Association Mapping for Drought Tolerance and Yield-Related Traits in Cowpea Accessions

The objective of this study were to conduct association mapping for drought tolerance at the seedling stage and yield-related traits. 60 cowpea accessions were used in the study. Single-nucleotide polymorphisms (SNPs) discovered through genotyping by sequencing (GBS) were used for genotyping. Association mapping was conducted using single-marker regression (SMR) in Q Gene, and general linear model (GLM) and mixed linear model (MLM) built in TASSEL. The population of the cowpea accessions were analysed using STRUCTURE 2.3.4 and the peak of delta K in the greenhouse showed seven population types, whereas the peak of delta K in the glasshouse indicated the presence of six population types. One SNP marker, 14083649|F|0-9 was associated with NP with a p value <0.001. Fifty SNP markers were associated with PWT at p <0.001. Four SNP markers, 14074781|F|0-16, 100047392|F|0-36, 14083801|F|0-28 and 100051488|F|0-49 were associated with AVSPD at p <0.001. SNP markers, 14074781|F|0-16, 14083801|F|0-28 and 100051488|F|0-49 were associated with PL at P <0.001. Five SNP markers, 100047392|F|0-36, 14083801|F|0-28, 100072738|F|0-34, 14076881|F|0-49 and 14076881|F|0-49 were associated with PWDTH at p <0.001. The 65 SNP markers identified can be used in cowpea molecular breeding to select for AVSPD, NP, PL, PWDTH, PWT, and RR through marker assisted selection (MAS).

The Middle Jurassic-Lower Cretaceous Rosso Ammonitico succession of Monte Inici (Trapanese Domain, western Sicily); sedimentology, biostratigraphy and isotope stratigraphy

The pelagic Jurassic successions of the Trapani region of western Sicily are dominated by the characteristic Tethyan Rosso Ammonitico lithofacies. In order to revise the stratigraphy (sedimentology, microbiofacies, ammonite and calpionellid biostratigraphy, isotope stratigraphy) and to define a reference section, a well exposed succession of Rosso Ammonitico, spanning the Callovian-Upper Berriasian interval, has been selected in the eastern sector of Monte Inici, Trapani province. A sedimentological study has enabled us to distinguish three subfacies within the Rosso Ammonitico: nodular, pseudo-nodular, and intraclastic nodular subfacies. The two latter subfacies are characterized by the presence of intraclasts produced largely by mechanical abrasion, that suggest a formation by hydrodynamic processes. Increasing hydrodynamic energy is inferred from Lower Kimmeridgian to Upper Berriasian deposits. The vertical evolution of the microfacies shows the greatest skeletal diversity in the Middle Oxfordian, coinciding with a peak of delta 13 C. Ammonites are abundant in the Middle Oxfordian-Lower Kimmeridgian, where several ammonite zones have been recognized. With the aid of calpionellids we have been able to identify the Jurassic-Cretaceous boundary and to recognize high frequency biostratigraphic intervals in the Berriasian, that can be correlated throughout palaoetethys. The delta 13 C curve shows a marked positive peak at the base of the section (Lower to Middle Callovian) and a second, composite, positive excursion in the Middle-Upper Oxfordian. From the base of the Kimmeridgian, delta 13 C values slowly decrease, remaining low in the Berriasian. Oxygen isotope values exclude late burial diagenetic overprinting and the carbon peaks are interpreted as reflecting carbon cycle perturbations due to high biological productivity that may mirror global palaeoenvironmental variations. The Middle Oxfordian peak coincides with the highest skeletal diversity, with the first occurrence of the nodular facies, and with the onset of cherty limestones (lateral equivalents of radiolarites) in the southern sector of Monte Inici, and in localities to the west and north. The heteropy between Rosso Ammonitico and radiolarites s.l. suggests that sedimentation was controlled by local palaeotopography.