Molecular analysis of the genus Asparagus based on matK sequences and its application to identify A. racemosus, a medicinally phytoestrogenic species

The plant Asparagus racemosus is one of the most widely used sources of phytoestrogens because of its high content of the steroidal saponins, shatavarins I-IV, in roots. The dry root of A. racemosus, known as "Rak-Sam-Sip" in Thai, is one of the most popular herbal medicines, used as an anti-inflammatory, an aphrodisiac and a galactagogue. Recently, the interest in plant-derived estrogens has increased tremendously, making A. racemosus particularly important and a possible target for fraudulent labeling. However, the identification of A. racemosus is generally difficult due to its similar morphology to other Asparagus spp. Thus, accurate authentication of A. racemosus is essential. In this study, 1557-bp nucleotide sequences of the maturase K (matK) gene of eight Asparagus taxa were analyzed. A phylogenetic relationship based on the matK gene was also constructed. Ten polymorphic sites of nucleotide substitutions were found within the matK sequences. A. racemosus showed different nucleotide substitutions to the other species. A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the matK gene was developed to discriminate A. racemosus from others. Only the 650-bp PCR product from A. racemosus could be digested with BssKI into two fragments of 397 and 253-bp while the products of other species remained undigested. Ten commercially crude drugs were analyzed and revealed that eight samples were derived from A. racemosus while two samples of that were not. Thus, the PCR-RFLP analysis of matK gene was shown to be an effective method for authentication of the medicinally phytoestrogenic species, A. racemosus.     

Antimicrobial electrospun silk fibroin mats with silver nanoparticles for wound dressing application

In this report, silk fibroin (SF) mats coated with silver nanoparticles (AgNPs) were manufactured as a prototypic wound dressing and evaluated for antimicrobial properties. SF was extracted from cocoons of Thai silkworms Bombyx mori (variant Nangnoi Si Sa Ket) and fabricated into nonwoven mats by electrospinning. In a one-step synthesis method, colloidal AgNPs were prepared from silver nitrate by gamma irradiation and inspected by transmission electron microscopy. Using the in vitro disc diffusion and growth-inhibition assays, AgNP-coated SF mats effectively inhibited the growth of Staphyllococus aureus and Pseudomonas aeruginosa when the coating solution containing colloidal AgNPs was 4 mM, or equivalent to 50.4 ng/cm² of adsorbed AgNPs. Based on these results, the AgNP-coated SF mats can potentially be used as antimicrobial wound dressings.     

Colonization and infestation ability of Bolboschoenus maritimus Palla in rice paddies of the Camargue,France

Bolboschoenus maritimus is one of the major weed constraints for irrigated rice‐cropping systems in the Camargue, France. This perennial plant propagates mainly through the production of numerous tubers. Observations in both controlled conditions and on‐field studies were used to enhance the level of knowledge of the biology, functioning and infestation dynamics of B. maritimus, with a view to rationalize weed control practices. It was found that B. maritimus displayed a great potential to produce a large number of shoots, rhizomes and tubers. Its propagation in the field plots depended on the initial weed density and its spatial colonization did not show any preferred direction (isotropic). Further observations that were made in the paddy fields showed an interaction between the different cultural practices that were tested and the infestation dynamics of B. maritimus. Efficient control of B. maritimus infestation in the field should make use of the data reported here, based on three levels: (i) prevention of weed stem proliferation during the cropping season with specific herbicides; (ii) elimination of the tubers after the rice crop; and (iii) reduction of the tuber‐germinating ability.     

Suppressing weeds in direct-seeded lowland rainfed rice: Effect of cutting dates and timing of fertilizer application

Weeds cause substantive yield losses in rainfed rice, particularly direct-seeded rice (DSR). Two field experiments were conducted in 2005 in north-east Thailand to examine the effects of cutting date and timing of fertilizer application on suppressed weed, growth and yield of DSR. Treatments consisted of two fertilizer applications to the main plots (top-dressing at the date of cutting and 15 days after cutting; DAC) and four cutting dates of the sub-plots. Rice and weed cutting was performed at 30, 45, 60 and 75 days after seeding (DAS), compared with an untreated control. Cutting resulted in a higher growth rate and improved grain yield of rice compared to the untreated control. Weed cutting at 60 DAS resulted in the greatest leaf area index, which contributed to the maximum number of tiller as well as maximum plant dry mass when observed at 30 DAC. Lower densities and dry weights of weeds at 30 DAC were observed when cutting was done 60 DAS, resulting in a higher grain yield than the other cutting dates. Timing of fertilizer application had no significant effect on the density and dry weight of grasses and broad-leaved weeds, but did have a significant affected on, resulting in the lowest density of sedges at 45 DAC was observed with fertilizer applied at cutting date. Rice grain yield was higher with top-dressing of fertilizer at 15 DAC than with fertilizer applied at cutting date. The cutting treatments resulted in higher net incomes than the untreated control. These results indicate that rice and weed cutting at an appropriate growth stage is an alternative method to chemical weed control for DSR in rainfed riceland.     

Rates and timing of phosphorus fertilizer on growth and yield of direct-seeded rice in rain-fed conditions

Abstract

Phosphorus deficiency in soil and erratic rainfall limit rice production in Northeast Thailand. The objective of this study was to investigate rice's response to different rates and times of phosphorus fertilizer. A field trial was conducted in a farmer's field with a split plot design. Main plots were established using three rates: 15, 30, and 60 kg P ha^?1. Five types of sub-plot were established as follows: (1) P fertilizer was applied by banding below the seeds' depth before seeding (BBS), (2) broadcasting and incorporation into the soil before seeding, and (3) topdressing at three different DAS (days after seeding). Fertilizer was spread onto the soil surface at 10, 20, and 30 DAS. Significant grain-yield increases were affected by time or rate of fertilizer application. Grain yields were maximized by a rate of 60 kg P ha^?1. Fertilizer application by BBS produced higher grain yield than did other treatments, giving higher root-length density and shoot growth, phosphorus uptake, and greater phosphorus-use efficiency than did fertilizer applied by broadcasting or delayed topdressing. BBS resulted in the highest phosphorus enrichment in soil volume with a rate of 60 kg P ha^?1. The high solubility of fertilizer in a localized placement may satisfy the seedlings' high initial demand of phosphorus and provide sufficient phosphorus availability to allow high productivity. Based on these data, in regions with low soil phosphorus availability where rainfall is also erratic, the management of sub-seed banding placement at the start of a crop at the rate of 60 kg P ha^?1 is recommended as the optimum phosphorus fertilizer practice.