North Eastern Ethiopia is a major sorghum-growing region. A total of 415 sorghum landraces were sampled to represent the range of agro-ecologies (three altitude ranges) as well as spatial ...heterogeneity, that is, 4 zones: North Welo, South Welo, Oromiya and North Shewa with each zone containing 2 to 5 districts. The landraces were genotyped with simple sequence repeats (SSR) and inter simple sequence repeats (ISSR) markers. High genetic diversity was observed among the landraces for both marker systems. STRUCTURE analysis revealed 4 clusters of genetically differentiated groups of landraces. Cluster analysis revealed a close relationship between landraces along geographic proximity with genetic distance between landraces increasing with an increase in geographic distance. The grouping of landraces based on districts was influenced by clinal trend and geographic proximity. The F sub(ST) statistics showed significant geographic differentiation among landraces at various levels of predefined geographic origin but a large portion of the variation was among landraces within rather than between predefined populations. The landraces from North Shewa were predominantly in one cluster, and landraces from this area also exhibited the greatest allelic diversity and the highest number of private alleles. There was low variation among the highland Zengada landraces, but these landraces were quite strongly differentiated and fell into one population cluster. The low to moderate genetic differentiation between landraces from various geographic origins could be attributed to gene flow across the region as a consequence of seed exchange among farmers.
The genetic variability of 28 sorghum genotypes of known senescence phenotype was investigated using 66 SSR markers well-distributed across the sorghum genome. The genotypes of a number of lines from ...breeding programmes for stay-green were also determined. This included lines selected phenotypically for stay-green and also RSG 03123, a marker-assisted backcross progeny of R16 (recurrent parent) and B35 (stay-green donor). A total of 419 alleles were detected with a mean of 6.2 per locus. The number of alleles ranged from one for Xtxp94 to 14 for Xtxp88. Chromosome SBI-10 had the highest mean number of alleles (8.33), while SBI-05 had the lowest (4.17). The PIC values obtained ranged from zero to 0.89 in Xtxp94 and Xtxp88, respectively, with a mean of 0.68. On a chromosome basis, mean PIC values were highest in SBI-10 (0.81) and lowest in SBI-05 (0.53). Most of the alleles from B35 in RSG 03123 were found on chromosomes SBI-01, SBI-02 and SBI-03, confirming the successful introgression of quantitative trait loci associated with stay-green from B35 into the senescent background R16. However, the alternative stay-green genetic sources were found to be distinct based on either all the SSRs employed or using only those associated with the stay-green trait in B35. Therefore, the physiological and biochemical basis of each stay-green source should be evaluated in order to enhance the understanding of the functioning of the trait in the various backgrounds. These genetic sources of stay-green could provide a valuable resource for improving this trait in sorghum breeding programmes.
CO sub(2)-pressurized liquid hot water was applied to pretreat Sorghum stalk to increase its accessibility for enzyme hydrolysis. Pretreatment temperatures tested ranged from 180 to 220 degree C, and ...reaction times varied between 10 and 30 min. The highest total reducing sugar yield of 81.54% was obtained for the sample pretreated at 200 degree C and 20 min. Different from the N sub(2)-pressurized liquid hot water process, the generated carbonic acid in the CO sub(2)-pressurized method acted as catalyst in the pretreatment process. It was found that the reducing sugar yield increased significantly at lower temperature and shorter reaction time with the addition of CO sub(2). Finally, X-ray diffraction and scanning electron microscope analysis were used to investigate the microstructure of the Sorghum stalk before and after the pretreatment. copyright 2016 American Institute of Chemical Engineers Environ Prog, 36: 208-213, 2017
The aim of this study was to estimate the genetic variability of sorghum landraces grown in lower eastern Kenya based on simple sequence repeats (SSRs) markers. A total of 44 landraces obtained from ...the farmers and four improved varieties were analyzed using 20 SSR markers. All markers were polymorphic with polymorphism information content (PIC) value ranging from 0.04 to 0.81 with a mean of 0.49. Heterozygosity ranged from 0.00 to 0.04 suggesting that each detected a single genetic locus and that each of the sorghum accession used was stable. The alleles ranged between 2 and 10 and an average of 5.05 alleles per primer pair. The gene diversity ranged from 0.04 to 0.83 with a mean value of 0.53. All possible allele combinations ranged from 2 to 10, while major allele frequency ranged from 0.32 to 0.98. Genetic distances varied from 0.15 to 0.90 with two genotypes Karuge 1 and Karuge 2 obtained from Kiritiri in Mbeere having the minimum (0.15) and indication of very close relatedness. The diversity of the landraces was structured more on geographical locations and on seed colorations than agro-ecological conditions. Such intraregional genetic proximity in sorghum landraces would arise through seed exchanges among farmers. Analysis of molecular variation indicated higher variation within populations than among the groups. The genetic diversity can be exploited in hybridization programs to improve sorghum varieties grown by farmers in semi arid areas.
