Sudirman Yahya

The qTSN Positive Effect on Panicle and Flag Leaf Size of Rice is Associated with an Early Down-Regulation of Tillering

The qTSN4 was identified as rice QTL (Quantitative Traits Locus) increasing total spikelet number per panicle and flag leaf area but potentially reducing panicle number depending on the environment. So far, this trade-off was mainly observed at grain maturity and not specifically studied in details, limiting the apprehension of the agronomic interest of qTSN4. This study aimed to understand the effect of qTSN4 and of the environment on panicle sizing, its trade-off with panicle number, and finally plant grain production. It compared two high yielding genotypes to their Near Isogenic Lines (NIL) carrying either QTL qTSN4 or qTSN12, two distinct QTLs contributing to the enlarged panicle size, thereafter designated as qTSN. Traits describing C sink (organ appearance rate, size, biomass) and source (leaf area, photosynthesis, sugar availability) were dynamically characterized along plant and/or panicle development within two trials (greenhouse, field), each comparing two treatments contrasting for plant access to light (with or without shading, high or low planting densities). The positive effect of qTSN on panicle size and flag leaf area of the main tiller was confirmed. More precisely, it could be shown that qTSN increased leaf area and internode cross-section, and in some cases of the photosynthetic rate and starch reserves, of the top 3–4 phytomers of the main tiller. This was accompanied by an earlier tillering cessation, that coincided with the initiation of these phytomers, and an enhanced panicle size on the main tiller. Plant leaf area at flowering was not affected by qTSN but fertile tiller number was reduced to an extent that depended on the environment. Accordingly, plant grain production was enhanced by qTSN only under shading in the greenhouse experiment, where panicle number was not affected and photosynthesis and starch storage in internodes was enhanced. The effect of qTSN on rice phenotype was thus expressed before panicle initiation (PI). Whether early tillering reduction or organ oversizing at meristem level is affected first cannot be entirely unraveled. Further studies are needed to better understand any signal involved in this early regulation and the qTSN × Environment interactions underlying its agronomic interest.

Respons Fisiologi Beberapa Genotipe Kedelai yang Bersimbiosis dengan MVA terhadap Berbagai Tingkat Cekaman Kekeringan

Present research was aimed to study physiological changes of soybean which were inoculated with vesicular arbuscular mycorrhizal fungi (VAM). Glomus etunicatum was exposed to moderate and severe drought condition. Symbiotic association with VAM improved adaptability as it was shown by the increasing leaf proline content. The MLG 3474 and Sindoro are the more tolerant genotypes while the responses of plant to VAM on improving the adaptability to drought were larger on Lokon.

The Physiologic Response of Soybean Genotypes to VAM Inoculation on Selected Drought Stress Levels

The term of allelopathy refers to chemical interactions (inhibitory or stimulatory) between plants, between plants and microorganisms, and between microorganisms. The wealth of information on the processes, procedures, and practices of allelopathy has contributed to understanding this field of science. Recently, researches of allelopathy have been conducted in laboratory, greenhouse, and field with multifaceted standpoint in some concerning area: (i) allelochemicals identifications and screening test; (ii) ecological and physiological aspects of allelopathy; (iii) genetic studies and the possibilities of using plant breeding or genetic manipulation to enhance allelopathic varieties; (iv) the use of allelopathic potential in the biological control, including as natural pesticide, of weeds and plant diseases as eco-friendly approach for sustainable agriculture scheme. Key words: Allelochemicals, biological control, sustainable agriculture

Respon Beberapa Genotipe Kedelai Terhadap Tingkat Cekaman Kekeringan Tanah Ultisol

This research was aimed to find out the tolerant and susceptible soybean genotypes to drought stress. Twenty two genotypes were tested on three levels of drought stress, based on soil moisture conditions: 80% of field capacity (FC ), 60% FC and 40% FC. The experiment was conducted in plastic house at the experimental field of Meteorological Station, Sampali, Medan, from February to May 2000. The results show that increasing on the severity of drought caused significantly reduced growth and yields, which indicated by the reduction on shoot dry weight, stem diameter, filled pod number, seed number/plant and seed dry weight. The level of growth and yield reductions varied 1 among genotypes. The highest variation was shown at the drought level of 60% FC. Sindoro and Lokon were selected as tolerant and susceptible genotypes, consecutively. It was concluded that the adaptation of tolerant plants strongly related to their ability to improve the root system and to reduce the transpiration surfaces. Key words: Soybean, Drought, Tolerant, Susceptible

Kejut Tanam Cara Pindah Cabutan pada Pembibitan Kelapa Sawit

To find out the possibility of long distance transplanting from the pre to main nursery of oil palm, a research had been conducted to study the effect of bare-root (soiless) and delayed transplanting on seedling growth. The research was a two factor factorial experiment, seedling age of 2 and 3 months, and 5 level transplanting times: conventional (direct planting), bare-root and delayed-transplanting for 1, 3, 5, and 7 days. The experiment was arranged in a randomized complete design. The results indicated that 95 - 100% of the seedlings with bare root and delayed transplanting were successfully survive and continuous to grow. Two month old seedlings were able to overcome the transplanting shock better than three month old seedlings. The seedling of bare-roots and delayed- planting for up to 7 days, still performed a normal growth and there was no significant difference among time of delayed-plantings. The seedlings of delayed transplanting grew two weeks later than the conventional transplanting Key words: Transplanting shock, Bare-root method, Delayed planting.

Efficiency of Watering on Cacao Seedling Inoculated with Mycorrhiza

The use of mycorrhiza-plantation crop association has not been widely applied, due to lack of information on the positive effect of the association on the tree crops. The plastic house study was established to evaluate the effect of inoculation of mycorrhiza fungi on the watering efficiency of cacao seeding. Four inoculation treatment of mycorrhiza fungi: without inoculant (control), endomycorrhiza (Gigaspora margarita), ectomycorrhiza (Scleroderma columnare) and double inoculant of both species, were combined on factorial arrangement with four rates of watering interval: once of every 1, 3, 5, and 7 days. Inoculation significantly improved seedling growth as shown by plant height, leaf area and dry shoot weight compared to control treatment. Double inoculation had the best result, followed by endomycorrhiza and ectomycorrhiza, consequtively. Inoculation also significantly increased watering efficiency on cacao nursery as many as 2 to 4 times compared to control and shortened the time of nursery period as long as one month.