Productivity assessment of an intensive whiteleg shrimp Penaeus vannamei farm based on Powersim-simulated growth rates

The main objective of intensive whiteleg shrimp Penaeus vannamei cultivation is to obtain high productivity to meet market needs. One of the efforts to boost production is to provide optimal feeding to increase the shrimp growth rate. This study analyzes the productivity of an intensive shrimp farm using Powersim simulations based on specific growth rates (SGR) and average daily growth (ADG) to determine the resulting production criteria. The cultivation lasted for 90 days by stocking 16 grow-out ponds with post-larvae (PL10) at a density of 80 PL per m². Shrimp samples were weighed every 10 days after day-30 of culture until harvest. The average productivity obtained from this study was 8.86 t/ha/crop. According to our criteria, this productivity level was low, presumably, due to the low growth rate that may have resulted from low-quality larvae, sublethal nitrite concentrations, low survival rate, and high feed conversion ratio. The SGR-based and ADG-based simulations using Powersim Studio 10 Express confirm the low production, which does not meet the criteria for intensive farming. However, ADG-based simulation shows that the prolonged culture to 126 days results in higher shrimp production and productivity that fall into the lower level of the intensive system. This study also proposes production criteria and productivity ranges for whiteleg shrimp farming.

     

Leaf blast disease reduction by rice-phyllosphere actinomycetes producing bioactive compounds

Fungal leaf blast, caused by Pyricularia oryzae, is a devastating disease of rice plants that annually causes severe production losses worldwide and is one of the top 10 fungal diseases that threaten global food security. Thus, a reliable control strategy against this disease is essential. In this study, the antagonistic activity of indigenous phyllosphere actinomycetes was elucidated against P. oryzae in vitro and in planta to develop an efficient, effective and environmental friendly approach to protect rice plants against P. oryzae. Of 75 isolates of actinomycetes isolated from the rice phyllosphere, 18 isolates inhibited P. oryzae by >45%. According to analysis of their 16 S rRNA gene sequences, the majority of the 18 isolates belonged to Streptomyces genera; others were identified as belonging to Saccharothrix, Gordonia, or Lentzea. Isolates that potentially produced a bioactive compound(s) were identified among the 18 isolates: 17 isolates (94.44%) had a domain marker for nonribosomal peptide synthetase (NRPS) gene and 12 (66.67%) had type-I polyketide synthase (PKS) gene in their corresponding genome. Interestingly, isolates JSN1.9, SKB2.14, and SKB2.3 suppressed disease suppression by approximately 88%. To our knowledge, this is the first report on the application of rice-phyllosphere actinomycetes producing bioactive compounds to control leaf blast disease in Indonesia. Thus, these findings have escalated the potential application of phyllosphere actinomycetes as a supreme biocontrol agent against fungal leaf blast disease.