Considerable effort has been made to improve drought-stress tolerance in sorghum by incorporating the stay-green trait into drought-susceptible elite sorghum varieties. Keeping track of the several ...genes involved in the expression of this complex trait during the breeding program is an enormous task. In this study, the fidelity of recently identified SSR markers were tested for introgression of stay-green QTLs into elite sorghum lines. Of the 102 SSR loci tested, seventy- eight (78) markers were found to be polymorphic between the donor lines (B35 and E36-1) and the recipient lines (Sekedo and Seredo). In total, 25 polymorphisms were detected in SSR loci flanking key stay-green quantitative trait loci (QTLs) from the B35 donor line, and 6 in E36-1. In B35, 5 SSR markers were linked to the QTL StgA, 6 linked to StgB, 3 linked to Stg1, 2 linked to Stg2, 4 linked to Stg3 and 5 linked to Stg4. In contrast, only 6 polymorphic SSR markers were detected in the vicinity of key QTLs found in E36-1. Two were linked to LGA, 1 to LGJ and 3 to LGG. No markers were found linked to QTL LGD and LGH. Similar SSR polymorphisms were observed for markers needed to recover the recurrent parent genomes (RPG) in the subsequent backcross generations. These findings reveal the limitations of using E36-1 as a donor parent in marker-assisted selection (MAS) programmes for improvement of drought tolerance. Low hybridization efficiency (22.5%) was achieved using the anther dehiscence method. Such low hybridization efficiency requires use of molecular markers to easily identify plants harbouring the required genotypes.
Progress in molecular plant breeding is limited by the ability to predict plant phenotype based on its genotype, especially for complex adaptive traits. Suitably constructed crop growth and ...development models have the potential to bridge this predictability gap. A generic cereal crop growth and development model is outlined here. It is designed to exhibit reliable predictive skill at the crop level while also introducing sufficient physiological rigour for complex phenotypic responses to become emergent properties of the model dynamics. The approach quantifies capture and use of radiation, water, and nitrogen within a framework that predicts the realized growth of major organs based on their potential and whether the supply of carbohydrate and nitrogen can satisfy that potential. The model builds on existing approaches within the APSIM software platform. Experiments on diverse genotypes of sorghum that underpin the development and testing of the adapted crop model are detailed. Genotypes differing in height were found to differ in biomass partitioning among organs and a tall hybrid had significantly increased radiation use efficiency: a novel finding in sorghum. Introducing these genetic effects associated with plant height into the model generated emergent simulated phenotypic differences in green leaf area retention during grain filling via effects associated with nitrogen dynamics. The relevance to plant breeding of this capability in complex trait dissection and simulation is discussed.
Arbuscular mycorrhizal (AM) fungi contribute to plant nitrogen (N) acquisition. Recent studies demonstrated the transport of N in the form of ammonium during AM symbiosis. Here, we hypothesize that ...induction of specific ammonium transporter (AMT) genes in Sorghum bicolor during AM colonization might play a key role in the functionality of the symbiosis.
