In vitro and in vivo selection of probiotic purple nonsulphur bacteria with an ability to inhibit shrimp pathogens: acute hepatopancreatic necrosis disease‐causing Vibrio parahaemolyticus and other vibrios

Shrimp cultivation has been faced with huge losses in productivity caused by infectious shrimp pathogenic vibrios, especially Vibrio parahaemolyticus that causes acute hepatopancreatic necrosis disease (AHPND). Hence, purple nonsulphur bacteria (PNSB) were isolated from shrimp ponds for investigating their abilities to control shrimp pathogenic Vibrio spp. and their use as probiotics for sustainable shrimp cultivation. Based on their probiotic properties, strains S3W10 and SS15 were selected because of their strong abilities to produce amylase, gelatinase and vitamin B12. However, only three PNSB strains (SS15, TKW17 and STW181) strongly inhibited V. harveyi_KSAAHRC and V. vulnificus_KSAAHRC including V. parahaemolyticusAHPND strains by secreting antivibrio compounds. Four selected PNSB also grew in the presence of pancreatic enzymes, and they were identified as Rhodobacter sphaeroides for strains S3W10, SS15 and TKW17 and Afifella marina for strain STW181. The effects of a mixed culture were also investigated as follows: T1 (S3W10 + SS15), T2 (S3W10 + TKW17) and T3 (S3W10 + STW181) on postlarval white shrimp (Litopenaeus vannamei) for 60 days by comparison with a control. All three probiotic PNSB sets significantly improved the digestive enzyme activities and shrimp growth with their proliferation in shrimp gastrointestinal tract although the shrimp survival was not significantly different. They also significantly reduced the cumulative mortality of shrimp exposed to a virulent AHPND strain (V. parahaemolyticusSR2). This is the first to conclude that selected probiotic PNSB strains have great potential to be used for shrimp cultivation to control vibrios including AHPND strains.     

Comparison of cavity modification and community involvement as strategies for hornbill conservation in Thailand

We monitored breeding success of hornbills in Thailand for four sympatric species at Khao Yai National Park during 1981-2002 and six species at Budo-Sungai Padi National Park during 1994-2002. Within a 60 km² study area at Khao Yai, the well protected area, use of available cavities ranged from 94% in 1984 to 50% in 1993. Competition for nesting cavities was 40% of cavities available indicating the shortage of suitable cavity. We monitored the cavity condition and modified 48 cavities and, between 1996 and 2000, these contributed annually 23-45% of nestings that were successfully fledged (n = 352). Within the 90 km² at Budo Mountain, with heavy human disturbance, use of available cavities for nesting decreased from 81% in 1997 to 30% by 2001 and of successful fledging from 96% in 1997 to 55% in 1999, but both increased once our involvement with local communities had eradicated poaching and reduced disturbance. Competition for nesting cavities here was 26% of cavities available indicating the effect of poaching. Both strategies were successful in the short term but long-term management of cavities in large forest trees is required at Khao Yai and of forest disturbance at Budo.     

New sources of rice blast resistance obtained from Thai indigenous upland rice germplasm

Upland rice production plays an important role in both household consumption and crop rotation. Until now, a blast resistant upland variety has not been released in Thailand. The bimodal pattern of rain distribution in Thailand’s upland rice production areas create a favorable environment for the outbreak of leaf blast when seedling-tillering, and neck blast within the heading stage. The use of genetically resistant cultivars has proven to be an effective way to cope with this problem. In this study, 256 indigenous upland rice plants were screened for blast resistance under greenhouse and field conditions. Ten indigenous upland rice varieties, ULR292, ULR242, ULR219, ULR162, ULR161, ULR134, ULR109, ULR098, ULR081, and ULR066, were identified as resistant to leaf blast disease in both natural infection and artificial inoculation, under greenhouse conditions. Additionally, six of the ten varieties, ULR162, ULR161, ULR134, ULR109, ULR098, and ULR081, were found to be resistant to neck blast under field conditions. These new sources of blast resistance identified from indigenous upland rice varieties proved more resistant than the check varieties, depicting their potential for further use in Thailand’s rice blast resistance improvement program.     

Effect of water exchange with mangrove enclosures based on nitrogen budget in <Emphasis Type="Italic">Penaeus monodon</Emphasis> aquaculture ponds

ABSTRACT:   A model experiment in which water was circulated between shrimp aquaculture ponds (Ponds 1, 2, and 5), and mangrove enclosures (Ponds 3 and 4), was carried out at the Samut Songkhram Coastal Aquatic Research Station, Thailand, from March through July 2003. Five ponds with a size of 40 m × 20 m and 1.5 m deep were used for this experiment. Ten thousand shrimp larvae Penaeus monodon at the PL-15 stage were stocked in Ponds 1 and 5, and 20 000 larvae were stocked in Pond 2. Mangrove Rhizophora mucronata (476 trees) had been planted in each of Ponds 3 and 4 in July 2002. Approximately 30% of the water in Ponds 2 and 5 was moved to the mangrove enclosures by siphon (Ponds 3 and 4, respectively) every Thursday, and the same amount was returned to the shrimp ponds by pump every Monday over the 136-day experiment. Shrimp incorporated 30.3, 25.6, and 33.7% of the input nitrogen as feed in Ponds 1, 2, and 5. Since 2.02 kg N in Pond 2 and 0.76 kg N in Pond 5 was transported to the mangrove ecosystem, and 4.26 kg N in Pond 2 and 3.98 kg N in Pond 5 was retained in water and mud, it was estimated that between 2.1 and 5.2 unit areas of mangroves is required to remove the nitrogen remaining in the aquaculture pond.     

Phosphorus budget in shrimp aquaculture pond with mangrove enclosure and aquaculture performance

ABSTRACT:   An experiment in which water was circulated between shrimp aquaculture ponds stocked with 10 000 or 20 000 PL-15 stage Penaeus monodon , and mangrove enclosures each planted with 476 Rhizophora mucronata per enclosure, was carried out at the Samut Songkhram Coastal Aquatic Research Station, Faculty of Fisheries, Kasetsart University, Thailand. Shrimp survival rate was significantly higher ( P  < 0.001, Fisher's exact test) in ponds where 10 000 larvae was stocked and water was exchanged with the mangrove enclosure, compared with the control pond with no water exchange, over the 136 day experimental period. Phosphorus transport to the mangrove enclosure was estimated to be 0.41 kgP and 0.18 kgP over the experimental period and change in phosphorus content in mud was reduced there compared with the control pond. A load reduction effect to the environment was confirmed in this aquaculture system with mangrove enclosure compared with the phosphorus budget in the control pond, and 6.2 or 8.9 ha of mangrove area was estimated to be required by 1 ha shrimp ponds to fully process the phosphorus.