Induced variability in morphological and reproductive characteristics of pysalis ixocarpa brot. by radiation

The present investigation was conducted at Kaha Research Station, Vegetables Research Institute, Ministry of Agriculture, Dokki, Giza, during the three successive seasons, 2008, 2009 and 2010. It aimed to study the effect of gamma rays on vegetative and yield contributing characters of two tomatillo cultivars _Cisneros- and _Solo-. Dry seeds of each cultivar were exposed to 10 gamma ray doses ranged from 0 to 30 Kr emitted from Cobalt 60 and sown in Petri- dishes in the laboratory. Based on the results of this preliminary study six gamma- ray doses were chosen; 0, 2, 4, 6, 8 and 10 Kr to study the irradiation effects on most agronomic characters during M1 and M2 generations. Some deviants in the vegetative and yield characters were selected in M2 as macromutants, These selected macromutations within each dose progeny were raised and tested in M3. Percentages of M1 seed germination and plant survivals decreased, at all gamma ray dose compared with control. The assigned lethal dose (LD50) of gamma- rays for germination and plant survival of both cultivars was 6 to 9 Kr. In M1- generation the mean averages of plant height, stem length, number of internodes, number of branches, stem diameter, number of fruits, fruit weight, number of seeds per fruit and 1000 seed weight traits were lesser than the control. In M2-generation the chlorophyll mutations which screened from M2- irradiated progenies were: albino, xantha, chlorine and variegated. The macro mutants which selected in M2 and proved to be bred true in M3 were: giant, dwarf, heavy branching/ high yield, early flowering, late flowering, trifurcate stem, sterile, flower mutant, fruit mutants. In both cultivars giant mutant showed the highest frequency of macromutants. The frequency of total macro mutants was relatively higher at doses (8 and 10 Kr) and the highest frequency was at 10 Kr. The anatomical measurements of both dwarf and giant mutants showed thinner internode diameter. Most of the included tissues participated by different magnitudes in reducing the diameter of the mutant stem. Meanwhile, in heavy branching\\ high yield mutant, the whole stem diameter was larger over the control. Most tissues shared by various magnitudes in increasing the whole stem diameter in this mutant. Longitudinal sections of giant mutant proved that the length of cortical and pith cells increased at the expense of their width. In contrary longitudinal sections of dwarf mutant revealed that parenchyma cells of cortex and pith were reduced in their vertical and horizontal dimensions below the control. However, in heavy branching/ high yield mutants both vertical and horizontal dimensions of cortex and pith cells excelled the control. The giant and grooved fruit mutants showed the highest percentage compared with control of total carbohydrate, carotenoides, phenols, flavonoides and ascorbic acids