Department of Crop Sciences - Research Articles

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Effects of liming on microbial activity and N mineralization in broiler manure-amended soils from Bizana, Eastern Cape, South Africa.
(Taylor and Francis, 2013-03-07) Jezile, G.G.; Westfall, D.G.; Peterson, G.; Child, D.R.; Turner, D.P.; Van Averbeke, W.
A laboratory incubation study was conducted to determine the effects of liming on microbial activity and N mineralization in two Bizana soils amended with broiler manure. The experimental layout was a 4 x 3 complete factorial experiment with three replicates, arranged in a randomized design. Soil pH, CO2 evolution, and mineral N concentration were measured. After 56 days the soil pH ranged from 4.50 to 5.74 and 4.99 to 5.94, in the Magusheni and Nikwe soils, respectively. The effect of liming on microbial activity and N mineralization differed between the soils. In the Nikwe soil (acid saturation 4.0%), microbial activity and N mineralization increased as the rate of broiler manure application was raised, but liming had no effect. In the Magusheni soil (acid saturation 25%), microbial activity increased as both lime and chicken manure application rates increased, but liming reduced N mineralization, suggesting N immobilization was being driven by an active microbial population in the limed soils. The rates of lime and/or chicken manure application, percentage Ca2+ and soil acid saturation were important factors influencing microbial activity and N mineralization, but the effect of soil pH on N mineralization was not evident in either of the soils.
Seed germination and vegetative propagation of Helichrysum odoratissimum.
(Elsevier B.V., 2023-08-23) Makena, Ivy Masefako; Matsiliza-Mlathi, Babalwa; Kleynhans, Riana
Helichrysum odoratissimum is a popular indigenous herb of South Africa, well known for its aromaticity. It offers potential as a source of extracts for the development of cosmeceutical products as it has been reported to be a natural antibiotic, and has antifungal, antimicrobial, antioxidant and antiviral properties. In order to be commercialized, a sustainable production system is required to ensure a consistent supply of good quality material. Therefore, the production of H. odoratissimum by seed and stem cutting was evaluated. The interactive effect of different seed priming methods and temperature levels were investigated on germination indices of H. odoratissimum seeds. A randomized complete block design with three replicates was used to evaluate the effect of season, cutting position, rooting hormone and growth media on survival percentage, number of buds, number of leaves, rooting percentage, number of roots per cutting and root length of H. odoratissimum stem cuttings. Data for both aspects was analysed using ANOVA and means with significant differences were separated with a t-test at 5% level of significance. Smoke treated seeds incubated at 20 °C had a significantly higher germination percentage (91,7%), mean germination rate (0.59) and coefficient velocity of germination (59.5) compared to most other treatments. Almost all factors tested in vegetative propagation significantly affected parameters measured. Apical cuttings taken during autumn resulted in significantly higher survival (78.5) and rooting percentages (71.1%) compared to other seasons. Cuttings planted in a perlite, vermiculite and sand mixture during autumn significantly outperformed all other season/media combinations with regards to rooting percentage (75%). PGR application improved the number of roots obtained significantly in autumn and winter, but not in summer and spring, compared to the control. It was therefore concluded that, for higher seed germination H. odoratissimum seeds must be primed with smoke water and incubated at 1520 °C and cuttings may be taken autumn for higher rooting and survival rates as well as improved root length. A PGR application can be beneficial depending on the type of medium used.
Insights into the Phylogeny, nodule function, and biogeographic distribution of microsymbionts nodulating the orphan kersting’s groundnut [Macrotyloma geocarpum (Harms) Marechal & Baudet] in African Soil.s
(American Society for Microbiology, 2019-05-16) Mohammed, Mustapha; Jaiswal, Sanjay K.; Dakora, Felix D.
