Host Genotype and Tissue Type Determine DWV Infection Intensity

Varroa mite-vectored viruses such as Deformed wing virus (DWV) are of great concern for honey bee health as they can cause disease in individuals and increase colony mortality. Two genotypes of DWV (A and B) are prevalent in the United States and may have differential virulence and pathogenicity. Honey bee genetic stocks bred to resist Varroa mites also exhibit differential infection responses to the Varroa mite-vectored viruses. The goal of this project was to determine if interactions between host genotype could influence the overall infection levels and dissemination of DWV within honey bees. To do this, we injected DWV isolated from symptomatic adult bees into mite-free, newly emerged adult bees from five genetic stocks with varying levels of resistance to Varroa mites. We measured DWV-A and DWV-B dissemination among tissues chosen based on relevance to general health outcomes for 10 days. Injury from sham injections did not increase DWV-A levels but did increase DWV-B infections. DWV injection increased both DWV-A and DWV-B levels over time with significant host stock interactions. While we did not observe any differences in viral dissemination among host stocks, we found differences in virus genotype dissemination to different body parts. DWV-A exhibited the highest initial levels in heads and legs while the highest initial levels of DWV-B were found in heads and abdomens. These interactions underscore the need to evaluate viral genotype and tissue specificity in conjunction with host genotype, particularly when the host has been selected for traits relative to virus-vector and virus resistance.

Genetic Diversity And Population Structure of Indian Mustard (Brassica Juncea) Based On Morphological and Molecular Markers

Rapeseed-mustard is one of the most important oilseed crops and providing a major source of edible oil in the world besides having other economic importance like leafy vegetables, ornamentals, and hedge crops. However, the genetic diversity present in the Brassica gene pool has not been investigated in detail. To address this problem, a study was conducted on 76 genotypes of B. juncea including cultivars, exotic lines, registered genetic stocks, advanced breeding lines, and germplasm lines. The genetic diversity was analyzed with the help of 50 polymorphic SSR and EST-SSR markers. For these genotype-marker combinations, a total of 126 alleles were amplified. Using molecular and phenotypic data, the dendrogram was constructed based on Jaccard’s similarity coefficient and Manhattan dissimilarity coefficient and linkage algorithm UPGMA. All the genotypes were grouped into 5 clusters based on their dissimilarity matrix. Population structure analysis grouped the genotypes in 8 clusters and various degrees of admixture was also observed. The grouping of genotypes appears effective as per their pedigree. The marker data was found more accurate to characterize the diversity and study the population structure than the quantitative trait data. The results of the present investigation will provide useful information for the identification of important alleles for future studies and pave the way to enhance genetic gains in Indian mustard.

Genetic Identification and Diversity of Stocks of The African Bonytongue, Heterotis Niloticus (Osteoglossiformes: Arapaiminae), in Nigeria, West Africa

Inland fisheries are an important source of protein and income for people in Africa, and sustainable fisheries management requires knowledge of regional stocks. Presently, information regarding genetic diversity of African freshwater fishes is very limited. Here we present findings from a spatial analysis of genetic patterns in the African bonytongue, Heterotis niloticus, an important component of inland fisheries in West Africa. The species is common throughout Western and Central Africa and the Nile Basin; and has been introduced for aquaculture in locations across Africa. Nigeria has the largest fishery for African bonytongues, representing ~86% of the global total. Recent declines in yields at some Nigerian locations, however, suggest current levels of exploitation may be unsustainable. Habitat degradation also may be impacting some stocks. Despite its commercial and nutritional importance, the African bonytongue has been the subject of scant research to support management. We examined patterns of genetic diversity in natural populations of H. niloticus at four locations in Nigeria, including Kainji Lake, a reservoir on the Niger River in north-central Nigeria, and three southtern localities (Ethiope River, Igbokoda River, and Epe Lagoon), as well fish from the Ouémé River delta near Porto Novo, Benin. Eighty-five specimens were genotyped for nine microsatellite-loci. Genetic diversity estimates were highest at Kainji Lake, and substantially lower at southern localities. High levels of genetic differentiation were detected between samples from Kainji Lake and those from the southern localities. Low, yet significant FST values were observed among samples from southern Nigerian localities that were more differentiated from the sample from nearby coastal Benin. We thus recommend that African bonytongues from the five locations be considered distinct genetic stocks and managed accordingly.

