Identification of Lychee Varieties by Morphological, Electrophoretic and Cytogenetic Methods

Abstract

Identification was carried out on nineteen different varieties of lychee (Litchi chinensis Sonn.) from field germplasm at Chiang Rai Horticultural Research Centre. The variety names are Kalok Bai Tao, Kalok Bai Yao, Kalok Bai Oa, Kwang Jao, Kim Jeng, Kom, Kom Lum Jeak, Juck Kra Put, Jean Lek, Jean Yai, Brewster, Luk Lai, Sa Laek Tong, Sam Pao Kaew, Haew, O-Hia, Hong Huay1, Hong Huay2 and Hakip. Morphological method was used to examine both quantitative and qualitative characters of leaves, flowers, fruits and seeds of each variety. Differences among varieties were shown in keys to varieties using leaf colour, leaf shape, leaf base, leaf apex and leaf margin. Some specific characteristics were found in some varieties i.e. obtuse leaf apex in Kim Jeng; smallest leaf and fruit size in Kom and largest fruits and seeds in Juck Kra Put.

            Electrophoretic method was used to determine isozyme patterns from mature leaf isozyme extraction, using 0.05 M Tris-HCl buffer, pH 8.4 (150 mM NaC1, 10 mM cysteine, 1mM ascorbic acid, 1 mM CaCl₂ 1 mM Na₂ -EDTA, 2% nicotine). Polyacrylamide vertical slab gel electrophoresis at 8.5 per cent and 10 per cent were used for peroxidase and acid phosphatase, respectively. Banding patterns from zymograms showed that the nineteen varieties can be classified into fourteen groups by peroxidase. Those with similar banding patterns were separated by acid phosphatase. Cytogenetic method was used to investigate root tips of 0.5-1.0 cm long. Mitotic tissues were fixed at approximately 9 a.m. with paradichlorob enzene, followed by HC1 hydrolysis and carbol fuchsin and lacto-propionic orcein staining. All varieties possess the same chromosome number of 2n=30. An individual variety can then be identified by the chromosome size and shape.