Plant breeding of some tropical fruits in Thailand; durian, mango, rambutan, tangerine, pummelo and papaya

Abstract

Until recently, most Thai fruit cultivars were improved by chance seedlings and selected by Thai farmers. However, some commercial cultivars were selected and improved by plant breeders. A durian breeding program was commenced by the Department of Agriculture in 1956. Eighteen cultivars were selected to be parent plants for 55 reciprocal crosses and produced 7,634 F1 hybrid seedlings. Three promising lines were selected as commercial cultivars, namely, 'Chanthaburi 1', '2' and '3' in 2006 and characterized by DNA fingerprinting. Subsequently, 253 lines of F2 generation, 4,278 F1 lines from 51 new crosses between 1998 and 2002, 110 interspecific hybrids from 45 crosses between 1988 and 1992 and 21 crosses in 2000 are being investigated for high tolerance to Phytophthora palmivora, high yield and good fruit quality. Between 2006 and 2016, three lines were released namely, 'Chanthaburi 4', '5' and '6' in 2013 and another three will be released namely, 'Chanthaburi 7', '8', '9' in 2016. Exploration, collection, conservation, characterization, documentation and utilization of mango and rambutan species were studied in 2000-2003. Two lines of mango (CB0007 and CB0010) and one line of rambutan (CB0023) 'Thong Muang Trat' with long shelf life were selected. A mango breeding project was conducted on 60 crosses and 2 hybrids namely, 'Chanthaburi 1' and '2' were released with early maturity. In addition, the commercial cultivars 'Nam Dok Mai', 'Nam Dok Mai Si Tong' are exported. From 1974-1983, rambutan cultivar improvement was achieved by reciprocal crossing between five parents and 'Plew#3' was released to farmers. Acute and chronic gamma irradiation for mutation induction in tangerine (C. reliculata) and pummelo (C. grandis) to produce seedless cultivars or those containing fewer seeds were conducted between 2000-2006. Two seedless M1V4 pummelo 'Kao Thong Dee' resulted. Moreover, 8 promising lines were further investigated and one of them, A4V3-22-2 has good eating quality, 0-2 seeds fruit-1 and high yield namely, 'Phare 1'. Pummelo cultivar improvement has been conducted from 2006-2010 for high yield, high quality. Evaluation of 425 F1 hybrid pummelos showed that some have good growth, have started to set fruit and are being evaluated. In addition, 2 citrus species ('Thabtim' and 'Cleopatra') used as rootstocks have good compatiblity and result in good growth of cultivar 'Kao Thong Dee'. DOA papaya breeding was commenced in 1984. The DOA approved 'Khaek Dam Si Sa Ket' was selected as a new cultivar in 1994. 'Khaek Dam' was crossed to 'Coimbatire No. 2' (CO2) and 'Phichit' line was approved in 1997. A cross between the 'Khaek Dam' and the 'Florida Tolerant' cultivar, resulted in new cultivars, 'Khaek Dam Tha Phra' and 'Khon Kaen 80' which were approved in 1997 and 2010, respectively. In addition, genetic engineering was undertaken by the DOA in collaboration with Cornell University. The coat protein gene (CP gene) of PRSV was transferred into Thai papaya, 'Khaek Dam' and 'Khaek Nuan' cultivars. Currently, one cultivar 'Khaek Dam' (R3 300KD) and two 'Khaek Nuan' (R3 319-1KN-180 and R3 319-1KN-181) cultivars were selected for the R3 PRSV resistance. However, GMO research is still limited at the present in Thailand.