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The grafting technique has successfully mitigated crop losses from diseases and stress in vegetable production; however, vegetable grafting in Tanzania is very limited. Field and greenhouse experiments conducted in Tanzania's mainland and islands compared the response of tomato determinate cv. 'Tanya' to production challenges when ungrafted and grafted onto five tomato rootstocks ('Hawaii 7796', 'Tengeru 1997', 'Tengeru 2010', 'R3034', and 'Shelter'), one eggplant variety ('EG 203'), and one wild Solanum species (Solanum elaeagnifolium). The visual symptoms of bacterial wilt varied significantly with location and season, ranging from 8 to 100%, attributed to varying bacterial wilt pressures and strains of Ralstonia solanacearum isolated (Phylotype I sequevars 17, 18, and 31). 'EG203' and 'Hawaii 7796' emerged as the most effective rootstocks, reducing wilting by 49.8 and 51.0% and improving yield by 57.2% and 27.7% on average across experiments conducted in three locations (Moshi, Pemba, and Unguja) over two seasons. Combining reduced water supply with grafting resulted in an average reduction in wilting of 76%, while also boosting yields by an average of 3.6 times in experiments conducted in Arusha over two seasons. Grafting onto 'Hawaii 7796' and 'Shelter' significantly improved 'Tanya' yields by 38.3% and 41.6% on average over two seasons, only under standard nutrient application rates. While certain rootstocks improved crop performance, yields across various sites and seasons were significantly hampered by pest pressure. These findings support grafting's potential to mitigate damage from common stresses, emphasizing the need for further research to identify suitable rootstocks for optimizing returns on investments in grafted plants in Tanzania.

Since 2000, the World Vegetable Center (WorldVeg) has been promoting vegetable grafting technologies to manage soil-borne diseases (e.g., bacterial wilt) and abiotic stresses (e.g., waterlogging) in South-East Asia (Vietnam, Philippines, Indonesia, Cambodia and Lao PDR), South Asia (India, Bangladesh, Sri Lanka, Nepal and Bhutan), Oceania (Solomon Islands and Fiji), East Africa (Tanzania), West Africa (Mali and Burkina Faso), Central Asia (Uzbekistan, Armenia and Tajikistan), and Central America (Honduras and Belize). For sustainable vegetable production in developing countries, efforts are being focused on low cost-effective and simplified grafting technologies, i.e., low-cost healing chambers and grafting tubes as well as open-pollinated rootstock cultivars or those developed from wild species. Vegetable grafting has been introduced in existing value chains by training nursery operators and farm women as skill development. Moreover, grafting was also tested and promoted, along with rain shelters, for production of off-season tomatoes. The recommended rootstocks for open field production included: tomato line Hawaii 7996 (resistant to bacterial wilt and Fusarium wilt); eggplant lines EG190, EG203, and EG219 (resistant to bacterial wilt, Fusarium wilt, root-knot nematode, and short-term waterlogging); and several bacterial wilt resistant bell and hot pepper cultivars. Experience in Asia showed the impact of grafting tomato onto selected eggplant rootstocks (EG195, EG203, and EG210) which enabled the production during hot-wet periods by increasing the resistance to soil-borne diseases and flooding. For instance, vegetable grafting technology was successfully practiced in Vietnam to help stabilize tomato production (81.4 t ha -1) with the benefit-cost ratio of 4.6 for grafted compared with 3.5 for non-grafted plants. Currently, the World Vegetable Center is focusing on developing multiple biotic and abiotic stress-tolerant rootstocks and interspecific lines with vigor