For the first time, combining a split-root experiment and microdissection technology, we were able to assess the precise expression pattern of two AM-inducible AMTs, SbAMT3;1 and SbAMT4. Immunolocalization was used to localize the protein of SbAMT3;1.
The expression of SbAMT3;1 and SbAMT4 was greatly induced locally in root cells containing arbuscules and in adjacent cells. However, a split-root experiment revealed that this induction was not systemic. By contrast, a strictly AM-induced phosphate transporter (SbPt11) was expressed systemically in the split-root experiment. However, a gradient of expression was apparent. Immunolocalization analyses demonstrated that SbAMT3;1 was present only in cells containing developing arbuscules.
Our results show that the SbAMT3;1 and SbAMT4 genes are expressed in root cortical cells, which makes them ready to accommodate arbuscules, a process of considerable importance in view of the short life span of arbuscules. Additionally, SbAMT3;1 might play an important role in N transfer during AM symbiosis.
O plantio direto de brócolis de cabeça única no inverno, sobre diferentes culturas de cobertura, implantadas em sistema de aléias de guandu, em rotação com milho verde no verão, sob manejo orgânico, ...foi objetivo deste estudo. O delineamento foi em blocos ao acaso, em parcelas sub-divididas em faixas, com dois pré-cultivos: Sorghum bicolor e consórcio (sorgo + Crotalaria juncea); faixas separadas pelas aléias (Cajanus cajan). O consórcio aportou maior biomassa (64,8 t ha-1 e 21,3 t ha-1; 49,2 t ha-1 e 14,9 t ha-1 ) que o sorgo (51,9 t ha-1 e 18,0 t ha-1 ; 40,5 e 12,5 t ha-1 matéria fresca e matéria seca) nos 1º e 2º ano (2013/2014). A produção de brócolis na palha do sorgo com poda do guandu foi de 7,81 t ha-1 e 4,72 t ha-1, e sem poda 6,55 t ha-1 e 3,17 t ha-1; na palha do coquetel foi maior, sendo com poda do guandu de 9,86 t ha-1 e 6,12 t ha-1, e sem poda 8,46 t ha-1 e 4,46 t ha-1 (2013/2014). O aporte de material orgânico oriundo dos resíduos das culturas anuais forneceu um total de 24,43 t ha-1 matéria seca (resíduos brócolis e milho verde + vegetação espontânea) no sistema produtivo. Das aléias de guandu que não foram podadas, colheu-se 581 kg ha-1 de feijão guandu seco e beneficiado. O emprego de adubos verdes em pré-cultivo, aliado a aleias de guandu, no plantio direto orgânico de brócolis rotacionado com milho-verde, melhora a fertilidade do solo e mantém a sustentabilidade do sistema de produção agroecológico.
An experiment was carried out to evaluate the response of sorghum stay-green quantitative trait locus (QTL) introgression lines under induced post-flowering drought stress. The QTL introgression was ...done in 2006 to 2008 from known stay-green lines to the locally adapted varieties through marker assisted backcrossing. The field experiment was carried out in 2009/2010 and involved two irrigation levels and 14 genotypes organized in a split plot design with three replications. Analysis of variance showed significant difference among the genotypes for all the measured nine morpho-physiological quantitative characters. Significant differences were also observed in leaf area, head exsertion, grain yield and hundred seed weight for irrigation indicating that the two irrigation levels were able to differentiate the genotypes for these characters. Genotype-by-irrigation interaction was significant only for head weight and 100 seed weight. In general, a yield reduction of up to 49% was observed in an induced post-flowering moisture deficit. Grain yield had strong positive correlation with head weight (r=0.66) and hundred seed weight (r=0.52) under conditions of moisture deficit. Most of the stay-green introgression lines included in this experiment maintained at least 25% of their green leaf area until maturity though some showed early leaf senescence, but there was no associated increase in grain yield. Possible reasons are discussed.
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