Kersting’s groundnut [Macrotyloma geocarpum (Harms) Marechal & Baudet] is a neglected indigenous African legume adapted to growth in N-deficient soils due to its ability to fix atmospheric N2 via symbiosis with rhizobia. Despite its nutritional and medicinal uses, to date there is little information on the phylogeny and functional traits of its microsymbionts, aspects that are much needed for its conservation and improvement. This study explored the morphogenetic diversity, phylogenetic relationships, and N2-fixing efficiency of Kersting’s groundnut rhizobial isolates from contrasting environments in Ghana, South Africa, and Mozambique. BOX-PCR fingerprinting revealed high diversity among the rhizobial populations, which was influenced by geographic origin. Of the 164 isolates evaluated, 130 BOX-PCR types were identified at a 70% similarity coefficient, indicating that they were not clones. Soil pH and mineral concentrations were found to influence the distribution of bradyrhizobial populations in African soils. Phylogenetic analysis of 16S rRNA genes and multilocus sequence analysis of protein-coding genes (atpD, glnII, gyrB, and rpoB) and symbiotic genes (nifH and nodC) showed that Kersting’s groundnut is primarily nodulated by members of the genus Bradyrhizobium, which are closely related to Bradyrhizobium vignae 7-2T, Bradyrhizobium kavangense 14-3T, Bradyrhizobium subterraneum 58-2-1T, Bradyrhizobium pachyrhizi PAC48T, the type strain of Bradyrhizobium elkanii, and novel groups of Bradyrhizobium species. The bradyrhizobial populations identified exhibited high N2 fixation and induced greater nodulation, leaf chlorophyll concentration, and photosynthetic rates in their homologous host than did the 5 mM KNO3-fed plants and/or the commercial Bradyrhizobium sp. strain CB756, suggesting that they could be good candidates for inoculant formulations upon field testing. IMPORTANCE Rhizobia play important roles in agroecosystems, where they contribute to improving overall soil health through their symbiotic relationship with legumes. This study explored the microsymbionts nodulating Kersting’s groundnut, a neglected orphan legume. The results revealed the presence of different bradyrhizobial populations with high N2-fixing efficiencies as the dominant symbionts of this legume across diverse agroecologies in Africa. Our findings represent a useful contribution to the literature in terms of the community of microsymbionts nodulating a neglected cultivated legume and its potential for elevation as a major food crop. The presence of potentially novel bradyrhizobial symbionts of Kersting’s groundnut found in this study offers an opportunity for future studies to properly describe, characterize, and delineate these isolates functionally and phylogenetically for use in inoculant production to enhance food/nutritional security.
Nodulation and effective nitrogen fixation of macroptilium atropurpureum (siratro) by burkholderia tuberum, a nodulating and plant growth promoting beta-proteobacterium, are influenced by environmental factors
(Springer, 2013-01-07) Angus, Annette A.; Lee, Andrew; Lum, Michelle R.; Shehayeb, Maya; Hessabi, Reza; Fujishige, Nancy A.; Yerrapragada, Shailaja; Kano, Stephanie; Song, Nannie; Yang, Paul; De Los Santos, Paulina Estrada; De Faria, Sergio M.; Dakora, Felix D.; Weinstock, George; Hirsch, Ann M.
Background and aims Burkholderia tuberum STM678T was isolated from a South African legume, but did not renodulate this plant. Until a reliable host is found, studies on this and other interesting beta-rhizobia cannot advance. We investigated B. tuberum STM678T’s ability to induce Fix+ nodules on a small-seeded, easy-topropagate legume (Macroptilium atropurpureum). Previous studies demonstrated that B. tuberum elicited either Fix- or Fix+ nodules on siratro, but the reasons for this difference were unexplored. Methods Experiments to promote effective siratro nodule formation under different environmental conditions were performed. B. tuberum STM678T’s ability to withstand high temperatures and desiccation was checked as well as its potential for promoting plant growth via mechanisms in addition to nitrogen fixation, e.g., phosphate solubilization and siderophore production. Potential genes for these activities were found in the sequenced genomes. Results Higher temperatures and reduced watering resulted in reliable, effective nodulation on siratro. Burkholderia spp. solubilize phosphate and produce siderophores. Genes encoding proteins potentially involved in these growth-promoting activities were detected and are described. Conclusions Siratro is an excellent model plant for B. tuberum STM678T. We identified genes that might be involved in the ability of diazotrophic Burkholderia species to survive harsh conditions, solubilize phosphate, and produce siderophores.
Symbiotic N nutrition, C assimilation, and plant water use efficiency in Bambara groundnut (Vigna subterranea L. Verdc) grown in farmers’ fields in South Africa, measured using 15N and 13C natural abundance.
(Springer, 2013-07-16) Mohale, Keletso C.; Belane, Alphonsus K.; Dakora, Felix D.
