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Mealybug wilt of pineapple (MWP) is the most important disease of pineapple worldwide. During the months of September and November 2020, pineapple production fields of the cultivar Hawaiiana and hybrid MD-2 in Satipo and Chanchamayo provinces of Peru, showed typical symptoms of MWP. Based on symptoms, the disease incidence level ranged between 70 and 90%. Symptomatic and asymptomatic foliar samples were collected and tested by RT-PCR using primers specific for pineapple mealybug wilt virus (PMWaV) 1, 2, and 3. Selected amplified fragments were sequenced and analyzed with bioinformatics tools. PMWaV-1, 2, and 3 were detected in symptomatic samples of both cultivars but not in asymptomatic samples. PMWaV-1 showed a nucleotide identity of 91.70% with PMWaV-1 from Thailand; PMWaV-2, 99.81% with PMWaV-2 from Thailand; and PMWaV-3, 99.09% with PMWaV-3 from Cuba. Mixed infections of PMWaV-1, 2, and 3 were also detected in both cultivars. To our knowledge, this is the first report of PMWaV-1, 2, and 3, associated with pineapple in Peru. [ABSTRACT FROM AUTHOR]

Pineapple is one of the most economically important fruits in tropical countries, particularly in Thailand. Canned pineapple is currently Thailand's main exported commodity to many countries, including the United States, Russia, Germany, Poland, and Japan. Fungal diseases are considered a permanent threat to fruits in the pre- and post-harvest stages, leading to considerable economic losses. Fungal disease is one of the primary causes of massive yield losses in pineapples around the world. Colletotrichum species are the most common fungal pathogens affecting different tropical fruits. Although there are many reports regarding Colletotrichum species associated with pineapple, they do not have molecular data to confirm species identification. However, the occurrence of Colletotrichum species on pineapple has not been reported in Thailand so far. In this study, we isolated and identified Colletotrichum fructicola on pineapple in northern Thailand and have proven its pathogenicity to the host. This is the first report of the occurrence of Colletotrichum in pineapple, based on morpho-molecular approaches. [ABSTRACT FROM AUTHOR]

Internal browning (IB) is a main problem of Queen pineapple during cold storage. The effects of exogenous salicylic acid (SA) or abscisic acid (ABA) on IB alleviation of the pineapple during cold storage were investigated. 'Sawi' pineapples were peduncle-infiltrated with 2 mM SA or 380 µM ABA for 3 d at 13°C followed storage at 13°C for 14 d. IB incidence and IB-related factors including lipid peroxidation, antioxidant capacity and antioxidant enzymes activities of the tissue adjacent to core were investigated after storage for 7 and 14 d followed by 2 d at room temperature (RT). Both SA and ABA treatments obviously alleviated IB development. ABA lowered TP content, MDA accumulation and the activities of LOX, PAL and PPO and induced POD activity. SA lowered PAL and PPO activity, delayed LOX activity and MDA increase, enhanced phenols, antioxidant activity and both antioxidant enzyme yields. Both ABA and SA peduncle infiltration alleviated IB incidence of Queen pineapple during cold storage. Although ABA could reduce the IB incidence better than SA, due to the efficiency of lower reactions of browning-related enzymes and lipid peroxidation, exogenous SA application might be a better choice for commercial use. Abbreviations: Total phenols (TP), Malondialdehyde (MDA), Lipoxygenase (LOX), Phenylalanine ammonia lyase (PAL), Polyphenol oxidase (PPO), Peroxidase (POD) and Internal browning (IB) [ABSTRACT FROM AUTHOR]