Crops Responses to Mite Infestation: It's Time to Look at Plant Tolerance to Meet the Farmers' Needs

Oryza sativa cv. Nipponbare and Oryza barthii as Unexpected Tolerance and Susceptibility Sources Against Schizotetranychus oryzae (Acari: Tetranychidae) Mite Infestation

Cultivated rice (Oryza sativa L.) is frequently exposed to multiple stresses, including Schizotetranychus oryzae mite infestation. Rice domestication has narrowed the genetic diversity of the species, leading to a wide susceptibility. This work aimed to analyze the response of two African rice species (Oryza barthii and Oryza glaberrima), weedy rice (O. sativa f. spontanea), and O. sativa cv. Nipponbare to S. oryzae infestation. Surprisingly, leaf damage, histochemistry, and chlorophyll concentration/fluorescence indicated that the African species present a higher level of leaf damage, increased accumulation of H₂O₂, and lower photosynthetic capacity when compared to O. sativa plants under infested conditions. Infestation decreased tiller number, except in Nipponbare, and caused the death of O. barthii and O. glaberrima plants during the reproductive stage. While infestation did not affect the weight of 1,000 grains in both O. sativa, the number of panicles per plant was affected only in O. sativa f. spontanea, and the percentage of full seeds per panicle and seed length were increased only in Nipponbare. Using proteomic analysis, we identified 195 differentially abundant proteins when comparing susceptible (O. barthii) and tolerant (Nipponbare) plants under control and infested conditions. O. barthii presents a less abundant antioxidant arsenal and is unable to modulate proteins involved in general metabolism and energy production under infested condition. Nipponbare presents high abundance of detoxification-related proteins, general metabolic processes, and energy production, suggesting that the primary metabolism is maintained more active compared to O. barthii under infested condition. Also, under infested conditions, Nipponbare presents higher levels of proline and a greater abundance of defense-related proteins, such as osmotin, ricin B-like lectin, and protease inhibitors (PIs). These differentially abundant proteins can be used as biotechnological tools in breeding programs aiming at increased tolerance to mite infestation.

Tolerance in Maize Landraces to Diabrotica speciosa (Coleoptera: Chrysomelidae) Larvae and Its Relationship to Plant Pigments, Compatible Osmolytes, and Vigor

The rootworm Diabrotica speciosa (Germar) is native to South America and causes severe economic losses to several crops due to root feeding and disease spread. In maize (Zea mays L.), losses in production come from larval rootworm attack on plant roots resulting in plant health problems, including stalk lodging. More options for controlling this pest are needed to create well balanced, integrated pest management programs for farmers in this region. Natural sources of tolerance in maize genotypes are important for maize breeding programs, and this study investigated the expression of tolerance in several Brazilian maize landraces to D. speciosa. Plant vigor and compounds associated with plant health, including chlorophylls, carotenoids, glycine betaine, and proline were assessed for each landrace. Five landraces and one maize cultivar were selected based on their levels of antibiosis-resistance to D. speciosa that were determined in a prior screening. The percent reduction in plant growth was used as the measure of tolerance. The landrace Azteca was classified as tolerant to D. speciosa larval feeding, displaying less reduction in plant matter despite having lower plant vigor. This landrace also had higher amounts of chlorophyl and carotenoid pigments, suggesting a positive correlation between tolerance to D. speciosa and higher contents of these photosynthetic pigments. The compatible osmolytes glycine betaine and proline do not seem to be associated with tolerance in maize landraces to D. speciosa larvae. Landrace Azteca seems promising for plant breeding, and repeated field studies are needed to confirm its suitability in maize integrated pest management.

Resistance of some commercial walnut cultivars and genotypes to Aceria tristriata (Nalepa) (Acari: Eriophyidae) and its correlation with some plant features

BACKGROUND

The walnut leaf gall mite (WLGM) (Aceria tristriata (Nalepa)) is one of the major pests of walnut in western Iran. The use of a resistant variety is an economical and environment-friendly method of pest control. The aim of the present study is to assess resistance of some walnut cultivars and genotypes in relation to WLGM. Also, the current research aimed to study a possible correlation between resistance with plant morphological and biochemical features.

RESULTS

Based on the leaf damage index (number of galls per leaf and plant, the percentage of infested leaves and the percentage of leaf injury area) induced by WLGM, the studied cultivars and genotypes were classified into four groups from susceptible to approximately resistant. Free-choice experiments indicated that Jamal and Chandler cultivars were colonized by lower densities of WLGM, whereas Seedling, Hartly, Lara and Z60 hosted denser populations. In antibiosis assay, the highest mite density was created in the galls on the leaves of Seedling and Hartly, whereas lowest mite density was observed in galled leaves of Chandler and Jamal cultivars.

CONCLUSION

Results from biochemical assays showed that nearly all evaluated biomarkers had negative correlation with number of galls per leaf and mite density. Generally, resistant cultivars (Chandler, Jamal and Pedro) significantly produced defensive compounds more than those of controls after mite infestation. Also, it is worth noting that, the content of photosynthetic pigments significantly reduced in susceptible cultivars after mite infestation. The obtained results from this study can be useful for provisional resistance screening. © 2019 Society of Chemical Industry.