Bambara groundnut (Vigna subterranea L. Verdc) is the second most important indigenous food legume in Africa. The aim of this study was to evaluate plant growth, N2 fixation, N contribution, C accumulation, and plant water relations of Bambara groundnut grown in 26 farmers’ fields in Mpumalanga Province of South Africa. The data revealed marked (p ≤0.05) differences in plant dry matter (DM) yield, N concentration and content, δ15N, the proportion of N derived from symbiotic fixation (%Ndfa), and actual amounts of N-fixed between and among the 26 farms surveyed. Bambara groundnut plants obtained 33–98 % (mean=72 %) of their N nutrition from symbiotic fixation and contributed 4–200 kg N fixed ha−1 (mean=102 kg N-fixed ha−1). Plant density correlated positively with %N (r =0.31***), δ15N (r =0.126***), and amount of N-fixed (r =0.15*), indicating that the high %Ndfa values obtained for Bambara groundnut in this study and the low symbiotic N yield associated with some farms were due to low plant density rather than poor symbiotic functioning. Bambara groundnut obtained more N from soil (e.g., 173 kg N ha−1) than from symbiosis (e.g., 135 kg N fixed ha−1) in some fields, implying that the N2-fixing efficacy of the microsymbionts nodulating Bambara groundnut was low at some locations in South Africa. The data from this study showed δ13C values ranging from −28.01 to −26.20‰, which indicates differences in plant water use efficiency on the different fields studied. Furthermore, the positive correlations between δ13C and N-fixed (r =0.15*) and between δ13C and N content (r =0.14*) suggest a functional relationship between water use efficiency and N2 fixation, just as the positively significant correlations between δ15N and DM yield (r =0.24***), N-fixed and DM weight (r =0.76**), and N content and DM yield (r =0.99*), as well as N-fixed and C content (r =0.76**) also indicate a functional relationship between N2 fixation and photosynthesis. In the same way, the positive correlation between δ13C and DM weight (r =0.14*), or δ13C and C content (r =0.15*), also implies a functional link between water use efficiency and plant growth. Thus, an increase in water use efficiency in Bambara groundnut, whenever it occurs, seems to functionally enhance plant growth, symbiotic N2 fixation, and photosynthetic activity, just as N2 fixation in nodules also seems to stimulate leaf photosynthesis.
Rhizosphere acid and alkaline phosphatase activity as a marker of P nutrition in nodulated cyclopia and aspalathus species in the Cape fynbos of South Africa.
(Elsevier B.V., 2013-08-01) Maseko, S.T.; Dakora, F.D.
Cyclopia and Aspalathus species are important economic legumes in the Cape fynbos of South Africa, as they are used for making Honeybush and Rooibos tea, and for trade in the cut wildflower industry. The aim of this study was to assess acid and alkaline phosphatase activity in the rhizosphere of Cyclopia genistoides, Cyclopia subternata, Aspalathus caledonensis and Aspalathus aspalathoides as an indicator of P supply and P nutrition in the nutrient-poor soils of the Cape fynbos. Whether at Kokrivier or Kanetberg, the P enzyme activities were much higher in the rhizospheres of the legumes C. genistoides, C. subternata, A. caledonensis, and A. aspalathoides compared to those of the non-legumes Leucadendron strictum, Elegia thyrsoidea and Mimetes cucullatus, or bulk soil. As a result, plant-available P concentration in the rhizosphere, as well as shoot P levels closely mirrored acid and alkaline phosphatase activity in the rhizosphere of each plant species. Relative to younger plants, older Cyclopia species exhibited, much greater acid and alkaline phosphatase activity in the rhizosphere and this again resulted in much higher plant-available rhizosphere P. C. subternata plants developed from cuttings at Kanetberg showed greater rhizosphere acid and alkaline phosphatase activity than seedlings and bulk soil. As a result, the concentration of plant available-P and organic P were much higher in the rhizosphere of cuttings than seedlings, leading to greater shoot P in cuttings than seedlings. Taken together, these data suggest that rhizosphere P enzyme activity can be used as a good indicator of P supply and P nutrition in Cyclopia cuttings and seedlings, but less so in Aspalathus species in the Cape fynbos. The enhanced P nutrition in plants from cuttings probably accounts for the higher tea yields obtained by farmers when they use cuttings instead of seedlings in their plantations.
Response of promiscuous-nodulating soybean (Glycine max L. Merr.) genotypes to bradyrhizobium inoculation at three field sites in Mozambique.
(Springer, 2015-12-30) Gyogluu, Cynthia; Boahen, Stephen K.; Dakora, Felix D.
Soybean cultivation in Mozambique is dominated by smallholder farmers who use little or no inputs such as bacterial inoculants, often resulting in low yields. This study assessed the ability of TGx and non-TGx soybean genotypes to nodulate with native rhizobia in Mozambican soils and evaluated the yield and symbiotic response of TGx and non- TGx soybean to inoculation with Bradyrhizobium japonicum strain WB74 at three IITA experimental sites in Mozambique. The data revealed significant inoculation, location and genotypic effects. Both TGx and non-TGx soybean genotypes showed effective nodulation in Bradyrhizobium-inoculated and uninoculated field plots. Inoculant application increased plant growth by 32 %, %N by 18 %, N content by 45 %, %Ndfa by 11 %, fixed N by 64 %, and grain yield by12% when compared to uninoculated control. Symbiotically, the soybean genotypes performed better at Ruace than at Nampula, and poorly at Mutequelesse. Genotypes TGx1910-14F, 427/5/7, TGx1937-1F and Solitaire accumulated the most biomass at Ruace and Nampula when compared to Mutequelesse, and individually contributed over 200 kg N.ha−1 during the cropping season. However, grain yield was much higher at Nampula than at Ruace and Mutequelesse. Independent of the location, four soybean genotypes produced similar amounts of grain yield in inoculated and uninoculated plots. Whether with or without inoculation, Solitaire and TGx1908-8F each produced about 2.0 t.ha−1 of grain, while TGx1910-14F and TGx1937-1F yielded between 1.5 and 1.7 t.ha−1. These four varieties were identified as the best for use by resource-poor farmers in Mozambique, while genotype 427/5/7, which produced about 2.4 t.ha−1 of grain with inoculation, was seen as ideal for well-resourced farmers.
