Annals of Applied Biology ISSN 0003-4746 RESEARCH ARTICLE Phenological growth stages of bael (Aegle marmelos) according to the extended Biologische Bundesantalt, Bundessortenamt und Chemische Industrie scale K. Kishore, K.K. Mahanti & D. Samant Central Horticultural Experiment Station (ICAR-Indian Institute of Horticultural Research), Bhubaneswar, India Keywords Bael; BBCH scale; crop management; phenology. Correspondence K. Kishore, Central Horticultural Experiment Station (ICAR-Indian Institute of Horticultural Research), Aiginia, Bhubaneswar 751019, India. Email: kkhort12@gmail.com Received: 10 August 2016; revised version accepted: 21 November 2016. doi:10.1111/aab.12347 Abstract Bael (Aegle marmelos) is an important rutaceous fruit widely cultivated in India. This crop is revered for its high economic and therapeutic value. However, its phenology has not yet been described systematically. Detailed description of phenological growth stages of bael using the extended Biologische Bundesan- talt, Bundessortenamt und Chemische Industrie (BBCH) scale has been worked out and reported in this paper. Eight principal growth stages and 37 secondary growth stages for bud, leaf development, shoot growth, inflorescence emer- gence, flowering, fruit development, fruit maturation and senescence have been distinctively defined. The sequential progression of principal growth stages has been described according to the phenological growth pattern and climatic requirements of different phenophases. The extended BBCH scale is broadly applicable for bael cultivation as it describes all the phenophases pertaining to vegetative and reproductive stages. Because of the relative importance of phenophases in crop management and crop improvement, the BBCH scale will facilitate adoption of better crop management practices, crop improvement and characterisation of bael germplasm. Moreover, the extended BBCH scale will be a useful tool in assessing impact of climate change on crop yield and fruit quality. Introduction Bael, Aegle marmelos (L.) Correa, is indigenous to Indian subcontinent. It is also naturalised in Southeast Asian countries like Indonesia, Malaysia, Myanmar and Viet- nam (Sharma et al., 2007). Bael is cultivated primarily in semi-arid and arid regions. However, it is also grown in tropical and subtropical humid regions of India. Bael is also known as bel, belo, bhel, Bengal quince, stone apple and Japanese bitter apple. It is the only member of the mono- typic genus Aegle (Parmar & Kaushal, 1982). It belongs to the family Rutaceae, the citrus family, comprising of 1900 species across 160 genera (Groppo et al., 2008). Other important species in this family are mandarin (Citrus reticulata Blanco), sweet orange (Citrus × sinensis L. Osbeck), lemon (Citrus × limon), acid lime [Citrus × aurantifolia (Cristm.), grapefruit (Citrus × paradisi Macf.), Swingle], pomelo (Citrus × grandis L. Osbeck) and wood apple (Limonia acidissima L.). Bael is known for its therapeutic value as most of its plant parts (fruit, leaf, bark, root, seed) are important ingredients of several traditional medicines effective against various human ailments (Gutierrez et al., 2007). Bioactive compounds like marmelosin and psoralen in fruits have antibacterial, laxative, digestive and restorative properties. Leaves and bark contain skimmianine, aegelin, marmesinin and marmin, which have anti-cancerous, anti-oxidative, antibacterial, antipyretic and analgesic properties (Maity et al., 2009). Ripe fruit is rich source of fibre, protein, vitamins and minerals. Bael also has great mythological and religious significance as its trifoliate leaves are used as offering during Hindu religious rituals (Patkar et al., 2012). Bael is a deciduous, hardy, slow growing, medium tree (6–8 m) with aromatic leaves and flowers. Leaves are alternate, oval and pinnately compound with three or five (rare) leaflets. Flowers are bisexual, pentamer- ous, sweetly scented, greenish white in colour and ento- mophilous. Nectar is secreted beneath the ovary, which is Ann Appl Biol (2017) 1 © 2017 Association of Applied Biologists