An Intimate Relationship Between Eriophyoid Mites and Their Host Plants - A Review

Eriophyoid mites (Acari Eriophyoidea) are phytophagous arthropods forming intimate relationships with their host plants. These mites are associated with annual and perennial plants including ferns, and are highly specialized with a dominant monophagy. They can be classified in different ecological classes, i.e., vagrant, gall-making and refuge-seeking species. Many of them are major pests and some of them are vectors of plant pathogens. This paper critically reviews the knowledge on eriophyoids of agricultural importance with emphasis on sources for host plant resistance to these mites. The role of species belonging to the family Eriophyidae as vectors of plant viruses is discussed. Eriophyoid-host plant interactions, the susceptibility within selected crops and main host plant tolerance/resistance mechanisms are discussed. Fundamental concepts, subjects, and problems emerged in this review are pointed out and studies are suggested to clarify some controversial points.

Unraveling Rice Tolerance Mechanisms Against Schizotetranychus oryzae Mite Infestation

Rice is the staple food for over half of the world's population. Infestation of Schizotetranychus oryzae (Acari: Tetranychidae) causes great losses in rice productivity. To search for rice genotypes that could better tolerate S. oryzae infestation, we evaluated morphological and production parameters in Brazilian cultivars, and identified two cultivars with contrasting responses. Leaf damage during infestation was similar for all cultivars. However, infestation in Puitá INTA-CL resulted in reduction in the number of seeds per plant, percentage of full seeds, weight of 1,000 seeds, and seed length, whereas infestation in IRGA 423 increased weight of 1,000 seeds and seed length. Reduction in seed weight per plant caused by infestation was clearly higher in Puitá INTA-CL (62%) compared to IRGA 423 (no reduction detected), thus Puitá INTA-CL was established as susceptible, and IRGA 423 as tolerant to S. oryzae infestation. Photosynthetic parameters were less affected by infestation in IRGA 423 than in Puitá INTA-CL, evidencing higher efficiency of energy absorption and use. S. oryzae infestation also caused accumulation of H2O2, decreased cell membrane integrity (indicative of cell death), and accelerated senescence in leaves of Puitá INTA-CL, while leaves of IRGA 423 presented higher levels of total phenolics compounds. We performed proteomics analysis of Puitá INTA-CL and IRGA 423 leaves after 7 days of infestation, and identified 60 differentially abundant proteins (28 more abundant in leaves of Puitá INTA-CL and 32 in IRGA 423). Proteins related to plant defense, such as jasmonate synthesis, and related to other mechanisms of tolerance such as oxidative stress, photosynthesis, and DNA structure maintenance, together with energy production and general metabolic processes, were more abundant in IRGA 423. We also detected higher levels of silicon (as amorphous silica cells) in leaves of infested IRGA 423 plants compared to Puitá INTA-CL, an element previously linked to plant defense, indicating that it could be involved in tolerance mechanisms. Taken together, our data show that IRGA 423 presents tolerance to S. oryzae infestation, and that multiple mechanisms might be employed by this cultivar. These findings could be used in biotechnological approaches aiming to increase rice tolerance to mite infestation.

Unraveling Rice Tolerance Mechanisms Against Schizotetranychus oryzae Mite Infestation

Rice is the staple food for over half of the world's population. Infestation of Schizotetranychus oryzae (Acari: Tetranychidae) causes great losses in rice productivity. To search for rice genotypes that could better tolerate S. oryzae infestation, we evaluated morphological and production parameters in Brazilian cultivars, and identified two cultivars with contrasting responses. Leaf damage during infestation was similar for all cultivars. However, infestation in Puitá INTA-CL resulted in reduction in the number of seeds per plant, percentage of full seeds, weight of 1,000 seeds, and seed length, whereas infestation in IRGA 423 increased weight of 1,000 seeds and seed length. Reduction in seed weight per plant caused by infestation was clearly higher in Puitá INTA-CL (62%) compared to IRGA 423 (no reduction detected), thus Puitá INTA-CL was established as susceptible, and IRGA 423 as tolerant to S. oryzae infestation. Photosynthetic parameters were less affected by infestation in IRGA 423 than in Puitá INTA-CL, evidencing higher efficiency of energy absorption and use. S. oryzae infestation also caused accumulation of H₂O₂, decreased cell membrane integrity (indicative of cell death), and accelerated senescence in leaves of Puitá INTA-CL, while leaves of IRGA 423 presented higher levels of total phenolics compounds. We performed proteomics analysis of Puitá INTA-CL and IRGA 423 leaves after 7 days of infestation, and identified 60 differentially abundant proteins (28 more abundant in leaves of Puitá INTA-CL and 32 in IRGA 423). Proteins related to plant defense, such as jasmonate synthesis, and related to other mechanisms of tolerance such as oxidative stress, photosynthesis, and DNA structure maintenance, together with energy production and general metabolic processes, were more abundant in IRGA 423. We also detected higher levels of silicon (as amorphous silica cells) in leaves of infested IRGA 423 plants compared to Puitá INTA-CL, an element previously linked to plant defense, indicating that it could be involved in tolerance mechanisms. Taken together, our data show that IRGA 423 presents tolerance to S. oryzae infestation, and that multiple mechanisms might be employed by this cultivar. These findings could be used in biotechnological approaches aiming to increase rice tolerance to mite infestation.