Sintho Wahyuning Ardie

Nutrient culture media with agar is effective for early and rapid screening of iron toxicity tolerance in rice

The breeding for iron toxicity tolerant rice needs an effective, efficient, and reliable screening method. The study was aimed to evaluate the best method for screening iron tolerant genotypes at the seedling stage in the greenhouse. Two rice genotypes, Mahsuri (tolerant) and IR64 (sensitive) were grown in three modified media solutions namely, Yoshida-conventional solution (YCS), Yoshida with etylenediamintetraacetic acid (1:2) (YES), and Yoshida with 0.2% agar (YAS). Three levels of iron were tested to observe the severity of their leaf bronzing score (LBS). The optimized solution in the greenhouse was then evaluated using 24 rice genotypes. Using the same genotypes interrelationship, the LBS in the greenhouse with grain yield and its attributes was validated under acute and moderate Fe toxicity in the field. The results showed that the optimized media culture was YAS with 400 mg L-1 of FeSO4. This media had more stable pH and redox potential, it could maintain sufficient Fe2+ supply over 10 days, and it could discriminate of LBS between tolerant and sensitive genotypes. Evaluation using the optimized media solution showed that there was a significant variation among genotypes in shoot dry weight and a significant correlation of relative reduction of shoot dry weight with LBS. The LBS in the greenhouse was correlated with LBS in acute iron stress in the field (r=0.673**) and the grain yield (r= -0.618**). This study has proven that YAS culture media can be used as early identification of iron toxicity tolerant genotypes for supporting breeding programs.

Efficiency of Genetic Transformation via Pollen-Tube Pathway of Jatropha (Jatropha curcas L.) Based on Histochemical and Molecular Analysis

The genetic transformation via pollen-tube pathway is an alternative method to overcome the constraints imposed by genotype specificity in transformation and regeneration in jatropha (Jatropha curcas L.) tissue culture. Therefore, it is necessary to establish important parameters for efficient genetic transformation of jatropha via pollen-tube pathway. The objective of the research was to study the efficiency of direct transformation of jatropha via pollen-tube pathway based on histochemical and molecular analysis. Solution of purified pCAMBIA1301 DNA plasmid carrying a hptII marker gene and a gus reporter gene with concentration level of 0.05, 0.25, 0.50 µg µl-1 were applied to stigma of flowers at 1, 2, 4, 7, 10 h after pollination. Seedling of IP3A, IP3P and JcUMM18 jatropha’s genotypes derived from 15 combination treatments of plasmid DNA concentration and application time, also wild type was subjected to histochemical and molecular analyses. Based on those analyses, the efficiency of transformation via pollen-tube pathway of three jatropha genotypes ranged from 1.5-16.7%. PCR analysis showed that a number of positive plants were identified by using specific primers hptII and gus, i.e. 1-3 and 3-7 plants of the 15 combined treatments, respectively. It indicated that the transformation efficiency via the pollen-tube pathway varied in each jatropha genotype. Keywords: Jatropha curcas L., pCAMBIA1301, plasmid DNA, stigma-drip

Efektivitas Metode Modifikasi Bulk untuk Pemuliaan Padi Adaptif pada Kondisi Fosfor Tanah Suboptimum

Phosphorus deficiency is common in rice cultivated soils and particularly acting as a limiting factor in the acid sulfate and acid upland soils. Improved variety adapted to low soil-P condition is needed to reduce the need of P fertilizer and to increase rice yield. A study was conducted on the application of modified bulk selection method in rice breeding to develop lines adapted to low soil-P condition. The materials used in the study were two populations of F3 generation derived from crosses of IR6008023/Bernas Prima and Gampai/Progol. The materials were planted on P sub-optimum condition at Muara Experiment Station, Bogor, West Java, to obtain F4 and F5 population, selected using modified bulk method. The F5 population were planted on two environment conditions, namely on P optimum (36 kg/ha P2O5) and on P sub-optimum (without P fertilizer) to obtain F6 population. A total of 40 lines from each population were selected, so that 160 F6 lines were obtained. The F6 lines were evaluated on P+ and P- conditions, using augmented design. Result showed that selection for lines adapted to P- should be done on P- condition, whereas for those adapted to P+ could be done on either P+ or P- condition. Lines selected for P- were different from those selected for P+, and some lines selected for both P- and P+ felt at different yield ranks. It was concluded that modified bulk method followed by line selection was effective to develop breeding lines adapted to P- or P+. For P-, the modified bulk and line selection should be conducted in P-, whereas for P+, the modified bulk could be planted on P+ or P-, but the line selection should be conducted on P+ condition.

Comparative expression profiling of three early inflorescence stages of oil palm indicates that vegetative to reproductive phase transition of meristem is regulated by sugar balance

Breeding and seed production activities in oil palm have been hampered because of the inability of the male parent Pisifera to produce male inflorescence as source of pollen under normal conditions. Researchers are using complete defoliation to induce male inflorescences, but the biological and molecular processes responsible for this morphological change are yet to be revealed. To understand the underlying network of genes that initiate and control this phenotypically documented activity, we initiated a study aimed at identifying differentially expressed genes (DEGs) in three stages of an oil palm inflorescence under complete defoliation stress using RNA-seq. Sequencing on an Illumina platform produced 82631476 reads consisting of 8345779076 bases. A total of 60700 genes were obtained after transcript filtering and normalisation and 54% of them were downregulated. Differences in gene expression levels were significant between tissues under stress. The farther the distance between tissues, the more DEGs recorded. Comparison between stage 2 and stage 1 induced 3893 DEGs whereas 10136 DEGs were induced between stage 3 and stage 1. Stress response genes and flower development genes were among the highly expressed genes. This study suggests a link between complete defoliation and meristem differentiation from vegetative to reproductive phase in oil palm.