Selection of new distinct sweet potato clones using chemical mutagen agents and gamma-ray radiation

الملخص EN

Improving sweet potato plants by traditional breeding methods has some limitations.

Furthermore, the existence of self- and cross-incompatibility in sweet potato limits the use of genetic resources and causes a difficult for the breeders through cross breeding.

Breeding using mutants as gamma rays and chemical mutagen agents such as colchicine and sodium azide can be used as a key approach in improving sweet potato genotypes, since it is a clonally propagated crop.

Therefore, the objectives of this study are production improved clones of sweet potato with high productivity and quality.

This investigation was carried out through the years of 2014, 2015 and 2016.

Physical and chemical mutagenesis were performed using gamma ray radiation, colchicine and sodium azide which were applied to stem cuttings of ^"Abees and Mabrouka^" cultivars to produce new sweet potato clones prone to have both high productivity and tuber roots quality.

Cuttings were treated with three different mutagens: 1) exposed to gamma radiation with four doses (30, 50, 70 and 90 Gy), 2) soaked in colchicine solution with three concentrations (100, 300 and 500 mg/L) for sixteen hours and 3) soaked in sodium azide solution with three concentrations (50, 75 and 100 mg/L) for sixteen hours.

Fifteen new clones were selected among three hundred ones according to tuber root morphological and physical characteristics for planting in a field trial along with the above-mentioned local sweet potato cultivars for evaluation in two different locations in Alexandria and El-Gharbeya governorates.

Generally, the tested sweet potato genotypes were significantly differed for all the studied characters, viz.

, vegetative characters, yield and yield components, physical and morphological tuber root characteristics.

Most studied characters showed strong dependence on the environmental factors (locations).

The interaction between genotype and environment; had highly significant effects on all studied traits.

The obtained results expressed such positive and significant correlations among sweet potato yield per feddan with each of fresh foliage weight (kg), plant length (m), number of main branches per plant, number of tuber roots per plant, average tuber root weight (kg), marketable yield per plant and percentage of marketable yield per plant.

So, the aforementioned characters were considered as good indicators for the prediction of high sweet potato crop production.

It is worth mentioning that; three clones (No.

3, 4 and 6) were superior to all tested genotypes especially in yield and quality characters as total sugars and dry matter percentages.

These clones considered suitable for both domestic and foreign markets.

The clone No.

16 is starchy one and dedicated to be suitable for starch industry due to its superiority compare to all tested clones in terms of starch content.