Pathogenic Variability of the Jackfruit-Bronzing Bacterium Pantoea stewartii Subspecies stewartii Infection to Jackfruit Varieties and Its Pivotal Plant Hosts in Malaysia

Abstract

Infection with Pantoea stewartii subspecies stewartii, which causes jackfruit-bronzing disease, is a huge problem faced by the jackfruit industry in Malaysia. This study was carried out to assess the disease ratings and aggressiveness performance of 28 Pantoea stewartii subspecies stewartii isolated from jackfruit-bronzing diseased jackfruits from four collection areas (Jenderam in Selangor State, Maran and Muadzam Shah in Pahang State, and Ipoh in Perak State) in Peninsular Malaysia, inoculated into jackfruit varieties (Tekam Yellow J33, Hong J34 and Subang Chap Boy J39), the sweetcorn variety, Mas Madu (two-week-old seedlings and nine-week-old seedlings), the cucumber variety, Rocky, and the pineapple variety, MD2. The results revealed that Pantoea stewartii subspecies stewartii produced symptoms upon all inoculations in the pathogenicity testing, thus fulfilling Koch’s postulates, except in the case of J39 and sweetcorn (two-week-old seedlings). No disease symptoms (disease rating 0) were observed in J39 and sweetcorn (two-week-old seedlings) within 14 days post-inoculation (14 dpi). The disease progression (based on disease ratings) proved that the jackfruit variety J39 was the most resistant, whereas J33 and J34 were susceptible to jackfruit-bronzing disease. The disease ratings of the 14-dpi period revealed a variability of disease progression among the 28 bacterial isolates, where the isolate JEN-14 had the fastest and highest disease ratings when inoculated into J33, J34, nine-week-old sweetcorn seedlings, cucumber, and pineapple. Likewise, the AUDPC value, based on disease rating, across the 28 isolates indicated that JEN-14 is the most aggressive and significant of the isolates (J33, J34, nine-week-old sweetcorn seedlings, cucumber, and cucumber pineapple inoculation; p < 0.05). Even though isolates from Jenderam (other than JEN-14) and Maran had better disease ratings and the area under the disease progress curve (AUDPC) values than isolates from Muadzam Shah and Ipoh, no significant differences were found among the isolates (p < 0.05). Based on our findings, we identified the isolate JEN-14 as the best potential candidate to assist in jackfruit-bronzing disease resistance breeding in the future. Last but not least, the methods, disease ratings, and variations of the aggressiveness profiles among the isolates from this study may be beneficial and significant by providing disease-rating references and appropriate screening approaches when selecting the most appropriately aggressive isolates for evaluating the defense response in the disease resistance breeding program.

Pantoea stewartii subsp. stewartii, the causative agent of Thai jackfruit’s bronzing disease and its possible host range in Vietnam

“…4D). No black spots appeared, as described by Abidin (Abidin et al 2021), while the pulbof cv. Labang (Fig.…”

“…Other popular fruits were coconut, pineapple, pomelo, guava, and longan (Vo 2023a), as well as near durian and mango orchards, so testing for possible cross-infection was required. In addition, Pss caused severe losses in maize (Scala et al 2023), and could infect cucumber, corn, and pineapple (Abidin et al 2021). This study used the common Pss strain, HCM09, for pathogenicity tests with jackfruit varieties, fruits, and crops in vitro and under greenhouse conditions.…”

“…A pathogenicity test on Thai jackfruit was conducted using the method described by Abidin (2021). Bronzing symptoms were assessed daily for up to 2 weeks of inoculation.…”

“…The phenotypic characterization of each isolate that produced typical disease symptoms was determined via colony morphology, pigmentation, and biochemical testing according to Gapasin (2014) and Abidin (2021). A homogenous suspension of test organism with 10 8 cfu • ml -1 was prepared for the tobacco hypersensitivity test.…”

“…In addition, Pss has been reported as a causative agent of bacterial leaf wilt of sugarcane in China (Cui et al 2021). The Pss pathogen isolated from bronzing jackfruit in Malaysia could affect sweetcorn, pineapple, and cucumber in vitro (Abidin et al 2021). In addition, other Pantoea species are severe pathogens of rice that cause diseases worldwide (Azizi et al 2020), as well as on other crops such as strawberries (Abdel-Gaied et al 2022) in the field and cabbage heads in storage (Eichmeier et al 2017).…”