Physiological Performance of Rice Seeds Treated to Thiamethoxam and Placed under Storage

High-yielding crops can only achieve their potential when the appropriate technological tools are applied and weather conditions do not impose restrictions. One such technological tool is the treatment of seeds, in which different products are used and, in some cases, cause little-known effects capable of modifying the plant’s metabolism and/or its morphology. The insecticide thiamethoxam alters the plant’s physiology and morphology, accelerating its development, thus enhancing its vigor. The objective of this study was to evaluate the influence of thiamethoxam on the physiological performance of rice seeds during storage. The research was conducted in a green-house and at the laboratory of the Department of Plant Science, Faculty of Agronomy Eliseu Maciel —UFPel (Federal University of Pelotas). Rice seeds from cultivars INIA Olimar and El Paso L144 were treated to a commercial product containing 350 grams of active ingredient thiamethoxam at doses of 0, 100, 200, 300, 400 and 500 g per 100 kg of seed. Seeds were tested for physiological quality immediately after being treated (check treatment) and at 3, 6, 9 and 12 months under storage, through germination test, cold test, accelerated aging and greenhouse emergence test. The concentration range from 200 to 400 g a.i. 100 kg-1 seed yielded the highest germination and seed vigor values for both rice cultivars during the storage period.

Hybrid Rice Seed Treatment with Pesticides Improves Its Physiological Quality and Performance

Pathogens in the soil or transmitted by seeds can reduce the stand of plants, affecting the yield of the crop. Furthermore, in the case of rice, the low temperature is a limiting factor in culture. The treatment of seeds with insecticides is an alternative to reduce the damage caused by pests incidents during the early stages of plant development and in some cases, may assist in the germination of seeds exposed to low temperatures. In this sense, the objective of this study was to evaluate the influence of seed treatment with insecticides in the physiological quality and yield of hybrid rice seeds, cv. Inov CL. For this, three experiments were conducted with treated seeds in different doses of thiamethoxam + lambda-cyhalothrin and fipronil totaling seven treatments, including the control (no product). In the first experiment, it was determined seed germination to 10°C, 13°C, 16°C, 20°C and 25°C. In the second experiment, it was assessed seed vigor through accelerated aging, cold test and emergency field. The third experiment was carried out into the field to observe the number of panicles m-2 and crop yield. It is concluded that treatment of hybrid rice seeds, cv. Inov CL with thiamethoxam + lambda-cyhalothrin and fipronil increases the germination percentage of seed and early seedling performance. Treatment of hybrid rice seeds, cv. Inov CL with thiamethoxam + lambda-cyhalothrin provides greater germination and early seedling performance compared to treatment with fipronil. Treatment of hybrid rice seeds, cv. Inov CL with thiamethoxam + lambda-cyhalothrin in dosages of 500 mL 100 kg-11 of seeds or 500 mL 45 kg-1 of seeds increases grain yield.

Isoenzyme Expression in Bean Seed Germination Treated with Thiamethoxam with and without Drought Stress

The thiamethoxam acts as enhancer, allowing maximizing the expression of seed vigor. Isozymes are products of gene expression, highly influenced by the environment, because genes that control its expression are manifested in certain stages of development and in specific organs and tissues, or even under the action of certain stimulus. This study evaluated the isoenzyme expression in bean seedlings from seeds treated with thiamethoxam. Bean seeds were used, cultivar Pérola and IAPAR Siriri, submitted or not to drought stress. Seeds were treated at doses of thiamethoxam: 0, 1, 2, 3, 4 and 5 mL·kg-1 of seed. Isozymes were extracted from seedlings collected five days after sowing. We evaluated the expression of isoenzymes: Glutamate Oxalacetate transaminase (GOT), acid phosphatase (FAC), peroxidase (PO), Esterase (EST), malate dehydrogenase (MDH) and glutamate dehydrogenase (GTDH). Interpretation of the results was based on visual analysis of electrophoresis gels, considering the presence/absence and the intensity of each electrophoretic band. Bean seeds treated with thiamethoxam with doses up 3 mL·kg-1 of seed are higher germination untreated, even when submitted to drought stress. The expression of isozymes GOT, FAC, PO, EST, MDH and GTDH is not affected significantly in bean seedlings of Pérola and IPR Siriri under different doses of thiamethoxam with and without drought stress.

Ecology of Upland Rice Plants and Seeds Subjected to Growth Regulator

The objective of this work is to verify the influence of the plant regulator trinexapac-ethyl on plant growth and physiological quality of upland rice seeds. We used an upland rice genotype, and the growth regulator was the trinexapac-ethyl. The experiment was completely randomized in a 4 × 8 factorial design related to four concentrations of the plant regulator trinexapac-ethyl [0 (without growth regulator), 0.25, 0.50, and 0.75 L c.p. ha-1] and 7 plant collection times [14, 28, 42, 56, 70, 84, 98 days after emergence (DAE)], with four replicates. To determine growth attributes, we evaluated total dry matter, dry matter production rate, relative growth rate, leaf area ratio, leaf matter, leaf area index, solar energy conversion efficiency and partition of assimilates. The physiological quality of the seeds was evaluated based on germination, first germination count, field emergence, emergence speed index and seedling dry matter. Plant growth was affected by the growth regulator. Total dry matter, dry matter production rate and solar energy conversion efficiency decreased, while leaf area index, leaf area ratio and leaf matter increased due to the effects of the growth regulator. The dry matter partition of plants changed in plants subjected to the growth regulator, with a delay in the targeting of assimilates to reproductive organs and a greater allocation to roots at the end of the cycle in plants subjected to the doses 0.50 and 0.75 L·ha-1 of growth regulator. Seed vigor was adversely affected by the growth regulator.

Accelerated Aging in Tomato Seeds

The tomato plant (Lycopersicum esculentum L.) is a perennial, shrubby-like vegetable with high reproductive ability, which behaves like a typical annual crop. The aim of this work was to select suitable tests to assess the quality of different lots of tomato seeds. Six batches of tomato seeds were assessed for parameter values: moisture content, germination, first count, accelerated aging (standard: 40 mL of water;saline solution: 11 g NaCl/100mL of water and saturated saline solution: 40 g NaCl/100mL water) and seedling emergence in soil. Accelerated aging through the use of saturated salt solution for 48 h or 72 h at 41°C resulted in an alternative and efficient way to evaluate the physiological quality of tomato seeds. The standard accelerated aging test was less efficient and exhibited higher moisture variation.