Aphids cause considerable damage to numerous crops all over the world and insecticides are the main means of controlling them, despite their detrimental impacts on human and environmental health. This study assessed the effectiveness of the parasitoid Aphidius colemani Viereck (Hymenoptera: Braconidae), a mixture of predatory ladybird beetles, Hippodamia variegata Goeze, Chilocorus calvus Chiccl, and Cheilomenes propinqua Mulsant (Coleoptera: Coccinellidae), and an entomopathogenic strain of Aspergillus flavus Link (Eurotiales: Trichocomaceae), collected locally in Tanzania, to control Aphis fabae Scopoli (Hemiptera: Aphididae). After assessing the predation and parasitism rates of these natural enemies at different aphid densities in laboratory experiments, their ability to control aphids on kalanchoe was assessed in a greenhouse experiment over two seasons. The largest number of A. fabae parasitized or consumed in the laboratory was found at a density of 160 aphids per predator, or parasitoid. At that density, an adult female of A. colemani parasitized 114 A. fabae per day, on average, and adults of C. calvus, H. variegata, and C. propinqua consumed 75, 72, and 85 aphids per day, respectively. A. flavus spores applied at 1 × 107 spores ml−1 reduced the aphid population by 7.9 and 12.6 times within 10 days in the first and second seasons of the greenhouse experiments, respectively, as opposed to 2.8 and 2.5 times by releasing a mixture of the ladybirds at a rate of 5 adults/m2, and by 3.3 and 9.5 times by releasing A. colemani at a rate of 2 adults/m2. This study confirmed the potential of these locally collected bio-control agents for controlling A. fabae. However, use of the isolated A. flavus strain was undermined by its production of aflatoxin. Further research is therefore required to tap into the potential of a non-toxic strain of A. flavus and/or other entomopathogenic fungi.

Staple-based diets in Southern Africa need to be diversified with vegetables and fruits to increase nutrition and income generation. The vegetable and fruit sectors face biotic constraints and lacks year-round water supply, which will be exacerbated by climate change. Rapid urbanization and the ensuing supermarket revolution pose another challenge to the sector, with consumption habits set to change drastically. Food safety is another grave concern, while only more intensive and profitable production systems may be able to target export markets. To overcome these constraints, innovations need to tackle technological, institutional and organizational change simultaneously, and this is especially true for the massive postharvest losses in vegetable and fruit chains. The seed sector equally needs to start using a value chain approach, ensuring strategic linkages of seed producers to key value chain actors. Suggested policy actions are increasing consumer demand, implementing quality standards through voluntary labels, improving market access through farmer aggregation, shifting agricultural research towards horticulture and focusing on traditional African vegetables instead of commoditized export crops.

Numerous studies have highlighted the merits of grafting to improve the performance of vegetable crops. However, the technique is hindered by several obstacles, including the synchronization of seedlings used as scions and rootstocks, and the effects of rootstocks and climatic conditions on grafting success rates. This study sought to gain insights into how such technical obstacles affect tomato grafting. An initial experiment conducted in a greenhouse set out to assess the relevance of using degree-days to predict the growth rates of seedlings used for grafting (i.e., stem diameters above cotyledons). The success rate for grafting a tomato variety (Tanya) on 10 different rootstocks from different species—namely tomato, eggplant, african eggplant, and a wild species—was assessed at different temperatures (i.e., 15, 20, 25, 30, 35, and 40 °C). The effects of grafting on plant vigor (i.e., fresh biomass), number of leaves, and plant height, and on the hydraulic conductivity of xylem vessels in the plant stem were assessed 2 weeks after grafting. The results show the advantage of using degree-days to predict the ready-to-graft stage of seedlings, as it reduced the discrepancy among trials. The grafting success rate was more than 90% at 15 and 20 °C, but decreased significantly with higher temperatures, down to 20% at 40 °C. Larger variations in growth rate for seedlings used as scions and rootstocks, a lower grafting success rate, and less vigor were recorded for heterografted plants than for homografted plants. The lower hydraulic conductivity measured in the stems of grafted plants, especially heterografted plants, was consistent with the lower plant vigor observed. Further studies are needed to investigate how grafting affects the hydraulic conductivity of xylem vessels in later developmental stages of grafted plants.

