|Doan, Hung - University Of California|
|Bell, Alois - Al|
|Davis, R - University Of California|
|Stipanovic, Robert - Bob|
|Nichols, Robert - Cotton, Inc|
Submitted to: European Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/8/2015
Publication Date: 9/12/2015
Citation: Crutcher, F.K., Doan, H.K., Bell, A.A., Davis, R.M., Stipanovic, R.D., Nichols, R.L., Liu, J. 2015. Evaluation of methods to detect the cotton wilt pathogen Fusarium oxysporum f. sp. vasinfectum race 4. European Journal of Plant Pathology. 144(1):225-230.
Interpretive Summary: Fusarium oxysporum f. sp. vasinfectum (Fov) race 4, a cause of cotton wilt disease, has become an increasingly important problem in the cotton producing areas of the San Joaquin Valley of California. Currently, it is found only in this area, but it can be introduced into new areas of cotton production by the movement of seed. To prevent the transmission and movement of this disease to other cotton production areas, a diagnostic kit was developed for use in cotton fields. It is an important diagnostic tool to identify plants infected with Fov race 4. Herein, an evaluation of the specificity of this kit is reported. The kit was assessed with 36 unique samples of Fov from the U.S. and from many locations around the world. Fov isolates that tested positive with the diagnostic kit were expected to be negative; however, these specific isolates have not been found within the US and do not constitute an immediate threat to cotton production.
Technical Abstract: Fusarium wilt caused by Fusarium oxysporum f. sp. vasinfectum (Fov) is an economically significant disease of cultivated cottons (Gossypium hirsutum and G. barbadense). Fov race 4 has spread among soils planted to cotton in the San Joaquin Valley of California and has caused serious losses. Because Fov 4 is seed borne and persists in infested soils, it is a potential threat to all US cotton production. Tests have been developed to rapidly identify race 4 in the laboratory and the field, including a race 4 specific PCR and a test kit for use with fungal mycelium and infected plant tissue. Currently, the test kit is the only available method to identify race 4 in the field. Both the PCR and kit tests were evaluated on a panel of 36 Fov isolates that represented all described races and most genotypes from several geographic origins. As expected, race 4 isolates gave positive reactions as did race 7 isolates. Though race 7 isolate 1760 is not vegetatively compatible with race 4 type strain, the other isolate of race 7 is compatible. Both race 7 isolates and race 4 have identical partial sequences in three nuclear genes. In addition, the race 3 type strain gave a positive reaction. All the other isolates, including the Australian isolates, were negative. The diagnostic tests clearly distinguished race 4 from races 1, 2, 6, and 8 but not from the race 3 and race 7 isolates tested here, which have etiology similar to that of race 4.