSR markers were mapped using existing mapping populations. Linkage map positions of these EST-SSR were compared by homology search with mapped rice genomic sequences on the basis of pearl millet-rice synteny. Most new EST-SSR markers mapped to distal regions of linkage groups, often to previous gaps in these linkage maps. These new EST-SSRs are now are used by ICRISAT in pearl millet diversity assessment and marker-aided breeding programs. Conclusion This study has demonstrated the potential of EST-derived SSR primer pairs in pearl millet. As reported for other crops, EST-derived SSRs provide a cost-saving marker development option in pearl millet. Resources developed in this study have added a sizeable number of useful SSRs to the existing repertoire of circa 100 genomic SSRs that were previously available to pearl millet researchers.

Abstract Background With the advances in DNA sequencer-based technologies, it has become possible to automate several steps of the genotyping process leading to increased throughput. To efficiently handle the large amounts of genotypic data generated and help with quality control, there is a strong need for a software system that can help with the tracking of samples and capture and management of data at different steps of the process. Such systems, while serving to manage the workflow precisely, also encourage good laboratory practice by standardizing protocols, recording and annotating data from every step of the workflow. Results A laboratory information management system (LIMS) has been designed and implemented at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) that meets the requirements of a moderately high throughput molecular genotyping facility. The application is designed as modules and is simple to learn and use. The application leads the user through each step of the process from starting an experiment to the storing of output data from the genotype detection step with auto-binning of alleles; thus ensuring that every DNA sample is handled in an identical manner and all the necessary data are captured. The application keeps track of DNA samples and generated data. Data entry into the system is through the use of forms for file uploads. The LIMS provides functions to trace back to the electrophoresis gel files or sample source for any genotypic data and for repeating experiments. The LIMS is being presently used for the capture of high throughput SSR (simple-sequence repeat) genotyping data from the legume (chickpea, groundnut and pigeonpea) and cereal (sorghum and millets) crops of importance in the semi-arid tropics. Conclusion A laboratory information management system is available that has been found useful in the management of microsatellite genotype data in a moderately high throughput genotyping laboratory. The application with source code is freely available for academic users and can be downloaded from http://www.icrisat.org/gt-bt/lims/lims.asp.

Castor is an industrially important oilseed crop. Vascular wilt caused by the soil borne fungus Fusarium oxysporum f. sp. ricini is a serious disease of castor. Use of resistant cultivars is the only viable option for management of wilt disease problem in castor production. Excellent sources of resistance to wilt have been found in castor germplasm. In this study, a set of four castor inbred lines (48–1, CI-1, AP42 and AP48) was characterized for inheritance of resistance to wilt by studying segregating populations generated by crossing these inbred lines with eight different susceptible genotypes. An artificial screening method (sick pot) with a new scoring system (days to wilt) was used for evaluation of plant progenies for reaction to the pathogen infection. The reaction of F1s indicated that the nature of resistance in 48–1, CI-1 and AP48 is recessive whereas it was dominant in AP42. Inheritance results from eight F2 populations showed that resistance to wilt is conferred by a single locus in one population and at least two loci, which interact in complementary way, in other seven populations. Different modes of inheritance were also observed when the same resistant source was crossed with different susceptible parents, indicating the possible role of genetic backgrounds in determining resistance. Overall, the results suggested that Mendelian resistance to wilt is predominant in the castor genotypes, which can be exploited for breeding cultivars. Particularly, AP42 with dominant nature of resistance will be of great interest to hybrid breeding. [ABSTRACT FROM AUTHOR]