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 Symbiotic nitrogen contribution by a long-duration pigeonpea genotype intercropped with maize in South Africa Authors Poster Board Number 1 1 Cherian Mathews, 2 Wim van Averbeke and 2 Felix Dakora 1 Department of Agriculture, P/Bag X11318, Nelspruit-1200 2 Tshwane University of Technology P/Bag X680, Pretoria-0001 As a crop, pigeonpea has a huge market value in South Africa due to the growing Asian population. Large quantities of pigeonpea grown is currently imported to meet local demand. This indicates the need to evaluate pigeonpea genotypes for growth, grain yield and symbiotic performance in order to identify genotypes for use in local cropping systems. Field experiments were conducted at Nelspruit during 2007, 2008 and 2009 cropping seasons to assess N2 fixation and yield potential of pigeonpea (Cajanus cajan L. Millspaugh) in intercropping systems used by resource-poor farmers in Africa. Three intercropping systems (within-rows, alternate rows, and paired rows) and their sole cropped pigeonpea (cv. ICEAP00040) and maize (cv. ZM521) were used in a randomized complete block design with five replications. Destructive sampling was done at four stages of legumes (i.e. maize tasseling, maize harvest, pigeonpea flowering, and pigeonpea harvest) for dry matter yield and measurement of N2 fixation using 15 N natural abundance. The results of two cropping seasons (2007-08 and 2008-09) are presented here. Dry matter yield was significantly (p=0.01) lower in intercropped pigeonpea relative to monoculture, but was positively correlated with N content, δ 15 N and amount of N-fixed. The N content per plant was highest in monocultured pigeonpea as a result of its larger dry matter yield. In both seasons, the δ 15 N values of intercropped pigeonpea were lower than monoculture, and were lowest in plants on same-row intercropping and/or alternate row intercroping. As a result, %Ndfa values were significantly greater under these cropping systems. The average amount of Nfixed was up to 173 kg ha -1 in monoculture and 153 kg ha -1 in intercrop, levels which peaked at pigeonpea flowering in both seasons. The results show that pigeonpea can contribute substantial amounts of symbiotic N and thus enhance soil productivity under traditional cropping systems. 116 2011
17 th International Congress on Nitrogen Fixation Fremantle, Western Australia 27 November – 1 December 2011 Title Growth inhibition of Sinorhizobium medicae in the presence of amino acids and the absence of supplemented calcium is alleviated by a mutation in the low pH inducible gene lpiA. Author Wan Adnawani Meor Osman 1,2 , Ravi Tiwari 1 , Lambert Brau 1 , Vanessa Melino 1 & Wayne Reeve 1 . Poster Board Number 2 1 Centre for Rhizobium Studies, Murdoch University, Murdoch, 6150, Western Australia. Australia 2 Department of Biological Sciences, Faculty of Sciences and Technology, University Malaysia Terengganu, 21030 Kuala Terengganu, Terengganu, Malaysia. Sinorhizobium medicae WR101 was identified as a mTn5-GNm induced mutant of WSM419 that expressed acid inducible GUS activity. Characterisation of the mutation revealed that the promoterless gusA gene in mTn5-GNm was fused to the low pH inducible gene lpiA. The LpiA protein contains a COG0392 signature (indicative of an integral membrane protein) domain revealing that this protein is most likely a transmembrane protein. In addition, LpiA also contains three other domains of unknown function including DUF470, DUF471 and DUF472 which share 83%, 62% and 58% similarity to proteins found in animal pathogens, plant pathogens and other symbionts, respectively (Reeve et al., 2006). An in depth characterisation of the phenotype of the mutant cells revealed that the lpiA mutation disrupted the acid-tolerance response (ATR) associated with S. medicae WSM419. In addition to this, we have now found that the lpiA mutation enables the mutant to grow on amino acid rich media devoid of calcium. In contrast, the wild-type strain WSM419 cannot grow in this condition and requires calcium to overcome the growth inhibition found with amino acid containing rich media. Complementation analysis has revealed that mutant growth can be severely inhibited on media containing amino acids in the absence of sufficient calcium. These observations have demonstrated that the absence of LpiA is essential for growth on calcium deficient media containing amino acids. Potential reasons for the growth inhibition of S. medicae by amino acids in the absence of calcium will be presented. 117 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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