The health benefits of fruit and vegetable consumption can be jeopardized by pesticide residues, especially in developing countries, due to their misuse. While vegetable growing under cover is growing in popularity worldwide as an effective technique for improving yields while reducing pesticide use, these protected cultivation techniques often remain underutilized by smallholder farmers. A cost-benefit analysis was conducted with fifty smallholder farmers in northern Tanzania over two seasons to compare the profitability of growing cabbage in open plots and under inexpensive low tunnels. Although all farmers significantly improved their yields under nets over the two seasons (9.85, as opposed to 6.80 kg m−2 and 10.09, as opposed to 8.63 kg m−2, in each season respectively) and reduced their pesticide use (by 3.5 and 2.8 times), the large variations in market prices observed between seasons called into question the profitability of this cultivation technique. With the conducive market conditions of the second season, it would have taken 5.3 crops cycle on average, i.e. less than 2 years, to recoup the investment costs of low tunnels, whereas with the poor market conditions observed in the first season, the investment in tunnels compounded the negative economic results obtained from growing cabbages in an open field. Consequently, our results showed that using low tunnels could be a suitable alternative for reducing pesticide use, but this technique was not economically viable with the existing marketing systems used by the farmers. For this technique to be adopted, further work is needed to identify changes in vegetable marketing systems that would promote the use of cultivation techniques that reduce pesticide use.

Nondestructive methods such as near infrared spectroscopy (NIRS) are increasingly used in sorting lines to assess quality traits of unripe fruit, i.e. dry matter (DM) and total soluble solid (TSS) contents, in order to create homogenous batches of fruit. The use of this approach is based on the assumption that fruit quality traits at harvest are reliable indicators of their post-harvest behavior and their quality after ripening. The present study tested this assumption by analyzing the relationships between quality traits at harvest and after ripening. In parallel, models were developed to determine the capacity of NIRS measurements on unripe fruit at harvest to predict their shelf life and quality after ripening. The quality traits DM, TSS content, pulp color (PC) and titratable acidity (TA) of 92 mangoes from different harvests, production years, and orchards were compared at harvest and after ripening. Previously developed NIRS models were used to nondestructively assess the quality traits of the mangoes at harvest. New partial least squares (PLS) regressions using different variable selection procedures and preprocessing techniques were used to predict fruit shelf life and fruit quality after ripening based on NIRS measurements at harvest. Weak relationships (r² < 0.41) were found between fruit quality traits measured at harvest and after ripening, except for DM content (r² = 0.61). The PC of mango measured at harvest was found to be the best indicator of fruit shelf life. Errors of PLS regressions to predict the TSS content (RMSEV = 1.1%), titratable acidity (RMSEV = 0.52%), and the Hue angle of the flesh (RMSEV = 1.86°) were in the same range as those of linear regressions based on quality traits assessed at harvest except for PC. This work provides evidence that fruit maturity and quality should be assessed using different indicators.

Horticulture as the part of agriculture sector plays the role for food security, economic growth and nutrition improvement. In developing countries where agriculture is regarded as the backbone of most countries' economy it draws attention for most governments as the main source of employment and livelihood for the majority. Agricultural extension has been the key facilitator for achieving high crop productivity and an enabler to knowledge resources for these countries. However, lack of clear information for vegetable cultivations, crop requirements, climatic information, pests and diseases to constantly help farmers to come up with proper potential yield of the vegetable crops reduce the potential of horticulture in improving the farmers livelihood and countries economic gain , Therefore, this study aims at bringing the ICT- enabled extension support system for farmers to help them make decision on proper ways of cultivating their crops based on locations' and timely climatic condition.

Fruit physiology is strongly affected by both fruit temperature and water losses through transpiration. Fruit temperature and its transpiration vary with environmental factors and fruit characteristics. In line with previous studies, measurements of physical and thermal fruit properties were found to significantly vary between fruit tissues and maturity stages. To study the impact of these variations on fruit temperature and transpiration, a modelling approach was used. A physical model was developed to predict the spatial and temporal variations of fruit temperature and transpiration according to the spatial and temporal variations of environmental factors and thermal and physical fruit properties. Model predictions compared well to temperature measurements on mango fruits, making it possible to accurately simulate the daily temperature variations of the sunny and shaded sides of fruits. Model simulations indicated that fruit development induced an increase in both the temperature gradient within the fruit and fruit water losses, mainly due to fruit expansion. However, the evolution of fruit characteristics has only a very slight impact on the average temperature and the transpiration per surface unit. The importance of temperature and transpiration gradients highlighted in this study made it necessary to take spatial and temporal variations of environmental factors and fruit characteristics into account to model fruit physiology.