THREE DECADES OF DURIAN BREEDING PROGRAM IN THAILAND AND ITS THREE NEWLY RECOMMENDED F₁ HYBRIDS

Durian breeding program was conducted in Thailand by using conventional breeding procedures. Durian germplasm was surveyed and collected from various horticultural research centers of the Department of Agriculture, such as Chanthaburi, Surat Thani, Trang and Yala Horticultural Research Centers (HRC) between 1956 and 2000. Characterization and evaluation were investigated by using morphological and DNA fingerprinting. Clonal selection of existing commercial cultivars namely: 'Mon Thong', 'Chani', 'Kan Yao', 'Kradum Thong' and chance-seedling trees was conducted between 1986-1988 at Chanthaburi HRC, by means of quality contest. The three selected trees based on their specific characters were released and distributed to the farmers. At the Chanthaburi HRC, at least 68 cultivars were collected, characterized and evaluated. Eighteen cultivars were selected to be parental plants for 55 reciprocal crosses and produced 7,634 F₁ hybrids seedlings between 1986 and 1990. During 1999 to 2006, some of these F₁ hybrids were characterized and evaluated on 26 characters; however only five characters (fruit weight, percentage of flesh, aborted seed, flesh thickness and eating quality) were the main criteria for F₁ selection along with early, moderate, late maturity, percentage of fruit setting and yield. The variation of F₁ hybrids was investigated and also, the Thai Durian standard (1998) was applied to use for selection. The 29 promising F₁ hybrids were confirmed for their quality at least three years and compared with the commercial variety for seven years. The first three promising lines were selected to be new recommended F₁ hybrid cultivars, namely, 'Chanthaburi 1', '2' and '3'. The DNA fingerprinting for these promising lines was studied to identify their specific characters or banding patterns. Also, 253 selved promising 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 to produce new F₁ hybrids with high tolerance to Phytophthora palmivora, high quality, yield and varying fruit quality and size to meet the requirements of the consumers and markets.