Applications of biotechnology to tropical fruit crops in Australia and worldwide
Tropical fruits play an important role in the world economy. They make a substantial contribution to human nutrition and are used for medicine, timber, fuel and livestock feed. The major tropical fruit crops are banana, mango, pineapple, papaya and citrus; however, it is estimated that more than 400 species are harvested in the Asia, Pacific and Oceania region. Other regions such as Central and South America are rich in tropical fruit biodiversity. During the last 20 years, biotechnology has been applied to many tropical fruit species. In Australia, micropropagation systems have been developed for banana, pineapple, papaya, ginger, passionfruit and coffee; and good embryogenic protocols have been employed in banana, mango and papaya. Cryopreservation protocols are being developed for many of the major tropical fruit species. Transformation systems have been used to produce disease resistant cultivars of banana and papaya; and, to prevent blackheart, to control flowering and delay ripening of pineapple. The single significant commercial application of transformation has been the Papaya Ringspot resistant papaya in Hawaii. Molecular marker technology has been used to identify genotypes and to confirm intergeneric hybrids between papaya and related Vasconcellea species. Molecular maps have been developed for some species. Genetic diversity within populations and between related wild species has been determined for some fruits. Specific DAF markers have been identified for sex determination in papaya; a SCAR marker has been developed to identify dwarfism in bananas; and, a CAPS marker to identify a PRSV-P resistant gene in highland papaya. The major application in genomics has been the rapid progress in sequencing the papaya genome in Hawaii.