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Then R.,Kasetsart University | Then R.,Cambodian Agricultural Research and Development Institute CARDI | Siangliw J.L.,Kasetsart University | Vanavichit A.,Kasetsart University | And 3 more authors.
Kasetsart Journal - Natural Science | Year: 2011

Drought hinders rice production and yield stability in rainfed lowland ecosystems. Quantitative trait loci (QTL) for root traits on chromosomes 1, 2, 7 and 9 in backcross introgression lines (BIL) of elite rice variety IR64, derived from Azucena/IR64, were designated as Targets 1, 2, 7 and 9 in the present study. Severe stress developed during the period of optimum flowering as indicated by 98-100% yield reduction. Significant phenotypic variations in BIL were observed on days to flowering (DF), delay in flowering (DeF), panicle exsertion rate (PEX), percent spikelet sterility (PSS) and grain yield (GY). Variations among target QTL were also found in the traits studied, particularly under drought stress, indicating that BIL containing Targets 1 and 2 had early DF, higher PEX, lower PSS and higher GY under stress than those with Targets 7 and 9. Targets 7 and 9 lacked QTL for root thickness, indicating that it plays a role in drought tolerance under rainfed lowland conditions. Early flowering BIL had an advantage over later flowering ones because water can be extracted at the early drought stage, which can support the PEX and result in low PSS. In a very severe drought at the flowering stage, PSS directly affected GY. Further study of root morphology and early flowering under stress are necessary to improve rice yields under rainfed lowland conditions. Source


Shin E.-H.,Chonnam National University | Choi J.-H.,Chonnam National University | Abd El-Aty A.M.,Cairo University | Khay S.,Cambodian Agricultural Research and Development Institute CARDI | And 4 more authors.
Biomedical Chromatography | Year: 2011

2,4-D, dicamba and 4-CPA with auxin-like activity have been intensively used in agriculture, for the control of unwanted broadleaf weeds. An analytical method involving HPLC coupled with UVD was developed for the simultaneous analysis of these three analytes in Chinese cabbage, apple and pepper fruits (representative non-fatty samples) and brown rice and soybean (representative fatty samples) using liquid-liquid partitioning and column cleanup procedures. The residues were confirmed via tandem mass spectrometry (MS/MS) in ion electrospray ionization (ESI) mode. The standard curves were linear over the range of the tested concentrations (0.25-10-μg/mL), as shown by a marked linearity in excess of 0.9999 (r2). The average recoveries (mean, n = 3) ranged from 94.30 to 102.63 in Chinese cabbage, from 94.76 to 108.47 in apple, from 97.52 to 102.27 in pepper, from 76.19 to 101.90 in brown rice, and from 74.60 to 107.39 in soybean. The relative standard deviations (RSDs) were <9% in all tested matrices. The limits of detection and quantitation were 0.006 and 0.02 mg/kg, respectively. Samples purchased from local markets were analyzed to evaluate the applicability of the methods developed herein. The concentration of the 2,4-D residue was measured at 0.102 mg/kg in the soybean sample; however, this level is exactly the same MRL set by the Korea Food and Drug Administration. This developed method deserves full and complete consideration, as it clearly displays the sensitivity, accuracy and precision required for residue analysis of 2,4-D, dicamba and 4-CPA in food crops. © 2010 John Wiley & Sons, Ltd. Source


Chanthy P.,University of New England of Australia | Chanthy P.,Cambodian Agricultural Research and Development Institute CARDI | Martin R.J.,Agricultural Systems Research Cambodia Co. | Gunning R.V.,Australian Department of Primary Industries and Fisheries | Andrew N.R.,University of New England of Australia
Australian Journal of Entomology | Year: 2013

This is the first assessment of insect assemblages on soybean crops in Cambodia. Sweep netting and beat sheeting collection methods were used to evaluate the effectiveness of sampling arthropods and their collection efficiency in soybean crops and to determine soybean insect diversity and composition at two sites. Overall, arthropod populations sampled by sweep netting were substantially different compared to populations collected by beat sheeting. The sweep netting caught significantly higher numbers of most Orders; however, the beat sheeting caught a significantly higher number of Acari. Beat sheeting was also effective for sampling Nezara viridula which is a major invertebrate pest of soybean. There was a significant interaction between location and collection methods for both Hemiptera and Hymenoptera assemblages. Selection of insect sampling method depends on many factors such as plant type, plant structure, field conditions, ease of use, cost of use and target insect species. However, the sweep netting was best for fast flying insects such as hymenopteran wasps and those located in upper parts of the plant canopy. The use of different sampling methods to assess pest, predator/parasitoid and general community structure in crops is crucial for assessing Integrated Pest Management strategies. © 2013 Australian Entomological Society. Source


Sopheap U.,Cambodian Agricultural Research and Development Institute CARDI | Patanothai A.,Khon Kaen University | Aye T.M.,International Center for Tropical Agriculture
International Journal of Plant Production | Year: 2012

In Cambodia, cassava is mostly grown with little or no fertilizer inputs, but the magnitudes of nutrient balances are not known. This study was conducted to assess nutrient balances for cassava cultivation in Kampong Cham province in Northeast Cambodia. Forty five households in four cassava production zones were interviewed in relation to their cultural practices and crop residue management, upon which sources of nutrient inputs and outputs were based. Chemical fertilizer, manure, planting materials and rainfall were the defined inputs, while cassava roots and stumps were the outputs. Crop cutting was undertaken in the cassava fields of the 45 households to obtain weights of roots and other plant parts. Nutrient balances were calculated for the individual fields based on nutrient contents of the component sources obtained from the literatures. The results showed negative balances for all the nutrients evaluated. The imbalances were most serious for N, K and Ca with the averages of -64.45 kg N, -52.83 kg K and -10.83 kg Ca ha -1, but were less serious for P and Mg with the averages of -2.85 kg P and -7.20 kg Mg ha -1. These negative balances were the consequence of low nutrient inputs in current practices where only a few farmers applied low rates of chemical fertilizer or manure. Continued use of current practices will threaten the sustainability of cassava production in Cambodia. For long term productivity of the crop, the application of organic manures together with lime and chemical fertilizers high in N and K is recommended. Source


Sopheap U.,Cambodian Agricultural Research and Development Institute CARDI | Patanothai A.,Khon Kaen University | Aye T.M.,International Center for Tropical Agriculture
International Journal of Plant Production | Year: 2012

Cassava (Manihot esculenta Crantz) is currently the most important upland crop of Cambodia, but information on yield variations and causal factors which is important for efficiently targeting efforts to increase production is still lacking. The objectives of this study were to determine the yield variations and causal factors for cassava production in Kampong Cham province in Cambodia. Forty five households in four production zones were selected for the study. A farm survey employing semi-structured interviews, combined with field visits, were used for the collection of information on farmers' practices in cassava cultivation, while crop cutting was done to provide estimates of cassava yields. The data were analyzed for yield variations, yield gaps and causal factors. The results showed large variations in yield among farmers' fields, ranging from 12.7 to 37.2 t ha -1. The fields were divided into five yield categories, with the mean yields of the lower four categories ranging from 76.0 to 34.2% of the maximum yields, with corresponding yield gaps ranging from 8.9 to 24.4 t ha -1. The main yield constraints identified were soil nutrient deficits, short crop duration and weed competition. The highest yielding fields had no production constraints, but the number and/or the level of constraints increased in fields with lower crop yields. However, for different fields with similar yield levels, the main production constraints sometimes differed. The results clearly indicated that there are opportunities for yield improvement and narrowing of yield gaps through the adoption of field specific improved technologies and management practices. Source

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