Silicon improves the emergence and sanity of rice seedlings obtained from seeds infected with Bipolaris oryzae

This study investigated the importance of silicon (Si) in rice grain husk in association with fungicide treatment for preventing Bipolaris oryzae transmission from seed to seedling and the improvement in seedling emergence. Plants from cv. Oochikara and its mutant (lsi1 mutant) defective in active Si uptake were grown in nutrient solution without (-Si) or with (+Si) Si and their panicles were inoculated with B. oryzae. Seeds were evaluated for brown spot severity (BSS) and husk Si concentration. The Si concentration in the husks of cv. Oochikara plants was up to four times higher than the lsi1 mutant plants. BSS was significantly reduced in the husks of the seeds obtained from +Si plants, particularly for cv. Oochikara. A higher percentage of seedling emergence occurred for +Si plant seeds, particularly for cv. Oochikara, and a lower percentage of infected seedlings was observed for the +Si cv. Oochikara treatment, particularly for the fungicide treated seeds. Fungicide was not efficient in preventing seedling infection by B. oryzae for seeds with BSS greater than 50%. High Si concentration in the husk resulted in lower BSS and the fungicide efficiency was greater with a low BSS on seeds from +Si plants, particularly for cv. Oochikara

Rice grain resistance to brown spot and yield are increased by silicon

Brown spot, caused by Bipolaris oryzae, is one of the most important diseases of rice and can cause a reduction in yield and grain quality. The effect of silicon (Si) on the resistance of rice grains to brown spot was investigated. Plants from cv. Oochikara and its mutant, defective in the Lsi1 transporter (lsi1 mutant), were grown in hydroponic culture either with Si (+Si; 2 mM) or without Si (-Si). Panicle inoculation with B. oryzae was carried out at the beginning of the milk-grain stage. Panicles were harvested at physiological grain maturity. The supply of Si significantly increased Si concentration in husks compared to -Si plants. Si concentration in husks from cv. Oochikara was up to three times greater than the lsi1 mutant. In the presence of Si, brown spot severity was reduced by 88% in grains from cv. Oochikara and by 53% in grains from lsi1 mutant. Brown spot severity was 77% lower for grains of cv. Oochikara than for the lsi1 mutant, both plant types were grown in the presence of Si. Panicle inoculation reduced significantly the following yield components: number of grains per panicle, the weight of 1000 grains and the percentage of filled grains. Si significantly increased these yield components, especially for inoculated panicles. Considering kernel quality, the panicle inoculation with B. oryzae significantly reduced the yield of husked kernel, yield of whole kernel and kernel diameter, especially for grains from -Si plants. For panicles from +Si plants, the kernel quality was improved under inoculation, compared to -Si plants. Results from this study show that Si improved rice yield and kernel quality in panicles inoculated with B. oryzae. Furthermore the functional Lsi1 gene contributed significantly for increasing the yield of whole kernel and kernel diameter, possibly due to the increasing Si concentration in husks

Equipamentos de pulverização aérea e taxas de aplicação de fungicida na cultura do arroz irrigado Spraying equipment and rates of fungicide application in irrigated rice

O controle eficiente de doenças na cultura do arroz irrigado depende da seleção correta do equipamento, da taxa de aplicação e da indicação certa do produto químico. O objetivo deste trabalho foi verificar a deposição de gotas na cultura do arroz comparando-se bicos hidráulicos no sistema convencional, eletrostático e atomizador rotativo de disco, em diferentes taxas de aplicação por via aérea; para tanto, foram estudadas a densidade e a penetração de gotas nos estratos médio e inferior, produtividade e rendimento de engenho do arroz. Os tratamentos avaliados foram: bico hidráulico 20 e 30 L ha-1, eletrostático 5 e 10 L ha-1 e atomizador rotativo de disco 6, 10 e 15 L ha-1. Não foram verificadas diferenças de produtividade e os equipamentos bico hidráulico 20 L ha-1 e atomizador rotativo de disco 15 L ha-1 proporcionaram maior rendimento de engenho. Maiores taxas de aplicação usando-se bicos hidráulicos e atomizador rotativo proporcionaram maior penetração e, consequentemente, também maior densidade de gotas nos dois estratos avaliados.<br>The efficient chemical control in irrigated rice depends on the correct selection of equipment, rates of application and correct statement of the chemical product. The objective of this study was to evaluate the hydraulic nozzle equipment, electrostatic system and rotary-disk atomizer for aerial application of fungicides, relating to penetration and density of droplets with application rates and equipment in the middle and lower strata, in addition to the productivity and hulling yield in irrigated rice. The treatments were: nozzle hydraulic 20 and 30 L ha-1, electrostatic system 5 and 10 L ha-1, rotary-disk atomizer 6, 10 and 15 L ha-1. There was no difference in productivity and equipment hydraulic nozzle 20 L ha-1 and rotary-disk atomizer 15 L ha-1 showed a higher hulling yield. On average, higher rates had higher penetration and density in both the evaluated canopy strata