Rice (Oryza sativa L.) is a very important cereal worldwide, since it is the staple food for more than half of the world’s population. Iron (Fe) deficiency is among the most important agronomical concerns in calcareous soils where rice plants may suffer from this deficiency. Current production systems are based on the use of high-yielding varieties and the application of large quantities of agrochemicals, which can cause major environmental problems. The use of beneficial rhizosphere microorganisms is considered a relevant sustainable alternative to synthetic fertilizers. The main goal of this study was to determine the ability of the nonpathogenic strain Fusarium oxysporum FO12 to induce Fe-deficiency responses in rice plants and its effects on plant growth and Fe chlorosis. Experiments were carried out under hydroponic system conditions. Our results show that the root inoculation of rice plants with FO12 promotes the production of phytosiderophores and plant growth while reducing Fe chlorosis symptoms after several days of cultivation. Moreover, Fe-related genes are upregulated by FO12 at certain times in inoculated plants regardless of Fe conditions. This microorganism also colonizes root cortical tissues. In conclusion, FO12 enhances Fe-deficiency responses in rice plants, achieves growth promotion, and reduces Fe chlorosis symptoms.

Iron (Fe) is an essential micronutrient for crop productivity, but its low availability in alkaline and calcareous soils limits the growth of rice (Oryza sativa L.), which employs a combined strategy for its acquisition based on the release of phytosiderophores (PS) and the use of specific transporters. In this study, the effect of the rhizospheric bacterium Pseudomonas simiae WCS417 and the halotolerant yeast Debaryomyces hansenii CBS767 as inducers of responses to Fe deficiency in rice grown under hydroponic conditions was evaluated. Plants were inoculated in nutrient solutions with and without Fe, and PS production and the expression of genes associated with biosynthesis and transport were determined by qRT-PCR. The results showed that both microorganisms significantly increased PS production compared to controls, especially under Fe-deficient conditions, although P. simiae also exerted an effect under Fe sufficiency. Furthermore, induction of key genes (OsNAAT, OsIRO2, OsTOM1, OsYSL15, and OsIRT1), as well as genes related to the ethylene pathway (OsEIN2, OsACS2, and OsACO3), was observed, pointing to a regulatory role for this hormone in the response. In conclusion, P. simiae and D. hansenii act as inducers of Fe acquisition mechanisms in rice, offering a sustainable biotechnological approach to improve iron nutrition in limiting environments.

Se desarrollo una investigación durante la época seca desde el año 2020 al 2023, con el objetivo de cuantificar el efecto del déficit hídrico en las diferentes etapas fenológicas del cultivo del maíz. El estudio se desarrolló en la Estación Experimental El Ejido-Los Santos. La unidad experimental constó de seis surcos de 5.2 m de largo. Se evaluaron cuatro niveles de estrés en distintas etapas del cultivo y dos híbridos. Para establecer los distintos niveles de deficiencia hídrica, se suspendió el riego por goteo luego de llegar a la fecha indicada hasta finalizar la misma. Los tratamientos tuvieron un arreglo Factorial en Fajas 4 x 2 en un diseño de Bloques Completos al Azar con tres repeticiones. Se calculó la Tasa de crecimiento Relativo y absoluto para cada tratamiento. Las variables climáticas se obtuvieron de una estación meteorológica portátil tipo Davis. El análisis estadístico indicó que hubo diferencias estadísticas altamente significativas para el Factor Etapa de la deficiencia hídrica para casi todas las variables. Se observó que el estrés en el secado de grano (85 a 110 dds) no difirió estadísticamente de las parcelas sin déficit hídrico (riego durante todo el desarrollo del cultivo), estos presentaron rendimientos de grano de 5.32 y 5.24 tha-1, respectivamente. La fase de prefloración fue la menos afectada con una reducción de 26 %. Mientras que, la etapa floración y llenado del grano (50 a 84 dds) fue la más afectada con una reducción del 55 % del rendimiento.

Calcareous soils, characterized by high pH and calcium carbonate content, often limit the availability of essential nutrients for crops such as rice (Oryza sativa L.), reducing yield and nutritional quality. In this study, we evaluated the effect of the halotolerant yeast Debaryomyces hansenii (Dh) on the growth, nutrient uptake, and phosphorus acquisition mechanisms of rice plants cultivated in calcareous soil under controlled greenhouse conditions. Plants inoculated with Dh, particularly via root immersion, exhibited significantly higher SPAD chlorophyll index, plant height, dry matter content, and grain yield compared to controls. Foliar concentrations of Cu, Fe, Zn, and Mn also increased under certain conditions, suggesting improved micronutrient acquisition. Although phosphorus levels in leaves were not significantly enhanced, Dh stimulated acid phosphatase activity in both P-sufficient and P-deficient treatments. At the molecular level, Dh upregulated the expression of acid phosphatase genes (OsPAP3, OsPAP9) and a phosphate transporter gene (OsPTH1;6), confirming its influence on P-related physiological responses. These findings demonstrate that D. hansenii functions as a plant growth-promoting yeast (PGPY) and may serve as a promising biofertilizer for improving rice productivity and nutrient efficiency in calcareous soils, contributing to sustainable agricultural practices in challenging edaphic environments.