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1.
Abstract

Inter-generic grafting of highly nematode susceptible watermelon (Citrullus lanatus) cultivars onto nematode-resistant wild watermelon (Cucumis africanus) and wild cucumber (Cucumis myricoarpus) had on average 36% graft survival ratios, which was attributed to unequal stem diameters at the graft union. Cucumis species had smaller stem diameters at the graft union, whereas Citrullus had bigger ones. The objective of the study was to improve inter-generic graft compatibility of Citrullus and Cucumis through optimizing the sizes of stem diameters during grafting. Cucumis species were raised in a 160-hole seedling tray and primed seeds of Citrullus were raised in a 200-hole seedling tray seven days after emergence of Cucumis in order to reduce the stem diameters. At grafting, stem diameter ratios in various treatments were equal to one, whereas at 66 days after grafting the ratios were grater than one, with the exception of those of intact plants. Survival of grafts from grafting to 66 days after grafting was 100%, translating into relative improvement of 186%. Improved survival of grafts would invariably promote the potential uses of inter-generic grafting among wild and cultivated watermelon in management of soil-borne pathogens.  相似文献   

2.
Cucurbitacins from Cucumis africanus and Cucumis myriocarpus fruits are widely used in various industries. However, propagation of the two Cucumis species had been elusive due to seed dormancy, with seedlings performing poorly. The objective of this study was to determine the kind of seed dormancy under natural conditions and to eliminate the possibility of microbial degradation of inhibitory chemical compounds by germinating treated C. africanus and C. myriocarpus seeds under in vitro conditions. Forty seeds each, grouped as untreated, leached and leached-scarified (LS) batches, were arranged in a completely randomised design, with five replicates. Seeds in Murashige and Skoog medium were germinated under in vitro conditions for seven weeks at 25°C and 50–60% relative humidity. In both Cucumis species, untreated seeds did not germinate, whereas the LS seeds germinated in both species. In addition to the LS seeds, leached seeds in C. africanus germinated, but completely failed to germinate in C. myriocarpus. In all Cucumis species, seedlings from LS seeds outperformed those from leached seeds, suggesting that both chemical and physical dormancies were involved in seed dormancy and poor performance of seedlings in the two Cucumis species.  相似文献   

3.
ABSTRACT

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.  相似文献   

4.
Abstract

Host resistance in managing the southern root-knot nematode (Meloidogyne incognita) is limited by the existence of races of this nematode species. Pepper (Capistrano frutens) cultivar ‘Capistrano’ released for resistance against M. incognita races 3 and 4 in Central and South America, was evaluated for host-status and host-sensitivity to M. incognita race 2 in Limpopo Province, South Africa. Plants in pots uninoculated or inoculated with nematodes were arranged in a completely randomized design, with 15 replications. At 120 days after inoculation, the reproductive factor was less than unity, while nematode infection had no effect on plant growth. Thus, the cultivar is resistant to M. incognita race 2 and could be included in crop rotation systems intended to suppress population densities of M. incognita race 2.  相似文献   

5.
ABSTRACT

A pot experiment was carried out to investigate the tolerance of cucumber plants (Cucumis sativus L.) to root-knot nematode after inoculation with Glomus intraradices. Plants were inoculated with G. intraradices for four weeks and then transplanted in soil treated with Meloidogyne incognita for a further five weeks. The low phosphorus (P) loamy soil was amended with 50 and 100 mg P kg?1 soil. Mycorrhizal colonization increased shoot dry weight, shoot length, leaf numbers, root fresh weight and shoot P concentration, whereas nematode penetration and reproduction were significantly decreased. Similarly, P fertilization usually increased shoot growth and significantly decreased the number of galls and the number of egg masses and eggs per g root. Our results indicate that inoculation with G. intraradices and P fertilizer confer tolerance of cucumber plants to M. incognita by enhancing plant growth and by suppressing reproduction and/or galling of nematodes during the early stages of plant growth.  相似文献   

