ABSTRACT The large type (LT) of Leersia has recently been recognized as a perennial weed inhabiting paddy levees in Japan. Although the LT has been treated as L. sayanuka owing to confusion in plant identification, it differs from L. sayanuka in both morphological and ecological characteristics. To clarify the genetic relationships between the LT and other Japanese Leersia species, including L. sayanuka , we determined chromosome numbers and performed phylogenetic analyses using sequences of the partial nuclear GPA1 gene and four chloroplast genome regions. The chromosome counts, phylogenetic analysis of partial GPA1 sequences, and observed sterility together suggest that the two LT accessions examined in this study are tetraploid (2 n = 48) plants of hybrid origin, most likely F 1 hybrids between tetraploid lineages of L. sayanuka (2 n = 48) and L. oryzoides (2 n = 48). The phylogenetic analysis of chloroplast DNA sequences supported this inferred hybrid origin, with LT haplotypes clustering closely with those of either L. sayanuka or L. oryzoides . Our findings provide novel insights into the origin of LT and suggest that it is unlikely to represent intraspecific variation within L. sayanuka .
Effective weed management requires more than a species inventory; it requires evidence that the same taxa dominate occurrence, density, biomass, and canopy occupation and that dominance varies spatially. We surveyed 120 rice fields across 16 localities in former Hau Giang Province, now part of Can Tho City, in the Vietnamese Mekong Delta. Weed communities were assessed in 1200 1-m2 quadrats distributed equally between field interiors and bunds. Occurrence, density, field uniformity, fresh and dry biomass, canopy cover, composite dominance indices, qualitative functional categories, and locality-level similarity were quantified. Forty-eight species from 15 families were recorded; Poaceae accounted for 25 species (52.1%). Four taxa formed a consistent management-priority core: Echinochloa crus-galli, Oryza sativa f. spontanea, Leptochloa spp., and Fimbristylis miliacea. Together, they represented 91.6% of relative mean field density, 90.1% of relative canopy cover, 90.4% of relative fresh biomass, and 99.3% of relative dry biomass. E. crus-galli ranked first in composite importance value (111.92). Presence-absence indices indicated a broadly shared regional species pool, whereas abundance-weighted similarity showed substantial differences in dominance among localities. The findings support a two-scale management strategy: regional surveillance of the four recurrent priority taxa combined with field-specific adjustment of water management, crop establishment, control timing, sanitation, and seedbank suppression.
This study aimed to identify weed composition, distribution, and dominance under water-scarce conditions in 45 fields across three locations in the KADA granary area of Malaysia during the main- and off-season of 2014/2015. The survey employed a quantitative method using 0.5 m & times; 0.5 m quadrats, with 20 samples per rice field laid out systematically in an inverted W pattern. Resultantly, the survey revealed variations in weed composition and prevalence between rice planting seasons, driven by varying moisture stress levels that favored specific weed survival traits under fluctuating water availability. A total of 30 weed species were identified from 14 different families, comprising 6 grasses, 6 sedges, and 18 broadleaved weeds. Based on the relative abundance and ranking of the weeds in the surveyed rice fields, Fimbristylis miliacea (84.2%), followed by Leptochloa chinensis (41.6%), Scirpus grossus (30.1%), and Ischaemum rugosum (23.6%) were the most prevalent and abundant species in the off-season 2014. Conversely, the 2014/2015 main-season was highly dominated by Echinochloa crus-galli (62.8%), followed by L. chinensis (37.3%), Limnocharis flava (25.1%), and F. miliacea (22.3%). Sorenson's index values (92.9%-100.0%) during the 2014 off-season indicate high weed species similarity across districts, while lower values (59.6%-76.6%) in the 2014/2015 main-season suggest slight variations in weed composition between districts. These findings provide critical baseline data for developing targeted weed control strategies to enhance rice yield and promote sustainable agricultural practices.
ABSTRACT Weed management is a critical challenge in Malaysian rice cultivation, with the emergence of herbicide‐resistant weeds posing a significant threat to productivity and sustainability. This review explores the potential of florpyrauxifen‐benzyl, a novel aryloxyphenoxypropionate herbicide, as a promising tool for addressing these issues. The background of rice plantation in Malaysia, mode of action, efficacy against key weed species, and environmental safety profile of florpyrauxifen‐benzyl are discussed. Prominently featured, florpyrauxifen‐benzyl exhibits efficacy against a diverse range of weed species in rice cultivation, encompassing graminaceous weeds, cyperaceous weeds, and dicotyledonous weeds without a negative impact on rice growth and productivity. Furthermore, florpyrauxifen‐benzyl has the ability to control herbicide‐resistant weeds, and the environmental impact is considered to be low. While florpyrauxifen‐benzyl exhibits promising potential for weed management in rice fields, further research is crucial. Long‐term efficacy and potential impacts on non‐target organisms need to be thoroughly evaluated to ensure its sustainable application in agriculture.
Early detection of invasive alien species is critical for preventing ecological disturbance and economic loss. Alternanthera philoxeroides, an invasive aquatic plant native to South America, has become widespread in Japan, posing major threats to paddy-field agriculture. Conventional monitoring depends largely on visual surveys, which are inefficient for identifying low-density populations or fragmented plant debris. This study aimed to develop simple, field-deployable methods for A. philoxeroides detection using (1) environmental DNA (eDNA) analysis based on the suspended glass fiber (SGF) method combined with loop-mediated isothermal amplification (LAMP), and (2) LAMP-based detection using pressed sap from weed debris collected at drainage pumping stations. The SGF + LAMP approach reliably detected A. philoxeroides eDNA at most sites within its known distribution range, whereas pressed sap-based analysis detected A. philoxeroides even in severely decomposed debris and at weight ratios as low as 0.1%. Both methods were validated in a catchment with no prior A. philoxeroides records, confirming its establishment along riverbanks and subsequent invasion in paddy fields. Collectively, these approaches enable rapid, sensitive, on-site detection without requiring specialized equipment or taxonomic expertise, providing practical tools for the early monitoring and management of A. philoxeroides and other invasive plants in agricultural water networks.
