Warm and cold events in the southeast Atlantic/southwest Indian Ocean region and potential impacts on circulation and rainfall over southern Africa

1998 ◽  
Vol 69 (1-2) ◽  
pp. 49-65 ◽  
Author(s):  
C. J. C. Reason
Keyword(s):  
Indian Ocean ◽  
Southern Africa ◽  
Indian Ocean Region ◽  
Southwest Indian Ocean ◽  
Ocean Region ◽  
Cold Events

Recurrent daily OLR patterns in the Southern Africa/Southwest Indian Ocean region, implications for South African rainfall and teleconnections

2008 ◽  
Vol 32 (4) ◽  
pp. 575-591 ◽  
Author(s):  
Nicolas Fauchereau ◽  
B. Pohl ◽  
C. J. C. Reason ◽  
M. Rouault ◽  
Y. Richard
Keyword(s):  
Indian Ocean ◽  
South African ◽  
Southern Africa ◽  
Indian Ocean Region ◽  
Southwest Indian Ocean ◽  
African Rainfall ◽  
Ocean Region

scholarly journals Genetic and Pathological Diversity Among Xanthomonas Strains Responsible for Bacterial Spot on Tomato and Pepper in the Southwest Indian Ocean Region

Plant Disease ◽  
2010 ◽  
Vol 94 (8) ◽  
pp. 993-999 ◽  
Author(s):  
A. A. Hamza ◽  
I. Robène-Soustrade ◽  
E. Jouen ◽  
L. Gagnevin ◽  
P. Lefeuvre ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Development Program ◽  
Housekeeping Genes ◽  
Agricultural Pests ◽  
Bacterial Spot ◽  
Indian Ocean Region ◽  
Southwest Indian Ocean ◽  
Synonymous Mutations ◽  
Strain Collection ◽  
Ocean Region

Bacterial spot of tomato and pepper, a major problem in tropical climates, can be caused by several Xanthomonas genospecies. We examined the genetic and pathological diversity of a collection of 72 strains from the southwest Indian Ocean region as part of a regional research and development program to update inventories of agricultural pests and pathogens. Xanthomonas euvesicatoria, X. perforans, X. gardneri, and X. vesicatoria were identified in our strain collection. The identification of strains at the species level was consistently achieved by amplified fragment length polymorphism (AFLP) and multilocus sequence analysis (MLSA). Overall, X. euvesicatoria was the species recovered prevalently. MLSA data based on four housekeeping genes identified two to three sequence types per genospecies. It suggested that sequence variations primarily consisted of synonymous mutations, although a recombination event spanning several hundred nucleotides was detected for some strains of X. euvesicatoria on the atpD gene coding for the F1-F0-ATPase β subunit. The pathogenicity of strains was consistent with data found in the literature. Some pathological variations were primarily observed among strains identified as X. euvesicatoria. This study provides the first ever comprehensive description of the status of Xanthomonas species that cause bacterial spot of tomato and pepper in the southwest Indian Ocean region.

scholarly journals First Report of Xanthomonas citri pv. citri-A Causing Asiatic Citrus Canker in Mayotte

Plant Disease ◽  
2013 ◽  
Vol 97 (7) ◽  
pp. 989-989
Author(s):  
J. Hoarau ◽  
C. Boyer ◽  
K. Vital ◽  
T. Chesneau ◽  
C. Vernière ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Sweet Orange ◽  
Citrus Canker ◽  
Negative Control ◽  
Sterile Water ◽  
Citrus Species ◽  
Indian Ocean Region ◽  
Southwest Indian Ocean ◽  
Mexican Lime ◽  
Ocean Region

