The native plant microbiome is composed of diverse communities that in uence its overall health, with some species known to promote plant growth and pathogen resistance. Here, we show the antibacterial and growth promoting activities of autoclaved culture metabolites (ACMs) from native endophytic bacteria (NEB) in a papaya cultivar that is tolerant to bacterial crown rot (BCR) caused by Erwinia mallotivora . Initially, bacterial colonization in recovering tissues of this cultivar was observed before onset of tissue regeneration or 'regrowth'. We further isolated and characterized these bacteria and were able to identify two culturable stem NEB under genera Kosakonia (EBW), related to Enterobacter , and Sphingomonas (EBY). We also identi ed root NEB (BN, BS and BT) under genus Bacillus . Inhibition assays indicated that ACMs from these NEB promptly (18-30h) and e ciently inhibited (60-65%) E. mallotivora proliferation in vitro. Interestingly, when ACMs from BN and EBW were inoculated in surfacesterilized papaya seeds, germination was variably retarded (20-60% reduction) depending on plant genotype, but plant biomass accumulation was signi cantly stimulated, at around two-fold increase. Moreover, greenhouse experiments show that ACMs from all isolates, especially EBW, signi cantly reduced BCR incidence and severity in susceptible genotype, at around two-fold. In general, our observations of pathogen antagonism, plant growth promotion leading to disease reduction by ACMs of native endophytic bacteria suggested its contribution to increased tness of papaya and tolerance against the (re)emerging BCR disease.

The native plant microbiome is composed of diverse communities that influence its overall health, with some species known to promote plant growth and pathogen resistance. Here, we show the antibacterial and growth promoting activities of autoclaved culture metabolites (ACMs) from native endophytic bacteria (NEB) in a papaya cultivar that is tolerant to bacterial crown rot (BCR) caused by Erwinia mallotivora . Initially, bacterial colonization in recovering tissues of this cultivar was observed before onset of tissue regeneration or 'regrowth'. We further isolated and characterized these bacteria and were able to identify two culturable stem NEB under genera Kosakonia (EBW), related to Enterobacter , and Sphingomonas (EBY). We also identified root NEB (BN, BS and BT) under genus Bacillus . Inhibition assays indicated that ACMs from these NEB promptly (18-30h) and efficiently inhibited (60-65%) E. mallotivora proliferation in vitro. Interestingly, when ACMs from BN and EBW were inoculated in surface-sterilized papaya seeds, germination was variably retarded (20-60% reduction) depending on plant genotype, but plant biomass accumulation was significantly stimulated, at around two-fold increase. Moreover, greenhouse experiments show that ACMs from all isolates, especially EBW, significantly reduced BCR incidence and severity in susceptible genotype, at around two-fold. In general, our observations of pathogen antagonism, plant growth promotion leading to disease reduction by ACMs of native endophytic bacteria suggested its contribution to increased fitness of papaya and tolerance against the (re)emerging BCR disease.

Bacterial crown rot (BCR) is a re-emerging disease of papaya (Carica papaya) in Southeast 26 Asia caused by a gram-negative, facultative anaerobic bacterium, known as Erwinia 27 mallotivora. Ultrastructural observations using SEM revealed colonization of bacterial 28 community common in a BCR-tolerant genotype, before onset of tisue regeneration or 29 'regrowth'. This observation led to the hypothesis that papaya-associated bacteria might play a 30 role in BCR tolerance. Isolation, characterization and identification using 16S rRNA sequence 31 of bacteria associated with the tolerant 'regrowth' genotype resulted to the discovery of two 32 endophytic bacteria, of genera Kosakonia (isolate EBW) and Sphingomonas (isolate EBY). 33Papaya root-associated Bacillus isolates were also identified to belong to the B. 34 amyloliqufaciens clade (isolate BN, BS) and B. thuringiensis clade (isolate BT). Separate 35 inhibition assays indicated that, papaya latex and autoclaved culture metabolites (ACMs) from 36 isolated bacteria promptly (between 18-30h) and efficiently inhibited (60-65%) E. mallotivora 37 proliferation in vitro. Moreover, when ACMs from BN and EBW were inoculated in surface-38 sterilized papaya seeds, it variably retarded seed germination (20-60% reduction), depending 39 on plant genotype, but significantly stimulated plant growth and biomass accumulation, at 40 around two-fold increase. Interestingly, ACMs from all isolates, especially EBW, significantly 41 reduced BCR incidence and severity in susceptible genotype at around two-fold. Finally, these 42 results indicated that tolerance of papaya against E. mallotivora infection is probably 43 influenced by host innate properties such as tissue regrowth and pathogen inhibition by plant 44 latex, and acquired properties including pathogen antagonism, growth promotion and defense 45 biopriming through metabolites from beneficial endophytic and root-assocaited bacteria. 47Keywords: bacterial crown rot, defense biopriming, Bacillus, endophytic bacteria 48 49 82 perhaps a mechanism for resistance or tolerance (Magdalita et al., 2016). Breeding for 83 resistance and development of management strategies against the bacterial crown rot disease 84 are already in its early stages in the Philippines. Regrowth hybrid lines with good marketable 85 qualities and with resistance to papaya ringspot disease are currently under preliminary field 86 trials and back-cross F3 progenies are now in the pipeline (Magdalita et al., 2015). 88However, there are no reports yet regarding the events in pathogenesis up to the recovery of 89 papaya from the crown rot disease. Regrowth tissue examination was done initially in this study 90 to gain insight to probable role of beneficial microbes in disease tolerance. This was followed 91 by antimicrobial assays using papaya latex, culture metabolites from bacterial endophytes and 92 root-associated microbes and priming for disease resistance. Antimicrobial activity and 93 defence biopriming of beneficial microbes were thought to be acquired m...

Anthracnose is a foliar and fruit disease caused by Colletotrichum spp. affecting a wide range of crops. Infection occurs early followed by quiescence in fruits, such as in banana, where chemical-based pesticides are used as a dependable fungal control for many years. There is an increasing need for a safe control and as implicated in the Organic Agriculture Act of 2010 (RA 10068) in the Philippines. This scenario drove the use of alternative pest control such as the use of biologicals and natural products. In this study, seven bacteria were isolated from wild honey, produced by Apis mellifera, wherein four (BC2, BC3, BC6 and BC7) were found to be an effective antagonist against Colletotrichum musae in in vitro conditions. These bacteria were identified to belong to the genus Lactobacillus spp. (BC2, BC3, BC7) and Bacillus spp. (BC6) based on sugar utilization tests, morphological and cultural growth in PDPA. For the in vivo test, different dilutions of wild honey were used and it was found out that lower concentrations were effective as biopesticide spray to prevent anthracnose infection. Lastly, we report herewith the first isolation of bacteria with biological control potential from wild honey, and to apply the raw or natural product as biopesticide in postharvest fruits.