No abstract

Clubroot is a disease of cruciferous crops that causes significant economic losses to vegetable production worldwide. We applied high-throughput amplicon sequencing technology to quantify the effect of Trichodermaharzianum LTR-2 inoculation on the rhizosphere community of Chinese cabbage (Brassica rapa subsp. pekinensis cv. Jiaozhou) in a commercial production area. T. harzianum inoculation of cabbage reduced the incidence of clubroot disease by 45.4% (p < 0.05). The disease control efficacy (PDIDS) was 63%. This reduction in disease incidence and severity coincided with a drastic reduction in both the relative abundance of Plasmodiaphora brassicae, the causative pathogen of cabbage clubroot disease, and its copy number in rhizosphere soil. Pathogenic fungi Alternaria and Fusarium were also negatively associated with Trichoderma inoculation according to co-occurrence network analysis. Inoculation drastically reduced the relative abundance of the dominant bacterial genera Delftia and Pseudomonas, whilst increasing others including Bacillus. Our results demonstrate that T. harzianum LTR-2 is an effective biological control agent for cabbage clubroot, which acts through modulation of the soil and rhizosphere microbial community.

Intensifying livestock production by integrating perennial forages has great potential to contribute to sustainable development and livelihoods in the Mekong region. However, the approach taken must be informed by the environmental, social, and cultural context of the region. Accordingly, we review published research papers and reports from relevant research for development projects to identify options for sustainably integrating forages into farming systems, with a focus on sand-dominant soils of southern Laos and Cambodia. First, we examine existing livestock management practices to determine the compatibility of forages as an option to intensify livestock production. Second, we review the environmental properties of rainfed lowland rice systems with sandy soils and their implications for forage growing. Third, we identify and compare the suitability of existing forage genetics that is adapted to these environmental properties. Fourth, we propose adapted varieties, outline appropriate management options, and discuss the sustainable engagement of smallholders in the production of forages. The key findings are as follows: (1) Forages appear compatible with the sociocultural properties of smallholder farming systems in southern Laos and Cambodia because there is an awareness of existing limitations to livestock production, widespread desire to possess livestock for cultural reasons, and mounting pressure to improve the productivity of grazing areas and the efficiency of labor.(2) The limiting properties of the environment are drought, soil acidity, flooding, and soil infertility, which must be addressed in the selection and management of forage genetics. (3) Broadly adapted perennial tropical grasses and herbaceous legumes exist, but these are unlikely to thrive in lowland ecosystems of southern Laos and Cambodia that are prone to both annual flooding and drought. (4) Variations in surface hydrology at the farm scale often result in differentiated environments suitable for differing varieties. Brachiaria sp. hybrid "Mulato II," Panicum maximum, and Stylosanthes guianensis are recommended for droughtprone, acidic sands that are safe from prolonged submergence and would require the least additional management, whilst Paspalum atratum is recommended for low-lying areas with access to irrigation. (5) The transition to perennial forage integration appears to be accessible to farmers and can allow them to rapidly accumulate benefits in terms of saved labor; however, efforts to intensify animal production have been slow and must contend with multiple challenges: poor understanding of animal husbandry and health, cultural views relating to the role of animals in production systems, and poor access to forage and livestock services. These must all be addressed if sustainably intensified animal production is to be achieved in these and similar regions.