Evaluation of some clones derived from two sweet potato cultivars under water deficit conditions

الملخص EN

Sweet potato (Ipomoea batatas, L.) is one of the root crops worldwide especially developing countries as a popular staph food, but due to its highly heterozygosity as cross-pollinated crop wherein many of its traits exhibit constant variation.

Also, sweet potato is sensitive to water deficits especially during its formation stage including vine development and storage root induction.

Therefore, this study was undertaken in corporation between ElSabaheya Horticultural Research Station and the Experimental and Research Farm of The Faculty of Agriculture (Saba-Basha), Alexandria University, Alexandria governorate, Egypt, to develop distinct sweet clones.

Stem cuttings of both Abees and Mabrouka cultivars were exposed to gamma ray radiation or immersed in colchicine or sodium azide solutions.

8 promising clones were selected to be evaluated under water deficit conditions in two field trials in comparison with their mother plants during the summer seasons of 2017 and 2018.

Four irrigation levels (100, 75, 50 and 25% of ET0) were applied.

The gained results revealed that the best results for the vegetative growth characters were achieved with the treatment of 100 % of evapotranspiration, except for number of main branches / plant which possessed the highest mean values with the treatment 25 % of evapotranspiration.

Tuber root yield character and its component traits were significantly affected by both studied variables (sweet potato genotypes and irrigation levels).

As for the main effect of irrigation levels on tuber root yield/feddan and its component characters, there are significant and direct proportional relationship between the independent variable (irrigation levels) and dependent one (studied traits).The highest average values for tuber root yield/feddan were scored at 100 % of irrigation level during the two seasons, followed with the treatment 75 % of irrigation level; while 25 % of irrigation treatment possessed the lowest mean values.

The highest average values were recorded for marketable tuber root yield (%) were recorded at 100 % of irrigation level; while the lowest mean values were scored at 25 % of irrigation treatment.

Carotene content and percentages of total sugar and starch were not significantly affected by different levels of irrigation from 100% down to 50% except for starch percentage during the second season.

The obtained results, clearly demonstrated that there are large and mainly positive direct effects of both average tuber root weight (g) and number of tuber roots/plant on sweet potato yield (ton/fed.).

In briefly, It is recommended to select clone A1 (It was developed as a mutation resulting from the exposure of Abees cv.

to gamma ray) because it is characterized by a high productivity (ton / fed.) at 100% irrigation level or when there is a shortage of water supply (75% of evapotranspiration) compared with other tested sweet potato genotypes.

Also, clone M1 (It was developed as a mutation resulting from immerging of Mabrouka cv.

in colchicine solution) could be selected because of its high productivity, suitable for starch extraction, both when irrigation water is available or even when there is a shortage of irrigation water up to 75% of evapotranspiration.

Clone M2 (It was developed as a mutation resulting from immerging of Mabrouka cv.

in colchicine solution) could be the best choice where severe water shortage conditions (50% and 25% of evapotranspiration) are found.