Genomic Improvement of Rice for Drought, Aluminum, and Iron Toxicity Stress Tolerance

 The opportunity of plants to escape from unwanted environments is almost nonexistent due to their sessile characteristic. Drought, aluminum (Al), and iron (Fe) toxicity under acid soil conditions are the major constraints as abiotic stresses in rice cultivation, particularly in tropical areas. These abiotic stress tolerance mechanisms are contributed by morphological, physiological, biochemical, and anatomical alterations that affect yield. The level of tolerance to these abiotic stresses is inherited quantitatively and controlled by several genes as quantitative trait loci. The objectives of this review were to highlight the current progress in investigating genes responsible for the drought, Al, and Fe toxicity, and their utilization for genomic improvement in rice. The mechanisms at the levels of morphology, physiology, biochemistry, anatomy, and particularly at the molecular level were discussed in the review. Overall, this review presents a systemic brief of drought, Al, and Fe tolerance mechanisms, recent progress in exploring genes responsible for these traits to the latest innovation in the genomic improvement of high-yielding multi-tolerant rice variety. This review could assist as guidelines for researchers and rice breeders.

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The expression of OsPLA2-III and OsPPO genes in rice (Oryza sativa L.) under Fe toxicity stress

Lipids are an important biomolecule in plants because of their structural and functional roles in plant cells. Moreover, they could act as signal molecules in the defense system of plants suffering from biotic and abiotic stresses. Furthermore, plants develop various tolerance strategies to cope with iron (Fe) toxicity, for example, by involving genes in the detoxification process and other mechanisms. Therefore, the objective of this research was to investigate the expression of OsPLA2-III and OsPPO genes during Fe stress conditions. It was carried out using two-week-old seedlings of two rice varieties, namely, IR64 (Fe-sensitive variety) and Pokkali (Fe-tolerant variety). The seedlings were treated with 400 ppm FeSO4.7H2O in the nutrient culture solution and compared with control that received 1 ppm FeSO4.7H2O. Furthermore, leaf bronzing, chlorophyll content and relative expression of OsPLA2-III and OsPPO genes were observed. An in-silico study was also performed to predict the interaction between OsPLA2-III and OsPPO proteins. The results showed that the Fe toxicity induced leaf bronzing, decreased leaf chlorophyll content, and increased the expression levels of OsPLA2-III and OsPPO genes. Therefore, both genes were suggested to have a role in plant tolerance mechanism during Fe toxicity stress through the lipid signaling pathway.

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The Effectiveness of Nutrient Culture Solutions with Agar Addition as An Evaluation Media of Rice Under Iron Toxicity Conditions

Background: Evaluation of the tolerance level of rice to iron (Fe) toxicity stress can be done using a hydroponic system in a nutrient culture solution under a controlled condition. This study aimed to obtain a nutrient culture solution that effective as a medium for evaluating the response of rice under Fe toxicity stress condition.

Methods: This experiment was carried out by comparing the effectiveness of three kinds of nutrient culture media, namely Yoshida’s Half-Strength solution (HSY), Yoshida’s Half-Strength + 0.2% agar solution (HSYA), and Yoshida’s Full-Strength + 0.2% agar solution (FSYA) using two rice genotypes, Inpara 5 (sensitive to Fe toxicity) and Mahsuri (tolerant to Fe toxicity). Leaf bronzing level, plant dry weight, and pH of nutrient culture media were observed in this experiment.

Results: The results showed that the stress response as represented by bronzing score in Inpara 5 leaves was known to be higher than that of Mahsuri in the three nutrient culture media. The decrease of root and shoot dry weight in Inpara 5 was higher than that of Mahsuri. In addition, the decrease in the pH of nutrient culture solution media without an agar addition (HSY) occurred faster than the media with the agar addition (HSYA and FSYA).

Conclusion: The HSYA and FSYA media exhibited similar pattern of pH declining but causing significant different in growth responses between Inpara 5 and Mashuri indicating the HSYA medium is considered more efficient compared to the FSYA medium because it only requires a smaller amount of agar.

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Profil pertumbuhan tanaman kelapa sawit transgenik P5CS setelah aklimatisasi

Transformasi genetik untuk merakit tanaman yang toleran kekeringan telah dilakukan dengan mengintroduksikan gen P5CS ke dalam kalus kelapa sawit. Planlet transgenik telah dihasilkan dan telah melalui uji cekaman kekeringan in-vitro. Salah satu tahapan krusial dalam rekayasa genetik adalah aklimatisasi tanaman sebelum ditanam di lapang. Penelitian ini bertujuan mengevaluasi tingkat keberhasilkan aklimatisasi dan mengkarakterisasi pertumbuhan planlet kelapa sawit transgenik P5CS setelah aklimatisasi. Sebanyak 17 planlet non-transgenik dan 26 planlet transgenik P5CS diaklimatisasi pada media tanam dengan komposisi top soil : kompos (1:3; v:v) selama 4 minggu. Tinggi tanaman, kecepatan penambahan tinggi, jumlah daun, panjang, lebar, serta rasio panjang:lebar daun diamati dalam penelitian ini hingga minggu ke-6 setelah aklimatisasi. Hasil penelitian menunjukkan bahwa daya hidup planlet non-transgenik dan transgenik P5CS masing-masing 76,5% dan 76,9% dengan karakter pertumbuhan yang bervariasi antar klon tanaman. Tinggi tanaman transgenik P5CS hasil aklimatisasi pada minggu ke-6 yaitu 8,5-25,4 cm dengan kecepatan penambahan tinggi 0,100-0,267 cm/minggu dan jumlah daun 1-3 helai. Panjang, lebar, serta rasio panjang:lebar daun tanaman transgenik P5CS hasil aklimatisasi yaitu 7,0-17,0 cm, 1,0-3,0 cm, dan 4,4-9,8. Terdapat 4 kelompok tanaman kelapa sawit transgenik P5CS hasil aklimatisasi berdasarkan karakter pertumbuhannya menggunakan teknik Unweighted Pair Group Method with Arithmetic Mean (UPGMA). Kelompok 1 terdiri dari tanaman T-30(1). Kelompok 2 terdiri dari tanaman T-12(3), T-12(4), dan T-12(5). Kelompok 3 terdiri dari tanaman T-13, T-14(2), T-22, T-23, T-24, T-25(1), T-25(2), dan T-26. Kelompok 4 terdiri dari tanaman T-1, T-3(1), T-3(2), T-5, T-6, T-10, T-11, dan T-12(2).

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