6.
Most beetroot (Beta vulgaris) cultivars in South Africa are exotic and were specifically bred for root-knot (Meloidogyne species) nematode populations in their countries of origin. Due to the widespread distribution of different Meloidogyne species and races, exotic cultivars should be matched with nematode populations in importing countries. The objective of this study was to determine the interrelations between exotic beetroot cultivars ‘Detroit Red Dark’ and ‘Crimson Globe’ with Meloidogyne species in the predominant beetroot-producing regions in South Africa. Different inoculum series of M. incognita and M. javanica were used on the two beetroot cultivars. At 56 days after initiating the treatments, roots of both cultivars had small undeveloped root galls, with the reproductive factor values of M. incognita on ‘Detroit Dark Red’ being above and below unity at low (≤125 inoculation) and high (≥250 inoculation) nematode levels, respectively. Growth of ‘Detroit Dark Red’ was significantly stimulated and inhibited at low and high nematode infection levels, respectively. In contrast, RF values for M. javanica on ‘Crimson Globe’ were below unity, without any significant effects on plant growth. In conclusion, ‘Detroit Dark Red’ was tolerant to M. incognita, whereas ‘Crimson Globe’ was resistant to M. javanica.  相似文献   

7.
Interference of nematode infection with mineral malnutrition (MMN) elements in biofortificated cultigens could devalue the health potential of such crops for humans. A pot trial was conducted to determine the response of selected MMN elements in African ginger (Siphonochilus aethiopicus) pseudo-stems to the southern root-knot (Meloidogyne incognita) nematode. Fifty-six days after inoculation, the sensitivity of the pseudo-stems to nematode infection was confirmed, with 23–45% reduced potassium in pseudo-stem tissues, but had no effect on other MMN elements. In conclusion, population densities of M. incognita race 2 should be managed to enhance the potential uses of S. aethiopicus as a biofortification crop.  相似文献   

8.
Cucurbitacin B in fruit of wild watermelon (Cucumis africanus) is an active ingredient in products that range from pesticides to various medicines. Reports suggested that cucurbitacins occur in all parts of C. africanus, without specifying whether they are equally distributed or not. Should the active ingredient not be equally distributed in all organs, it would not be prudent to combine the organs for those products that are produced from raw organs of C. africanus plants, like the phytonematicides. A study was, therefore, conducted to determine whether cucurbitacin B was equally distributed in all organs of C. africanus plants. Cucurbitacin B was quantified from oven-dried organs (52°C for 72?h) using isocratic elution Shimadzu HPLC Prominence. Concentration of cucurbitacin B was higher in fruit than in other organs, where the concentrations were not different. Relative to cucurbitacin B concentration in fruit, leaves, roots and vines had 94%, 70% and 67% less cucurbitacin B concentrations, respectively. In conclusion, leaves, roots and vines would introduce the dilution effect when combined with fruits in product development and should therefore not be included.  相似文献   

9.
Experimental System: Fermented dried fruit of wild cucumber (Cucumis myriocarpus Naude.) Had been successfully used as Nemarioc-AL phytonematicide in managing plant-parasitic nematodes in various cropping systems. However, the specialised oven-drying equipment are inaccessible to most resource-poor smallholder farmers in marginalised communities. Procedures: The objective of this study was to determine the efficacy of fermented crudes extracts of C. myriocarpus fruit when used in fresh form as Nemarioc-AL phytonematicide on management of population densities of root-knot (Meloidogyne species) nematodes and growth of tomato (Solanum lycorpersicum L.) plants. Seedlings at five leaf-stage were transplanted into pots containing 2700?ml steam-pasteurised river sand and Hygromix at 3:1 (v/v) ratio. Each seedling was inoculated with approximately 3000 eggs and second-stage juveniles (J2) at transplanting. The phytonematicide was applied at 0%, 2%, 4%, 8%, 16%, 32% and 64%, arranged in a randomised complete block design, with five replications and validated in time. Results: At 56 days after treatment, nematode variables and phytonematicide concentrations exhibited negative quadratic relations, with coeffients of determination (COD) ranging from 93% to 97%. Similarly, plant variables and phytonematicide concentrations exhibited positive quadratic relations, with COD from 96% to 98%. Conclusions: In conclusion, when prepared from fresh fruit of C. myriocarpus, Nemarioc-AL phytonematicide was suitable for use in managing nematode population densities of Meloidogyne species in tomato production.  相似文献   

