WO2015166408A2

WO2015166408A2 - Method for improving the production of cultured aquatic animals in combined rice-aquaculture systems

Info

Publication number: WO2015166408A2
Application number: PCT/IB2015/053084
Authority: WO
Inventors: Thuyen PHAM QUANG; Stefan TEMPEL
Original assignee: Bayer CropScience LP
Current assignee: Bayer CropScience LP
Priority date: 2014-04-29
Filing date: 2015-04-28
Publication date: 2015-11-05
Anticipated expiration: 2016-10-29
Also published as: PH12016502153A1; CN106659130A; WO2015166408A3

Abstract

The present invention relates to a process for growing aquatic animals in rice-aquaculture systems. The invention also relates to a method for improving the yield of production of cultured aquatic animals in such rice-aquaculture systems, whereby the rice is hybrid rice. Examples of grown aquatic animals in rice-aquaculture systems are shrimps, prawns, fishes, or any other grown aquatic animals.

Description

Method for improving the production of cultured aquatic animals in combined rice-aquaculture systems

Background information

Rice (Oryza sativa) cultivation is deeply associated with water. Paddy rice fields are usually flooded with water, either through irrigation or from rains. From this situation, since ancient times, rice farmers have developed aquaculture in association with the growing of their rice crop. Depending on the regions of the world, fishes have been cultivated in the flooded paddy fields, but also crustaceans like shrimps, prawns or even crawfish.

For example, Chinese rice growers have since long co-cultivated carps together with their rice crop in the same field. Mixing aquaculture with rice cultivation is also a known practice in Bangladesh where either fish or prawns are cultivated. A similar system is also found in Indonesia where it is known as the Tambak system.

This practice is known for inland-grown rice, but also in coastal regions where the fields are flooded with sea water, or at least brackish water, during certain periods of the year, thereby obliging rice growers to switch to another activity for the time the salinity is too high to grow rice. In the tidal regions of the Mekong delta in South Vietnam, the rice-shrimp rotation culture is developed since decades. However, like in many places where aquaculture is intensively run together with rice cultivation, growers face difficulties to maintain proper conditions for viably growing the two crops. One recurrent problem, especially when these agricultural practices intensify, is the nutritional and health conditions for the growth of the aquatic animals. There are therefore needs for improving such mixed aquaculture and rice growing systems.

Description of the invention

In all places known where such mixed aquaculture and rice growing systems exist, the varieties of rice grown are usually inbred rice varieties. Surprisingly, it has now been found that the use of hybrid rice varieties in mixed aquaculture and rice growing systems improves the nutritional and sanitary conditions for growing the aquatic animals, and eventually the yield of production of such aquatic animals, compared to the use of inbred rice varieties. Contrary to inbred rice varieties which are varieties genetically similar to their parents, hybrid rice varieties are rice varieties obtained from the cross of two distinct rice varieties as parental lines. This combined cross usually leads to rice varieties having a significantly improved yield, a phenomenon known as heterosis or "hybrid vigour".

Accordingly, the present invention relates to a method for growing both rice and an aquatic animal suitable to be grown in rice paddy fields, wherein the rice is a hybrid rice variety. According to a another embodiment, the invention provides a method for improving the growth of an aquatic animal suitable to be grown in rice paddy fields in a mixed aquaculture and rice growing system, wherein the rice is a hybrid rice variety.

According to another embodiment, the invention provides a method for increasing the yield of production of an aquatic animal suitable to be grown in rice paddy fields in a mixed aquaculture and rice growing system, wherein the rice is a hybrid rice variety.

According to another embodiment, the invention provides a method for increasing the density of phytoplankton in fields grown in a mixed aquaculture and rice growing system, wherein the rice is a hybrid rice variety.

According to another embodiment, the invention provides a method for increasing the density of beneficial bacteria in fields grown in a mixed aquaculture and rice growing system, wherein the rice is a hybrid rice variety. In a specific embodiment, the beneficial bacteria are bacteria of the species Bacillus sp., Nitrobacter sp., and/or Nitrosomas sp.

