Disease control strategies for extending storage life of papaya (Carica papaya), cultivars 'Red Lady' and 'Rathna'

Abstract

Anthracnose (Colletotrichum gloeosporioides), stem-end rot (Lasiodiplodia theobromae) and Phomopsis rot (Phomopsis caricae-papayae) are major post-harvest diseases in papaya resulting in relatively high postharvest losses, up to 45%, in Sri Lanka. The current consumer preference is for tropical fruits free of synthetic pesticides. The objectives of the present investigation were to identify major post-harvest pathogens in papaya fruits, test in vitro fungitoxic effect of basil oil (Ocimum basillicum) and alum (sodium aluminium sulphate) on major fungal pathogens of papaya fruit and develop a relatively safe, disease control strategy. Alum (1% w/v) and basil oil (0.12-0.16% v/v) in a liquid bioassay, indicated fungistatic and fungicidal efficacy on C. gloeosporioides, L. theobromae and P. caricae-papayae isolated from "Red Lady" and "Rathna" cultivars of papaya. In vivo investigation of fruits of both papaya cultivars harvested from fruit plantations in Sri Lanka ("Red Lady"-Yatawarawatta plantation, Kurunegala, "Rathna" -CIC plantation, Kekirawa and the Agricultural farm, Polonnaruwa) at 25% maturity level indicated that papaya washed in 1% (w/v) alum and subsequently sprayed with an emulsion solution of 0.16% (v/v) basil oil and enclosed in styrofoam sleeves could be stored for 14 days at 12-14 o C. The visual quality rating (VQR) was high (11-13), shriveling and "green islands" were low on fruits with zero disease severity where results were statistically similar to 500 mg/L Bavistin treatment. Physicochemical properties assessed were unaffected by the treatments and were comparable to the controls washed only in water. The organoleptic properties were slightly low in fruits subjected to cold temperature compared to fruits subjected to ambient temperature. No residues of basil oil could be detected on fruit peel by gas chromatography at the end of the experimental period of 14 days. The treatment strategy developed could be adopted for sea shipment or temperature-regulated supermarket storage of papaya fruits where storage life could be lengthened up to 14 days.

Stem-end rot in major tropical and sub-tropical fruit species

“…Papaya cultivars, 'Rathna' and 'Red Lady', stored at 12-14 ˚C following treatment with 1% (w/v) alum (sodium aluminium sulphate) or 1% alum and 0.16% (v/v) basil oil and enclosed in styrofoam sleeves were found free of postharvest diseases including SER (Abeywickrama et al, 2012). No residues of basil oil could be detected on fruit peel by gas chromatography at the end of the experimental period of 14 days (Abeywickrama et al, 2012).…”

“…(Hine et al, 1965). Later certain other genera including Botryodiplodia (Hunter and Buddenhagen, 1972;Abeywickrama et al, 2012), Phomopsis and occasionally Fusarium were found in diseased fruits (Hunter and Buddenhagen 1972). A stemend disease of papaya (Carica papaya L.) was reported to be caused by Mycosphaerella sp., the perfect stage of Ascochyta caricae-papayae (Chau et al, 1979).…”

“…Similarly, another study involving fumigation treatment with thyme oil, clove oil and cinnamon oil vapors resulted in inhibition of Colletotrichum gloeosporioides and L. theobromae growth in vitro (Perumal et al, 2016). Papaya cultivars, 'Rathna' and 'Red Lady', stored at 12-14 ˚C following treatment with 1% (w/v) alum (sodium aluminium sulphate) or 1% alum and 0.16% (v/v) basil oil and enclosed in styrofoam sleeves were found free of postharvest diseases including SER (Abeywickrama et al, 2012). No residues of basil oil could be detected on fruit peel by gas chromatography at the end of the experimental period of 14 days (Abeywickrama et al, 2012).…”

Lasiodiplodia theobromae in Citrus Fruit (Diplodia Stem-End Rot)

“…bananas and guava in tropical and subtropical regions in the world (Smoot et al, 1971;Mascarenhas et al, 1995;Alvindia and Natsuaki, 2007;Hashem and Alamri, 2009;Abeywickrama et al, 2012). This postharvest decay can lead to significant economic losses, and the fungus can also cause preharvest diseases on some horticultural crops, such as mango tree dieback disease (Khanzada et al, 2004).…”

Control of Postharvest Crown Rot Disease in Cavendish Banana with Aluminium Sulfate and Vacuum Packaging

“…Alum at 1% (w/v) prevented mycelial growth of crown rot pathogen L. theobromae and papaya stem end rot pathogen Phomopsis caricaepapayae during in vitro assay (Abeywickrama et al, 2012). Bestoon (2012) epidermidis, E. coli, Klebsiella pneumonia) and the results showed that the 20% of alum was found to be Minimum Inhibitory.…”