Asiatic citrus canker, caused by Xanthomonas citri pv. citri, is a bacterial disease of major economic importance in tropical and subtropical citrus-producing areas. X. citri pv. citri pathotype A can cause severe infection in a wide range of citrus species and induces erumpent, callus-like lesions with water-soaked margins evolving to corky cankers and leading to premature fruit and leaf drop and twig dieback on susceptible/very susceptible cultivars. A chlorotic halo is typically visible around canker lesions on leaves and young fruit, but not on mature fruit and twigs. This quarantine organism can strongly impact both national and international citrus markets. Long distance dispersal is mainly through infected propagative material. Asiatic citrus canker occurs on most islands in the Southwest Indian Ocean region (Comoros, Mauritius, Reunion, Rodrigues, and Seychelles islands), but was not yet reported in Mayotte (EPPO-PQR available at http://www.eppo.int ). In May 2012, typical canker-like symptoms were observed on sweet orange (Citrus sinensis) groves on Mtsamboro islet and soon after on the main island of Mayotte, mostly on sweet oranges, but also on Tahiti limes (C. latifolia) and mandarins (C. reticulata). Eighty-one Xanthomonas-like strains were isolated using KC semi-selective medium (4) from disease samples collected from both commercial groves and nurseries on different Citrus species located all over the island. Sixteen Xanthomonas-like isolates were tentatively identified as X. citri pv. citri based on a specific PCR assay with 4/7 primers (3). All strains but the negative control, sterile water, produced an amplicon of the expected size similar to X. citri pv. citri strain IAPAR 306 used as positive control. Multilocus sequence analysis targeting six housekeeping genes (atpD, dnaK, efp, gltA, gyrB, and lepA) (1,2) fully identified three strains from Mayotte (LJ225-3, LJ228-1, and LJ229-11) as X. citri pv. citri (and not other xanthomonad pathovars pathogenic to citrus or host range-restricted pathotypes of pathovar citri), and more specifically as sequence type ST2 composed of pathotype A strains of X. citri pv. citri (2) (including all strains from the Southwest Indian Ocean region). Eight strains were inoculated by a detached leaf assay (2) to Mexican lime SRA 140 (C. aurantifolia), Tahiti lime SRA 58, sweet orange cv. Washington Navel, alemow SRA 779 (C. macrophylla), and tangor cv. Ortanique (C. reticulata × C. sinensis) and developed typical erumpent, callus-like tissue at wound sites for all Citrus species, fulfilling Koch's postulates. Xanthomonas-like yellow colonies were reisolated from symptoms produced by the eight strains inoculated on Mexican lime. Boiled bacterial suspensions were assayed by PCR with 4/7 primers (3) and produced the expected 468-bp amplicon in contrast with the negative control (sterile water). No lesions developed on the negative control consisting of inoculations by 10 mM tris buffer (pH 7.2). Citrus canker-free nurseries and grove sanitation should be implemented for decreasing the prevalence of Asiatic canker in this island territory. References: (1) N. F. Almeida et al. Phytopathology 100:208, 2010. (2) L. Bui Thi Ngoc et al. Int. J. Syst. Evol. Microbiol. 60:515, 2010. (3) J. S. Hartung et al. Phytopathology 86:95, 1996. (4) O. Pruvost et al. J. Appl. Microbiol. 99:803, 2005.

scholarly journals First Report of Xanthomonas citri pv. citri Pathotype A Causing Asiatic Citrus Canker in Grande Comore and Anjouan

Plant Disease ◽  
2014 ◽  
Vol 98 (12) ◽  
pp. 1739-1739
Author(s):  
P. Grygiel ◽  
A. Seny-Couty ◽  
F. Abdou Hassani ◽  
C. Boyer ◽  
K. Boyer ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Sweet Orange ◽  
Citrus Canker ◽  
Negative Control ◽  
Citrus Species ◽  
Indian Ocean Region ◽  
Southwest Indian Ocean ◽  
Mexican Lime ◽  
Ocean Region ◽  
Grande Comore

