Effectiveness of botanical preparations for the control of rice weevil (Sitophilus oryzae) during rice seed storage and their impact on the rice seed viability : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Seed Technology at Massey University, Palmerston North, New Zealand

Food security and the maintenance of seed quality from harvest to planting are key issues for peasant farmers. In Sierra Leone, up to 28% of rice seed can be damaged by rice weevil in the six months storage period. The use of chemical insecticides to control this insect is not practical for traditional farmers. Some tribes use pepper powder (Capsicum spp.) as a seed protectant. In this study, I have compared the effects of neem (Azadirachta indica) oil, neem powder, pepper (Capsicum frutescens cv. "Habanero") powder and lentil (Lens culinaris cv. "Raja") powder on the survival of adult rice weevil (Sitophilus oryzae) and weevil offspring during rice (Oryza spp.) seed storage, and on the germination of the rice. Treatment of stored rice with neem oil, neem powder and lentil powder gave some protection from rice weevil damage. Neem oil at the rate of 0.005ml/kg rice seed effectively controlled weevil damage without reducing the seed germination. Lentil and neem powders at the rate of 0.02g/kg rice seed gave effective protection against rice weevil damage with no reduction in viability of the seeds. Pepper powder did not kill adult rice weevil. Neem oil reduced the development of weevil offspring in rice seed, but the powders of neem, lentil and pepper did not. Low relative humidity of 42.5% in seed storage environment and a reduction in seed moisture content below 10% enhanced the mortality of adult rice weevils on rice seed

Quantitative Trait Loci for Vegetative Traits in Perennial Ryegrass (\u3cem\u3eLolium Perenne\u3c/em\u3e L.)

Physiological (EP) research in forage grasses relates traits such as leaf elongation rate (LER), leaf elongation duration (LED), and leaf appearance interval (ALf), to forage yield (Chapman & Lemaire, 1993). This paper reveals preliminary quantitative trait locus (QTL) discovery for eight EP traits in perennial ryegrass. It also investigates the potential role of multivariate analyses such as principal component analysis (PCA) in QTL analysis of EP data

Performance of Napier Grass (\u3ci\u3eCenchrus purpureus\u3c/i\u3e L.) Genotypes Grown under Limited Soil Moisture

Napier grass (Cenchrus purpureus Schumach L.) is an important perennial forage native to Africa and grown in many tropical and subtropical countries. It is considered as a short-term drought tolerant forage which is a useful trait in areas that are characterized by low precipitation during the dry season. To exploit the potential of this grass and identify water use efficient (WUE) genotypes, a field drought stress trial was conducted at Bishoftu, Ethiopia. Eighty-four Napier grass genotypes were planted in a p-rep design in four replications. The genotypes were evaluated for forage performance during the dry season of 2019 and 2020 based on agro-morphological traits under two soil moisture regimes- moderate water stress (MWS) and severe water stress (SWS). The results indicated the existence of significant diversity among the genotypes for agro-morphological traits and photosynthetic performance. Consistently high biomass producing genotypes with enhanced water use efficiency were observed across harvests in each soil moisture regime, which indicates the possibility of utilizing these genotypes for high biomass production under low soil moisture conditions after further validation in other environments

Genetic Diversity among and within Accessions of a Lablab (\u3ci\u3eLablab purpureus\u3c/i\u3e) Collection Maintained in the ILRI Forage Genebank

Lablab (Lablab purpureus L.) is an important annual multi-purpose legume used as a vegetable for human consumption, as forage for livestock, and as green manure and a cover crop to improve soil fertility. It has a high feed value with good digestibility and high crude protein content. The International Livestock Research Institute (ILRI) forage genebank holds a diverse set of 340 lablab accessions collected from different regions of the world. A total of 1,843 plants from 142 lablab accessions (1 to 29 plants per accession genotyped individually) were genotyped by the genotyping-by-sequencing (GBS) method of the DArTseq platform. The genotyping produced a total of 38,824 and 64,793 genome-wide single nucleotide polymorphism (SNP) and SilicoDArT high-density markers, respectively. The short sequence reads corresponding to the markers were mapped on the mungbean (Vigna radiata) reference genome, with approximately 37% of the SNPs and 26 % of the SilicoDArTs able to be mapped. A subset of 1,000 robust markers was filtered by different criteria and used for the diversity analysis. Clustering analysis using the discriminant analysis of principal components (DAPC) detected five major groups, each with further subgroups. Analysis of molecular variance (AMOVA) showed a highly significant (P \u3c 0.00001) variation, explaining more than 73 % of the variance among the accessions. A significant variation (P \u3c 0.005) was also observed among plants within accessions, which explained about 27 % of the variation. The results of this study provide a useful guide for the management and rationalization of activities of the lablab germplasm collection at the ILRI genebank. The substantial genetic diversity observed in the collection reveals the potential of the population for further genetic studies

Generation and analysis of expressed sequence tags (ESTs) for marker development in yam (Dioscorea alata L.)

