Vol. 1 No. 4 (2018): Vietnam Journal of Agricultural Sciences

The objectives of this study were to evaluate the effects of different fertilization ratios on the growth of pinto peanut (Arachis pintoi) propagated vegetatively under varying water regimes. The experiment was carried out in a net-house in a completely randomized design with three replicates. The N:P2O5:K2O ratios were applied at six levels: F1 (1:1:1), F2 (1:3:1), F3 (1:1:3), F4 (3:1:1), F5 (3:3:1), and F6 (3:3:3) while soil moisture included three different levels: 30% (W1), 60% (W2), and 100% (W3) field capacity. Water stress conditions were treated from 30-65 days after planting, and then the pots were irrigated to 100% field capacity. The results indicate that drought conditions significantly reduced (P<0.05) the growth of stolons, leaf appearance, number of secondary stolons, and dry matter, while the root/shoot ratio was higher compared to plants under well-watered conditions. There was no significant effect of the fertilization ratios on the number of secondary stolons. Higher-NP and NPK application ratios showed significant influences on the growth of A. pintoi under drought conditions by stimulating stolon lengths and the number of leaves, while the root/shoot ratio was decreased. Higher ratios of single fertilizers (N, P, or K) did not show a consistent effect on the growth of A. pintoi under drought conditions. The results suggest that a higher-NP fertilization ratio stimulates the growth of A. pintoi under both drought and well-irrigated conditions.

This study was conducted to establish the procedure for in vitro propagation of Japanese cherry (Prunus sp.) to produce large quantity of plantlets and initial planting materials for climate adaptation research of this plant in Hanoi. Single nodal stems were used as the primary explants and initially produced shoots on MS medium supplemented with 1 mg L-1 BA. The highest shoot multiplication rate (9.57 times) was obtained on MS medium containing 1 mg L-1 BA and 0.25 mg L-1 a-NAA after 8 weeks of culture. 100% of the shoots produced roots with a mean of 10.10 roots per plant within 4 weeks on ½ MSM medium with 4 mg L-1 IBA. The survival rate of in vitro derived plantlets after a 6 to 7-week-period of rooting during acclimatization using a soil: coco peat: smoked rice husks (2:2:1, v/v/v) substrate was 100% and acclimatized plantlets showed good growth and development. This is the first report on a practical and efficient in vitro multiplication protocol for Japanese cherry in Vietnam, starting from shoot initiation to establishment of plants under greenhouse conditions.

Bacterial rice leaf blight (BLB), caused by Xanthomonas oryzae pv. oryzae (Xoo), has a massive impact on the quality and productivity of rice. Besides BLB resistant rice cultivars, herbal extracts and nanosilver have increasingly demonstrated their important roles in controlling the disease as alternatives to synthetic chemical pesticides. Therefore, this research aimed to examine the Xoo antibacterial effects of several herbal extracts and nanosilver in vitro and in vivo. In the study, Wedelia chinensis Osbeck Merr., Clerodendrum fragrans Vent., Excoecaria cochinchinensis Lour., Polyathia longifolia var. Pendula, and Caesalpinia sappan L. were extracted by maceration with six types of solvents (distilled water, 70% ethanol, chloroform, n-hexane, and 100% acetonitrile), then used in an agar diffusion test to evaluate their Xoo antibacterial effects. The results showed that 70% ethanol was the best extracting solvent for the targeted plants. C. fragrans, E. Cochinchinensis, and C. sappan showed significant antibacterial effects with inhibition zone diameters of 28.50 cm, 21.00 cm, and 25.70 cm, respectively. Finally, the individual extract from C. fragrans, E. Cochinchinensis, and C. sappan were combined with nanosilver particles and used to access BLB inhibition capacity in vivo, using the rice cultivar IR24 as the target for Xoo infection. Application of the C. fragrans extract resulted in resistance of IR24 rice to BLB. Similar results were also observed in the infected rice when products combining nanosilver and E. cochinchinensis or C. sappan were applied to infected rice leaves.

This study aimed to compare the genetic gains of two different selection methods for agronomic traits in soybean. A population from the cross of VI045032 x 4904 (LSB10) was advanced using the bulk method and modified bulk method to the F6 generation. Measured traits were growth duration, plant height, height of the first pod node, number of pods per plant, the percentage of 3-seeded pods, 100-seed weight, individual yield, and yield. Both methods were equally efficient and could be used for segregating and the stabilizing phase of progenies/populations of soybean crosses. However, the bulk method appeared to be more efficient for the improvement of yield-related traits while the modified bulk method was more efficient for the improvement of morphological traits.  

In this report, we examine the unsteady Stokes equations with non-homogeneous boundary conditions. As an application of a Carleman estimate, we first establish log type stabilities for the solution of the equations from either an interior measurement of the velocity, or a boundary observation depending on the trace of the velocity and of the Cauchy stress tensor measurements on a part of the boundary. We then consider the inverse problem of determining the time-independent Robin coefficient from a measurement of the solution and of Cauchy data on a sub-boundary.