Genetic Dissection of Grain Size Traits Through Genome-Wide Association Study Based on Genic Markers in Rice

Grain size plays a significant role in rice, starting from affecting yield to consumer preference, which is the driving force for deep investigation and improvement of grain size characters. Quantitative inheritance makes these traits complex to breed on account of several alleles contributing to the complete trait expression. We employed genome-wide association study in an association panel of 88 rice genotypes using 142 new candidate gene based SSR (cgSSR) markers, derived from yield-related candidate genes, with the efficient mixed-model association coupled mixed linear model for dissecting complete genetic control of grain size traits. A total of 10 significant associations were identified for four grain size-related characters (grain weight, grain length, grain width, and length-width ratio). Among the identified associations, seven marker trait associations explain more than 10% of the phenotypic variation, indicating major putative QTLs for respective traits. The allelic variations at genes OsBC1L4, SHO1 and OsD2 showed association between 1000-grain weight and grain width, 1000-grain weight and grain length, and grain width and length-width ratio, respectively. The cgSSR markers, associated with corresponding traits, can be utilized for direct allelic selection, while other significantly associated cgSSRs may be utilized for allelic accumulation in the breeding programs or grain size improvement. The new cgSSR markers associated with grain size related characters have a significant impact on practical plant breeding to increase the number of causative alleles for these traits through marker aided rice breeding programs.     

Development of an in vitro oviduct epithelial explants model for studying sperm–oviduct binding in the buffalo

In this study, we developed an in vitro model for studying sperm–oviduct binding in the buffalo. Oviduct explants were prepared by overnight culture of epithelial cells in TCM‐199 medium under 5% CO₂ at 38.5 °C. Cryopreserved spermatozoa from buffalo bulls (n = 4) were incubated with the oviduct explants, and the sperm–oviduct explants complex was stained with JC‐1. The effect of sperm concentration (2, 3 and 4 million), size of the oviduct explants (<0.2, 0.2–0.3, 0.3–0.4 and >0.4 mm²) and time of incubation (1 hr and 4 hr) on binding index (BI—number of sperm bound to unit area of explants) was studied. No significant difference was observed in the BI among <0.2, 0.2–0.3 and 0.3–0.4 mm² size of explants; however, the BI decreased significantly (p < .05) when the size of explants exceeded 0.4 mm². The BI decreased significantly (p < .05) when the sperm concentration was increased to 4 million, while the duration of incubation did not have any significant effect on the BI. The interaction of bulls with explants size, sperm concentration and incubation time was not significant. The developed assay has the potential to be used as an in vitro model for studying sperm–oviduct binding in the buffalo.     

Antimicrobial activity of partially characterized analytes from Bacillus pumilus(B2)

This study was carried out to characterize the antimicrobial substance produced by the strain of Bacillus pumilus (B2) obtained from Novozymes Biologicals Inc. to compare its antimicrobial activity by agar well diffusion assay and bacteriocin activity assay via critical dilution method against seven different strains of Vibrio spp., specifically V. alginolyticus (A01), V. cholerae (C01), V. fluvialis (F01, F02), V herveyii (H), V. mimicus (M01), V. parahaemolyticus (P01) and V. vulnificus (V01, V02). All Vibrio spp. were isolated from the hemolymph and intestine of the white faeces disease‐infected moribund pacific white‐leg shrimp Litopenaeus vannamei (Boone 1931) and one strain (V. harveyi) from its diseased postlarva. The cell‐free neutralized supernatant (CFNS) of B2 showed moderate thermo‐stability being stable up to 70°C for 60 min with, however, reducing activity above 80°C for 20 min. B2 antimicrobials showed a stable activity within the pH ranging from 6 to 10 at room temperature and at 4°C, while residual antimicrobial activity of crude CFNS showed tolerance to salinity up to 7% of sodium chloride below 4°C. No B2 activity was obtained while exposed to proteolytic enzyme, such as proteinase k and pepsin, while its activity kept stable exposed to lipase. Initial B2 characterization for antimicrobial substance in CFNS revealed proteinaceous in nature owing to activity loss against proteolytic enzymes and no lipid moiety activity against lipase, which could be categorized as bacteriocin‐like inhibitory substance having potential application against several strains of Vibrio spp. in aquaculture.