The soil-borne fungus Fusarium oxysporum (Fo) and the nematode Meloidogyne incognita (Mi) are destructive pathogens that cause substantial yield losses to tomato (Solanum lycopersicum L.) crops worldwide. The present study sought to elucidate the physiological, biochemical, and cytological responses of tomato cultivars (Gailing maofen 802 and Zhongza 09) by root invasion of Fo (1 × 10⁵ CFUmL⁻¹) and Mi (1500 second-stage juveniles (J2) alone and in combination after 14 days. Results revealed that combined inoculation of Fo and Mi significantly increased disease intensity, electrolyte leakage, and hydrogen peroxide and malondialdehyde contents; and decreased photosynthetic capacity and enzyme activity in both cultivars as compared to their solo inoculation. Increasing the disease intensity reduced the maximum morphological traits, such as shoot length, total dry weight, and total chlorophyll contents, in G. maofen 802 (by 32%, 54.2%, and 52.3%, respectively) and Zhongza 09 (by 18%, 32%, and 21%, respectively) as compared to the control. Others factors were also reduced in G. maofen 802 and Zhongza 09, such as photosynthetic capacity (by 70% and 57%, respectively), stomatal conductance (by 86% and 70%, respectively), photochemical quantum yield of photosystem II (YII) (by 36.6% and 29%, respectively), and electron transport rate (by 17.7% and 10%, respectively), after combined inoculation of Fo and Mi. Furthermore, the combined infestation of Fo and Mi resulted in reduced activity of plant-defense-related antioxidants in G. maofen 802 compared with their single application or control. However, these antioxidants were highly up-regulated in Zhongza 09 (by 59%–93%), revealing the induction of tolerance against studied pathogens. The transmission electron microscopy (TEM) results further demonstrated that root cells of Zhongza 09 had unique tetrahedral crystal-like structures in the membrane close to mitochondria under all treatments except control. Therefore, it is concluded that Mi caused severe root damage, suppressed plant growth, depleted antioxidants, and caused high generation of ROS in the presence of Fo as compared to its solo inoculation. Tolerant cultivars adopted different mechanistic strategies at the structural and cellular levels to tolerate the Mi and Fo stresses.

The root-knot nematode is one of the most damaging plant-parasitic nematodes worldwide, and the ecofriendly alternative approach of biological control has been used to suppress nematode populations. Here the nematicidal activity of Aspergillus japonicus ZW1 fermentation filtrate against Meloidogyne incognita was evaluated in vitro and in greenhouse, and the effects of A. japonicus ZW1 fermentation filtrate on seed germination and the active compound of A. japonicus ZW1 fermentation filtrate were determined. The 2-week fermentation filtrate (2-WF) of A. japonicus ZW1 exhibited markedly inhibitory effects on egg hatching, and 5% 2-WF showed potential nematicidal activities on second-stage juveniles (J2s); the mortality of J2s was 100% after 24 h exposure. The internal contents of nematodes were degraded and remarkable protruded wrinkles were present on the body surface of J2s. The nematicidal activity of the fermentation was stable after boiling and was not affected by storage time. A germination assay revealed that 2-WF did not have a negative effect on the viability and germination of corn, wheat, rice, cowpeas, cucumbers, soybeans, or tomato seeds. The pot-grown study confirmed that a 20% fermentation broth solution significantly reduced root galls and egg numbers on tomatoes, and decreased galls and eggs by 47.3% and 51.8% respectively, over Czapek medium and water controls. The active compound from the A. japonicus ZW1 fermentation filtrate was isolated and identified as 1,5-Dimethyl Citrate hydrochloride ester on the basis of nuclear magnetic resonance (NMR) and LC-MS (liquid chromatograph-mass spectrometer) techniques. Thus, fermentation of A. japonicus ZW1 could be considered a potential new biological nematicide for the control of M. incognita.

Yuanjiang dry–hot valley is located in the southwest of mainland China. It is a sparsely vegetated area with a fragile arid ecosystem. Although the valley previously had forest cover, it has become a tropical montane savannah in recent decades. Mechanisms controlling plant species distribution in such dry–hot valleys are unclear. Clarifying this will be beneficial to sustainable ecosystem management in dry–hot valleys. This study explored the relationship between diversity patterns of plant species and their environments in the lowland of this dry–hot valley. To achieve this, transects and plots were arranged along the river channel. Alpha and beta diversity indices were calculated to quantify biodiversity changes between species and environments. Estimated species, rarity, and abundance indices were also utilized to examine the correlation among species, their population size, and their environment: Species_estimated (expected number of species in t pooled plots), Singletons (the number of species with only one individual in t pooled plots), Uniques (the number of species living in one plot in t pooled plots), ACE (species richness estimator with coverage-based abundance), ICE (species richness estimator with coverage-based incidence), and Chao2 (species richness estimator extrapolated from Singletons). Fifty years of meteorological records, including temperature and precipitation, were utilized as climate variables. The results indicated the following findings: (1) alpha diversity was higher closer to the river, whereas the beta diversity was higher towards the lower sections of the river (Bray–Curtis < 0.5), but this trend was reversed in the perpendicular transects; (2) total phosphorous (TP) and total potassium (TK) were higher on flatter ground, tending to be associated with raised nitrogen (TN) and organic matter (OM); (3) soil nutrients were higher towards the lower sections of the river, corresponding to an increased number of species; (4) water supply determined plant distribution, with soil condition determining water retention; (5) the estimated species and their rarity and abundance indices were associated with proximity to the river, indicating heterogeneity of habitats and soil condition; and (6) fern species could be used as indicators representing the xeric environment of Yuanjiang dry–hot valley. Plant cover was reduced at low altitudes, with high temperatures and a low water supply. These results draw attention to the need for specific policy formation to protect the microhabitats and manage the environment of the Yuanjiang valley.