Mechanisms of genotypic differences in tolerance of iron toxicity in field-grown rice
Mechanisms of genotypic differences in tolerance of iron toxicity in field-grown rice
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DOI：
10.1016/j.fcr.2023.108953
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发表时间：
2023-07
影响因子：
5.8
通讯作者：
Toavintsoa Rajonandraina;T. Rakotoson;M. Wissuwa;Y. Ueda;T. Razafimbelo;A. Andriamananjara;G. Kirk
中科院分区：
文献类型：
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作者：
Toavintsoa Rajonandraina;T. Rakotoson;M. Wissuwa;Y. Ueda;T. Razafimbelo;A. Andriamananjara;G. Kirk
在世界上许多地方，铁（Fe）毒性是水稻产量的主要制约因素，因为还原性铁在水稻土中的溶解度比好氧土壤中的铁大，导致植物过量吸收铁。水稻基因库的耐受性存在基因型差异，但迄今为止只发现了弱效应等位基因，这主要是因为多个关键的生理过程决定了耐受性。过去的大多数研究都是在苗期进行的营养液筛选，而不是在整个生命周期的田间条件下进行的。我们在马达加斯加中部高地的高铁毒性土壤中研究了不同基因型在田间条件下的耐受性机制。在整个生长期间，我们对幼苗和衰老组织进行了重复的植物采样，直到成熟。涉及多种机制，不同生长阶段不同机制的重要性不同。较高的粮食产量主要是由于健康的营养生长，通过减少铁吸收（排除）或通过年老组织的区隔化和组织耐受性最小化过量吸收的影响来实现。在生殖生长过程中，排异机制放松，导致新梢铁积累增加。但耐铁基因型仍然能够通过铁区隔化和组织耐受性的结合生长良好，因此籽粒灌浆可以相对畅通无阻地进行。在整个生长过程中，组织磷(P)和钾(K)浓度接近或低于缺乏限度。根际铁氧化排除会阻碍P和K离子进入根部，但其组织浓度的差异远小于生长速率的差异，因此生长速率明显驱动了吸收差异，对铁毒性的反应是更重要的制约因素。籽粒产量与视觉症状无相关性。为了确定有用的供体和育种标记，重要的是制定筛选方案，以捕获个体耐受机制，考虑生长阶段对其相对重要性和表达的影响，以及与矿物质营养等其他因素可能的相互作用。根据视觉症状选择耐受性，特别是在苗期，过于简单，尽管它在特定耐受性机制的研究中可能是有用的。
Iron (Fe) toxicity is a major constraint to rice yields in much of the world due to the greater solubility of reduced ferrous Fe in paddy soils compared with ferric Fe in aerobic soils and resulting excess uptake into the plants. There is genotypic variation in tolerance inOryzagene pools, but so far only weak-effect alleles have been identified, largely because multiple critical physiological processes determine the tolerance. Most past research has been done in nutrient solution screens at the seedling stage, and not under field conditions over the full life cycle. We investigated tolerance mechanisms in a diverse set of genotypes under field conditions in a highly iron toxic soil in the Central Highlands of Madagascar. We made repeated plant samplings of young and old tissues throughout the growth period until maturity. Multiple mechanisms were involved, and the importance of different mechanisms changed between growth stages. Higher grain yields were mainly due to healthy vegetative growth, achieved either by reducing Fe uptake (exclusion) or by minimizing the effect of excess uptake through compartmentalization in older tissues and tissue tolerance. Exclusion mechanisms were relaxed during reproductive growth, leading to increased Fe accumulation in shoots. But tolerant genotypes were nonetheless able to grow well through a combination of Fe compartmentalization and tissue tolerance, so that grain filling could proceed relatively unimpeded. Tissue phosphorus (P) and potassium (K) concentrations were close to or below deficiency limits throughout growth. Exclusion by ferrous Fe oxidation in the rhizosphere will impede access of P and K ions to roots, but the differences in their tissue concentrations were much smaller than differences in growth rates, so growth rates evidently drove the uptake differences and responses to Fe toxicity were the more important constraints. There was no relation between grain yield and visual symptoms. To identify useful donors and markers for breeding it is important to develop screening protocols that capture the individual tolerance mechanisms, allowing for the effects of growth stage on their relative importance and expression, and possible interactions with other factors such as mineral nutrition. Selection for tolerance based on visual symptoms, particularly at the seedling stage, is overly simplistic, though it can be useful in the study of specific tolerance mechanisms.