Incidence of Citrus leprosis virus C and Orchid fleck dichorhavirus Citrus Strain in Mites of the Genus Brevipalpus in Mexico.

The incidences of Citrus leprosis virus C (CiLV-C) and Orchid fleck dichorhavirus Citrus strain (OFV-citrus) were determined in field populations of Brevipalpus mites from 15 citrus-producing states in Mexico. Mites were collected from orange, grapefruit, mandarin, lime, and sweet lime orchards. Brevipalpus yothersi (Baker) (Trombidiformes: Tenuipalpidae) was the most abundant species followed by Brevipalpus californicus (Banks) (Trombidiformes: Tenuipalpidae), which confirmed previous reports. The viruses CiLV-C and OFV-citrus were found in both mite species. The incidence of CiLV-C, OFV-citrus and both viruses simultaneously (CiLV-C and OFV-citrus) was 17.2, 10.3, and 3.4% (n = 116) for B. yothersi, and 12.5, 20.8, and 4.1% (n = 24) for B. californicus, respectively. No significant difference was found when the incidence of these viruses was compared between both mite species. The importance of our results in relation to the epidemiology of leprosis is discussed.

Transmission of Citrus leprosis virus C by the Mite, Brevipalpus yothersi (Acari: Tenuipalpidae), on Four Species of Citrus.

Transmission of the virus, Citrus leprosis virus C (CiLV-C) (Cilevirus) by Brevipalpus yothersi Baker, on different citrus species was evaluated under greenhouse conditions. First, the relationship between acquisition access periods (AAPs; 1, 12, 24, 36, and 48 h) and virus concentration in mites was determined. Second, the ability of B. yothersi to transmit CiLV-C to orange, mandarin, grapefruit, and lime trees was measured. We then assessed the establishment of mites on the different citrus species as measured by their population increase on each species. We found no relationship between AAPs and virus load in mites. The virus was found in all mites tested but there was no difference in virus quantities among the treatments. We selected an AAP of 24 h for the transmission experiment. Brevipalpus yothersi transmitted the virus to all citrus species evaluated, but susceptibility was different. The number of infected leaves was greater on orange and mandarin compared with grapefruit and lime. Furthermore, populations of B. yothersi successfully established on orange and mandarin, but not on grapefruit and lime trees. The implications of our results in the virus-mite-citrus plant relationship are discussed.

The Avocado Sunblotch Viroid: An Invisible Foe of Avocado.

This review collects information about the history of avocado and the economically important disease, avocado sunblotch, caused by the avocado sunblotch viroid (ASBVd). Sunblotch symptoms are variable, but the most common in fruits are irregular sunken areas of white, yellow, or reddish color. On severely affected fruits, the sunken areas may become necrotic. ASBVd (type species Avocado sunblotch viroid, family Avsunviroidae) replicates and accumulates in the chloroplast, and it is the smallest plant pathogen. This pathogen is a circular single-stranded RNA of 246-251 nucleotides. ASBVd has a restricted host range and only few plant species of the family Lauraceae have been confirmed experimentally as additional hosts. The most reliable method to detect ASBVd in the field is to identify symptomatic fruits, complemented in the laboratory with reliable and sensitive molecular techniques to identify infected but asymptomatic trees. This pathogen is widely distributed in most avocado-producing areas and causes significant reductions in yield and fruit quality. Infected asymptomatic trees play an important role in the epidemiology of this disease, and avocado nurseries need to be certified to ensure they provide pathogen-free avocado material. Although there is no cure for infected trees, sanitation practices may have a significant impact on avoiding the spread of this pathogen.

Pectobacterium carotovorum subsp. brasiliense Causes Soft Rot and Death of Neobuxbaumia tetetzo in Zapotitlan Salinas Valley, Puebla, Mexico.

Neobuxbaumia tetetzo (Coulter) Backeberg (tetecho) is a columnar cactus endemic to Mexico. Tetecho plants, flowers, fruits, and seeds play an important role in the semiarid ecosystem, as they serve as a refuge and food for insects, bats, and birds, and are widely used by ethnic groups since pre-Hispanic times. Tetecho is affected by a soft rot that damages the whole plant and causes its fall and disintegration. Eight bacterial colonies of similar morphology were isolated from plants showing soft rot and inoculated in healthy tetecho plants, reproducing typical symptoms of soft rot 9 days after inoculation. Ten representative isolates were selected for phenotypic and genetic identification using 16s rDNA, IGS 16S-23S rDNA, and rpoS genes and for pathogenicity tests on several members of the cactus family and other plants. Based on the results, these bacterial isolates were identified as Pectobacterium carotovorum subsp. brasiliense. Inoculation of this bacteria caused soft rot in different cacti, fruits, leaves, and roots of other plants. This is the first report of the subspecies brasiliense of P. carotovorum causing soft rot and death in cacti in the world and the first report of this subspecies in Mexico.