Assessing genetic variation for Fusarium wilt race 4 resistance in tetraploid cotton by screening over three thousand germplasm lines under greenhouse or controlled conditions

Authors: ZHANG, JINFA - New Mexico State University; ABDELRAHEEM, ABDELRAHEEM - New Mexico State University; ZHU, YI - New Mexico State University; WHEELER, TERRY - Texas A&M Agrilife; DEVER, JANE - Texas A&M Agrilife; Frelichowski, James - Jim; Love, Janna; Ulloa, Mauricio; Jenkins, Johnie; McCarty, Jack; NICHOLS, ROBERT - Cotton, Inc; WEDEGAERTNER, TOM - Cotton, Inc

Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2020
Publication Date: 6/12/2020
Citation: Zhang, J., Abdelraheem, A., Zhu, Y., Wheeler, T.A., Dever, J., Frelichowski, J.E., Love, J., Ulloa, M., Jenkins, J.N., McCarty Jr, J.C., Nichols, R., Wedegaertner, T. 2020. Assessing genetic variation for Fusarium wilt race 4 resistance in tetraploid cotton by screening over three thousand germplasm lines under greenhouse or controlled conditions. Euphytica. 216:108. https://doi.org/10.1007/s10681-020-02646-2.
DOI: https://doi.org/10.1007/s10681-020-02646-2

Interpretive Summary: Cotton is the most important natural fiber crop for the textile industry, and one of its most destructive diseases worldwide is Fusarium wilt (FOV). This fungus caused wilt and death of plants with tremendous economic losses in cotton production. Resistant cotton varieties or germplasm lines against this fungus is the best method of control. In the USA, FOV race 4 (FOV4) is an emerging threat because no highly resistant commercial cotton variety is available. In this study, a total of 3258 lines with more than 1000 from the USDA-ARS National Cotton Germplasm Collection were screened in a greenhouse under controlled temperatures using soils inoculated with the FOV4 fungus. The overall detection rate of highly resistant lines was less than 1%. Temperature used ranged from 24 - 32 degrees to 20 - 21 degrees Celsius. Great damage to cotton by FOV4 occurs to small plants or seedlings under cold temperatures (20 - 21 degrees), suggesting that low temperature after spring planting under infested FOV4 fields may simulate or increase seedling disease mortality to FOV4. In addition, because of the difficulties of naturally infested FOV4 field screening of a large number of lines, a greenhouse or growth chamber screening under control temperature for resistance to FOV4 can speed up the process of potentially finding resistant lines to improve USA cotton.

Technical Abstract: Cotton (Gossypium spp.) is the most important natural fiber crop for the textile industry. Fusarium wilt, caused by Fusarium oxysporum f. sp. vasinfectum (FOV) with eight races, is one of the most destructive diseases in cotton. FOV race 4 (FOV4) is an emerging threat to cotton production in the US. In this study, a total of 3,258 lines including 3088 Upland cotton (G. hirsutum L.) lines and 170 Pima lines (G. barbadense L.) were evaluated in 21 tests in greenhouses or in temperature-controlled growth chambers for resistance to FOV4. A total of 2,224 lines from 13 tests were screened in commercial potting soil in the greenhouse under higher temperature (HT) conditions (24-32 degrees C), while 1,204 lines from 8 tests were screened in FOV4-infected farm soil in growth chambers at a lower temperature (LT) setting (20-21 degrees C), both with artificial inoculations. A subset of 170 Pima lines was evaluated in both temperature regimes. The results showed that, at 30 days post inoculation, both temperature regimes produced similar disease incidence (81.2 for HT vs. 86.8% for LT, P>0.05), but LT caused significantly higher disease severity ratings (DSR, 3.86 vs. 1.94) and plant mortality (81.7 vs. 7.5%) than HT. DSR and morality rate were highly significantly correlated at LT. Using the FOV4-infected soil and LT to screen 1,204 Upland and Pima germplasm lines with 20-40 plants for each line, 48.09% showed 100% mortality; 21.60% had a mortality rate between 70 and 99%; 5.33% had mortality below 30%; and 0.50% (6 lines) did not display any apparent FOV4 symptoms. The results indicated that FOV4 resistance may be heterogeneous in many existing germplasms and pedigree selection may increase frequencies of resistant plants. The study represents one of the first publicly reported large-scale screenings of cotton for FOV4 resistance in the US, providing useful information for breeding cotton for FOV4 resistance.