Yellow Mosaic Virus (YMV) is a serious disease of soybean. Resistance to YMV was mapped in 180 soybean genotypes through association mapping approach using 121 simple sequence repeats (SSR) and four resistance gene analogue (RGA)-based markers. The association mapping population (AMP) (96 genotypes) and confirmation population (CP) (84 genotypes) was tested for resistance to YMV at hot-spot consecutively for 3 years (2007-2009). The genotypes exhibited significant variability for YMV resistance (P < 0.01). Molecular genotyping and population structure analysis with 'admixture' co-ancestry model detected seven optimal sub-populations in the AMP. Linkage disequilibrium (LD) between the markers extended up to 35 and 10 cM with r2 > 0.15, and >0.25, respectively. The 4 RGA-based markers showed no association with YMV resistance. Two SSR markers, Satt301 and GMHSP179 on chromosome 17 were found to be in significant LD with YMV resistance. Contingency Chi-square test confirmed the association (P < 0.01) and the utility of the markers was validated in the CP. It would pave the way for marker assisted selection for YMV resistance in soybean. This is the first report of its kind in soybean.

The present study was carried out with a set of 96 diverse soybean genotypes with the objectives of analysing the population structure and to identify molecular markers associated with important agronomic traits. Large phenotypic variability was observed for the agronomic traits under study indicating suitability of the genotypes for association studies. The maximum values for plant height, pods per plant, seeds per pod, 100-seed weight and seed yield per plant were approximately two and half to three times more than the minimum values for the genotypes. Seed yield per plant was found to be significantly correlated with pods per plant (r = 0.77), 100-seed weight (r = 0.35) and days to maturity (r = 0.23). The population structure studies depicted the presence of seven subpopulations which nearly corresponded with the source of geographical origin of the genotypes. Linkage disequilibrium (LD) between the linked markers decreased with the increased distance, and a substantial drop in LD decay values was observed between 30 and 35 cM. Genomewide marker-traits association analysis carried out using general linear (GLM) and mixed linear models (MLM) identified six genomic regions (two of them were common in both) on chromosomes 6, 7, 8, 13, 15 and 17, which were found to be significantly associated with various important traits viz., plant height, pods per plant, 100-seed weight, plant growth habit, average number of seeds per pod, days to 50% flowering and days to maturity. The phenotypic variation explained by these loci ranged from 6.09 to 13.18% and 4.25 to 9.01% in the GLM and MLM studies, respectively. In conclusion, association mapping (AM) in soybean could be a viable alternative to conventional QTL mapping approach.

Background: Incomplete fusion has been found to be an important contributor in light heavy-ion (A 20) induced reactions even at slightly above barrier energies. Purpose: For better insight into the dynamics of incomplete fusion, the onset and influence of incomplete fusion need to be investigated in terms of projectile energy (E lab ) and entrance channel mass-asymmetry (μ A ). A rich set of experimental data on incomplete fusion may be useful to correlate the probability of incomplete fusion with the various entrance channel parameters and eventually to develop a theoretical model code for the same. Presently, there is no theoretical model available which can explain low-energy incomplete fusion data consistently. Methods: The excitation functions of complete and incomplete fusion residues populated in the 13 C+ 169 Tm system have been measured using the recoil-catcher activation technique followed by offline γ spectroscopy. The evaporation residues have been identified on the basis of characteristic γ lines and confirmed through the decay-curve analysis. Results: The excitation functions of xn and pxn channels are found to be in good agreement with the statistical model code PACE4; this suggests the population of these channels via complete fusion. Some residues are found to have a contribution from their higher charge isobar precursor decay. The precursor contribution has been deduced from the cumulative cross section using the standard successive radioactive decay formulations. The excitation functions of α-emitting channels are observed to be significantly enhanced as compared to the statistical model code PACE4. This enhancement may be attributed to the contribution from incomplete fusion. The incomplete fusion strength function for 13 C+ 169 Tm is compared with that obtained in the 12 C+ 169 Tm system. It has been found that the one-neutron (1n) excess projectile 13 C (as compared to 12 C) results in a less incomplete fusion contribution due to its relatively large negative alpha-Q value. Recently proposed "alpha-Q-value systematics" seems to explain incomplete fusion data.

No abstract

No abstract