Background: Anthracnose (Colletotrichum gloeosporioides) is a major limiting factor in the production of yam (Dioscorea spp.) worldwide. Availability of high quality sequence information is necessary for designing molecular markers associated with resistance. However, very limited sequence information pertaining to yam is available at public genome databases. Therefore, this collaborative project was developed for genetic improvement and germplasm characterization of yams using molecular markers. The current investigation is focused on studying gene expression, by large scale generation of ESTs, from one susceptible (TDa 95-0310) and two resistant yam genotypes (TDa 87-01091, TDa 95-0328) challenged with the fungus. Total RNA was isolated from young leaves of resistant and susceptible genotypes and cDNA libraries were sequenced using Roche 454 technology. Results: A total of 44,757 EST sequences were generated from the cDNA libraries of the resistant and susceptible genotypes. Greater than 56% of ESTs were annotated using MapMan Mercator tool and Blast2GO search tools. Gene annotations were used to characterize the transcriptome in yam and also perform a differential gene expression analysis between the resistant and susceptible EST datasets. Mining for SSRs in the ESTs revealed 1702 unique sequences containing SSRs and 1705 SSR markers were designed using those sequences. Conclusion: We have developed a comprehensive annotated transcriptome data set in yam to enrich the EST information in public databases. cDNA libraries were constructed from anthracnose fungus challenged leaf tissues for transcriptome characterization, and differential gene expression analysis. Thus, it helped in identifying unique transcripts in each library for disease resistance. These EST resources provide the basis for future microarray development, marker validation, genetic linkage mapping and QTL analysis in Dioscorea species

Development of genomic simple sequence repeat markers for yam

Yam ( Dioscorea spp.) is a major staple crop widely cultivated for its starchy tubers. To date, very few marker resources are publicly avail - able as tools for genetic and genomic studies of this economically important crop. In this study, 90 simple sequence repeat (SSR) markers were developed from an enriched genomic library of yellow Guinea yam ( D. cayenensis Lam.). Cross- amplification revealed that 85 (94.4%) and 51 (56.7%) of these SSRs could be successfully transferred to the two major cultivated species of D. rotundata Poir. and D. alata L., respec - tively. Polymorphisms in 30 markers selected on the basis of reliability and reproducibility of DNA bands were evaluated using a panel of 12 D. cayenensis , 48 D. rotundata , and 48 D. alata accessions. Accordingly, number of alleles per locus ranged from 2 to 8 in D. cayenensis (mean = 3.9), 3 to 30 in D. rotundata (mean = 13.9), and 2 to 22 in D. alata (mean = 12.1). The average observed and expected heterozygosi - ties were 0.156 and 0.634 ( D. cayenensis ), 0.326 and 0.853 ( D. rotundata ), and 0.247 and 0.836 ( D. alata ), respectively. Clustering based on six SSRs that were polymorphic in at least four of the five cultivated Dioscorea species studied, including D. cayenensis , D. rotundata , D. alata , D. dumetorum (Kunth) Pax., and D. bulbifera L., detected groups consistent with the phyloge - netic relationships of the species except for D. dumetorum . These new SSR markers are invalu - able resources for applications such as genetic diversity analysis and marker-assisted breedingYam ( Dioscorea spp.) is a major staple crop widely cultivated for its starchy tubers. To date, very few marker resources are publicly avail - able as tools for genetic and genomic studies of this economically important crop. In this study, 90 simple sequence repeat (SSR) markers were developed from an enriched genomic library of yellow Guinea yam ( D. cayenensis Lam.). Cross- amplification revealed that 85 (94.4%) and 51 (56.7%) of these SSRs could be successfully transferred to the two major cultivated species of D. rotundata Poir. and D. alata L., respec - tively. Polymorphisms in 30 markers selected on the basis of reliability and reproducibility of DNA bands were evaluated using a panel of 12 D. cayenensis , 48 D. rotundata , and 48 D. alata accessions. Accordingly, number of alleles per locus ranged from 2 to 8 in D. cayenensis (mean = 3.9), 3 to 30 in D. rotundata (mean = 13.9), and 2 to 22 in D. alata (mean = 12.1). The average observed and expected heterozygosi - ties were 0.156 and 0.634 ( D. cayenensis ), 0.326 and 0.853 ( D. rotundata ), and 0.247 and 0.836 ( D. alata ), respectively. Clustering based on six SSRs that were polymorphic in at least four of the five cultivated Dioscorea species studied, including D. cayenensis , D. rotundata , D. alata , D. dumetorum (Kunth) Pax., and D. bulbifera L., detected groups consistent with the phyloge - netic relationships of the species except for D. dumetorum . These new SSR markers are invalu - able resources for applications such as genetic diversity analysis and marker-assisted breedin