Nitrogen nutrition, carbon accumulation and δ13C of cyclopia and aspalathus species in different settings of the Cape fynbos, South Africa
(Oxford University Press, 2015-11-27) Maseko, Sipho T.; Dakora, Felix D.
Aims Cyclopia and Aspalathus are legumes harvested for production of Honeybush and Rooibos tea, respectively. Farmers grow these species from either seeds or cuttings over several years nwith continuous annual harvesting. The aims of this study were to assess the effect of plant age, plant species, toposequence, planting material and farmer practice on nitrogen (N) nutrition and water-use efficiency of two Cyclopia and Aspalathus species in the Cape fynbos. Methods The study was conducted using plants from Koksrivier farm located near Gansbaai (33° S 18° E, 39 m.a.s.l), and at Kanetberg farm near Barrydale (33° S 21° E, 830 m.a.s.l). The 15N natural abundance technique was used to determine N2 fixation, carbon (C) assimilation and δ13C in shoot of Cyclopia and Aspalathus species. Important Findings Older tea plantations of C. genistoides and C. subternata derived more N from fixation and exhibited greater water-use efficiency than younger plants. At Koksrivier, Aspalathus caledonensis and A. aspalathoides showed greater water-use efficiency and derived more N from fixation than Cyclopia genistoides. Annual harvesting of C. genistoides decreased N2 fixation. At Kanetberg, C. subternata plants on the upper and middle slopes derived more N from atmospheric fixation than those on the lower slope. C. subternata plants grown from seedlings recorded greater %Ndfa than cuttings. N2 fixation and water-use efficiency of Cyclopia was affected by age, slope and planting material. Further, symbiotic N nutrition and water-use efficiency of Cyclopia and Aspalathus were related.
Microsymbiont diversity and phylogeny of native bradyrhizobiaassociated with soybean (Glycine max L. Merr.) nodulation in SouthAfrican soils.
(Elsevier GmbH., 2016-05-27) Naamala, Judith; Jaiswal, Sanjay K.; Dakora, Felix D.
The genetic diversity and identification of slow- and fast-growing soybean root nodule bacterial isolates from different agroclimatic regions in Mpumalanga, Limpopo and Gauteng Provinces of South Africa were evaluated. The 16S-rDNA-RFLP analysis of 100 rhizobial isolates and eight reference type strains placed the isolates into six major clusters and revealed their site-dependent genomic diversity. Sequence analysis of single and concatenated housekeeping genes (atpD, glnII and gyrB), as well as the symbiotic gene nifH captured a considerably higher level of genetic diversity and indicated the dominance of Bradyrhizobium diazoefficiens and Bradyrhizobium japonicum in Mpumalanga, Limpopo and Gauteng Provinces. Gene sequence similarities of isolates with type strains of Bradyrhizobium ranged from 97.3 to100% for the 16S rDNA, and 83.4 to 100% for the housekeeping genes. The glnII gene phylogeny showed discordance with the other genes, suggesting lateral gene transfer or recombination events. Concatenated gene sequence analysis showed that most of the isolates did not align with known type strains and might represent new species from South Africa. This underscores the high genetic variability associated with soybean Bradyrhizobium in South African soils, and the presence of an important reservoir of novel soybean-nodulating bradyrhizobia in the country. In this study, the grouping of isolates was influenced by site origin, with Group I isolates originating from Limpopo Province and Groups II and III from Mpumalanga Province in the 16S rDNA-RFLP analysis.
Multienvironment testing for trait stability and G × E interaction on N2 fixation, plant development, and water-use efficiency of 21 elite groundnut (Arachis hypogaea L.) genotypes in the Guinea Savanna
(Frontiers Media, 2019-09-12) Oteng-Frimpong, Richard; Dakora, Felix D.