10.
Iron and Zn absorption, interactions, and Cu inhibitions were characterized in cucumber (Cucumis sativus L.), watermelon (Citrullus lanatus Thunb.), and pumpkin (Cucurbita moschata Poir.) by kinetic parameters Vmax and Km. Influx and Vmax values for Fe and Zn absorption decreased in each species as plant age increased. For the Michaelis constant, Km, Fe values in cucumber and watermelon and Zn values in watermelon and pumpkin were relatively unchanged with increased plant age. Km values for Zn absorption in cucumber and Fe absorption in pumpkin decreased as plant age increased. Among species, watermelon appeared to have a particularly effective uptake mechanism for Zn at low solution concentrations. Non‐competitive inhibition of Zn absorption by Fe (20, 50 uM) was indicated in each species. Iron uptake in pumpkin was inhibited non‐competitively by Zn (5, 10 uM), however no significant effects of Zn on Fe absorption were evident in either watermelon or cucumber. Copper (0.5, 1, 5 uM) inhibited uptake of Fe non‐competitively and Zn competitively in each species.  相似文献   

11.
Glasshouse experiments were conducted to assess the influence of arbuscular mycorrhizal (AM) fungi (Glomus mosseae and Gigaspora margarita) and organic fertilizers (cow dung, horse dung, goat dung and poultry manure) alone and in combination on the reproduction of the nematode Meloidogyne incognita and on growth and water loss of tomato. Meloidogyne incognita decreased water loss of tomato from the first week onwards after inoculation. AM fungi increased water loss of both nematode-infected and uninfected plants. Glomus mosseae was better at improving growth of tomato and reducing galling and nematode multiplication than G. margarita, but the rate of water loss was similar with both fungi. Addition of organic fertilizers improved growth of tomato, but decreased the rate of water loss. There was less galling and nematode multiplication with poultry manure, which improved tomato growth more than goat dung, while cow dung was the least effective organic fertilizer. Greatest plant growth and least nematode reproduction were observed in plants inoculated with M. incognita along with G. mosseae and poultry manure.  相似文献   

12.
A pot experiment was conducted to evaluate the influence of pre-inoculation of cucumber plants with each of the three arbuscular mycorrhizal (AM) fungi Glomus intraradices, Glomus mosseae, and Glomus versiforme on reproduction of the root knot nematode Meloidogyne incognita. All three AM fungi tested significantly reduced the root galling index, which is the percentage of total roots forming galls. Numbers of galls per root system were significantly reduced only in the G. intraradices + M. incognita treatment. The number of eggs per root system was significantly decreased by AM fungus inoculation, no significant difference among the three AM fungal isolates. AM inoculation substantially decreased the number of females, the number of eggs g−1 root and of the number of eggs per egg mass. The number of egg masses g−1 root was greatly reduced by inoculation with G. mosseae or G. versiforme. By considering plant growth, nutrient uptake, and the suppression of M. incognita together, G. mosseae and G. versiforme were more effective than G. intraradices.  相似文献   

13.
A cucurbit species named Praecitrullus fistulosus (Stocks) Pangalo, which thrives in India, is considered to be a distant relative of watermelon. Recent experiments indicated that it has mild resistance to whiteflies (Bemisia tabaci). However, our attempts to cross various US plant introductions (PIs) of P. fistulosus with watermelon or other Citrullus PIs have not been successful. Thus, to determine genetic relatedness among those species, phylogenetic analysis [based on simple sequence repeat (SSR)–anchored (also termed ISSR), and randomly amplified polymorphic DNA (RAPD) markers] was conducted among PIs of P. fistulosus, Citrullus lanatus var. lanatus (watermelon), C. lanatus var. citroides and the wild Citrullus colocynthis. Phylogenetic relationships were also examined with Cucumis melo (melon), Cucumis sativus (cucumber), and wild Cucumis species including C. africanus, C. metuliferus, C. anguria, C. meeusei, and C. zeyheri. Wide genetic distance exists between Citrullus and Cucumis groups (8% genetic similarity). Phylogenetic relationships among Citrullus species and subspecies are closer (25–55% genetic similarity) as compared with those among most Cucumis species (14–68% genetic similarity). P. fistulosus appeared to be distant from both Cucumis and Citrullus species (genetic similarity between P. fistulosus and Cucumis or Citrullus groups is less than 3%). Although wide genetic differences and reproductive barriers exist among cucurbit species examined in this study, they are still considered as potential germplasm source for enhancing watermelon and melon crops using traditional breeding and biotechnology procedures.  相似文献   

