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The bacterial diversity on the surface of the Chinese Wolfberry (Lycium barbarum) affects the storage tolerance of the fruit. We analyzed the bacterial diversity on the surfaces of eight varieties of Chinese wolfberries using high-throughput sequencing before and after storage. A total of 737 OTUs, including 584 species, 423 genera, 243 families, 153 orders, and 62 classes, were identified by bioinformatic analysis of the OTUs at the 97% similarity level. There were no significant differences among fruit varieties just after picking (O period). The dominant genera during the O period were Massilia and Pseudomonas. However, after a 144-hour storage period (S period), there were significant changes in both the decay rate and surface bacterial compositions. The Z1 variety showed the highest rate of decay, and its surface microbiota was dominated by Pantoea (84.34%), while the variety with the lowest decay rate was O, dominated by both Pantoea (69.06%) and Rosenbergiella (16.99%).

RESUMEN Se determinó la tolerancia a la desecación y al almacenamiento de la semilla de cuatro variedades de Psidium guajava de gran impor- tancia económica para el banco de germoplasma de la Corporación Colombiana de Investigación Agropecuaria -CORPOICA. Las evaluaciones de la tolerancia a la desecación y al almacenamiento de la semilla se realizaron en los bancos de ger- moplasma del Programa de Recursos Genéticos del Centro Internacional de Agricultura Tropical (CIAT). Se evaluó la dinámica de la viabilidad utilizando tetrazolio, mientras que la germina- ción fue estimada conforme a los criterios esta- blecidos por Baskin 2002. El vigor fue evaluado de acuerdo con los criterios facilitados por el ISTA 2016. Las semillas de las 4 variedades de Psidium guajava presentaron tolerancia a la desecación. La germinación y el vigor aumentó con la disminución del contenido de humedad de la semilla, lo que indica que existen mecanismos que favorecen la liberación de la latencia durante la desecación en el almacenamiento. El ensayo de tolerancia al almacenamiento mostró que la calidad fisiológica de la semilla (viabilidad, ger- minación y vigor) disminuye cuando la semilla se almacena con un contenido de humedad del 5% a -20°C durante 12 meses. La temperatura que permite conservar la calidad fisiológica de las semillas de guayaba es de 7±2°C. Sin embargo, el contenido de humedad varía de acuerdo con el material. Las semillas de la variedad Palmira ICA I conservan su viabilidad cuando son alma- cenadas con un contenido de humedad del 5% (93,33%), Cimpa Pulpa Roja y Manzana conser- van su viabilidad con contenidos de humedad del 7,5% (94 y 94,44%) y las semillas del material Cl-0440 se conservan cuando son almacenadas con un contenido de humedad de 10% (94,66%). Estos resultados indican que existen diferencias genéticas entre los 4 materiales estudiados. Al tomar en cuenta los resultados de la tolerancia a la desecación y al almacenamiento de la semilla, se propone que la semilla de las 4 variedades presentan un comportamiento intermedio en el almacenamiento. ABSTRACT Tolerance to desiccation and storage of the seed of 4 varieties of Psidium guajava of great economic importance for the germplasm bank of the Colombian Agricultural Research Corporation was determined. Seed tolerance to desiccation and storage evaluations were carried out at germplasm banks of the Genetic Resources Program of the International Center for Tropical Agriculture (CIAT). Viability dynamics were evaluated using tetrazolium, while germination was estimated according to criteria established by Baskin 2002. Vigor was evaluated according to criteria provided by ISTA 2016. Seed of the 4 varieties of Psidium guajava showed tolerance to desiccation. Germination and vigour increased with the loss of moisture content, indicating that there are mechanisms which favor the release of dormancy during desiccation and storage. The storage tolerance test showed that seed physiological quality (viability, germination and vigour) decreases when the seed is stored with a moisture content of 5% at -20°C during 12 months. Temperature of 7±2°C allows to conserve physiological quality of the 4 varieties. However, moisture content in which physiological quality of seed is conserved varies according to variety. Seeds of the Palmira ICA I variety retained their viability when stored at a moisture content of 5% (93.33%), Cimpa Pulpa Roja and Manzana retained their viability with moisture content of 7.5% (94 and 94.44%) and seeds of Cl-0440 material are conserved when they are stored at a moisture content of 10% (94.66%). These results indicate there are genetic differences between the 4 varieties. According to the results of tolerance to desiccation and storage, it is proposed that the seed of the 4 varieties present an intermediate behavior in storage.

Reduction in germination of crop seeds due to depletion of food reserves and decline in synthetic activity due to ageing has become a serious concern to groundnut growers who need adequate, high quality seeds to sustain groundnut production. Therefore, to stimulate farmers’ interest in groundnut production, an experiment was conducted to evaluate some groundnut varieties for their tolerance to seed ageing stress, with a view to recommending varieties that can be considered for production in tropical countries. Seeds of nine elite groundnut genotypes, sourced from The International Crops Research Institute of Semi-Arid Tropics (ICRISAT), Kano and three other genotypes sourced from local seed dealer in Ibadan, Nigeria were subjected to seed quality assessments in the seed testing laboratory of Institute of Agricultural Research and Training, Ibadan. The seed lots were subjected to accelerated ageing procedures of 42 °C temperature and 100% relative humidity for 24 hours. Twenty-five seeds of each genotype were drawn from each genotype in three replicates at 3, 6, 12 and 24 hours of ageing. The drawn samples were reassessed to determine their tolerance ability to ageing stress. Percentage germination was transformed using arc-sine before the data on preliminary seed germination and seedling vigour data and seed ageing data were subjected to analysis of variance (ANOVA) using SAS™ Means were separated using Duncan Multiple Range Test (DMRT) at 5% level of significance while k-means non-hierarchical clustering analysis was used to group the genotypes based on their response to the ageing. Result showed that seeds of the groundnut genotypes differ in their response to ageing stress factors. Seeds of ‘Samnut-24’, ‘Samnut-25’ and ‘Ex-Dakar’ (R) were found to be more tolerant to ageing stress while ‘Samnut 22’ and ‘Boro White’ were susceptible to ageing stress. Optimum ageing for 24 hours is recommended for testing seeds of groundnut varieties for storage tolerance