Background Pepper (Piper nigrum L.) is among key spice crops grown in Morogoro district of Tanzania. Most of the pepper types grown in the district are only known by their local names as Babu kubwa, Babu ndogo, Babu kati and Ismailia. This may limit information on germplasm collection or genetic resource for plant improvement and trade in markets with variety specifications. The aim of this study was to generate preliminary information of the pepper types based on their morphological characteristics for easy comparison with other known pepper varieties in the spices industry. Methods The evaluation of pepper morphological characters was conducted following a randomized complete block design with three replications and four treatments (pepper types). Observations were recorded with respect to 28 characters (9 qualitative and 19 quantitative) which entail vegetative (8) and reproductive (20) traits. The quantitative data for vegetative, inflorescence and berry characters were subjected to analysis of variance. Mean separation test was conducted using Turkey’s Honest Significance Test at (α = 0.05). Correlation and regression analyses were performed to explore the relationship between yield and yield attributes of pepper. Results Babu kubwa and Babu ndogo pepper types were characterized by erect and horizontal branching habit, whereas the others showed hanging habit. Babu kubwa had longer spikes (12.4 cm), leaves blade (17.9 cm), leaf petiole (2.8 cm), wider leaves (12.9 cm) and larger berries (5.8 mm) than all other pepper types. Babu kubwa and Babu kati had cordate and acute leaf bases, respectively while other types had round leaf base shapes. The highest number of flowers was recorded on Babu kubwa (93.5) and Ismailia (90.7) with spikes weighing 7.6 g and 7.5 g, respectively compared to other types. Babu ndogo and Ismailia had compact spikes, while other types had medium loose spikes. Babu kati had the highest number of spikes kg−1 (282.6) due its lower spike weight compared to other types. The highest weight of 100 fresh spikes (704.3 g) and 1000 fresh berries (164.2 g) was recorded on Ismailia. Spike length was significantly positively correlated to yield (r = 0.23, R2 = 0.08, p < 0.001). However, yield had a significant negative correlation with the number of spikes kg−1 (r =  −0.85, R2 = 0.017, p = 0.001) and fresh weight of 1000 berries (r = −0.91, R2 = 0.003, p = 0.04). Conclusions The pepper types grown in Morogoro district differed significantly based on most of the evaluated traits. This information can be used to formulate methods and strategies for conservation and in turn genetic improvement of the crop. Despite that the pepper types literary matched with characters of some well-known commercial varieties, confirmation of genetic relatedness is yet needed. Further studies need to be conducted in consecutive years and involve assessment of internal quality attributes. Other studies should encompass wider range of pepper types from other producing areas in Tanzania in order to establish their morphological distinctness, genetic diversity and interrelationships in relation to the globally known commercial varieties.

Background: Pepper (Piper nigrum L.) is an important spice produced by small-scale farmers in Morogoro district of Tanzania for both local and export markets. Recently, farmers have reported a decline in crop productivity due to spike shedding and stem wilting of pepper plants. The study was conducted to obtain baseline information on the extent of the disorders. Methods: An altitudinal transect survey was conducted in Morogoro district from October to November 2018. Data were collected from 216 pepper farmers through a questionnaire, focus group discussions, and field observations. Chi square tests (α = 0.05) were used to compare differences between gender, pepper cultivars by wards and yield, spike shedding and stem wilting by pepper cultivars and plant species used to support pepper vines. Fisher's exact test at (α = 0.05) was used to compare the effects of production constraints and altitude. A regression analysis was performed to explore the relationship between altitude and the incidence of spike shedding and stem wilting. Results: The majority of interviewees (69%) had observed spike shedding and stem wilting of pepper on their farms for > 3 years. Spike shedding was more prominent at 300 meters above sea level (masl, 85.7%), while stem wilting was reported by most (66.7%) farmers at 457 masl. The most affected pepper cultivar was reported to be "Babu kati" in Mtombozi (19.2% of respondents) and "Ismailia" in Mkuyuni and Kibogwa (28.9% of respondents) wards, while in Kibungo ward cultivar "Babu ndogo" (85.7% of respondents) and in Konde ward cultivar "Babu kubwa" (53.8% of respondents) were most affected. Approximately 53% of respondents reporting the disorders used Jatropha to support the pepper vines, and 93% of the farmers reported the disorders to occur during the dry season. A greater proportion of the interviewed farmers (92.1%) reported applying no measures to control spike shedding and stem wilting of pepper. Conclusions: Incidence of spike shedding and stem wilting was higher at a low altitude compared to high altitude areas. The magnitude of the disorders differed among pepper cultivars regardless of support plants species used. Poor adoption of key agronomic practices and lack of any information on control measures may be contributing to the high incidence of the disorders in the study area. The study demonstrates the extent of the problem, and provides a baseline for identifying the causal agent(s) of spike shedding and stem wilting, which in turn will allow appropriate control measures to be selected.