14.
Ralstonia solanacearum and Meloidogyne incognita are two soilborne pathogens that cause serious damage and great losses in the production of tomato. For this purpose, a bacterial isolate, Bacillus thuringiensis CR-371, and an actinomyces isolate, Streptomyces avermectinius NBRC14893, were examined for their ability to protect tomato from root-knot nematode and bacterial wilt diseases under glasshouse conditions. Treatment of tomato roots with B. thuringiensis CR-371 and S. avermectinius NBRC14893 followed by challenge inoculation with R. solanacearum and M. incognita significantly decreased disease severity of bacterial wilt alone, root-knot nematode alone, or mixed infection by both pathogens compared to the control. Furthermore, pretreatment of tomato roots with B. thuringiensis CR-371 and S. avermectinius NBRC14893 significantly reduced bacterial proliferation of R. solanacearum both in pathogen alone inoculated plants and in plants co-inoculated with R. solanacearum and M. incognita. In conclusion, our results suggest that the treatment of tomato roots with B. thuringiensis CR-371 and S. avermectinius NBRC14893 simultaneously suppresses bacterial wilt and root-knot nematode diseases. Therefore, B. thuringiensis CR-371 and S. avermectinius NBRC14893 could provide new options for integrated pest management strategies against plant diseases, especially against bacterial-nematode disease complexes that cause synergistic yield losses.  相似文献   

15.
Globally, most of the crop-related developmental projects collapsed due to the existence of aggressive plant-parasitic nematodes. Intensive South African biofortification efforts using exotic and local sweet potato (Ipomoea batatas) cultivars have hardly considered the inclusion of nematode resistance in plant breeding, despite the withdrawal of most nematicides from agrochemical markets. The objective of this study was to screen 12 selected biofortification sweet potato cultivars for host-status to South Africa tropical root-knot (Meloidogyne species) nematodes. Three exotic orange-fleshed, three local orange-fleshed and six cream-fleshed cultivars were used in three separate experiments of M. javanica and races 2 and 4 of M. incognita. In each experiment, 6000 eggs and second-stage juveniles/plant were used for inoculation, with nematode assessment performed at 56 days after inoculation. All tested biofortification exotic (except for cv. ‘W-119’) and local cultivars were hosts to Meloidogyne species and races, whereas three non-biofortication local cultivars, namely, ‘Bosbok’, ‘Blesbok’ and ‘Mvuvhelo’ were non-hosts. In conclusion, the findings suggested the likelihood of the existence of non-host-status in certain exotic and local sweet potato cultivars for use in plant breeding programmes against South African Meloidogyne species and races.  相似文献   

16.
《Applied soil ecology》2001,16(2):179-185
A 60-day glasshouse experiment was conducted to assess the influence of two strains of Pseudomonas fluorescens (GRP3 and PRS9), organic manure, and inorganic fertilizers (urea, diammonium phosphate (DAP), muriate of potash and monocalcium phosphate) alone and in combination on the multiplication of Meloidogyne incognita and growth of tomato. Pseudomonas fluorescens GRP3 was better at improving tomato growth and reducing galling and nematode multiplication than PRS9. Organic manuring resulted in less galling and nematode multiplication than occurred with DAP. However, DAP was found better in reducing nematode multiplication and improving plant growth than urea. Muriate of potash was the inorganic fertilizer least effective in reducing galling and nematode multiplication. Pseudomonas fluorescens GRP3 with organic manure was the best combination for the management of M. incognita on tomato but improved management of M. incognita can also be obtained if DAP is used with the GRP3 strain of P. fluorescens.  相似文献   

