Storing cowpea (Vigna unguiculata) seeds in active cattle kraals for suppression of Callosobruchus maculates

Post-harvest seed damage of cowpeas (Vigna unguiculata) by cowpea weevils (Callosobruchus maculates) is increasingly becoming a threat to food security among marginal communities. Effects of storing cowpea seeds in active cattle kraals (ACK) as an alternative to pesticide for suppression of C. maculates and improving seed quality were studied in three marginal communities of South Africa. A set of 500 seeds in 10 containers were infested with 20 C. maculates and inserted in 30-cm-deep holes within the ACK, while similar containers served as controls at the farmer level. At 120 days, relative to controls, ACK had reduced the final weevil population density by 76 to 82%, floating seeds by 86 to 98% and damaged sunken seeds by 36 to 53%, but increased undamaged sunken seeds by 358 to 572%. The treatment increased seedling emergence by 14 to 32%. In conclusion, suppression of weevil numbers and improvement of seed quality suggested that ACK may serve as alternative to pesticides in storage of cowpea seeds for planting in marginal communities and therefore, ensuring continued food security of this important crop.Keywords: Active cattle kraal, Callosobruchus maculates, seed quality, Vigna unguiculat

Using relative penetration and maleness indices in Meloidogyne incognita to establish resistance type in Cucumis myriocarpus

Resistance in plant-parasitic nematodes is broadly classified as pre-infectional or post-infectional. Prebreeding establishment of resistance type in plant-parasitic nematodes is essential where germplasm is to be introgressed into the rootstock breeding lines since only post-infectional resistance is introgressible. A study was conducted to determine whether resistance in wild cucumber (<i>Cucumis myriocarpus</i>) rootstocks to the southern root-knot nematode (<i>Meloidogyne incognita</i>) was pre- or postinfectional. Seven treatments: 0, 200, 600, 1000, 1400, 1800 and 2200 eggs and juveniles, were arranged in a randomised complete block design with 10 replicates. At harvest, 56 days after inoculation, therelative penetration index [RPI = (Pfin root/Pfin soil) – 1] and the relative maleness index [RMI = (Pftotal males/Pftotal females) – 1] were each greater than one, with the reproductive factors of M. incognita alsobeing less than one at all levels, without any yield loss. The RPI and RMI suggested that resistance in C. myriocarpus to M. incognita was  post-infectional. Thus, the resistance germplasm in this plant couldbe introgressed into wild watermelons in the development of nematode-resistant rootstock lines for the management of M. incognita race 2 in highly nematode-susceptible watermelon cultivars.Key words: Citrullus lanatus, nematode resistance, reproductive potential, watermelon

Management of Meloidogyne incognita in nematodesusceptible watermelon cultivars using nematoderesistant Cucumis africanus and Cucumis myriocarpus rootstocks

Watermelon (Citrullus lanatus) cultivars are highly susceptible to the southern root-knot nematode (Meloidogyne incognita), with considerable yield losses when this nematode is not managed. Empirical evidence suggested that wild watermelon (Cucumis africanus) and wild cucumber (Cucumis myriocarpus) were highly resistant to M. incognita race 2. The objective of this study was two-fold; viz. to determine whether (1) C. africanus and C. myriocarpus seedling rootstocks would be compatible with watermelon cv. ‘Congo’ and ‘Charleston Gray’ and (2) the two Cucumis spp. rootstocks would retain their nematode-resistance capabilities when grafted with the two highly nematode-susceptible watermelon cultivars. The eight treatment combinations were arranged in a randomised complete block design, with six replications. At harvest, 56 days after transplanting the grafted seedlings, with highly susceptible watermelon cultivars had no effect on nematode-resistance capabilities of C. africanus and C. myriocarpus. Also, the two Cucumis spp. were compatible with the two watermelon cultivars. Consequently, C. africanus and C. myriocarpus rootstocks have the potential for use as resistant rootstocks in the management of M. incognita race 2 in watermelon production.Key words: Cucumis spp., root galls, resistant rootstocks, reproductive factor, watermelon cultivars

Medicinal plant cultivation for sustainable use and commercialisation of high-value crops

Many traditional healing systems are based on natural biological resources, and there is a general shift in most parts of the world towards natural medicine, with direct implications on the demand and supply of medicinal plants. This review highlights the economic importance of medicinal plants, their contribution to healthcare systems, and potential opportunities for rural economic development through cultivation.  A systematic literature review with specific search terms related to medicinal plants was used to collect scientific and non-scientific information from peer-reviewed literature and grey literature databases. The findings indicate that trade in medicinal plants is increasing, and although they are considered minor crops compared to major food crops, their value is among the highest in the list of traded plants globally. The trade also serves as a revenue source for many rural livelihoods, with women playing a significant role. Medicinal plants contribute to primary health care in many developing countries, and they are also an essential source of modern drug discovery. Cultivation of medicinal plants offers emerging rural farmers an opportunity to grow these plants as new and alternative crops, thus reducing unsustainable wild harvesting and competition with established commercial farmers who mostly focus on food crops. Furthermore, medicinal plant cultivation should be promoted as one of the options for local economic development and sustainability through job creation, the revival of the rural economy, and income generation for small businesses, such as the transport businesses, involved in the value chain. Land accessibility, financial resources, and direct market access for rural communities can elevate their contribution to the industry. Formalisation of the lower levels of the medicinal plant trade is also recommended. Significance:• Cultivation is a viable option for biodiversity conservation of medicinal plants and ensuring a goodquality supply of plant materials.• Cultivation of medicinal plants – a source of natural products used in product development – can contribute to job creation, income generation, and rural economies in developing countries.• This review underlines the importance of medicinal plants in product development, the contribution of the industry to economies of different countries, and the potential for cultivation