Groundnut production constitutes an integral part of the livelihoods of the people in the Guinea savanna of West Africa. This region accounts for over 70% of the total groundnut production in Ghana, 90% in Nigeria, and 100% in Mali and Burkina Faso. However, harsh environmental conditions often result in drastic yield reductions. In this study, we identified groundnut genotypes with superior symbiotic efficiency, greater pod yield, and plant water use efficiency from 21 advanced groundnut breeding lines from ICRISAT after testing them at three locations in the Guinea savanna of Ghana over two consecutive years. Average N contribution by the groundnut genotypes ranged from 48 to 108 kg N ha−1, and mean pod yield from 580 to 2,100 kg ha−1. Genotype 17 (ICGV-IS 08837) produced about 2.5-fold more pods than genotype 1 (Chinese), which was the most widely cultivated variety by farmers. Of the 21 genotypes studied, genotype 16 (ICGV 99247) recorded the highest shoot δ13C value and was superior in water-use efficiency, which was consistent with stability estimates and mean performance. We also measured the effects of G × E on pod yield, N2 fixation, shoot δ13C, and mega-environments for testing groundnut in the Guinea savanna, and these were all significant, although the effect was minimal on shoot δ13C values. Of the locations studied, Nyankpala and Damongo were more discriminating, and each constituted a mega-environment for conducting future groundnut trials in the Guinea savanna. Genotype 3 (ICG 6222) emerged as the best cultivar for the Damongo mega-environment, while genotype 17 was the best genotype for the Nyankpala mega-environment. The genotypes exhibiting the highest sensitivity of N2 fixation in the environment included genotype 3 (ICG 6222), genotype 4 (ICGV 00068), and genotype 10 (ICGV 03315) (bi > 1.3), while Pi estimates ranked genotypes 3, 10, and 17 as the best groundnut cultivars in terms of symbiotic N contribution. Based on the results of this study, genotype 17 (ICGV-IS 08837), genotype 3 (ICG 6222), genotype 10 (ICGV 03315), and genotype 4 (ICGV 00068), which were the most outstanding in terms of the overall pod yield, shoot biomass production, and amount of N-fixed, were the most suitable candidates to recommend for use in developing new varieties for the Guinea savanna of Ghana. Genotype 17 (ICGV-IS 08837) has already been released as a commercial variety for the Guinea savanna of Ghana since October 2018.
Presence of diverse rhizobial communities responsible for nodulation of common bean (Phaseolus vulgaris) in South African and Mozambican soils.
(Oxford University Press (OUP), 2016-11-21) Zinga, Mwajuma K.; Jaiswal, Sanjay K.; Dakora, Felix D.
The diversity and phylogeny of root-nodule bacteria isolated from common bean grown in Mozambique and different provinces of South Africa was studied by restriction fragment length polymorphism (RFLP) and phylogenetic analysis. The combined restriction banding pattern of 16S rRNA and nifH profile-generated dendrogram grouped all test isolates into four major clusters with XXI restriction groups and three clusters with VIII restriction groups. Location-based clustering was observed with the 16S rRNA RFLP analysis. Phylogenetic analysis of 16S rRNA, glnII, gyrB and gltA sequences showed that common bean was nodulated specifically by Rhizobium etli in Mozambican soils, and by a diverse group of Rhizobium species in South African soils (e.g. R. etli, R. phaseoli, R. sophoriradicis, R. leucaenae and novel group of Rhizobium spp.). Isolates from the Eastern Cape region of South Africa were dominated by R. leucaenae. Overall, the results suggested high nodulation promiscuity of common bean grown in Southern Africa. The nifH and nodC sequence analysis classified all the test isolates with R. etli group, except for isolates TUTPVSA117, TUTPVSA114 and TUTPVSA110 which delineated with R. tropici group. This finding was inconsistent with the phylogram of the housekeeping genes and is probably an indication of horizontal gene transfer among the Rhizobium isolates tested.
Symbiotic effectiveness and ecologically adaptive traits of native rhizobial symbionts of bambara groundnut (Vigna subterranea L. Verdc.) in Africa and their relationship with phylogeny.
(Nature Research, 2019-08-13) Ibny, Fadimata Y.I.; Jaiswal, Sanjay K.; Mohammed, Mustapha; Dakora, Felix D.
