Inheritance of rice cold tolerance at the seedling stage

Abstract

Rice (Oryza sativa L.) cold tolerance at the initial stages of development is a highly desirable trait to be incorporated into the state of Rio Grande do Sul, Brazil, cultivars, but selection for this trait must be performed under controlled temperature conditions, which limits the number of lines that can be evaluated. Knowledge of the inheritance of this trait is important to define breeding strategies. So the aim of this paper was to study the genetic basis of rice cold tolerance at the vegetative stage. Six genotypes with constrasting cold tolerance reactions were crossed in a diallel scheme without the reciprocals. The parents and the F 1 and F 2 generations were cultivated in a greenhouse until the V 4 stage, when they were submitted to 10°C for ten days and evaluated for plant survival after seven days of recovery under normal temperature. The results obtained by the diallel analysis of the F 1 generation indicated significance of both additive and non-additive effects, but the general combining ability was more important. The evaluation of the F 2 generation revealed oligogenic inheritance with one or two dominant alleles responsible for cold tolerance in the cold tolerant parents and two complementary genes with recessive alleles segregating in the crosses involving sensitive and intermediate genotypes.Key words: Oryza sativa L., genetics, low temperature, vegetative stage Herança da tolerância do arroz ao frio no estádio de plântula RESUMO: A tolerância ao frio nos estádios iniciais de desenvolvimento do arroz (Oryza sativa L.) é uma característica altamente desejável para incorporar em cultivares do Rio Grande do Sul (RS), porém a seleção para esta característica deve ser feita sob condições de temperatura controlada, o que limita o número de linhas que pode ser avaliada. O conhecimento da herança desta característica é importante para definir estratégias de melhoramento genético, assim o objetivo do presente trabalho é estudar a base genética da tolerância ao frio no estádio vegetativo do arroz. Seis genótipos com reações contrastantes de tolerância ao frio foram cruzados num esquema dialélico sem os recíprocos. Os genitores e as gerações F 1 e F 2 foram cultivados em casa-de-vegetação até o estádio V 4 , quando foram submetidos a 10°C por dez dias e avaliados quanto à sobrevivência de plantas após sete dias de recuperação sob temperatura normal. Os resultados obtidos pela análise dialélica da geração F 1 indicaram significância tanto dos efeitos aditivos quanto não-aditivos, mas a capacidade geral de combinação foi mais importante. A avaliação da geração F 2 revelou uma herança oligogênica com um ou dois alelos dominantes responsáveis pela tolerância ao frio nos genitores tolerantes e dois genes complementares com alelos recessivos segregando nos cruzamentos envolvendo genótipos sensíveis e intermediários.

Osmotic priming of rice seeds subjected to low temperatures

“…Petroline) primed in distilled water at 15 ºC, for 48 h, and assessed by different methods and storage periods, which have not presented advantage on percentage of seedlings in the field (Caseiro and Marcos-Filho, 2005). Likewise, for seeds of two different cultivars of cauliflower (Marcos-Filho and Kikuti, 2008) and cucumber (Gurgel-Junior et al, 2009) the priming did not change the percentage of germination, what emphasizes that this technique generally does not promote changes in germination percent , what is consistent with data found in the literature. There was statistically significant reduction on germination percent of the seeds, when the period of osmotic priming with potassium nitrate has been increased to all treatments assessed (Table 1).…”

“…Cold tolerance is a characteristic highly desirable for the rice genotypes to be grown in the south of country (Cruz et al, 2010). However, the origin of most cultivars commercially used in that region is tropical, what largely contributes to reduction of productivity of rice crop in the state of Rio Grande do Sul (Mertz et al, 2009).…”

“…Among these techniques the priming, or physiological conditioning, is characterized by immersion of seeds during a given time period (hours or days) into an aqueous solution with osmotic potential known and previously established; and aims at reducing seed germination period, as well as synchronize and improve seedling emergence. It is also a way of subjecting seeds to a hydration control that is sufficient to allow starting the respiratory process, which is essential to germination of the seeds, but that should not be insufficient to allow protrusion of radicle during germination process (Gurgel-Junior et al, 2009). Among osmotic agents most commonly used are included the inorganic osmotic agents such as salts (NaCl, KNO 3 , and MgSO 4 ), and organic osmotic agents such as sugars (mannitol and sorbitol), polyethylene glycol (PEG), and glycerol (Kissmann et al, 2011).…”

Plant Abiotic Stress: Temperature Extremes

“…In some subtropical regions such as Brazil (comprising approximately 1 million ha of rice), cold stress at the vegetative stage accounts for up to a 20% yield loss (Cruz et al, 2010).…”

Genetic Variation and Combining Ability Analysis of Bruising Sensitivity in Agaricus bisporus

“…Not only the sign of SCA value, also the magnitude of the value is meaningful. It was suggested that the high magnitude means high genetic divergence and high heterosis in the hybrids [32]. In addition, hybrids displaying heterosis are said to have favorable combining ability [13].…”