Comparative efficacy of cucurbitacin phytonematicides and Velum on growth and fruit quality of watermelon cultivar ‘Congo’ and suppression of Meloidogyne enterolobii under field conditions

Globally, the guava root-knot nematode (Meloidogyne enterolobii) is becoming an emerging threat of note in crops with or without Mi resistance genes. Watermelon (Citrullus lanatus) cultivars are highly susceptible to Meloidogyne species, with all cultivars without genotypes with resistance to the genus. In contrast, nematode management options for watermelon production had since the withdrawal of fumigant nematicides been constrained. The objective of this study was to investigate the comparative efficacy of the locally-developed cucurbitacin phytonematicides and commercially available synthetic chemical nematicide Velum on growth and fruit yield and quality of watermelon cv. ‘Congo’, along with its accumulation of foliar nutrient elements and suppression of M. enterolobii population densities under field conditions. Nemarioc-AL and Nemafric-BL phytonematicides were each applied biweekly at 2% per seedling using 500 ml solution, while Velum was applied once using 500 ml solution at 0.08 ml/15 L chlorine-free water. At 90 days after the treatments, relative to untreated control, the two phytonematicides and Velum (a.i. fluopyram) significantly increased plant growth, fruit yield and quality, although with the accumulation of phosphorus in leaf tissues, with efficacies of the three products being comparable. Similarly, relative to untreated control, the three products significantly reduced nematode eggs and juveniles in roots and juveniles in soil, with efficacies that were significantly comparable. In conclusion, the benefits of phytonematicides on the productivity of watermelon cv. ‘Congo’ and suppression of population densities of M. enterolobii were comparable

Influence of cucurbitacin-containing phytonematicides on selected nutrient elements in leaf tissues of green bean under greenhouse conditions

Cucurbitacin-containing phytonematicides consistently reduce nematode population densities in various crops. However, there is no information on how these products affect the accumulation of essential nutrient elements in crops. The objective of this study was to determine the influence of Nemafric-BL and Nemarioc-AL phytonematicides on accumulation of essential nutrient elements in leaf tissues of green bean (Phaseolus vulgaris L.) under greenhouse conditions. Weekly application of phytonematicides each at 0%, 2%, 4%, 8%, 16% and 32%, were assessed on plant growth variables, nematode suppression and nutrient elements (Ca, K, Na, Fe, Zn) in leaf tissues of green bean at 56 days after initiating the treatments. Phytonematicide concentrations significantly (P ≤ 0.05) affected nematode numbers and nutrient elements, without affecting plant growth. Calcium (R2 = 0.97), K (R2 = 0.93), Na (R2 = 0.94) and Fe (R2 = 0.91) each with increasing Nemafric-BL phytonematicide concentration exhibited positive quadratic relations. In contrast, K (R2 = 0.97) and Fe (R2 = 0.98) each with increasing Nemarioc-AL phytonematicide concentration exhibited positive quadratic relations, whereas Na (R2 = 0.92) and Zn (R2 = 0.72) each with increasing phytonematicide concentration exhibited negative quadratic relations. In conclusion, accumulation of essential nutrient elements in green bean leaf tissues and increasing phytonematicide concentrations exhibited density-dependent growth patterns prior to the eventual expression of plant growth responses

Survival, flowering and productivity of watermelon (Citrullus lanatus) cultivars in inter-generic grafting on nematode-resistant Cucumis seedling rootstocks in Meloidogyne-infested fields

A new procedure for optimising stem diameters of watermelon (Citrullus lanatus) and nematode-resistant wild indigenous Cucumis species suggested that the two genera were highly compatible, with rootstock seedlings retaining their ability to suppress Meloidogyne species. A field study was initiated using the new procedure to determine the influence of inter-generic grafting of Citrullus cultivars onto Cucumis species on survival of grafts, flowering, fruit yield and accumulation of essential nutrient elements under field infested with Meloidogyne species. Four weeks after transplanting, Cucumis africanus and C. myriocarpus rootstocks increased flowering by 70-81% and 96-77% in two watermelon cultivars. At harvest, 66 days after transplanting, rootstocks reduced nematode reproductive factor values by 92-93% and 94-96%, but increased fresh fruit yield by 46-60% and 48-115% and dry shoot weight by 50-66% and 30-104% in watermelon cultivars. Rootstocks had no effect on accumulation abilities of essential nutrient elements in leaves except for Mn and Zn. Inter-generic grafting of Citrullus cultivars onto Cucumis species improved the productivity of the former in areas heavily infested with Meloidogyne species. Thus, inter-generic technology with optimised stem diameters needs to be expanded to other genera where incompatibility challenges had been limiting the use of this technology. © 2012 Friends Science Publishers.status: publishe

Host-status of 20 sweet potato lines to Meloidogyne species in South Africa

Experimental system: Due to serious economic challenges posed by root-knot (Meloidogyne species) nematodes in sweet potato (Ipomoea batatas) production, the Sweet Potato Programme (SPP) of the Agricultural Research Council (ARC) in South Africa has since included screening for nematode host-status in its breeding-selection activities. Procedures: 20 sweet potato lines were screened against M. javanica, M. incognita race 2 and M. incognita race 4 in parallel trials inoculated with 3000 eggs and second-stage juveniles (J2) per established cutting. Results: At 56 days after inoculation, the reproductive potential (RP) of all test Meloidogyne species on sweet potato line 1990-10-2 was zero, whereas RP values on other lines were 19.48–342.7, 31.9–995.1 and 10.3–380.44 ranges for M. javanica, M. incognita race 2 and M. incognita race 4, respectively. Conclusion: Among the test sweet potato lines, line 1990-10-2 was non-host to populations of tropical Meloidogyne species in South Africa and could, therefore, be subjected to nematode resistance tests