Effect of gamma ray on induction of dwarfism-like 'Irwin' mango (Mangifera indica L.) after treatment.
Weng YiTzu, Chang LoongSheng
Author Affiliation: Department of Horticulture, National Taiwan University, China.
Journal of the Chinese Society for Horticultural Science 46 : 259-266
Abstract : Reduction of mango tree size would provide an opportunity to increase land utilization efficiency and to decrease production costs. The use of mutagenesis for fruit tree breeding could overcome some limitations, such as the long juvenile period of seedlings and introduce important horticultural traits such as plant size reduction, fruit colour, and compact growth habit. The responses of mango, treated with ?-radiation, were investigated on cv. Irwin in the greenhouse and in the field. The survival ratio of Irwin seedlings was 65.2% after 2-kR ?-irradiation. The same dosage was applied again on visually normal-looking Irwin seedlings, which were surveyed after secondary shoot growth in the greenhouse. Comparisons were made on (1) the control, without radiation treatment, (2) one dose of radiation, and (3) 2 doses of radiation. The mean plant height of the half-year-old control seedlings in the greenhouse was 42.4 cm, which was significantly higher than the irradiated seedlings. The mean plant height of the control mango seedlings was 78.7 cm four months after planting in the field. The single dosage radiation group had a mean plant height of 55.1 cm. The double dose radiation group was as high as the control. Plant heights less than 50 cm would considered as dwarf which occupied 45.6% of the single treatment group in July of 1998. The proportion was 13.8% of the plant height less than 50 cm for the double dose radiation group. The height of dwarf Irwin plants were about 64 cm surveyed in January of 1999. However, the mean plant height of the tall group was about 140 cm and the intermediate group was about 95 cm. The irradiation treatment dramatically affected plant height according to the independence test of chi-square (?2=28.12, p0.01). The frequency distribution after radiation treatment could be divided into three groups. The distribution of dwarfism was distinct to the distribution of tall group of the plant height. The radiation was effectively reducing the plant height of Irwin.