The common bean (Phaseolus vulgaris L.) is the world’s most important legume for human consumption. Anthracnose (ANT; Colletotrichum lindemuthianum) and angular leaf spot (ALS; Pseudocercospora griseola) are complex diseases that cause major yield losses in common bean. Depending on the cultivar and environmental conditions, anthracnose and angular leaf spot infections can reduce crop yield drastically. This study aimed to estimate linkage disequilibrium levels and identify quantitative resistance loci (QRL) controlling resistance to both ANT and ALS diseases of 180 accessions of common bean using genome-wide association analysis. A randomized complete block design with four replicates was performed for the ANT and ALS experiments, with four plants per genotype in each replicate. Association mapping analyses were performed for ANT and ALS using a mixed linear model approach implemented in TASSEL. A total of 17 and 11 significant statistically associations involving SSRs were detected for ANT and ALS resistance loci, respectively. Using SNPs, 21 and 17 significant statistically associations were obtained for ANT and angular ALS, respectively, providing more associations with this marker. The SSR-IAC167 and PvM95 markers, both located on chromosome Pv03, and the SNP scaffold00021_89379, were associated with both diseases. The other markers were distributed across the entire common bean genome, with chromosomes Pv03 and Pv08 showing the greatest number of loci associated with ANT resistance. The chromosome Pv04 was the most saturated one, with six markers associated with ALS resistance. The telomeric region of this chromosome showed four markers located between approximately 2.5 Mb and 4.4 Mb. Our results demonstrate the great potential of genome-wide association studies to identify QRLs related to ANT and ALS in common bean. The results indicate a quantitative and complex inheritance pattern for both diseases in common bean. Our findings will contribute to more effective screening of elite germplasm to find resistance alleles for marker-assisted selection in breeding programs.

We report here on the characterization of a cDNA library from seeds of Jatropha curcas L. at three stages of fruit maturation before yellowing. We sequenced a total of 2200 clones and obtained a set of 931 non-redundant sequences (unigenes) after trimming and quality control, ie, 140 contigs and 791 singlets with PHRED quality ≥10. We found low levels of sequence redundancy and extensive metabolic coverage by homology comparison to GO. After comparison of 5841 non-redundant ESTs from a total of 13193 reads from GenBank with KEGG, we identified tags with nucleotide variations among J. curcas accessions for genes of fatty acid, terpene, alkaloid, quinone and hormone pathways of biosynthesis. More specifically, the expression level of four genes (palmitoyl-acyl carrier protein thioesterase, 3-ketoacyl-CoA thiolase B, lysophosphatidic acid acyltransferase and geranyl pyrophosphate synthase) measured by real-time PCR proved to be significantly different between leaves and fruits. Since the nucleotide polymorphism of these tags is associated to higher level of gene expression in fruits compared to leaves, we propose this approach to speed up the search for quantitative traits in selective breeding of J. curcas. We also discuss its potential utility for the selective breeding of economically important traits in J. curcas.

Jatropha curcas L. oil has been shown to be suitable for the production of biodiesel. However, this species has not been domesticated yet. Genetic breeding through conventional methods is time consuming and costly, hence, genetic transformation could contribute positively to the improvement of interesting traits. Although in vitro regeneration and stable genetic transformation has been pursued for several years, variation in transformation efficiency remains strongly genotype-dependent and indicates that protocols optimization is still needed. Thus, this study was carried out to introduce a chitinase gene from the Trichoderma viride fungus into the genome of a J. curcas superior genotype by inoculating leaf explants with Agrobacterium tumefaciens EHA 105 strain in axenic conditions. Some key parameters such as pre-culture period and antibiotic doses were optimized with 500 mg.L -1 cefotaxime and 100 mg.L -1 kanamycin concentrations being suitable for A. tumefaciens inhibition and explant selection, respectively. The best transformation efficiency (50%) was obtained when leaf explants were incubated on a culture medium promoting shoot regeneration at 15 days before the induction of the transformation process. Plants where chitinase gene amplicons could be detected were assessed for transgene copy number and expression levels by quantitative real-time polymerase chain reaction (PCR). One, two and three copies of the introduced gene were confirmed in nine transgenic lines with two of them that were assessed for gene expression and showed quantitative variation for this variable. These results bring valuable information for further gene insertions in breeding programs of J. curcas for fungal disease resistance.