Browsing by Author "Kamanga, Rowland"

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Cultivation of Tomato under Dehydration and Salinity Stress: Unravelling the Physiology and Alternative Tolerance Options
(IntechOpen, 2022-07-21) Kamanga, Rowland; Ndakidemi, Patrick
Tomato is an important fruit vegetable in the world, as a nutritional source and an income option for a majority of resource constrained households. However, tomato supply in developing countries is often fluctuating, with high scarcity in both supply and quality during rainy season. Unlike many crops, cultivation of tomato is a challenging task during rainy season, with high pest and disease infestation. Hence, dry season is the most favorable period for tomato cultivation. However, inadequate water supply poses a yet another significant hurdle, as the crop requires high soil moisture for optimum growth. According to a landmark study by FAO, Tomato has a yield response factor of 1.05, which signifies that a smaller decline in water uptake results into a proportionally larger decline in yield. Moreover, over the years, there have been increasing reports of soil salinization, which imposes similar effects to drought stress through osmotic effects of Na+ in the soil solution and oxidative stress through excessive generation of reactive oxygen species. This chapter will dissect how tomato plants respond to these abiotic stress factors on physiological, anatomical, and molecular levels and suggest options to improve the crop’s productivity under these constraining environments.
Drought Tolerance Mechanisms in Plants: Physiological Responses Associated with Water Deficit Stress in Solanum lycopersicum
(Advances in Crop Science and Technology, 2018-05-17) Kamanga, Rowland; Mbega, Ernest; Ndakidemi, Patrick
Drought is among the top largest causes of agricultural productivity losses globally. Tomato (Solanum lycopersicum L.) is a commercially important crop considerably hampered by drought. It is considered a drought sensitive crop with a yield response factor (Ky) 1.05. Although advancements in molecular research and plant breeding have led to release of drought tolerant cultivars in most developed countries, breeding efforts have focused on yield as the core selection index particularly in Sub-Saharan Africa (SSA) with less regard for drought tolerance. Several studies, however, have documented various physiological, morphological and biochemical adaptive drought tolerance and avoidance strategies in tomatoes and other crop species. It is argued that selection efficiency for drought tolerance breeding programs would be improved if physiological traits linked to drought tolerance are considered. This review presents an overview of previous research efforts in understanding physiological responses to drought, in crop species with particular attention to Solanum lycopersicum (Tomato). It further highlights research gaps, identifying unexplored domains and suggesting recommendations for future investigation.
Neem and Gliricidia Plant Leaf Extracts Improve Yield and Quality of Leaf Mustard by Managing Insect Pests’ Abundance Without Harming Beneficial Insects and Some Sensory Attributes
(MDPI, 2025-02-03) Kamanga, Rowland; Bhikha, Salifu; Kamala, Felix; Mwale, Vincent; Tembo, Yolice; Ndakidemi, Patrick
Production and consumption of vegetable crops has seen a sharp increase in the recent past owing to an increasing recognition of their nutraceutical benefits. In tandem, there has been unwarranted application of agrochemicals such as insecticides to enhance productivity and vegetable quality, at the cost of human health, and fundamental environmental and ecosystem functions and services. This study was conducted to evaluate the efficacy of neem and gliricidia botanical extracts in managing harmful insect pest populations in leaf mustard. Our results report that neem and gliricidia plant extracts enhance the yield and quality of leaf mustard by reducing the prevalence and feeding activity of harmful insect pests in a manner similar to synthetic insecticides. Some of the key insect pests reduced were Lipaphis erysimi, Pieris oleracea, Phyllotreta Cruciferae, Melanoplus sanguinipes, and Murgantia histrionica. However, compared to synthetic insecticides, neem and gliricidia plant extracts were able to preserve beneficial insects such as the Coccinellidae spp., Trichogramma minutum, Araneae spp., Lepidoptera spp., and Blattodea spp. Furthermore, plant extracts did not significantly alter sensory attributes, especially taste and odor, whereas the visual appearance of leaf mustard was greater in plants sprayed with neem and synthetic insecticides. Physiologically, plant extracts were also able to significantly lower leaf membrane damage as shown through the electrolyte leakage assay. Therefore, these plant extracts represent promising pesticidal plant materials and botanically active substances that can be leveraged to develop environmentally friendly commercial pest management products.
Screening and evaluation of salinity stress tolerance in local malawian tomato Cultivars
(Springer Nature, 2023-04-18) Kamanga, Rowland; Kopa, Fatuma; Sefasi, Abel; Ndakidemi, Patrick
Unravelling how crop plants respond to salinity stress, and their underlying morphological and physiological adaptations could provide benchmarks for development of crop improvement programs in salt affected regions. The purpose of this study was to screen for tolerance and identify morpho-physiological traits underlying salinity tolerance in locally adapted tomato (Solanum lycopersicum L.) cultivars. Six (6) popular Malawian tomato cultivars with unknown response to salinity stress were evaluated under greenhouse conditions by gradual exposure to 200 mM NaCl for 21 days. Shoot and root growth were markedly reduced in all cultivars after 21 days of salt stress. Derivation of stress susceptibility index (SSI) showed lowest and highest values in Mbambande (tolerant) and Phindu (sensitive) cultivars, respectively. The tolerant cultivar exhibited higher crop growth rate, relative growth rate and net assimilation rate but lower leaf area ratio and specific leaf area compared to the sensitive cultivar. Also, it reduced accumulation of Na+ to the leaves, but increased K+ accumulation, resulting into higher K+/Na+ ratios. Furthermore, the tolerant cultivar developed morphologically thicker leaves, that are described to necessitate Na+ sequestration, and also experienced the least salinity induced senescence (SIS). The most crucial morpho-physiological traits contributing to genotypic differences in salinity tolerance in the cultivars were found to be (1) enhanced leaf and root K+ accumulation (2) leaf Na+ exclusion and consequent higher K+/Na+ ratios, (3) development of thicker leaves, and (4) maintenance of root membrane integrity. Consideration of these traits in tomato breeding programs may provide some much-needed gains for salt tolerance.