Bambara groundnut (Vigna subterranea L. Verdc.) is an indigenous, drought-tolerant, underutilized African food legume, with the ability to fx atmospheric N2 in symbiosis with soil bacteria called rhizobia. The aim of this study was to assess the morpho-physiological, symbiotic and phylogenetic characteristics of rhizobia nodulating Bambara groundnut in Ghana, Mali and South Africa. The morpho physiologically diverse isolates tested were also found to exhibit differences in functional efficiency and phylogenetic positions. Based on Enterobacterial Repetitive Intergenic Consensus (ERIC)-PCR banding patterns, the isolates were grouped into eight major clusters. The concentrations of Ca, Na and K in soils had a significant (p≤0.01) effect on the distribution of rhizobia. Though many isolates were symbiotically very effective, the effectiveness index varied markedly (p≤0.05) among them. Moreover, the isolates also exhibited tolerance to a wide range of NaCl (0.5–7%), streptomycin (50–500µg.ml−1), and kanamycin (25–150µg.ml−1) concentrations. Additionally, these isolates could produce 0.02 to 69. 71µg.ml−1 of indole-3-acetic acid (IAA) in tryptophan-supplemented medium, as well as solubilize tri-calcium phosphate. Phylogenetic analysis of these rhizobial isolates using 16S rRNA, atpD, glnII, gyrB, recA and symbiotic (nifH and nodC) gene sequences revealed distinct and novel evolutionary lineages related to the genus Bradyrhizobium, with some of them being very close to Bradyrhizobium vignae, B. kavangense, B. subterraneum, B. elkanii and B. pachyrhizi.
Plant growth and N2 fixation in Cyclopia longifolia (Vogel L.) supplied with mineral nutrients in pot and field experiments.
(Elsevier B.V., 2016-12-19) Mndzebele, B. M.M.P.; Dakora, F.D.
Cyclopia longifolia Vogel L. is indigenous to the Cape fynbos, and widely grown for the production of Honeybush tea, a beverage with health benefits and economic potential in the cosmetic and nutraceutical industries. The aim of this study was to assess plant growth and symbiotic performance of Cyclopia longifolia in field and pot experiments. Field plants were supplemented with different levels of P,Mg and Ca at Kanetberg mountains using 0, 5, 25 and 50 mM of K2HPO4, MgCl2·6H2O and CaCl2·2H2O in split application, while P, Ca and Mg were applied as Super grow(20.3% P), CaMg·(CO3)2, and MgSO4·7H2O) at 0, 10, 20 and 50 kg·ha−1 to potted plants. Shoots were harvested at 240 and 300 days after last fertilisation for pot and field experiments respectively and analyzed for nodulation andN2 fixation. The data revealed significantly increased nodule number, nodule dry weight, root and shoot biomass in the pot experiment with P, Ca and Mg supply. Shoot dry matter, N content, amount of N-fixed, soil N uptake and tea yield of C. longifolia was significantly increased with increasing supply of P, Mg and Ca to field plants, and was highest at 50 mM level of each element. Applying different levels of Mn, Cu, Zn and Mo to field plants of C. longifolia also markedly increased shoot biomass, N content, δ15N, amount of N-fixed, soil N uptake and tea yield. The increase in δ15N values, and hence reduced %Ndfa, of Cyclopia longifolia plants supplied with P, Mg, Ca, Mn, Cu, Zn and Mo suggests that the endogenous soil concentration of these nutrients were more limiting for plant growth than for nodule functioning. As a result, supplying P, Mg, Ca, Mn, Cu, Zn and Mo increased plant growth and biomass, but not %N derived from fixation.
Accumulation of mineral elements in the rhizosphere and shoots of cyclopia and aspalathus species under different settings of the Cape fynbos.
(Elsevier B.V., 2016-10-19) Maseko, S.T.; Dakora, F.D.
Several species of the genus Cyclopia are cultivated for the production of Honeybush tea, largely without mineral fertilization. However, very little is known about the effect of annual harvesting, plant age, and type of planting material (cuttings vs. seedlings) on the mineral nutrition of Cyclopia. The aim of this study was to evaluate mineral nutrition in Cyclopia genistoides, Cyclopia subternata, Aspalathus caledonensis, and Aspalathus aspalathoides in relation to (i) plant species, (ii) plant age, (iii) farmer's practice, (iv) planting material, and (v) topo sequence at Koksrivier, Kanetberg, and Kleinberg in the Cape fynbos. A comparison of mineral concentrations in the rhizosphere and non-rhizosphere of 10-year-old C. genistoides at Koksrivier revealed significantly larger levels of P, Ca,Mg, Cu, Zn, and Mn in the former relative to the latter. There were also significantly greater levels of P, K, Ca,Mg,Na, and Mnin the rhizosphere of 10-year-old C. genistoides compared with 2-year-old plants at Koksrivier. The levels of P, K, Ca, Mg, Na, Fe, and Mn were significantly greater in the rhizosphere than Non rhizosphere soil of 5- and 8-year-old C. subternata plants at Kanetberg. Rhizosphere concentration of minerals were also measured and compared for C. subternata plants raised from cuttings and seedlings at Kanetberg, and P, Ca, and Cu were greater in the rhizosphere of plants cultured from cuttings. The concentration of minerals in the rhizosphere of A. aspalathoides, A. caledonensis, and C. genistoides, which co-occurred within the same tea plantation at Koksrivier, were significantly different, with P, K, Cu, Zn, and Mn being markedly greater in the rhizosphere soil of C. genistoides than the two Aspalathus species. Mineral nutrition under farmers' practice of annual harvesting was compared with unharvested material, and the levels of P, K, Na, Cu, Zn, and Mn were found to be significantly greater in shoots of the annually harvested plants.