The causal agent of Asiatic citrus canker, Xanthomonas citri pv. citri, is a bacterium of major economic importance in tropical and subtropical citrus-producing areas. X. citri pv. citri pathotype A can cause severe infection in a wide range of citrus species and induces erumpent, callus-like lesions with water-soaked margins evolving to corky cankers and leading to premature fruit, leaf drop, and twig dieback on susceptible cultivars. This quarantine organism can strongly impact citrus markets so it has consequently been subjected to eradication efforts and international quarantine regulations. Asiatic citrus canker occurs on most islands in the Southwest Indian Ocean region including the Mascarene and Seychelles archipelagos. In the Comoros archipelago, the disease was observed for the first time in Mohéli island in 1966 (2), but had not yet been reported in neighboring islands, Grande Comore and Anjouan. In September 2013, leaves of key lime (Citrus aurantifolia) and sweet orange (C. sinensis) showing symptoms of citrus canker were collected from Anjouan, Grande Comore, and Mohéli. Nine Xanthomonas-like strains (three from each of the three islands) were isolated using KC semi-selective medium (5) from diseased samples (LK126-3, LK127-7, LK128-2, LK131-10, LK137-1, LK141-3, LK144-5, LK145-5, LK146-2). Based on a specific PCR assay with 4/7 primers (4), all Xanthomonas-like strains were tentatively identified as X. citri pv. citri. All strains produced a 468-bp amplicon similar to X. citri pv. citri strain IAPAR 306 used as a positive control. Negative control reactions with sterile tris buffer did not produce amplicons. Multilocus sequence analysis (MLSA) targeting six housekeeping genes (atpD, dnaK, efp, gltA, gyrB, and lepA) (1,3) fully identified all strains from the Comoros as X. citri pv. citri. More specifically, eight strains were identified as sequence type ST2 composed of pathotype A strains of X. citri pv. citri (3) (including all strains from the Southwest Indian Ocean region) while one of them (LK141-3 from Mohéli) was identified as a new sequence type based on a non-synonymous single nucleotide polymorphism in gyrB (accession KJ941208). All strains were inoculated by a detached leaf assay (3) onto Mexican lime SRA 140 (C. aurantifolia), Tahiti lime SRA 58 (C. latifolia), sweet orange New Hall Navel SRA 343 (C. sinensis), grapefruit Henderson SRA 336 (C. paradisi), and Ortanique tangor SRA 110 (C. reticulata × C. sinensis). All citrus species inoculated produced typical erumpent, callus-like tissue at wound sites. Xanthomonas-like yellow colonies were re-isolated from lesions produced on Mexican lime. Boiled bacterial suspensions were assayed by PCR with 4/7 primers (4) and produced the expected amplicon, fulfilling Koch's postulates. No lesions developed on the negative control consisting of inoculations with sterile tris buffer. This is the first report of X. citri pv. citri-A causing Asiatic citrus canker in Grande Comore and Anjouan islands confirming the wide distribution of the pathogen in Southwest Indian Ocean islands. Canker-free nurseries and grove sanitation should be implemented to decrease the prevalence of Asiatic canker in the Comoros. References: (1) N. F. Almeida et al. Phytopathology 100:208, 2010. (2) J. Brun. Fruits 26:533, 1971. (3) L. Bui Thi Ngoc et al. Int. J. Syst. Evol. Microbiol. 60:515, 2010. (4) J. S. Hartung et al. Phytopathology 86:95, 1996. (5) O. Pruvost et al. J. Appl. Microbiol. 99:803, 2005.

A Contest of Status and Legitimacy in the Indian Ocean

2018 ◽  
Author(s):  
David Brewster
Keyword(s):  
Indian Ocean ◽  
International System ◽  
Special Role ◽  
Indian Ocean Region ◽  
Major Powers ◽  
Threat Perceptions ◽  
Ocean Region ◽  
The Status ◽  
The Indian Ocean ◽  
The Asymmetry

This chapter examines Indian and Chinese perspectives of each other as major powers and their respective roles in the Indian Ocean. It focuses on the following elements: (a) China’s strategic imperatives in the Indian Ocean Region, (b) India’s views on its special role in the Indian Ocean and the legitimacy of the presence of other powers, (c) China’s strategic vulnerabilities in the Indian Ocean and India’s wish to leverage those vulnerabilities, (d) the asymmetry in Indian and Chinese threat perceptions, and (d) Chinese perspectives of the status of India in the international system and India’s claims to a special role in the Indian Ocean. The chapter concludes that even if China were to take a more transparent approach to its activities, significant differences in perceptions of threat and over status and legitimacy will produce a highly competitive dynamic between them in the maritime domain.

