_____________________________________________________________________________________________________ *Corresponding author: E-mail: maneechat.n@gmail.com; Journal of Experimental Agriculture International 42(5): 122-138, 2020; Article no.JEAI.57727 ISSN: 2457-0591 (Past name: American Journal of Experimental Agriculture, Past ISSN: 2231-0606) Studies on Physio-chemical Properties of Maintainer, Restorer Lines and Hybrids of Chilies (Capsicum annuum L.) Maneechat Nikornpun 1* , K. Tunjai 1 , K. Kaewsombat 1 , T. Tarinta 1 and Danai Boonyakiat 1 1 Department of Plant and Soil Sciences, Faculty of Agriculture, Chiang Mai University, Chiang Mai 50200, Thailand. Authors’ contributions This work was carried out in collaboration among all authors. Author MN designed the study, carried out the field work, wrote the protocol and wrote the manuscript. Authors KT, KK and TT carried out the field and laboratory work. Author DB carried out the laboratory work with the other authors. Author KK managed the analyses of the study. All authors read and approved the final manuscript. Article Information DOI: 10.9734/JEAI/2020/v42i530526 Editor(s): (1) Dr. Iván Francisco García-Tejero, Instituto Andaluz de Investigacion y Formacion Agraria y Pesquera (IFAPA), Spain. Reviewers: (1) M. Lal Ahamed, India. (2) Champa Lal Khatik, India. Complete Peer review History: http://www.sdiarticle4.com/review-history/57727 Received 01 April 2020 Accepted 07 June 2020 Published 23 June 2020 ABSTRACT Physio-chemical properties of hybrid chilies (Capsicum annuum L.), parental lines and commercial varieties were evaluated in three experiments and showed significant differences among them. Heterosis, and heterobeltiosis were studied in hybrids while, combining abilities were investigated in maintainers and restorers. Positive statistical differences in the general combining ability of the maintainer lines for vitamin C, capsaicin and Hue were observed and general combining ability indicated that, CA1286 and CA1303, were good maintainers for the improvement of capsaicin and vitamin C. The other maintainers;-, CA1441 and CA1442, are good for the improvement of L* and Chroma. The maintainer, CA1441, was better than CA1442 for capsaicin content,- while the maintainer, CA1442, was better than CA1441 for vitamin C. Positivity and statistically significant differences among the restorers were observed for vitamin C, capsaicin, Hue and Chroma and the lines;-, CA 1447, CA 1448, CA 1449, CA 1450 and CA 1451, were useful for the improvement of these physio-chemical properties of chilies. Original Research Article