Analysing the value chain for African leafy vegetables in Limpopo Province, South Africa.
(Taylor and Francis, 2018-08-03) Senyolo, Grany M.; Wale, Edilegnaw; Ortmann, Gerald F.
The aim of this study has been to analyse the value chain of African leafy vegetables in the Limpopo Province of South Africa. This was done by identifying the prominent value chain actors, institutions governing the chain, the infrastructural endowments, key factors and challenges affecting the success or failure of the value chains for African leafy vegetables. Relationships among the value chain actors were weak, with transactions based mostly on spot markets. While smallholder farmers attain high gross margins, their intention to take part in the mainstream markets are prevented by lack of technical advice on production, lack of packaging and processing services, poor infrastructure, deficiency of contractual agreements between actors, and lack of access to finance. Although producers currently attain relatively higher gross margins, more benefits might be realized if government services (such as training, seed production and distribution) could either be decentralized or privatized. Future policy interventions should focus on promoting value addition along the African leafy vegetable chain, provision of cold storage facilities by municipalities closer to smallholder farmers in the rural areas and this will stabilize farm gate prices to encourage continuation of production.
Factors influencing the adoption of climate-smart irrigation technologies for sustainable crop productivity by smallholder farmers in arid areas of South Africa.
(MDPI, 2021-12-03) Serote, Batizi; Mokgehle, Salmina; Du Plooy, Christian; Mpandeli, Sylvester; Nhamo, Luxon; Senyolo, Grany
The adoption of climate-smart irrigation technologies amongst smallholder farmers generally remains low beside their role in combating food and nutrition security in a society and in climate change adaptation strategies. This study identified the factors influencing smallholder farmers’ decision to adopt Climate Smart Irrigation Technologies (CSIT) in the Limpopo Province of South Africa. Data were collected through the completion of a face-to-face structured questionnaire by 100 smallholder farmers selected through convenience and purposive sampling. A probit regression and OLS model were used to identify factors that influence the smallholder farmer’s decision to adopt CSIT and the level of adoption. The results indicated that only 46% of the smallholder farmers adopted climate-smart irrigation technologies and suggested that adoption is influenced positively by factors such as gender, age, district, farm size, staple food production and knowledge on CSIT. There is an urgent need for related stakeholders to transform the smallholder farmer subsector through improved extension services, training, adopting resilient crop varieties, promoting underutilized and nutrient-dense crops adapted to harsh local conditions, and other interventions. This should be done by promoting awareness to smallholder farmers regarding these interventions and new technologies that have the potential to improve rural livelihoods and enhance resilience and adaptation.
Essential oil vapours suppress the development of anthracnose and enhance defence related and antioxidant enzyme activities in avocado fruit.
(Elsevier B.V., 2013-02-03) Sellamuthu, Periyar Selvam; Sivakumar, Dharini; Soundy, Puffy; Korsten, Lise
Anthracnose caused by Colletotrichum gloeosporioides is a major postharvest disease in avocados that causes significant losses during transportation and storage. Complete inhibition of the radial mycelia growth of C. gloeosporioides in vitro was observed with citronella or peppermint oils at 8 L plate−1 and thyme oil at 5 L plate−1. Thyme oil at 66.7 L L−1 significantly reduced anthracnose from 100% (untreated control) to 8.3% after 4 days, and to 13.9% after 6 days in artificially wounded and inoculated ‘Fuerte’ and ‘Hass’ fruit with C. gloeosporioides. GC/MS analysis revealed thymol (53.19% RA), menthol (41.62% RA) and citronellal (23.54% RA) as the dominant compounds in thyme, peppermint and citronella oils respectively. The activities of defence enzymes including chitinase, 1, 3--glucanase, phenylalanine ammonia-lyase and peroxidase were enhanced by thyme oil (66.7 L L−1) treatment and the level of total phenolics in thyme oil treated fruit was higher than that in untreated (control) fruit. In addition, the thyme oil (66.7 L L−1) treatment enhanced the antioxidant enzymes such as superoxide dismutase and catalase. These observations suggest that the effects of thyme oil on anthracnose in the avocado fruit are due to the elicitation of biochemical defence responses in the fruit and inducing the activities of antioxidant enzymes. Thus postharvest thyme oil treatment has positive effects on reducing anthracnose in avocados.
