Strategies for vegetative propagation and viral cleaning of a miniature ornamental pineapple hybrid

This study assessed and compared different methods for vegetative propagation of a miniature ornamental pineapple hybrid (ORN-MUT), seeking to determine the best method for production of plantlets, as well as for removal of the PMWaV viral complex from plants cultured in vitro, for production of healthy parent plants. Pineapple wilt is a disease that can cause large economic and is caused by a viral complex called Pineapple mealybug wilt-associated virus (PMWaV). For this, four propagation methods were evaluated (conventional, stem sectioning, micropropagation and etiolation of nodal segments). The time necessary for each method and the number of plants formed were assessed. Stem tips (0.5 mm) were cultured and indexed for three PMWaV types. Conventional propagation produced 17 plantlets per plant in 566 days, stem sectioning produced 2.3 plantlets per stem in 591 days, while the conventional micropropagation technique produced 1,284 plants after four subcultures in 778 days. Stems etiolated for 60 days showed peak production in the second subculture, with 1,224 plants. This method required 883 days to obtain plants with ideal size for transplantation to the field. In turn, stems etiolated for 120 days produced 935 plants at the end of four subcultures, with peak output in the third subculture, in which the plants could be cultivated in the field after 943 days. Conventional micropropagation and etiolation for 60 days were the best methods for production of plantlets of the ORN-MUT hybrid. The results of this work showed that the cultivation of shoot tips is an efficient strategy to remove the PMWaV complex and obtain healthy mother plants and can be a useful tool for other varieties of pineapple.

Prevalence of Dysmicoccus brevipes (Cockerell, 1893) (Hemiptera: Pseudococcidae) in MD2 pineapple crop areas in Colombia

ABSTRACT Pineapple mealybug wilt has been reported as one of the most important diseases affecting pineapple crops worldwide. This study aimed to determine the prevalence of mealybugs associated with two agroclimatic zones of pineapple production in the department of Valle del Cauca, Colombia. The survey was conducted in the upper (Dagua, Restrepo, La Cumbre and Vijes) and lower (Buga and Palmira) land zones. A total of 75 MD2 pineapple plots in different development growth stages were evaluated. The mealybugs were recorded mainly in the upper land zone, with a prevalence of 32 %. Concerning the plots growth stages, the highest prevalence was observed in second-cycle plots (13.3 %), followed by third-cycle ones, including abandoned plots (9.3 %), and first-cycle plots (6.7 %), which were associated with the use of pesticides. Dysmicoccus brevipes was the only mealybug species (Pseudococcidae) found on pineapples in the study area.

Bromelia pinguin (wild pineapple).

Bromelia pinguin is a large, perennial bromeliad with spikey fronds that grow up to two metres long. It often grows in dense colonies. It is native to the Neotropical Region but has been introduced as an ornamental to Florida, Hawaii and other Caribbean islands as well as India and Sri Lanka. Though some sources consider it native to Cuba, it is also recorded as invasive, where it is invading forests and savannahs, displacing native vegetation and providing a niche for small invasive mammals. It is also an alternative host to Pineapple mealybug wilt-associated virus 2 (PMWaV-2), which threatens commercial pineapple farming in Cuba.

Molecular characterisation of ampeloviruses associated with mealybug wilt of pineapple disease in Ghana

Background: Mealybug wilt of pineapple (MWP) is the most destructive viral disease of pineapple worldwide. The disease is caused by pineapple mealybug wilt-associated virus (PMWaV), a member of the family Closteroviridae and the genus Ampelovirus, and transmitted by mealybugs. Methods: In order to understand the association between closteroviruses and MWP in Ghana, 24 pineapple plant samples showing typical symptoms of MWP were collected during a survey of the Central Region in 2019. Three quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assays with PMWaV species specific primers were performed to amplify the heatshock protein 70 gene (HSP70) of PMWaV-1,-2 and -3 in the pineapple samples. Purified qRT-PCR products of thirteen isolates which consist of PMWaV-1 (7 isolates), PMWaV-2 (4 isolates) and PMWaV-3 (2 isolates) were sequenced in both directions. Sequence and phylogenetic analyses were then conducted.Results: Three different species of Ampelovirus namely PMWaV-1, PMWaV-2, and PMWaV-3, were detected from the plant samples, with abundance of mixed infections. Sixteen out of the 24 samples (66.7%) were infected with at least one of the three species of Ampelovirus identified. PMWaV-2 had the highest infection rate of 62.5% across the districts; this was followed by PMWaV-1 and PMWaV-3 with infection rates of 33.3% and 8.3% respectively. Purified qRT-PCR products of thirteen isolates which consist of PMWaV-1 (7 isolates), PMWaV-2 (4 isolates) and PMWaV-3 (2 isolates) were sequenced in both directions. Sequence comparison using BlastN showed that all the seven sequences of the Ghanaian PMWaV-1 isolates (GenBank Accession Nos. MN427634 - MN427639 and MN399973) shared 95.2% to 99.7% nucleotide identity with each other and 95.2-100% with sequences of isolates previously published in GenBank. The four sequences of the Ghanaian PMWaV-2 isolates (GenBank Accession Nos. MN427642 - MN427645) shared nucleotide identity of 98.9–100% with each other and 98.2-100% nucleotide identity with sequences of isolates previously published in GenBank. Also, the two sequences of the Ghanaian PMWaV-3 isolates (GenBank Accession Nos. MN427640 and MN427641) shared 98.3% nucleotide identity to each other and 97.5- 99.3% nucleotide identity with sequences of isolates previously published in GenBank. Phylogenetic analyses of the nucleotide sequences of HSP70 gene of the 13 Ghanaian isolates and 24 sequences previously published in GenBank, clustered the PMWaV-1, PMWaV-2 and PMWaV-3 isolates into three distinct genetic groups with > 95% bootstrap support. Conclusion: The present study shows for the first time the occurrence of PMWaV-1, PMWaV-2 and PMWaV-3 in Ghana pineapple fields as well as in Africa.