Monitoring the distribution of banana bunchy top virus in South Africa: a country-wide survey.

Banana bunchy top disease is the most devastating viral disease of bananas worldwide and is caused by banana bunchy top virus (BBTV). The disease is spread by the banana aphid Pentalonia nigronervosa Coquerel (Hemiptera: Aphididae) and through infected propagation material. In 2016, the virus was detected for the first time in an isolated area in the South Coast region of KwaZulu-Natal Province (KZN), South Africa. The aim of this study was to conduct surveys across all banana-producing regions in South Africa, viz. KwaZulu-Natal, Mpumalanga, and Limpopo provinces. Over 1700 plant and aphid samples were collected from commercial farms and rural households in the three provinces, and more-intense sampling was done in the affected KZN region. A BBTV-specific PCR targeting DNA-R (encoding the master replication initiation protein, M-Rep) was used to detect virus-infected samples, and amplicons of the expected size were sequenced. Comparative phylogenetic analysis showed that the South African BBTV isolates clustered within the Pacific Indian Oceans genomic group, which includes isolates from India and other regions in Africa, with a bootstrap value of 94%. To date, the virus has been identified only in the South Coast region of KwaZulu-Natal Province. Intense management strategies, including scouting, removal of infected plants, and control of aphids, have been implemented in areas where positive samples were identified to minimize the spread of the virus.

Full genome sequence of a chrysanthemum-infecting tomato spotted wilt virus isolate from Zimbabwe obtained by next-generation sequencing.

Tomato spotted wilt virus (TSWV) is an economically important pathogen of many crops worldwide. However, prior to this study, only one complete genome sequence of an African TSWV isolate was available in public databases. This limits genetic diversity and evolutionary studies of the pathogen on the continent. TSWV was detected in symptomatic Zimbabwean chrysanthemum plants using late-ral flow kits. The presence of the pathogen was subsequently confirmed by double antibody sandwich enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction (RT-PCR). Total RNAs for RT-PCR and next-generation sequencing (NGS) were extracted using an RNA extraction kit. NGS performed on an Illumina HiSeq platform was used to recover the full TSWV genome and analyzed by different software packages. The tripartite genome of the Zimbabwe TSWV isolate consisted of L, M and S RNAs of 8914, 4824 and 2968 nucleotides, respectively. This isolate shared highest protein and nucleotide sequence identities with the isolate LK-1 from neighboring South Africa. The Zimbabwe TSWV isolate was found to be a non-recombinant and non-resistance-breaking. This study provides the first full genome of TSWV from Zimbabwe. It also adds useful information towards understanding the evolution of the pathogen. Keywords: Africa; tospovirus; phylogenetic analysis; recombination; virus identification.

Zucchini shoestring virus: a distinct potyvirus in the papaya ringspot virus cluster.

Zucchini shoestring virus (ZSSV) has been proposed to be a putative potyvirus in the papaya ringspot virus (PRSV) cluster, based on the sequence similarity of its coat protein to those of related potyviruses. ZSSV has been associated with the outbreak of a damaging disease of baby marrow (Cucurbita pepo L.) that had been observed throughout the province of KwaZulu-Natal, in the Republic of South Africa (RSA). We report the genome sequence of ZSSV, determined by next-generation sequencing of total RNA extracted from an infected baby marrow (Cucurbita pepo L.). The ZSSV genome is 10,295 nucleotides long excluding the poly(A) tail and displays a typical potyvirus organization. Algerian watermelon mosaic virus (AWMV; EU410442.1) was identified as the closest relative of ZSSV, sharing the highest nucleotide sequence identity of 65.68%. The nucleotide and amino acid sequence identity values for each protein support the differentiation of ZSSV as a member of a distinct species in the genus Potyvirus. This taxonomic position was also confirmed using the Pairwise Sequence Comparison online tool from the National Center for Biotechnology Information. Phylogenetic analysis of the polyprotein coding sequence of ZSSV grouped ZSSV together with AWMV and Moroccan watermelon mosaic virus, but in different clusters. ZSSV is the second cucurbit-infecting virus in the PRSV cluster present in RSA.

Development of transgenic sweet potato with multiple virus resistance in South Africa (SA).

Multiple infections of Sweet potato feathery mottle virus (SPFMV), Sweet potato chlorotic stunt virus (SPCSV), Sweet potato virus G (SPVG) and Sweet potato mild mottle virus (SPMMV) cause a devastating synergistic disease complex of sweet potato (Ipomoea batatas Lam.) in KwaZulu-Natal, South Africa. In order to address the problem of multiple virus infections and synergism, this study aimed to develop transgenic sweet potato (cv. Blesbok) plants with broad virus resistance. Coat protein gene segments of SPFMV, SPCSV, SPVG and SPMMV were used to induce gene silencing in transgenic sweet potato. Transformation of apical tips of sweet potato cv. Blesbok was achieved by using Agrobacterium tumefaciens strain LBA4404 harboring the expression cassette. Polymerase chain reaction and Southern blot analyses showed integration of the transgenes occurred in six of the 24 putative transgenic plants and that all plants seemed to correspond to the same transformation event. The six transgenic plants were challenged by graft inoculation with SPFMV, SPCSV, SPVG and SPMMV-infected Ipomoea setosa Ker. Although virus presence was detected using nitrocellulose enzyme-linked immunosorbent assay, all transgenic plants displayed delayed and milder symptoms of chlorosis and mottling of lower leaves when compared to the untransformed control plants. These results warrant further investigation on resistance to virus infection under field conditions.

beta-adrenoceptor blockade and physical activity: cardiovascular and metabolic aspects.

This paper assesses mechanisms that may contribute to the higher incidence of increased muscle fatigue during exercise and reduced exercise performance as observed with selective compared with non-selective beta-adrenoceptor antagonists. Published data and the results obtained in 8 healthy subjects (mean age 23 years) studied before and after acute beta-adrenoceptor blockade with pindolol (nonselective, 10 mg) and metoprolol (beta 1-receptor selective, 100 mg) suggest that the differences in the cardiovascular and respiratory effects between the 2 types of antagonists are marginal and cannot explain the discrepancies concerning exercise perception and performance. Conversely, basic differences between the 2 types of antagonists were shown in different groups of hypertensive men (mean age 32 years) studied before and after 4 weeks of treatment with pindolol (15 mg), and with metoprolol (200 mg) and acebutolol (cardioselective, 500 mg), by single crossover technique. Whereas lipolysis was similarly inhibited by both selective and non-selective antagonists, hypoglycaemia occurred only under non-selective blockade. It apparently reflects the inhibition of glycogen breakdown; concomitant rises in plasma adrenaline and ACTH probably reflect counter-regulatory mechanisms.