Tangerine (C. reliculata) and pummelo (C. grandis) are regarded as economically important species of citrus in Thailand. According to a 1998 DOAE report [1], the areas planted with tangerine account for 178,898 rai (≈ 28,623 ha) and for pummelo it is about 209,580 rai (≈33,532 ha). The total market value for tangerine accounts for about 5.5 billion Baht/year, (≈ US $ 170 Millions) whereas 2.1 Billions Baht/year (≈ US $ 64 Millions) for pummelo. Major diseases such as Phytophthora infection, Greening and Tristeza, which cause reduction of yield and decrease the fruit quality, are among the challenges currently addressed by the research community in Thailand.