Development of Novel Blackgram (Vigna mungo (L.) Hepper) Mutants and Deciphering Genotype × Environment Interaction for Yield-Related Traits of Mutants

Blackgram (Vigna mungo (L.) Hepper) yields are noticeably poor due to a shortage of improved varieties and an aggravated narrow genetic base. An attempt was made to isolate novel blackgram mutants by selecting for yield-related traits derived through gamma irradiation and testing the mutant genotype’s stability across the different environments. The irradiated blackgram populations M1-M5 were established in the background of cultivars ADT 3, Co 6, and TU 17-9. Desirable mutants were selected from M3 to M5 generations. It was observed in M2 and M3 that gamma rays showed higher mutagenic efficacy and generated good inherited variance for the yield-related traits. M4 established three divergent groups in each blackgram cultivar revealed by clustering analysis. The number of pods per plant, number of clusters per plant, and number of pods per cluster showed a strong direct association with single plant yield and could be considered as selection traits. G × E interactions were higher than the variation due to genotype for single plant yield. Limited environmental interaction was observed for the genotypes G24, G16, G36, G30, and G17, as revealed by AMMI, and the genotypes G18 and G29, as revealed by GGE. GGE biplot revealed the environment-specific genotypes G13 for E1 (Aduthurai), G7 for E2 (Kattuthottam), and G34 for E3 (Vamban) and also portrayed the highly discriminating (E3) and representative (E2) environments. Selected novel blackgram genotypes from this research are useful genetic stocks for genetic improvement and breeding.

Increasing temperature weakens the positive effect of genetic diversity on population growth

Genetic diversity and temperature increases associated with global climate change, are known to independently influence population growth and extinction risk. Whether increasing temperature may influence the effect of genetic diversity on population growth, however, is not known. We address this issue in the model protist system Tetrahymena thermophila. We test the hypothesis that at temperatures closer to the species thermal optimum (i.e., the temperature at which population growth is maximal), genetic diversity should have a weaker effect on population growth compared to temperatures away from the thermal optimum. To do so, we grew populations of T. thermophila with varying levels of genetic diversity at increasingly warmer temperatures and quantified their intrinsic population growth rate, r. We found that genetic diversity increases population growth at cooler temperatures, but that as temperature increases, this effect almost completely disappears. We also show that a combination of changes in the amount of expressed genetic diversity (G), plastic changes in population growth across temperatures (E), and strong GxE interactions, underlie this temperature effect. Our results uncover important but largely overlooked temperature effects that have implications for the management of small populations with depauperate genetic stocks in an increasingly warming world.

Genetic Differentiation of the Blue Swimming Crab Portunus pelagicus Along the Coastal Thai Waters Revealed by SSCP Analysis of Cytochrome c Oxidase Subunit I

The basic information on genetic diversity and population structure is essential for the construction of appropriate management schemes leading to sustainable fisheries of the blue swimming crab (Portunus pelagicus). Here, genetic heterogeneity of P. pelagicus (N=174) was examined by single-strand conformational polymorphism (SSCP) analysis of mitochondrial cytochrome c oxidase subunit I (PpCOI270). Seven SSCP genotypes were found across all investigated samples. The average genetic distance between pairs of geographic samples was 0.0014-0.7247. Significant geographic heterogeneity (P<0.05) and restricted levels of female gene flow between paired samples (0.03-1.60 individuals per generation) were observed except between Chanthaburi - Prachuap Kriri Khan and Ranong - Krabi (P>0.05; 6.54 and 16.17 individuals per generation) located in the same coastal regions. Therefore, the gene pool of P. pelagicus in Thai waters was genetically differentiated to different stocks even though it is biologically regarded as a potential dispersal species. Five geographic samples of P. pelagicus in Thai waters could be differentiated to three genetic stocks; Chanthaburi and Suratthani (stock A), Prachuap Khiri Khan (stock B) and Ranong and Krabi (stock C).

Population genetics of the freshwater fish Prochilodus magdalenae (Characiformes: Prochilodontidae), using species-specific microsatellite loci

Prochilodus magdalenae is a freshwater fish endemic to the Colombian Magdalena-Cauca and Caribbean hydrographic basins. The genetic structure patterns of populations of different members of Prochilodus and the historic restocking of its depleted natural populations suggest that P. magdalenae exhibits genetic stocks that coexist and co-migrate throughout the rivers Magdalena, Cauca, Cesar, Sinú and Atrato. To test this hypothesis and explore the levels of genetic diversity and population demography of 725 samples of P. magdalenae from the studied rivers, we developed a set of 11 species-specific microsatellite loci using next-generation sequencing, bioinformatics, and experimental tests of the levels of diversity of the microsatellite loci. The results evidenced that P. magdalenae exhibits high genetic diversity, significant inbreeding coefficient ranging from 0.162 to 0.202, and signs of erosion of the genetic pool. Additionally, the population genetic structure constitutes a mixture of genetic stocks heterogeneously distributed along the studied rivers, and moreover, a highly divergent genetic stock was detected in Chucurí, Puerto Berrío and Palagua that may result from restocking practices. This study provides molecular tools and a wide framework regarding the genetic diversity and structure of P. magdalenae, which is crucial to complement its baseline information, diagnosis and monitoring of populations, and to support the implementation of adequate regulation, management, and conservation policies.