Prospects of mutation breeding in grapefruit (Citrus paradisi Macf.)

Abstract

Grapefruit is considered as a minor citrus crop in Pakistan and its annual production is less than 0.5% of total citrus production. Grapefruit industry is depending upon pink flesh cultivar ‘Shamber’ and need varietal diversification. Mutation breeding has played a pivotal role in grapefruit crop improvement and most of the commercial cultivars are bud sports or induced mutants which were selected and later released as new cultivars. Flesh color enhancement, seedlessness and low furanocoumarin level have been main objectives for grapefruit breeders. An overview of potential of mutation breeding in grapefruit and leading mutants produced is presented in the following sections. Though physical mutagens have been more successful, breeders’ interest is rising in more precise and targeted mutagenesis technologies including CRISPR/Cas9 which has enormous potential in genome editing and could shorten breeding and selection cycle. The available leading grapefruit cultivars were screened for horticultural traits and potential candidate varieties has been selected for diversification and selection of better parents for breeding programs. Several putative mutants have been developed using gamma irradiated plant material. The effect of irradiation on plant growth, morphology and biochemical properties has been evaluated and salient findings are discussed. The developed genetically diverse material could be useful for future biotechnology applications.

Sustainable Approaches for Biodiversity and Bioprospecting of Citrus

“…Mutation breeding improves both genotypic and phenotypic traits, and has played a vital role in Citrus improvement [114]. Since 1970, 15 mutants of Citrus have been released which comprise mandarins, clementines, sweet oranges, grapefruits, and lemons with individual numbers 6, 6, 2, and 1, respectively [115]. Induced mutation by physical mutagens-for example, by gamma rays and chemical compounds acting as mutagens-enhances the induced genetic variability.…”

Citrus Biotechnology: Current Innovations and Future Prospects

“…Though conventional breeding has limitations in citrus due to its complex reproductive behavior, nucellar embryony, long juvenility, sterility, sexual incompatibility, and endogametic depression [9,10]. However, still, many hybrids have been developed by conventional breeding and recovered using in vitro tools.…”

“…Among countries, China (817), Japan (479), India (341) and the USA (139) are leading in mutant development whereas Pakistan has released 59 mutants in different crops [15]. In citrus, a total of 15 mutants have been released since 1970 including mandarins and clementine (6), sweet oranges (6), grapefruit (2), and lemon (1) [10]. Pakistan has registered a single mutant variety in citrus, a Kinnow mandarin induced mutant having less number of seeds and named it as "NIAB Kinnow" in 2017.…”

“…Rio Red is the main cultivar in China, India, and Argentine [33]. In Pakistan, Shamber is the main grapefruit variety that needs to be replaced with other potential candidate varieties like Star Ruby, Rio Red, and Flame [10].…”