Identification of resistance to Aspergillus flavus infection in cotton germplasm

Authors: MOORE, JOCELYN - University Of Louisiana At Lafayette; Rajasekaran, Kanniah - Rajah; Cary, Jeffrey; CHLAN, CARYL - University Of Louisiana At Lafayette

Submitted to: Journal of Crop Improvement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/6/2017
Publication Date: 9/21/2017
Citation: Moore, J., Rajasekaran, K., Cary, J.W., Chlan, C. 2017. Identification of resistance to Aspergillus flavus infection in cotton germplasm. Journal of Crop Improvement. 31(5):727-741. https://doi.org/10.1080/15427528.2017.1353564.
DOI: https://doi.org/10.1080/15427528.2017.1353564

Interpretive Summary: The fungus Aspergillus flavus infects oil-rich seeds of cotton, corn, peanut and tree nuts and produce aflatoxin which poses a significant health hazard to higher animals including humans. Cottonseed cake, after oil extraction, is often used as a protein-rich animal feed in several countries. Conventional breeding of crops resistant to the fungal toxin is possible only when the resistance is found in its germplasm. Cotton is one of the susceptible crops where the existence of native resistance to A. flavus has not been explored so far. This study reports on the possibility of innate resistance in cotton germplasm due to the presence of antifungal proteins in cotyledons. Seed cotyledons were artificially infected with a green fluorescent protein - expressing fungal strain and they were evaluated for the infection spread in 35 cotton varieties representing three different species including the commercially-cultivated upland cottons (Gossypium hirsutum). The results suggested that cotyledons from tree cotton species (Gossypium arboreum) showed resistance to fungal invasion, better than the other two species (Sea Island or Upland cottons). However, there was no relationship between the limited number of species used and resistance. Identification of native antifungal protein(s) is essential for breeding or genetic engineering of cotton for resistance to aflatoxin contamination.

Technical Abstract: Natural resistance of in cottonseed to Aspergillus flavus infection has not been explored to date. A green fluorescent protein (GFP) expressing -70 strain was used to assess the resistance of seed from thirty five35 cotton varieties including representatives from Gossypium arboreum, G. barbadense, and G. hirsutum. Mature cotyledons devoid of seedcoat were wounded, inoculated, and assessed for innate resistance to A. flavus infection using a seed screening assay. Of the initial 35 cultivars varieties tested, we observed a range of resistance to infection in representatives of all three species. A subset of 15 representatives was further analyzed. Within this group, G. arboreum cultivar A2 186 and G. hirsutum cultivar SA 1582 were most resistant to fungal infection. The most susceptible cultivar in this group was G hirsutum SA 1595. The remaining 12 representatives tested in the secondary screen (3 G. arboreum, 3 G. barbadense and 6 G. hirsutum lines) exhibited intermediate resistance. We did not observe any relationship between species and resistance. Within each species, there was a range of responses to fungal infection. Future studies using this methodology to screen additional diploid and tetraploid cotton lines may enable us to identify naturally resistant germplasm that can be used to develop cotton with enhanced resistance to fungal infection.