scholarly journals Circulation pattern controls of wet days and dry days in Free State, South Africa

2021 ◽  
Author(s):  
Chibuike Chiedozie Ibebuchi
Keyword(s):  
South Africa ◽  
Indian Ocean ◽  
Atmospheric Circulation ◽  
Southern Africa ◽  
Austral Summer ◽  
Free State ◽  
Austral Spring ◽  
Study Region ◽  
Southwest Indian Ocean ◽  
South Indian

AbstractAtmospheric circulation is a vital process in the transport of heat, moisture, and pollutants around the globe. The variability of rainfall depends to some extent on the atmospheric circulation. This paper investigates synoptic situations in southern Africa that can be associated with wet days and dry days in Free State, South Africa, in addition to the underlying dynamics. Principal component analysis was applied to the T-mode matrix (variable is time series and observation is grid points at which the field was observed) of daily mean sea level pressure field from 1979 to 2018 in classifying the circulation patterns in southern Africa. 18 circulation types (CTs) were classified in the study region. From the linkage of the CTs to the observed rainfall data, from 11 stations in Free State, it was found that dominant austral winter and late austral autumn CTs have a higher probability of being associated with dry days in Free State. Dominant austral summer and late austral spring CTs were found to have a higher probability of being associated with wet days in Free State. Cyclonic/anti-cyclonic activity over the southwest Indian Ocean, explained to a good extent, the inter-seasonal variability of rainfall in Free State. The synoptic state associated with a stronger anti-cyclonic circulation at the western branch of the South Indian Ocean high-pressure, during austral summer, leading to enhanced low-level moisture transport by southeast winds was found to have the highest probability of being associated with above-average rainfall in most regions in Free State. On the other hand, the synoptic state associated with enhanced transport of cold dry air, by the extratropical westerlies, was found to have the highest probability of being associated with (winter) dryness in Free State.

Heat and freshwater changes in the Indian Ocean region

2021 ◽  
Author(s):  
Caroline C. Ummenhofer ◽  
Sujata A. Murty ◽  
Janet Sprintall ◽  
Tong Lee ◽  
Nerilie J. Abram
Keyword(s):  
Indian Ocean ◽  
Indian Ocean Region ◽  
Ocean Region ◽  
The Indian Ocean

scholarly journals Spatiotemporal Evolution and Determinant Factors of the Intra-Regional Trade Community Structures of the Indian Ocean Region

2021 ◽  
Vol 10 (4) ◽  
pp. 214
Author(s):  
Lihua Yuan ◽  
Xiaoqiang Chen ◽  
Changqing Song ◽  
Danping Cao ◽  
Hong Yi
Keyword(s):  
Indian Ocean ◽  
Explanatory Power ◽  
Community Structures ◽  
Indian Ocean Region ◽  
Spatiotemporal Evolution ◽  
Regional Trade ◽  
Determinant Factors ◽  
Ocean Region ◽  
The Indian Ocean ◽  
The Impact

The Indian Ocean Region (IOR) has become one of the main economic forces globally, and countries within the IOR have attempted to promote their intra-regional trade. This study investigates the spatiotemporal evolution of the community structures of the intra-regional trade and the impact of determinant factors on the formation of trade community structures of the IOR from 1996 to 2017 using the methods of social network analysis. Trade communities are groups of countries with measurably denser intra-trade ties but with extra-trade ties that are measurably sparser among different communities. The results show that the extent of trade integration and the trade community structures of the IOR changed from strengthening between 1996 and 2014 to weakening between 2015 and 2017. The largest explanatory power of the formation of the IOR trade community structures was the IOR countries’ economic size, indicating that market remained the strongest driver. The second-largest explanatory power was geographical proximity, suggesting that countries within the IOR engaged in intra-regional trade still tended to select geographically proximate trading partners. The third- and the fourth-largest were common civilization and regional organizational memberships, respectively. This indicates that sharing a common civilization and constructing intra-regional institutional arrangements (especially open trade policies) helped the countries within the IOR strengthen their trade communities.

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