The quality and safety of pepper (Piper nigrum L.) are a function of crop management practices, harvest maturity, harvesting methods and subsequent handling after harvest, including storage conditions and processing methods. The review shows that volatile oil decreases with shade intensity (15-30%). Essential oil, oleoresin, piperine and monoterpenes (thujene, α-pinene, sabinene, limonene, α-phellandrene and linalool) increase with altitude, while β-caryophyllene and total phenol decrease with increase in altitude. Fermentation of ripe pepper fruits forms odorants (butanoic acid, 3-methylindole, and 4-methylphenol) attributing intense faecal/shed-like off-flavour white pepper powder. Low-drying temperature (≤56°C) and duration (≤3 hrs) lead to low bulk density (0.17 g/ml) and low moisture loss (31%). Excessive soaking of black peppercorns prior to mechanical decortication reduces volatile oil and increases moisture content and broken berries. Availability of heavy metals in grinding machines increases the level of heavy metals; Fe (69.8-1147 mg/kg), Pb (21.3-947 μg/kg) and V (64.1-1072 μg/kg) in pepper powder. Storing peppercorns along with other materials enhances cross-contamination of heavy metals; Pb, Cd and Cr. High moisture content (> 13%) and farmers' unawareness resulted in high (2200 to > 30000 cfu/g) mycotoxins contamination. Environmental and industrial pollutants such as plasticizers, bisphenol A, polycyclic aromatic hydrocarbons and pesticides are also pepper contaminants of high merit. Radiofrequency pasteurization, vacuum-assisted steaming, ethylene oxide fumigation, atmospheric pressure plasma, dry heat sterilization, gamma-irradiation and ultraviolet-C light treatments are among strategies to enhance the quality and safety of pepper. More precautions also have to be taken to regulate the shade, drying temperature and duration, soaking duration, hygienic processing and storage in order to retain quality, minimize the risk of microbial or chemical contaminations and comply with standards.

Seed traits are essential quantitative variables to assess seed quality and are also indicators of crop success. The World Vegetable Center Genebank in Arusha, Tanzania, has an important legume collection; however, there is limited information on seed traits per genotype, i.e., 1000-seed weight, the number of seeds per gram, germination percentage (GP), and mean germination time (MGT). In this study, 8 cowpea, 54 mungbean, and 15 soybean accessions were evaluated for the abovementioned parameters. A significant difference was observed among the genotypes of the selected legumes with respect to all the measured parameters. An intraspecific variation was also observed for the measured seed traits. The 1000-seed weight decreased with an increase in the number of seeds per gram. Unlike cowpea, the GP of mungbean and soybean accessions was significantly and negatively influenced by the number of seeds per 1 g. Hence, the smaller-sized seeds (with many seeds in 1 g) exhibited lower GP. It is concluded that the seed traits and initial quality among the selected legumes are strongly influenced by their genetic makeup. These results are useful to inform seed management, exchange, utilization, and have a high potential in breeding programs, and require further research attention.

Characteristics of seeds and their interactions with storage conditions are the main determinants of seed longevity during storage. A study conducted by the World Vegetable Center -Eastern and Southern Africa (ESA) genebank aimed at understanding the variability of seed metrics of six accessions and lines of African nightshade, Nduruma, Olevolosi, BG 04, and MW 25 which belongs to Solanum scabrum and MW 17 and BG 03 belonging to S. villosum stored for eight and six years. Results showed that on average accession Nduruma had the highest average weight of thousand seeds (1.06g) while MW 17 had the least weight (0.57g). BG stored for 8 years had the highest germination percentage (100%) and MW 17 stored for 8 years had the lowest germination percentage (57.5%). Based on genotype groups, released varieties had a significantly higher weight of 1000 seeds (0.90g) and lower moisture content (2.37%) compared to landraces (0.78g and 2.43% respectively). Weight of thousand seeds had a strong negative relationship with the number of seeds per gram (p < 0.001), R2 = 0.869, r = -0.932). Germination percentage of seed was positively influenced by seed weight (p = 0.112, R2 = 0.233, r = 0.482). As the weight of the seed increases, the number of seeds per gram decreased while germination percentage increased. The parameters analyzed can be used in the characterization of genotypes and species, seed germination, vigor, viability and longevity studies, seeding rate calibration, handling, and selection of seeds.