The aryloxyphenoxypropionate herbicides (APPs) are graminicides with excellent control of many grass weeds species, including weedy rice (Oryza sativa L.). These herbicides block the fatty acid biosynthesis by inhibiting the enzyme acetyl-CoA carboxylase (ACCase), resulting in the death of susceptible plants. Inducing mutation with gamma rays to rice seeds, two lines resistant to APPs herbicides were developed. Plant dose-response assays confirmed the resistance to the APPS herbicides quizalofop-p-ethyl and haloxyfop-p-methyl. The carboxyltransferase domain fragments of ACCase from the resistant biotype and susceptible control were sequenced and compared. A point mutation was detected in the amino acid position 2,027 (Rice Genome Annotation Project: Os05g22940.1). Results indicated that resistance to APPs is a consequence of an altered ACCase enzyme that confers resistance. The use of APPs herbicide-resistant rice lines represents an innovative and promising alternative for weedy rice control in paddy rice systems.

Abstract"Specialty rices" is a common name for varieties that present uncommon grains with distinctive features as pericarp color, grain shape and size or aroma. Most of these rices are related to cultural traditions and ceremonies, but some have higher nutritionally value than white rice. Considering that today people are searching for foods that could help to improve and maintain health, specialty rices would also be considered in some way as functional food. As a specific market, the economic values of these grains are also higher than those of white rice. So, the new red rice variety SCS119 Rubi and the new black rice variety SCS120 Onix were developed in order to attend the specific and economically important specialty rices market, and should be consumed as a whole rice grain. Experimental tests performed with these varieties showed that they could be recommended to all rice-producing regions of Santa Catarina State, Brazil.

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A B S T R A C TThis study evaluated the effect of temperatures during the phase of microsporogenesis on spikelet sterility of paddy rice and identified genotypes tolerant to low temperatures at this growth stage. The inbreds SC681, SC491, and SC676 and the cultivars Epagri 109 and SCS116 Satoru were assessed. The genotypes were submitted for three days in a growth chamber to five temperatures at microsporogenesis: 9, 12, 15, 18, and 21 o C. For each tested temperature, a control was kept in the greenhouse under environmental conditions. After harvest, full and empty spikelets were counted and weighed and the percentage of spikelet sterility was determined. Data were evaluated by variance analysis using the F test. Averages were compared by Tukey's test and regression analysis. The highest spikelet sterilities were observed when the genotypes were exposed to the temperatures of 9 and 12 o C. Genotype spikelet sterility was similar to that of the control at 21 ºC. The inbred SC 676 presented higher tolerance to lower temperatures is therefore potentially suited to generate a cultivar with adequate agronomic performance in rice growing areas prone to cold conditions at microsporogenesis.Esterilidade de espiguetas em genótipos de arroz irrigado afetada pela temperatura na microsporogênese R E S U M O Este trabalho teve como objetivo avaliar o efeito da temperatura na fase de microsporogênese sobre a esterilidade de espiguetas de arroz irrigado identificando, nesta fase, genótipos tolerantes a baixas temperaturas. Foram testadas as linhagens SC681, SC491 e SC676 e as cultivares Epagri 109 e SCS116 Satoru. Os genótipos foram submetidos por três dias em câmara de crescimento a cinco temperaturas na microsporogênese: 9, 12, 15, 18 e 21 o C. Para cada temperatura um tratamento testemunha foi mantido a temperatura ambiente na casa de vegetação. Após colheita realizaram-se a contagem e a pesagem das espiguetas cheias e vazias, determinando-se a percentagem de esterilidade. Os dados foram submetidos à análise de variância pelo teste F. Quando significativas, as médias foram comparadas pelo teste de Tukey e análise de regressão. A maior esterilidade foi observada nos genótipos submetidos às temperaturas de 9 e 12 ºC. A esterilidade foi similar entre testemunhas e a 21 o C. A linhagem SC676 apresentou maior tolerância à ocorrência de baixas temperaturas mostrando-se promissora para gerar uma cultivar com desempenho agronômico adequado, em regiões orizícolas propensas à ocorrência de frio na microsporogênese.

-SCS121 CL is a second-generation Clearfield® rice cultivar with resistance to herbicides of the imidazolinone group. The cultivar has modern plant type, lodging resistance, late maturity cycle, high yield potential, long grains and good cooking quality. The cultivar is recommended to all rice-producer regions of Santa Catarina, Brazil.

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