Mechanisms Of Lanthanum Silicate Nanomaterials For Enhancing Resistance To Rice Sheath Blight

The world population is expected to exceed the 10 billion mark by 2050,and the global grain output needs to increase by 60%to meet the food demand of human beings.At present,crop yield reduction caused by crop diseases and insect pests accounts for 20%-40%of global food crop output,which seriously threatens global food security.Therefore,the development of new and efficient crop diseases and insect pests control technology has become a hot research topic in the world.In recent years,nano-agricultural control technology has shown bright prospect in controlling crop diseases and insect pests.However,the disease control effect of single element nanomaterials（NMs）still needs to be improved.Therefore,the synthesis of composite nanomaterials with different morphologies can not only significantly improve the bioavailability of NMs,but also further broaden the application range of NMs in the field of crop disease regulation.Studies have shown that lanthanum（La）and silicon（Si）play the important roles in regulating crop disease resistance,but there are still a lack of relevant reports on the disease resistance and mechanism of La-Si nanocomposites.Therefore,La-Si nanocomposites with different morphologies were prepared,the optimal culture system of La-Si nanocomposites was constructed with rice as the test crop,and the internal mechanism of composite nanocomposites in regulating crop diseases was explored.The key discoveries are as follows:（1）Three kinds of La-based nanomaterials were synthesized,silicon-containing rod-like La₁₀Si₆O₂₇ nanorods（NRs,length 84.5±34.3 nm,width 10.1±2.7 nm）,silicon-containing spherical La₁₀Si₆O₂₇ nanoparticles（NPs,82.6±31.7 nm）,silica-free rod-like La（OH）₃ NRs（length 28.5±8.9 nm,width 7.8±2.1 nm）.La₁₀Si₆O₂₇ NRs exhibits strong electropositivity（33.4m V）.By adjusting the morphology and composition of NMs,the rod-like La₁₀Si₆O₂₇ NRs and La（OH）₃ NRs have better La³⁺release ability.（2）Foliar spraying(50-200 mg·L^-1)La₁₀Si₆O₂₇ nanorods（NRs）significantly reduced the incidence of rice sheath blight（46.2%-62.4%）.Foliar application of 100 mg·L^-1 La₁₀Si₆O₂₇NRs showed the best disease control performance,which not only significantly reduced the incidence of rice sheath blight by 62.4%,but also significantly increased the aboveground fresh weight of infected rice by 45.2%and the number of tillers by 140%.To sum up,La₁₀Si₆O₂₇NRs has a concentration effect on controlling rice sheath blight.（3）Subsequently,the disease control effects of lanthanum-based nanomaterials with different morphologies were studied.It was found that the disease control effect of 100 mg·L^-1different La based NMs was in the order of La₁₀Si₆O₂₇ NRs>La₁₀Si₆O₂₇ NPs>La（OH）₃ NRs>La₂O₃ NPs.At the same time,the ability of La₁₀Si₆O₂₇ NRs and La₁₀Si₆O₂₇ NPs to control crop diseases was significantly higher than that of the traditional pesticide thifluzamide.The mechanisms of La₁₀Si₆O₂₇ NRs regulating rice disease resistance are as follows:（1）La₁₀Si₆O₂₇NRs not only has high bioavailability and sustained release ability,but also can improve Si accumulation in rice.（2）Gene and metabolomic analysis showed that La₁₀Si₆O₂₇ NRs enhanced the system-acquired resistance,physical barrier and antioxidant enzymes activity of rice.The above results show that the composition and morphology of lanthanum-based nanomaterials have important impact on improving the disease resistance of rice.（4）The whole growth cycle experiment showed that,compared with the pesticide control group（thifluzamide）,foliar application of La₁₀Si₆O₂₇ NRs not only significantly increased the yield of rice（increased by 35.4%）,but also increased the content of starch（increased by 11.93%）and protein（increased by 4.2%）.At the same time,the application of La₁₀Si₆O₂₇ NRs did not cause the accumulation of La in rice grains.Finally,we found the net economic benefit of La₁₀Si₆O₂₇ NRs per hectare is 9.9 times that of traditional pesticides.In conclusion,the study found that composite La-based nanomaterials can inhibit the occurrence of rice sheath blight by regulating crop disease resistance.Meanwhile,the rod-like composite La-based nanomaterials(La₁₀Si₆O₂₇ NRs)has better disease control effect than other treatments,which could significantly increase the yield and the nutritional quality of diseased rice.Therefore,the results show that rational adjustment of the morphology and composition of nanomaterials is beneficial to improve the efficiency of nanomaterials in the field of crop disease control,and provides a new idea for the development of new and efficient nanoagricultural composite modifier in the future.