Shady A. Mottaleb, Essam Darwish, Menna Mostafa and Gehan Safwat
Soil salinity causes an annual deep negative impact to the global agricultural economy. In this study, the effects of salinity on early seedling physiology of two Egyptian cotton (Gossypium barbadense L.) cultivars differing in their salinity tolerance were examined. Also the potential use of a low cost mini-rhizotron system to measure variation in root system architecture (RSA) traits existing in both cultivars was assessed. Salt tolerant cotton cultivar ‘Giza 90’ produced significantly higher root and shoot biomass, accumulated lower Na+/K+ ratio through a higher Na+ exclusion from both roots and leaves as well as synthesized higher proline contents compared to salt sensitive ‘Giza 45’ cultivar. Measuring RSA in mini-rhizotrons containing solid MS nutrient medium as substrate proved to be more precise and efficient than peat moss/sand mixture. We report superior values of main root growth rate, total root system size, main root length, higher number of lateral roots and average lateral root length in ‘Giza 90’ under salinity. Higher lateral root density and length together with higher root tissue tolerance of Na+ ions in ‘Giza 90’ give it an advantage to be used as donor genotype for desirable root traits to other elite cultivars.
Aly Aly, Ezzat Hussein, Moawad Omar, Ibrahim El-Abbasi and Kamel Abd-Elsalam
Effect of fatty acid content on the level of cottonseed colonization by fungi
Non-sterilized seeds of 12 Egyptain cotton (Gossypium barbadense L.) genotypes were examined for qualitative and quantitative estimates of seed-borne fungi. Rhizopus stolonifer (39.7%), Aspergillus niger (33.5%), and Penicillium sp. (23.3%) were the most predominant fungi isolated from the seeds. Other fungi occurred at frequencies that ranged from 0.3 to 17.7%. Gas-liquid chromatography (GLC) analysis of fatty acid composition of the seeds revealed the presence of the following fatty acids: caproic, caprylic, capric, lauric, myristic, palmitic, margaric, stearic, oleic, linoleic, and linolenic. The total mean percentage of the monounsaturated fatty acids was 59.11%, while that of the unsaturated fatty acids was 16.72%. Isolation frequencies of Alternaria alternata, A. flavus, A. niger were not significantly correlated with the content of any fatty acid. Isolation frequencies of the other fungi were significantly correlated with the content of 1-2 fatty acids. Cladosporium sp. was a notable exception because its isolation frequency was significantly correlated with the content of caproic (r = 0.926, p < 0.01), caprylic (r = 0.638, p < 0.05), palmitic (r = -0.586, p < 0.05), and linoleic acid (r = 0.917, p < 0.01). It was possible to group the isolated fungi into 5 distinct categories based on their sensitivity to the fatty acids (the magnitude of R2 values). The results of the present investigation suggest that certain fatty acids regulate the colonization of cottonseed by fungi, and that the control of these fungi may be possible by modifying the fatty acid content of the seed.