random point mutations at high density and can cause allelic mutations throughout the genome of any species ( Okagaki et al., 1991 ). EMS mutagenesis to generate resistance to potyviruses has been reported for Arabidopsis ( Duprat et al., 2002 ; Lellis
rapidly being developed, reverse genetic approaches have been unavailable in common bean as a result of the absence of an effective transformation protocol and thus the inability to develop transposon-based or T DNA-based mutagenesis systems. TILLING has
Seeds of Antirrhinum majus (snapdragon), proprietary line OAK564, were treated with 0%, 0.10%, 0.25%, 0.5%, 0.75%, and 1.0% ethyl methanesulfonate (EMS) for 8, 10, and 12 h at room temperature. The experiment was replicated three times over time. Data were collected on percent seed germination, seedling survivability, and pollen viability to determine optimal conditions for induced mutagenesis in OAK564 seeds. In the pilot experiment, M1 seeds treated with 1.0% EMS for 12 h had the lowest seed germination rate among all 18 treatments. Based on this pilot experiment, a large-scale mutagenesis experiment was performed using three levels of EMS (0.5%, 0.75%, and 1.0%) for 10-h exposure period. Mutants were induced on all these treatments, and morphological changes in the M1 population were detected. These included dwarfism, chlorophyll deficiency, and leaf morphology abnormality. This indicated that the EMS treatments were successful in inducing mutations, and mutants were further characterized for morphological traits.
combine with in vitro selection and increase breeding efficiency significantly ( Cassells, 2002 ). It has been reported that in vitro mutagenesis with a combination of tissue culture techniques is one method for improving plant quality ( Arène et al., 2007
; Cohen and Naor, 2002 ; Gascó et al., 2007 ; Nardini et al., 2006 ; Solari et al., 2006 ; Soumelidou et al., 1994 ; Trifilò et al., 2007 ). Mutagenesis induction is a useful technique for accelerating the genetic improvement of both varieties and
genus and our observations of polyembryony, we chose to introduce variation in this species using mutagenesis. Mutation breeding is an important tool to improve plants exhibiting apomixis ( Lapins, 1983 ). Although S. confusa appears to be a
reductions in fertility will be biologically significant, even if imperfect. However, we expect that achieving complete sterility will be feasible in many cases given sufficient chromosomal disturbance or directed mutagenesis, as discussed below. We consider
landscapes due to its pest resistance and low water use, but its issue with lodging requires improvement. However, there is a narrow genetic base, and we are unaware of sources of diversity with which to breed. Mutagenesis is a common method used by plant
Carrot tissue cultures, germinating seed, and dry seed were exposed to gamma radiation. Irradiation accelerated germination of carrot seed in the M1 generation at low doses (0.5 and 1 krad), whereas higher doses delayed germination. A high negative correlation was observed between dose and survival of plants after seed irradiation. Plant size and root weight were 20 % to 35% greater than control plants after seeds, but not tissue cultures, were exposed to low doses of gamma irradiation. Higher doses reduced M1 plant size by >50% in germinating seed and tissue culture treatments but less for the dry seed treatment. Seed production decreased while phenotypic variation of M1 plants increased with increasing gamma ray dosage. Root weight and total dissolved solids were highly variable in M2 families. Less variation was observed in total carotene content and none was seen in sugar type (reducing vs. nonreducing sugars). Induced variation in root color and root shape was also observed. Irradiation of germinating seed and tissue cultures yielded more M2 variation than irradiation of dry seed. Putative point mutations were not observed. Unirradiated carrot tissue cultures did not yield significant M2 somaclonal variation. Average root weight of M2 plants increased with increasing gamma ray dosage, especially for the dry seed treatment.
The aim of this study was to isolate Phytopthora cactorum-resistant strawberry plants, regenerated from gamma-irradiated explants on a shoot regeneration medium. Three gamma doses (0, 5, 10, 15 krad) were used to irradiate strawberry axillary buds taken from in vitro-grown plants. After irradiation, axillary buds were cultured on a shoot regeneration medium containing 0.75 mg BA/liter and 0.4 mg IBA/liter. Shoot regeneration occurred mainly from axillary buds irradiated with 5 and 10 krad. The highest dose (15 krad) produced few shoots. The shoot regeneration rate was highest at the 50-krad dose. All the regenerated plants were transferred in the greenhouse. The crude extract of P. cactorum, isolated from the strawberry field, was prepared in sterile water; 1 ml of it was put directly in the center of the crown of each of 400 regenerated plants. After 2 weeks, leaves of most of the plants wilted. Only 20 plants survived the first round of selection; they grew slowly when compared with the control and also showed some tolerance to drought. Further investigations are in progress to reconfirm the resistance of selected putative disease-resistant strawberry plants.