Witches' broom (WB), associated with the presence of 'Candidatus Phytoplasma aurantifolia', is one of the most serious diseases of acid lime. This study determined incidence, distribution, and ...development of the disease, and morphological changes in leaves and branches of affected host plants. Survey in different parts of Oman showed that WB occurs in most regions in the country, where 108 out of 158 (68%) surveyed farms were found to have diseased trees. A survey of 6,926 acid lime trees showed that severity of WB was positively related (r = 0.948; P<0.01) to tree age. The mean percentage of symptomatic branches was 1% in 3-year-old trees compared to 63% in 12-year-old trees. To further characterize morphological changes in WB-affected limes, apical stems (40 cm long) were collected from three infected trees during the autumn of 2009 and spring of 2010. Increases in the numbers of leaves (1,208%), numbers of branches (309%) and total length of branches (712%) were recorded for symptomatic branches relative to non-symptomatic branches. In the spring of 2009 these respective increases were 159%, 243% and 121%. Overall area of leaves in the symptomatic branches was 81% less than for non-symptomatic branches in the autumn of 2009 and 34% less in the spring of 2010. This study is the first to characterize morphological changes in leaves and branches of acid lime affected by WB.
In Brazil, plants of
Thunbergia erecta
were observed showing symptoms of little leaf, yellowing and stunting typical of phytoplasma infection. Using PCR, a phytoplasma was identified in symptomatic ...plants, and sequence analysis showed that the phytoplasma shares a 99.3 % sequence identity with ‘
Candidatus
phytoplasma hispanicum’ and is a strain related to this species. To our knowledge, this if the first time a phytoplasma had been detected in
T. erecta
and within the Acanthaceae family.
Complex multi-trophic interactions in vectorborne diseases limit our understanding and ability to predict outbreaks. Arthropod-vectored pathogens are especially problematic, with the potential for ...novel interspecific interactions during invasions. Variations and novelties in plant–arthropod–pathogen triumvirates present significant threats to global food security. We examined aspects of a phytoplasma pathogen of citrus across two continents. ‘Candidatus Phytoplasma aurantifolia’ causes Witches' Broom Disease of Lime (WBDL) and has devastated citrus production in the Middle East. A variant of this phytoplasma currently displays asymptomatic or ‘silent’ infections in Brazil. We first studied vector capacity and fitness impacts of the pathogen on its vectors. The potential for co-occurring weed species to act as pathogen reservoirs was analysed and key transmission periods in the year were also studied. We demonstrate that two invasive hemipteran insects—Diaphorina citri and Hishimonus phycitis—can vector the phytoplasma. Feeding on phytoplasma-infected hosts greatly increased reproduction of its invasive vector D. citri both in Oman and Brazil; suggesting that increased fitness of invasive insect vectors thereby further increases the pathogen's capacity to spread. Based on our findings, this is a robust system for studying the effects of invasions on vectorborne diseases and highlights concerns about its spread to warmer, drier regions of Brazil.
The cultivation of pitaya has been recently established in several regions of the world, there is a lack of information on its management, especially regarding the control of diseases and pests. In ...places where pitaya is grown around the world, symptoms such as mosaic and mottling caused by simple or mixed viral infections have been reported. In Brazil, similar symptoms have also been observed, but the etiology of the disease has often not been investigated. This study aimed to detect and identify the virus species that infect pitaya in Brazil using RT‒PCR and molecular analysis of the coat protein (CP) gene of the viruses. A total of 212 samples of cladodes with suspected symptoms of viral disease were collected from different regions of Brazil and analysed. Four species of potexviruses were detected, cactus virus X (CVX), pitaya virus X (PiVX), zygocactus virus X (ZyVX) and schlumbergera virus X (SchVX), which appeared in single infections (35%) and mixed infections (65%). In the cases of mixed infection, two and/or three species of potexviruses were identified in the same plant. The CVX isolates were divided into two groups due to the deletion of 9 nucleotides at position 41 (5' → 3′) of the CP gene in one of them. This is the first study conducted on the viruses that infect pitaya in Brazil, showing the need to develop control measures that ensure productivity and profitability of pitaya crops in the country.
•The occurrence of four potexviruses species: CVX, PiVX, ZyVX and SchVX were detected in Brazilian orchard.•The symptoms were stronger in mixed infections, including rings in the cladodes.•The occurrence of potexviruses indicated that there must be an intensive movement of pitaya seedlings between producers.•The data obtained suggests that the production of healthy seedlings would be fundamental to in pitaya cultivation.
Com o objetivo de avaliar a produtividade da cúrcuma em função da época e densidade de plantio, este experimento foi instalado no período de outubro de 1994 a julho de 1995, em campo, na Universidade ...Federal de Lavras, no município de Lavras-MG. Foram avaliados os fatores épocas de plantio (20/out, 20/nov, 20/dez e 20/jan) e espaçamento entre plantas na linha de plantio (0,20; 0,35 e 0,50m), sob delineamento de blocos ao acaso, em parcelas sub-divididas, com três repetições. A produção de rizomas por planta e por área foram influenciados significativamente pela interação dos fatores avaliados. Maiores produtividades por planta (673,13g) e por área (24.678,82kg ha-1) foram obtidas nos plantios de 20 de novembro e espaçamentos entre plantas, respectivamente, de 0,36 e 0,30m.With the objective of evaluating the turmeric yield in function of time and plantation density, this experiment was installed in the period of october of 1994 to July of 1995, in field, at Universidade Federal de Lavras, in the city of Lavras-MG. The factors appraised were plantation times (20th/oct, 20th/nov, 20th/dec and 20th/jan) and spacing among plants in the plantation line (0.20; 0.35 and 0.50m). The experimental design used was randomized blocks, in split plot, with three replications. The production of rhizomes per plant and per area were significantly influenced by the interaction of the appraised factors. Higher production per plant (673.13g) and per area (24,678.82 kg ha-1) were obtained in the 20th/november planting and spacings among plants, respectively, of 0.36 and 0.30m.
Com o objetivo de avaliar a produtividade da cúrcuma em função da época e densidade de plantio, este experimento foi instalado no período de outubro de 1994 a julho de 1995, em campo, na Universidade ...Federal de Lavras, no município de Lavras-MG. Foram avaliados os fatores épocas de plantio (20/out, 20/nov, 20/dez e 20/jan) e espaçamento entre plantas na linha de plantio (0,20; 0,35 e 0,50m), sob delineamento de blocos ao acaso, em parcelas sub-divididas, com três repetições. A produção de rizomas por planta e por área foram influenciados significativamente pela interação dos fatores avaliados. Maiores produtividades por planta (673,13g) e por área (24.678,82kg ha-1) foram obtidas nos plantios de 20 de novembro e espaçamentos entre plantas, respectivamente, de 0,36 e 0,30m.
With the objective of evaluating the turmeric yield in function of time and plantation density, this experiment was installed in the period of october of 1994 to July of 1995, in field, at Universidade Federal de Lavras, in the city of Lavras-MG. The factors appraised were plantation times (20th/oct, 20th/nov, 20th/dec and 20th/jan) and spacing among plants in the plantation line (0.20; 0.35 and 0.50m). The experimental design used was randomized blocks, in split plot, with three replications. The production of rhizomes per plant and per area were significantly influenced by the interaction of the appraised factors. Higher production per plant (673.13g) and per area (24,678.82 kg ha-1) were obtained in the 20th/november planting and spacings among plants, respectively, of 0.36 and 0.30m.
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