ORIGINAL ARTICLE Potential of chitosan-loaded nanoemulsions to control different Colletotrichum spp. and maintain quality of tropical fruits during cold storage N. Zahid 1 , A. Ali 1 , S. Manickam 2 , Y. Siddiqui 3 and M. Maqbool 1 1 Faculty of Science, School of Biosciences, The University of Nottingham Malaysia Campus, Semenyih, Selangor Darul Ehsan Malaysia 2 Department of Chemical and Environmental Engineering, Faculty of Engineering, The University of Nottingham Malaysia Campus, Semenyih, Selangor Darul Ehsan Malaysia 3 Department of Plant Protection, Faculty of Agriculture, Universiti Putra Malaysia, Serdang, Selangor Darul Ehsan Malaysia Keywords anthracnose, biofungicide, chitosan, disease severity, nanoemulsions Correspondence Asgar Ali, Faculty of Science, School of Bio- sciences, The University of Nottingham Malay- sia Campus, Jalan Broga, 43500 Semenyih, Selangor Darul Ehsan, Malaysia. E-mail: asgar. ali@nottingham.edu.my 2012/0842: received 8 May 2012, revised 4 July 2012 and accepted 2 July 2012 doi:10.1111/j.1365-2672.2012.05398.x Abstract Aims: To investigate the antifungal activity of conventional chitosan and chitosan-loaded nanoemulsions against anthracnose caused by Colletotrichum spp. isolated from different tropical fruits. Methods and Results: In vitro results illustrated that conventional chitosan onwards 1Á5% concentration inhibited radial mycelial growth, conidial germination, sporulation and dry weight of mycelia for Colletotrichum musae (Berk. & Curt) Arx. isolated from banana, Colletotrichum gloeosporioides (Penz.) Penz and Sacc. isolated from papaya and dragon fruits. For further investigations, chitosan-loaded nanoemulsions were prepared, and chitosan at 2Á0% concentration with 200 nm droplet size gave the best results in terms of all the in vitro parameters tested for C. musae and at the same concentration with 600 nm droplet size for both the isolates of C. gloeosporioides. However, the results obtained at 2Á0% chitosan concentration with different droplet sizes were nonsignificantly different with 1Á0 and 1Á5% concentrations. Therefore, for in vivo studies, only 1Á0% chitosan with different droplet sizes was used. In terms of fungicidal effects and maintaining postharvest quality of banana, papaya and dragon fruits, chitosan at 1Á0% concentration with a droplet size of 200 nm in banana and 600 nm in papaya and dragon fruits showed the best results in delaying the onset of anthracnose and maintaining quality of all the fruits for up to 28 days of cold storage. Conclusion: Chitosan used in a conventional form showed good results but not as effective as in the form of nanoemulsions. Significance and Impact of the Study: The results of this study suggest that instead of applying chitosan in a conventional form, chitosan in the form of nanoemulsions could be more effective as a biofungicide for controlling anthracnose of fresh fruits. Moreover, it could be cost-effective as the amount of chemical used is reduced when applied in the form of nanoemulsions. Introduction Anthracnose caused by Colletotrichum spp. is a devastat- ing disease for most of the tropical fruits and vegetables. This ubiquitous fungal spp. is responsible for anthracnose of different tropical fruits such as banana, papaya and dragon fruits caused by C. musae and C. gloeosporioides, respectively (Ranasinghe et al. 2002; Bautista-Ban ˜os et al. 2003; Masyahit et al. 2009). Anthracnose can affect fruits at early stages of development in the field and also damage mature fruits during storage. More than 50% of losses of fresh fruits and vegetables are caused by © 2012 The Authors Journal of Applied Microbiology 113, 925--939 © 2012 The Society for Applied Microbiology 925 Journal of Applied Microbiology ISSN 1364-5072