Strategic Breeding of Underutilised Minor and Novel Fruit Crops in Southern Karnataka, India: A Critical Review of Genetic Resources, Breeding Pathways and Adoption Constraints

Southern Karnataka combines semi-arid plateau landscapes with the humid hill tracts of the Western Ghats, and this contrast supports an unusually wide range of minor indigenous fruit species alongside recently introduced tropical fruits. Jackfruit, jamun, tamarind, wood apple, karonda, Malabar tamarind, kokum and wild jack persist largely as heterogeneous seedling populations, whereas avocado, rambutan, dragon fruit, mangosteen and passion fruit are being trialled as novel diversification options. Interest in these crops has grown because of their nutritional value, tolerance of low-input conditions and premium markets, yet breeding outputs remain few. This critical narrative review examines how far the available evidence supports a strategic, region-specific breeding agenda for these crops. Peer-reviewed literature published from 2000 onwards was identified through international scholarly indexes and a national agricultural research repository, supplemented by reference-list screening and institutional sources, and was appraised qualitatively for design adequacy, representativeness, genetic inference and translational relevance. The synthesis shows that in situ characterisation of seedling populations has repeatedly revealed large variation in fruit size, flesh colour, sugars, acidity and bioactive compounds, with high estimated heritability for several yield and fruit traits, and that molecular markers confirm high diversity in jackfruit, jamun, avocado, wood apple and Garcinia. Chromosome-level genomes now exist for jackfruit and tamarind, and a draft genome exists for wild jack, but no marker–trait association has yet been translated into selection for any of these crops in the region. The clearest breeding successes arose from clonal fixation of farmer-identified trees, interspecific hybridisation in custard apple and open-pollinated progeny selection with mutagenesis in dragon fruit. Persistent constraints include long juvenile phases, dioecy and self-incompatibility, poorly synchronised flowering, fruit drop, emerging diseases and inefficient planting-material systems. Much of the regional characterisation remains in unpublished theses, and most published studies are single-site, short-duration and descriptive. A defensible agenda would prioritise multi-environment evaluation of already identified elite trees, trait-linked genomic tools for reproductive and quality traits, rootstock and propagation research, and institutional arrangements that reward custodian farmers. Without such integration, rich genetic diversity is unlikely to become adopted cultivars at scale.