Abstract:(2)Resumo -A obtenção comercial de sementes da linhagem macho-estéril é uma das limitações para viabilizar a produção de híbridos de arroz (Oryza sativa L.). Este trabalho buscou estudar três proporções entre a linhagem macho-estéril (linhagem A) e a mantenedora (linhagem B). As proporções estudadas foram 8:4, 10:2 e 14:4. As características avaliadas para determinar qual das proporções apresenta maior potencial foram: número e porcentagem de grãos cheios por panículas, e número de grãos de pólen por unidade d… Show more
“…The combination of the first two lines (A and B) produces seeds that originate from male-sterile plants (line A seeds). The cross between A and R lines produces hybrid seeds originating from fertile plants (Bragantini, Guimarães, & Cutrim, 2001).…”
The high price of rice hybrid seeds is one of the major limiting factors for increasing the use of this technology. An important step toward minimizing high rice hybrid seed cost is developing techniques that help improve hybrid seed yield. Our goal was to determine the proportion of seeds of line A (receptor) and line R (pollinator) that, under mixed sowing, would allow optimized rice hybrid seed production and grain quality. Trials were performed for two growing seasons in the southern region of Brazil. The cultivar INTA Puita was used as a pollinator and line 464 A as receptor. The experimental design was a randomized block with four replications. Treatments included six proportions of seeds of the INTA Puita (0.75, 1.5, 3.0, 6.0, 12.0, and 24.00%) mixture with seeds of line 464 A (99.25, 98.50, 97.00, 94.00, 88.00, and 76%, respectively). By increasing the percentage of the pollinator seeds (INTA Puita CL) from 0.75 to 24% in the mixture with the receptor (line 464 A), we increased yield of INTA Puita CL grains (7 to 2676 kg ha-1) and hybrid seeds (279 to 1493 kg ha-1). The mixture of different proportions of INTA Puita CL (pollinator) with the receptor (line 464 A) did not change the rice grain quality or the production cost. The cost of production per kg of hybrid seeds decreased quadratically with the increasing percentage of the pollinator (INTA Puita CL), from US$ 6.71 to US$ 1.23. Revenue achieved from the commercialization of the grains of INTA Puita CL with hybrid seeds 464 A showed quadratic increases with the increased percentage of INTA Puita cl in the mixture. Our results showed a potential technique that could be used to improve hybrid seed production, reduce cost per kg of hybrid seed and improve revenue from producing rice hybrid seeds.
“…The combination of the first two lines (A and B) produces seeds that originate from male-sterile plants (line A seeds). The cross between A and R lines produces hybrid seeds originating from fertile plants (Bragantini, Guimarães, & Cutrim, 2001).…”
The high price of rice hybrid seeds is one of the major limiting factors for increasing the use of this technology. An important step toward minimizing high rice hybrid seed cost is developing techniques that help improve hybrid seed yield. Our goal was to determine the proportion of seeds of line A (receptor) and line R (pollinator) that, under mixed sowing, would allow optimized rice hybrid seed production and grain quality. Trials were performed for two growing seasons in the southern region of Brazil. The cultivar INTA Puita was used as a pollinator and line 464 A as receptor. The experimental design was a randomized block with four replications. Treatments included six proportions of seeds of the INTA Puita (0.75, 1.5, 3.0, 6.0, 12.0, and 24.00%) mixture with seeds of line 464 A (99.25, 98.50, 97.00, 94.00, 88.00, and 76%, respectively). By increasing the percentage of the pollinator seeds (INTA Puita CL) from 0.75 to 24% in the mixture with the receptor (line 464 A), we increased yield of INTA Puita CL grains (7 to 2676 kg ha-1) and hybrid seeds (279 to 1493 kg ha-1). The mixture of different proportions of INTA Puita CL (pollinator) with the receptor (line 464 A) did not change the rice grain quality or the production cost. The cost of production per kg of hybrid seeds decreased quadratically with the increasing percentage of the pollinator (INTA Puita CL), from US$ 6.71 to US$ 1.23. Revenue achieved from the commercialization of the grains of INTA Puita CL with hybrid seeds 464 A showed quadratic increases with the increased percentage of INTA Puita cl in the mixture. Our results showed a potential technique that could be used to improve hybrid seed production, reduce cost per kg of hybrid seed and improve revenue from producing rice hybrid seeds.
The use of hybrid genotypes is a good alternative for increasing the flooded rice yield. However, there is a need for validation of the fertilizer management under different edaphoclimatic conditions and its greater profitability. This study aimed to evaluate the grain yield and profitability of rice hybrids in relation to N doses and fertilization with P and K. Five hybrid cultivars and the conventional IRGA 424 CL cultivar combined with four N doses (0, 100, 150 and 200 kg ha-1) were evaluated, all with fixed doses of 90 kg ha-1 of P2O5 and 150 kg ha-1 of K2O, besides an additional treatment without the addition of fertilizers. The N application increases, on average, by 10 and 35 % the flooded rice yield in years with favorable and unfavorable climatic conditions, respectively. Regardless of the year and genotype, the highest yields are obtained with doses of N between 106 and 200 kg ha-1, with the most profitable dose being the 150 kg ha-1 one (22 % higher than for the absence of N). The hybrids produce an average of 20 % more grains than the IRGA 424 CL cultivar, increasing the profitability by 18 %. In soil with adequate P and K availability, there is no increase in yield due to the application of these nutrients. However, in deficient soil, the fertilization with P and K increases the grain yield by 21 %.
The hypothesis of this study is based on the fact that parental line A-Clearfield® (male-sterile genotype) (Clearfield provide has tolerance to imidazolinone herbicides) and line R (male-fertile genotype-pollinator) is sensitive to the herbicide. So after flowering, we may apply an imidazolinone herbicide (Kifix®) to the plantings to kill line R, and harvesting only the hybrid seeds. The objective was to test the use of imidazolinone herbicide on parental lines (A-Clearfield® which is resistant to Kifix herbicide) and R no Clearfield® (non-resistant to Kifix genotype) as a strategy to improve production of hybrid seed in rice. Two trials were conducted to evaluate (A) the use of doses of imidazolinone herbicide in line R (plant control, number of grains per panicles, grain yield and seed germination; and (B) the use of different doses of imidazolinone herbicide in line A Clearfield® grain yield and seed germination. Trials were conducted in the tropical region of Brazil in randomized complete block design in factorial scheme 5 x 2 x 2. The treatments were the combination of five Kifix (Imazapyr, 525 g kg-1 + Imazapic, 175 g kg-1) rates applied on two no Clearfield® rice genotypes (first trial) or Clearfield® rice genotypes (second trial) in two growing seasons. The results showed application of herbicide doses higher than 150 g ha-1 after full flowering stage can cause reduction in growth and development of no Clearfield® rice. The use of Kifix herbicide in CL (Clearfield®) rice cultivars did not affect the grain yield, mass of 1000 grains, seed germination, first count germination, seedling emergence and seedling length. New researches should be done to define plant arrangement suitable for line R (no Clearfield®) and line A Clearfield® to find the optimum condition to produce hybrid seeds. From our results, we could see that the use of parental line A Clearfield® with a line R no Clearfield®, after flowering, provided the production of only hybrid seeds in the area, without reduction in seed quality.
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