TALK ABOUT EXOTICA PAPAYA

EXOTICA PAPAYA was a once popular papaya variety in Malaysia. Carica papaya L. or commonly known as papaya, is a major tropical crop consumed worldwide either as a vegetable or fresh fruit or processed products. In Malaysia, papaya was initially planted as a smallholder crop throughout the country. Eventually after 15 years of breeding and proper selection later a new variety named C. papaya L. var. Eksotika was released by the Malaysian Agricultural Research and Development Institute (MARDI) in 1987. This event changed the outlook of papaya planting from a smallholder crop to a plantation crop. Despite the blooming papaya business, the industry faced various disease issues that jeopardize its future. The most devastating was the papaya dieback disease, which affected approximately 800 hectares of plantation, destroyed approximately 1 million trees nationwide with total losses estimated at US$ 58 million. Even though Eksotika is a favored commercial variety with good eating and aesthetic quality fruit, its potential for more lucrative distant markets is tarnished with its short-shelf life fruits. Several strategies had been reported to address the challenges faced by Eksotika specifically against the dieback disease and the fruit’s short shelf-life. This review focuses on C. papaya L. var. Eksotika particularly on the strategies to address the challenges faced in order to sustain the economic value of this crop plant, which had contributed significantly to the Malaysian economy. This article in "Anim Agriculture Technology" I like to share and talk about the story of Malaysian Papaya Variety known as Exotica Papaya for all readers.

Accordant ti FAOSTAT (in 2017) reported that papaya fruit production in Malaysia was reduced nearly 40% while the export value declined up to 70% from 2003 to 2011. Papaya dieback disease was a significant reason contributing to these upsetting figures. At the beginning, there was ambiguity on the identity of the causal agent for this disease. Although it was first reported as Erwinia papayae  and later from MARDI confirmed the causal agent of papaya dieback disease in western parts of Malaysian peninsula was an Erwinia genus from the mallotivora species. Both species known of this Enterobacteriaceae family exhibited similar symptoms but isolates from infected papaya trees unveiled distinguishable biochemical tests positive for Erwinia mallotivora rather than to E. papayae. This was further supported by earlier observations made who reported that E. papayae was said to cause canker, however, in the advanced stage of papaya dieback as reported and there was no canker symptom observed. The mode of action of the Erwinia pathogen is through invading and colonizing the entire parts of a papaya plant including the shoot, leaf, bark, and fruit. Early symptoms of papaya dieback disease include yellowing and necrosis along leaf edges followed by water-soaked areas on the bases of leaf stalks, crowns and along the leaf mid-ribs. Subsequently, necrotic and water-soaked areas developed on stems and spread to the internal tissues, followed by secondary fungal infections associated with the septic parts. In some cases, blackened and greasy spot-on infection points were observed. Actually,  the progressive infection on the crown resulted in total disruption of the meristematic part of the papaya tree that bears the fruit. In the last infection stage, bending of water-soaked leaf stalks occurred leading to “die back” (aptly described the name of the disease), and the ultimate death of the tree. Until now, there is no effective way to control the disease once the pathogen gained entry into the plant.

Reported that the challenges of Eksotika like other crops in Malaysia, papaya industry faces various issues that jeopardize its future. There are numerous diseases and pests affecting papaya production, other than substandard quality fruits to be marketed inside or outside the country. The Eksotika Diseases later reported that a wide range of diseases had been documented for papaya varieties, whereby majority were due to pests (fruit flies, spider mite, and nematodes) aiming at the papaya foliage, fruits, and roots. Besides, microorganisms-related diseases were also reported such as papaya fruit spot papaya leaf curl, papaya mosaic, papaya powdery mildew,  papaya ring spot, fungal root rot in which later disease is the bacterial dieback or more commonly known as papaya dieback disease. An outbreak of papaya dieback disease was first identified in late 2003 near Batu Pahat, Johor (a state in southern Malaysian peninsula close-by Singapore) by the Johor State Department of Agriculture. Another devastating incident was later reported in Bidor, Perak (a state in the northern part of Malaysian peninsula close-by Thailand) in October 2004. By the end of 2006, the disease had spread to five other states on the west coast of the Malaysian peninsula namely Melaka, Negeri Sembilan, Pahang, Kedah, and Perlis. The outbreak affected ca. 800 hectare and resulted in the destruction of approximately 1 million trees nationwide. The damaged trees caused total fruit yield losses with estimated 200,000 metric tons, equivalent to US$ 58 million. Besides Eksotika, other varieties affected included Solo, Hong Kong, and Sekaki. FAOSTAT reported that papaya fruit production in Malaysia was reduced nearly 40% while the export value declined up to 70% from 2003 to 2011. Papaya dieback disease was a significant reason contributing to these upsetting figures. At the beginning, there was ambiguity on the identity of the causal agent for this disease. Although it was first reported as Erwinia papayae from MARDI confirmed the causal agent of papaya dieback disease in western parts of Malaysian peninsula was an Erwinia genus from the mallotivora species. Both species of this Enterobacteriaceae family exhibited similar symptoms but isolates from infected papaya trees unveiled distinguishable biochemical tests positive for Erwinia mallotivora rather than to E. papayae. This was further supported by earlier observations who reported that E. papayae was said to cause canker, however, in the advanced stage of papaya dieback as reported that there was no canker symptom observed. The mode of action of the Erwinia pathogen is through invading and colonizing the entire parts of a papaya plant including the shoot, leaf, bark, and fruit. Early symptoms of papaya dieback disease include yellowing and necrosis along leaf edges followed by water-soaked areas on the bases of leaf stalks, crowns and along the leaf mid-ribs. Subsequently, necrotic and water-soaked areas developed on stems and spread to the internal tissues, followed by secondary fungal infections associated with the septic parts. In some cases, blackened and greasy spot-on infection points were observed. Progressive infection on the crown resulted in total disruption of the meristematic part of the papaya tree that bears the fruit. In the last infection stage, bending of water-soaked leaf stalks occurred leading to “die back” (aptly described the name of the disease), and the ultimate death of the tree. Until now, there is no effective way to control the disease once the pathogen gained entry into the plant. Thanks....

By,

M Anem,

Putrajaya,

Malaysia.

(Febuary 2024).