Influence of <i>Meloidogyne incognita</i> and <i>Fusarium oxysporum</i> on Growth, Physiological, Biochemical, and Root Morphology in Tomato Hybrids Cultivars

Soil-borne pathogens can severely reduce vegetable crop output and quality. A disease complex may develop when many soil-borne pathogens attack a crop simultaneously, which can cause more damage. The soil-borne fungus <i>Fusarium oxysporum</i> (Fo) and the nematode <i>Meloidogyne incognita</i> (Mi) significantly reduce global tomato (<i>Solanum lycopersicum</i> L.) yields. After a soil-borne pathogenic infection, plants undergo numerous changes. Therefore, we conducted the present study to examine the impact of soil-borne pathogens Fo and Mi on the growth, physiology, biochemical, and root morphology of tomato cultivars Zhongza 09 (ZZ09) and Gailiang Maofen 802 (GLMFA and GLMFB) at 10, 20, and 30 days after-inoculation (DAI). The present study revealed that combined infections adversely damaged plant growth, photosynthetic pigmentation, gas exchange, biochemistry, and root morphology. The plant growth reduction in GLMFA and GLMFB was greater than in ZZ09. The chlorophyll content and photosynthetic indices declined dramatically; however, ZZ09 declined less than GLMFA and GLMFB plants. In GLMFA and GLMFB plants, the combined infection of Fo and Mi lowered plant-defense-related antioxidant activity compared to their single infection or control. ZZ09’s antioxidants were greatly up-regulated, indicating pathogen tolerance. ZZ09 had significantly lower gall and wilt disease indices than GLMFA and GLMFB. Moreover, the microscopic examination of roots showed that Fo and Mi infection damaged GLMFA and GLMFB more than ZZ09 plants. Thus, combined infection induced severe root damage, reduced plant growth, reduced antioxidants, and increased reactive oxygen species (ROS) production compared to single inoculation. However, the ZZ09 cultivar exhibited significantly stronger tolerance to combined infection.