IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

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17 th International Congress on Nitrogen Fixation Fremantle, Western Australia 27 November – 1 December 2011 Title Evaluation of elite commercial soybean varieties for N2 fixation and grain yield in South Africa Author Nyamande Mapope 1 and Felix D Dakora 2 Poster Board Number 27 1 Department of Crop Science, Tshwane University of Technology 2 Department Chemistry, Faculty of Science, Tshwane University of Technology South Africa is currently a net importer of soybean which is much needed for poultry production and the livestock industry. There is therefore an urgency to increase local production of soybean through breeding of improved varieties, their evaluation for adaptability, and selection for high grain yield and symbiotic performance. This study assessed plant growth, N2 fixation, and grain yield in thirteen commercially-bred, elite soybean genotypes under field conditions in the three soybean-producing provinces of South Africa. The varieties used originated from Pioneer, Pannar and Linkseed in South Africa. The experiments were laid out in a randomized block design with four replications. At pod filling (R6) stage, 10 soybean plants were randomly sampled from each plot, and oven-dried (60oC) separately, weighed and ground into fine powder (0.85mm) for 15N isotope analysis. The data obtained revealed marked differences in dry matter yield, N concentration, N content, δ15N, %Ndfa and actual amounts of N fixed among the thirteen soybean genotypes at each of the three sites. Dry matter yield ranged from 26 g.plant-1 for PAN1454 to 50 g.plant-1 for PAN737 at Balfour in Mpumalanga, and 33 to 73 g.plant-1 at Herman in the North West Province. The N concentrations of shoots also differed between and among genotypes at each site, and ranged from 2.2 % for 95Y20 to 3.5 % for PAN1666 at Balfour in Mpumalanga. The δ15N values ranged from -0.73 ‰ for PAN1454 to 2.33 ‰ for PAN1666 at Balfour in Mpumalanga. Cross site analysis also revealed significant interaction between site and varieties. PAN1666 showed the lowest %Ndfa (64%) and 95Y40 the highest %Ndfa (85%) across all sites. The actual amounts of N-fixed ranged from 114 kg.ha-1 for 95Y20 to 215 kg.ha-1 for PAN1666 across the sites. Soil N uptake was generally low across the sites, indicating greater dependence of these elite varieties on N2 fixed for their N nutrition. PAN1666 for accumulated greater dry matter and amount of N-fixed across all sites and was therefore the best variety for use by farmers. 142 2011
17 th International Congress on Nitrogen Fixation Fremantle, Western Australia 27 November – 1 December 2011 Title Ecophysiological studies and biodiversity of root-nodule bacteria nodulating Psoralea species in the cape fynbos of South Africa Authors Sheku A. Kanu 1 & Felix D. Dakora 2 Poster Board Number 28 1 Crop Science and 2 Chemistry Department, Tshwane University of Technology The tribe Psoraleae has 51 species, which are endemic to the Cape fynbos. However, little is known about the N contribution and microsymbionts associated with the nodulation of members of the tribe Psoraleae. In this study eight Psoralea species (namely, P. pinnata, P. repens, P. aphylla, P. asarina, P. monophylla, P. aculeata, P. restioides and P. laxa) growing in the fynbos were assessed for their symbiotic N nutrition and biodiversity of bacteria nodulating this tribe. Isotopic analysis of young branches with leaves showed that Psoralea species were highly dependent on N2 fixation for their N nutrition. The � 15 N and %Ndfa values of plant parts differed between species, and across the study sites. For example, at Betty‟s Bay, four Psoralea species (namely P. aculeata, P. aphylla, P. laxa and P. pinnata) showed strong differences in the � 15 N values of young branches with P. pinnata exhibiting the lowest stem � 15 N value of -2.00 ‰ and the highest %Ndfa value of 84%. Excavation of plants showed that all eight Psoralea species had round determinate root nodules. Surface sterilization, followed by streaking of nodule homogenates onto yeast-mannitol agar medium revealed bacterial isolates that differed in their growth rate, colony appearance, shape and texture. When 72 single-colony isolates from eight members of the tribe Psoraleae were tested for their ability nodulate P. pinnata, only 5 isolates (TUT54pp, TUT55pp, TUT57pp, TUT58pp and TUT60pp) effectively nodulated their original host together with 3 other isolates from P. asarina (TUT71pas), P. restioides (TUT23prt) and P. aculeata (TUT17pac). Although 7 isolates formed root nodules on siratro, only 5 (TUT1pm, TUT23prt, TUT32pap, TUT43pap and TUT45pap) were effective. The results from 16S rDNA sequencing revealed considerable microsymbiont diversity associated with the tribe Psoraleae with strains belonging to both α and β-proteobacteria. Taken together, these results suggest that Psoralea species have the potential to contribute to the N economy of the nutrient-poor soils of the Cape fynbos when associated with both .α and β-proteobacteria. 143 2011
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PrinciPal SPonSor: SPonSorS: Progra
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INVENTING THE FUTURE IN INOCULANTS
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17 ICNF Organising Committee Graham
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Cottesloe Beach © Tourism Western
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GeNeRAl INfoRmATIoN aTM’s Automat
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16:30 - 16:50 Felix Dakora Tshwane
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Thursday 1 December 2011 08:00 - 12
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IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

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