17.
Interactive effects of alternatives to methyl bromide on root-knot (Meloidogyne species) nematodes could provide information on whether to use the products combined or singularly. The objective of this study was to investigate the interactive effects of Nemarioc-AL phytonematicide, Steinernema feltiae and Trichoderma harzianum on eggs and reproductive factors of Meloidogyne incognita race 2 under greenhouse conditions. The interactive effects of Nemarioc-AL phytonematicide (N), S. feltiae (S) and T. harzianum (T) on population densities of M. incognita were examined in a 2?×?2?×?2 factorial experiment in pots filled with steam-pasteurised soil. Each tomato seedling was inoculated with 2000 eggs and second-stage juveniles (J2), with phytonematicide and biocontrol agents applied at commercial rates. At 56 days after the treatments, the second-order (N1S1T1) interaction reduced eggs and the reproductive factor (RF) in roots by 100% and 93%, respectively. Similarly, the first-order (N1S0T1) interaction reduced the two variables by 92% and 72%, respectively, whereas N1S1T0 interaction had 63% and 55% reduction effects, respectively. Nemarioc-AL phytonematicide was compatible with S. feltiae and T. harzianum and could, therefore, be used collectively to manage population densities of M. incognita.  相似文献   

18.
The potential effect of rhizobial inoculation on root knot nematodes in chickpea, mungbean and pigeonpea were studied under field condition. The seed treatment with respective rhizobium strains increased the nodulation, leghemoglobin content, bacteriod population, plant growth, yield and nitrogen uptake of three three food legumes compared to the plants without the rhizobium treatment. The nematode (1500?juveniles/kg soil) incited oval galls on the roots of the three legumes, and suppressed plant growth and yield. The galling, egg mass production and soil population of the nematode was greater on the plants without the rhizobium treatment. The pure culture and culture filtrate of the rhizobium strains suppressed the egg hatching and induced mortality to the juveniles of M. incognita over control. The nematode infection reduced the nodulation, bacteroid population and leghemoglobin contents of the nodules and NPK uptake by the plants. Hence, the rhizobia treatment shall be integrated to common agronomic practice of food legume cultivation so as to enhance crop productivity and to protect roots from nematode attack.  相似文献   

19.
Disease complex of carrot (Daucus carota L.) involving root knot nematode Meloidogyne incognita and two fungi Alternaria dauci and Rhizoctonia solani were studied in three soil types. More plant growth, chlorophyll, carotenoid and proline contents were found in carrot grown in fly ash mix soil than plants grown in sand mix soil and loamy soil. Inoculation of M. incognita, R. solani, and A. dauci reduced plant growth, chlorophyll and carotenoid but increased proline contents. Inoculation of M. incognita 20 days prior to a fungal pathogen caused a greater reduction in plant growth, chlorophyll and carotenoid than fungal pathogen was inoculated prior. Inoculation of A. dauci prior to R. solani or vice versa had a similar effect on plant growth, chlorophyll, and carotenoid. Nematode multiplication and galling was higher in plants grown in sand mix soil followed by loamy soil and fly ash mix soil. Both fungi had adverse effects on galling and nematode multiplication. Blight disease index caused by A. dauci was 3 and crown rot index by R. solani was also recorded 3. These disease indices were 5 when pathogens were inoculated in combinations.  相似文献   

20.
The release of active ingredient chemicals in conventional organic amendments is primarily through microbial degradation, whereas in granular phytonematicides, leaching through irrigation water had been implied as a probable mechanism. The objective of this study was to determine the role of effective microorganisms (EM) on the efficacy of Nemarioc-AG (NAG; G?=?granular formulation) phytonematicide on suppression of root-knot (Meloidogyne species) nematodes and growth of tomato (Solanum lycopersicum) plants. A 5?×?6 factorial experiment, with EM at 0%, 0.14%, 0.17%, 0.20% and 0.25% and phytonematicide at 0, 3, 6, 9, 12 and 15?g per plant, was conducted under microplot conditions. Each plant was inoculated with 11,000 eggs and second-stage juveniles (J2) of Meloidogyne incognita. Seventy days after initiating the treatments, the interactions were not significant (P?≥?.05) on all variables, but the main factors were highly significant. Regression of nematode population densities, root gall and dry shoot mass over increasing phytonematicide concentration exhibited quadratic relations, which were explained by 93%, 97% and 99%, respectively. In contrast, stem diameter and phytonematicide concentration had a positive linear relation, which was explained by 98%. Nematode numbers over increasing EM concentration exhibited quadratic relation, which was explained by 97%. All plant variables and EM had no significant relations. In conclusion, the efficacy of NAG phytonematicide on nematode suppression and plant growth was independent of EM activities, suggesting that irrigation water played a major role in the efficacy of the product in granular formulation.  相似文献   

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