Comparison of the contents of bioactive compounds and quality parameters in selected mango cultivars.
(Wiley, 2013-08-28) Sellamuthu, Periyar Selvam; Denoya, Gabriela Ines; Sivakumar, Dharini; Polenta, Gustavo Alberto; Soundy, Puffy
Mango cultivars Tommy Atkins, Zill, Peach, Sabre, Rosa and Phiva were analyzed for their quality parameters (fruit weight, flesh color chroma, L, h0, total soluble solid [TSS]/titratable acidity [TA], firmness), bioactive compounds (total phenols, carotenoids, ascorbic acid, antioxidant activity) and polyphenol oxidase (PPO) activity. Cv. Sabre showed highest total phenolic content (76.43 mg gallic acid/ 100 g FW), carotenoids (9.90 mg/100 g of FW), ascorbic acid content (69.71 mg/ 100 g of FW) and antioxidant activity (1.2 mg of gallic acid/g of FW), whereas cv. Peach mango contained lower bioactive compounds. Multivariate principal component analysis analysis showed higher concentration of bioactive compounds in cv. Sabre mango, whereas cv. Tommy Atkins was firm and heavier. Cv. Rosa and Phiva were moderately rich in bioactive compounds and lower in fruit weight and firmness, whereas cv. Peach was higher in TSS/ TA. The PPO activity was higher in cvs. Rosa and Zill.
Influence of postharvest storage temperature and duration on quality of baby spinach.
(American Society for Horticultural Science, 2015-10-01) Mudau, Ambani R.; Nkomo, Mpumelelo M.; Soundy, Puffy; Araya, Hintsa T.; Ngezimana, Wonder; Mudau, Fhatuwani N.
Spinach (Spinacia oleracea) is a member of the Amaranthaceae family. Baby spinach leaves have a very high respiration rate, thus postharvest quality is affected mostly by tissue decay and the development of off-odors. Thus, this study was conducted to investigate the influence of storage temperature and time on the postharvest quality of baby spinach. Baby spinach leaves were harvested 36 days after planting and subsequently stored at 4 and 22 C for 0, 2, 4, 6, 8, 10, or 12 days. Thereafter, the leaves were incubated for 72 hours at 40 C to dry. Minerals, trace elements, total phenols, total carotenoids, flavonoids, and antioxidant activities were measured. Concentration of magnesium (Mg), zinc (Zn), and iron (Fe) were declined after 8 days of storage at 4C, while at 22 C they declined after 2 days of storage. Mg, Zn, and Fe revealed a similar trend with significantly higher carotenoids found up to 6 days in storage at 4 C, while at 22 C the carotenoid levels declined after only 2 days. Total phenolic compounds gradually decreased in samples stored at 4 C. However, samples stored at 22 C showed a rapid decrease after 4 days. Both total antioxidant activities and vitamin C content showed a similar trend, with the content remaining constant at 4 C and decreasing after 6 days, whereas the total antioxidant activities and vitamin C for leaves stored at 22 C decreased immediately after 2 days. Results demonstrated that quality of baby spinach deteriorates as storage time and temperature increase.
Activity-guided isolation and identification of the major antioxidant and anticancer compounds from a commercial pelargonium sidoides tincture.
(Springer, 2015-08-20) Pereira, Andreia; Bester, Megan; Soundy, Puffy; Apostolides, Zeno
Extracts prepared from the roots of Pelargonium sidoides (DC) are commercially available for the treatment of respiratory related conditions. Recently, a commercial radix mother tincture of this plant was shown to have both antioxidant and anticancer effects especially related to the G0/G1 block in the Jurkat E6.1 cell line (unpublished results). Fractions were prepared by semipreparative HPLC, and their antioxidant and anticancer activities were determined. The more hydrophilic fractions isolated namely F6–F12 were all found to have strong reducing capacities and were able to scavenge peroxyl radicals. In the human lung cell line, NCI-H460, significant cellular antioxidant effects were observed. Anticancer activity was evaluated in the NCI-pre-screen panel (NCIH460, MCF-7 and SF-268) and the Jurkat E6.1 cell line. Fractions F7, F9, and F12 were found to inhibit the cell growth of these four cell lines (p\0.05), especially the Jurkat E6.1 cell line with the sulforhodamine B assay. Mass spectrometry analysis revealed that these active fractions contained several polyphenolic compounds such as gallic acid, trihydroxycoumarin, dihydroxycoumarin sulfates, proanthocyanidins, and phenolic glycosides. A phenolic acid glycoside sulfate not previously shown in P. sidoides extracts was also isolated. In conclusion, the antioxidant and/or anticancer activity of the P. sidoides tincture may be attributed to the presence of these polyphenolics.

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