Abstract:
The study of characterization of high temperature tolerant mutants of Chinese mustard seeds
induced by gamma irradiation were investigated. Seeds from eight cultivars,'Nua Chan','Tra-
Sing','Gangfu','Max 018','Fuso','Tra-Plawan','Tra-Dekbin', and 'Top Gun TA 061' were
irradiated at doses between 250-1,000 Gy and compared to non-irradiated control samples. Standard
germination and mutant characterization were carried out using 7 laboratory techniques including
abnormal seedling, germination index (GI), germination and GI at 35?C, accelerated aging test,
shoot and root length. Heat tolerance mutants of Chinese mustard seed induced by gamma
irradiation at dose of 250 Gy were the most promising for all tested cultivars. 'Tra-Sing','Fuso' and
'Nua Chan' were more sensitive to be induced for mutation by gamma irradiation compare to the
other cultivars. Irradiated seeds of seven cultivars (except 'Tra-Plawan') were grown in a green
house during summer (31-38?C). The characterization of high temperature tolerant mutants of
Chinese mustard seeds were evaluated by performed head formation. Heat tolerance of 'Nua Chan'
was found indicated by head formation of the non-irradiated seeds. 'Tra-Sing' seeds irradiated at
500 Gy performed head formation when compared to the other doses and the control sample.
Irradiation at 250-1,000 Gy induced flower formation in 'Nua Chan' and 'Max 018' seeds. This
blooming effect was also found in the 'Tra-Dekbin' seeds irradiated at 250 Gy. Irradiation at 500-
1,000 Gy exhibit flower formation in 'Gangfu' seeds. 'Fuso' and 'Top Gun TA 061' did not exhibit
head and flower formation. Field experiments were also carried out at three different locations
during winter season in Thailand. TO investigate head formation and yield of irradiated Chinese
mustard seeds 'Tra Dekbin' seeds irradiated at 250 and 1,000 Gy were grown in Phichit province
(17-20?C), 'Fuso' seeds irradiated at 250, 500 and 1,000 Gy were grown in Nakhon Sawan
province (7-10?C), and 'Gang fu', 'Max 018' as well as 'Top Gun TA 061' seeds irradiated at 250,
500, 750 and 1,000 Gy were grown in Ratchaburi province (12-18?C). They were always compared
to non-irradiated control samples. The comparison revealed that irradiated seeds at 500-1,000 Gy
exhibit lower total number of plant per unit area, lesser head formation (%), reduced total plant and
head weight. Our results suggest that gamma irradiation at dose above 250 Gy induced mutation in
Chinese mustard seeds. At higher temperature, only 'Tra-Sing' seeds irradiated at 500 Gy
performed head formation, however, additional flower formation was revealed in 'Nua Chan','Max
018','Gangfu' and 'Tra-Dekbin'. 'Nua Chan' was the most heat tolerant cultivar. In the field tests
at lower temperature, irradiated seeds of the five tested cultivars at 500-1,000 Gy showed lower
head formation (%), total plant and head weight compared to the dose at 250 Gy and control sample.