![]() ![]() ![]() Over the past 18 yr, Fusarium wilt race 4 (FOV4) has affected cotton (Gossypium spp.) production in the San Joaquin Valley of California, and more recently this pathogen was formally identified in 2017 in the El Paso, TX, region and in 2019 in New Mexico. No cultivars were identified with high resistance to Fov. The group of R-DP cultivars had excellent Mi resistance but were susceptible to Fov. ST 4946GLB2 had the lowest mortality (16.5%) and highest relative yield, while R-DP cultivars had the highest mortality and no difference in relative yield from the Mi-susceptible cultivars. All groups except R-DP averaged higher relative yield than the susceptible cultivars. Mi-susceptible cultivars averaged 23.3% mortality. Plant mortality (%) was higher for R-DP (28.1%) than for all other groups except ST 5600B2XF (24.8%). The S and R-FM groups had the highest transformed Mi densities LOG10(Mi + 1) (LMi = 3.22 and 3.01, respectively), while R-DP and R-PHY had the lowest LMi (2.21 and 1.85, respectively). Cotton cultivars were divided into groups based on company/Mi resistance: S = susceptible to Mi R-FM, R-DP, and R-PHY = resistance to Mi in FiberMax®, Deltapine®, and Phytogen® cultivars, respectively ST 4946GLB2 (moderate resistance to Mi and observed field tolerance to Fov) and ST 5600B2XF (resistance to Mi). However, SPS in susceptible Pima S-7 selected in field and greenhouse conditions did not decrease MR in their progeny, suggesting no or very low levels of frequencies of resistance gene(s) and resistant genotypes in this cultivar.Ĭotton (Gossypium hirsutum) cultivar trials were conducted in four fields (6 trials total) with Meloidogyne incognita (Mi)/Fusarium oxysporum f. SPS selected for no or low VD in Acala 1517–08 and Acala 1517–18 GLS in the greenhouse protocol had lower escapes and significantly reduced MR in their progeny compared to those selected in the field and unselected populations. However, MR in progeny rows in the field was not correlated with that in the greenhouse. 46.7–72.8%) than the field screening, although MR between the field and greenhouse screening was significantly and positively correlated. 22.2–39.5%) in the greenhouse screening which had lower coefficients of variation (28.3 vs. Results from 10 replicated tests each with 32 lines and 4 replications confirmed the higher MR (79.8 vs. 10–30%), suggesting a higher percentage of disease escapes in the field. ![]() 22.9%) with a much narrower range (75–89% vs. Results indicated that overall mean plant mortality rate (MR) in the greenhouse across the four years was more than three times mortality in the field (81.9 vs. Single plant selections (SPS) with no or low VD selected in a FOV4-infested field between 20 were progeny tested in both the field and greenhouse. To address plant selection efficiency under field conditions in a typical pedigree selection process for FOV4 resistance in cotton, a comparative analysis between the field and greenhouse evaluations and selections was performed. However, breeding for FOV4 resistance in Upland cotton is complex. ![]() FOV race 4 (FOV4) causes an early season disease with symptoms including seedling mortality and vascular discoloration (VD). vasinfectum (FOV) is one of the most destructive diseases. Upland cotton (Gossypium hirsutum L.) is the most important fiber crop in the world, and Fusarium wilt caused by the soil-borne fungus Fusarium oxysporum f. ![]()
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