|dc.description.abstract||A preliminary factorial experiment with Lupinus albus cv. Ultra, using three concentrations of the aklylating chemical ethyl methanesulphonate ( EMS ) and two treatment periods, examined the effects of this mutagen on field survival and fertility in the M₂ and M₂ generations, and the induction of characters suitable as genetic markers. A second, larger factorial experiment was set up to evaluate an optimum dose range with EMS for Ultra. Here, in addition to the six EMS concentrations and two treatment periods, the effects of scarifying seeds and aerating the treatment solution were also studied. The amount of physiological damage induced by different EMS doses was assessed from measurements of growth and fertility made from field emergence until pod fill. Only an M₁ population was grown in Experiment 2.
Experiment 1 showed that M₁ generation survival and per plant seed number and seed yield fell significantly as EMS concentration was treatment duration increased.
In the M₂ generation mean values for all characters except seed weight were lower in the mutagen treated plants than in the untreated checks.
The phenotypic variability of all parameters except seed yield was higher in mutagen treated m₂ plants than in the checks. As each M₂ treatment comprised no more than one-fifth the number of genotypes present in the checks, mutagenesis almost certainly brought about this increase in variability.
Observations until the M₄ generation of progenies of two M₂ plants with pink rather than the normal blue or white corolla pigmentation, indicated that these variants most likely arose from EMS mutagenesis. The distinctiveness of this mutant phenotype and moderate fertility of M₃ and M₄ progenies suggested its possible value as a genetic marker. However, further testing would be necessary on its mode of inheritance before the suitability of the character as a genetic marker could be established.
Among mutagens treatments, the highest phenotypic variabilities, frequencies of morphological mutants and indices of mutagenic efficiency occurred after two hour treatments with 0.4% and 1.0% ethyl methanesulphonate.
In the second experiment, only EMS concentration and treatment duration significantly influenced growth, survival and fertility of M₁ generation plants, and mutagen concentration was the more important factor. Neither seed scarification nor aeration of the treatment solution had important effects on growth and fertility. Increased EMS concentration and treatment period delayed emergence, reduced growth rate and survival, and lowered all components of seed yield except mean seed weight, which, as in Experiment 1, showed a significant positive linear correlation with EMS concentration.
Dose responses for survival, dry matter yield, seeds per pod, seeds per plant and seed yield per plant were quadratic: in both two and five hour treatments the largest decreases in means for these parameters occurred after the 0.2% to 0.4% increment in EMS concentration.
As observed in Experiment 1 the EMS dose reducing parameters of fertility to 50 per cent the control value was considerably lower than for parameters measured before flowering.
Linear regression equations for the highly significant correlations found between indices of early growth and eventual survival and fertility were proposed as w way to predict at an early stage the effect of a given EMS dose from measurements of, for example, emergence rate and seedling height.
Together, the results of Experiments 1 and 2 indicated that to maximize the selection potential for induced variation in quantitative and qualitative characters, EMS doses should allow sufficient M₁ fertility to give a high probability of recovering mutants in early segregating generations.
It was recommended that in mutagenesis with L. albus cv. Ultra, EMS concentrations should not exceed 0.4% nor treatment periods three hours.
The above results were discussed in relation to earlier studies on chemical mutagenesis in Lupinus and other genera, and suggestions made for lines of future research.||en