According to another embodiment, the invention provides a method for avoiding the development of phytoplankton species of the Dinophyta group (i.e. dinoflagellates) in fields grown in a mixed aquaculture and rice growing system, wherein the rice is a hybrid rice variety.

According to another embodiment, the invention provides a method for decreasing the level of infestation by Whitespot Syndrome Baculovirus virus (WSSV) of an aquatic animal suitable to be grown in rice paddy fields in a mixed aquaculture and rice growing system, wherein the rice is a hybrid rice variety. A mixed aquaculture and rice growing system is a cultivation system taking place in a field, where a rice crop is grown either concomitantly, i.e. at the same time, or consecutively, i.e. in alternate consecutive growing cycles (in rotation), with the growth of one or more aquatic animals suitable to be grown in rice paddy fields. In such cultivation systems, the field is usually flooded with water, either through irrigation or rains. Preferably, the rice crop is grown before the aquatic animal.

The aquatic animals suitable to be grown in rice paddy fields may be finfishes like e.g. carps, tilapia, catfish, or crustaceans like e.g. freshwater or marine prawns or shrimps, lobsters, crabs or crawfish. According to a specific embodiment, the aquatic animals are shrimps, preferably Tiger shrimps of the species Panaeus monodon or Whiteleg shrimps of the species Litopanaeus vannamei.

The hybrid rice varieties that can be suitable for carrying out the present invention are any hybrid rice varieties. Suitable hybrid rice varieties include the ones produced according to the classical 3-lines system based on the CMS (cytoplasmic) type of male sterility, or the 2-lines system based on a Temperature (TGMS) or Photoperiod (PGMS) type of male sterility, or any other type of male sterility (e.g. chemically-induced). Many different hybrid rice varieties have been developed in different rice- growing countries, which could be suited for the present invention.

Where the mixed aquaculture and rice growing system takes place in coastal places, the two crops are usually rotated in alternate growing cycles, the rice crop being grown in a rainy or wet season, and the aquatic animal being grown in a drier season when the fields may be subject to marine or brackish water flooding. In such places where the rice crop is then grown in a field having been flooded for some time with salted water prior to the rice crop being sown, the hybrid rice varieties are preferably varieties having the capacity to grow in soils and water containing a certain quantity of salt (i.e. sodium chloride). A hybrid rice variety having such capacity is bearing at least one trait for tolerance to saline environments, enabling it to grow despite the presence of a certain proportion of salt in the soil or the water. Such hybrid rice varieties have the capacity to withstand a concentration of salt in the soil or the water of at least 1 %c (one part per thousand), 5 %c, 10 %c, 15 %c, 20 %c, 25 %c, 30 %c or even 35 %c.

Examples of traits for salinity tolerance are e.g. the Saltol QTL (Quantitative Trait Loci) (Thompson et al, 2010, Rice 3, 148-160), or the SKC1 trait (Zhong-Hai Ren et al, 2005, Nature Genetics 37, 1141- 1146). Certain rice lines have also been identified to be tolerant to a certain amount of salt, and therefore to bear a salinity-tolerance trait that could be transferred to other rice lines and hybrids by breeding methods or by transgenesis (see review by Deepa Sankar et al, 2011, Research in Biotechnology 2(2), 1-10). Scientists at IRRI have also identified a salt-tolerance trait from the species Oryza coarctata and have recently been able to cross that trait into an Oryza sativa line (IRRI Annual Report 2012). Any hybrid rice variety bearing any such trait or a combination of such traits is suitable for carrying out the present invention.

Any hybrid rice variety being tolerant to a certain level of salt concentration in the soil is suitable for carrying out the present invention. Examples of hybrid rice varieties tolerant to a saline environment include hybrid rice varieties having the denomination B-TE1, Tej Vang, or PHB71. Other hybrid varieties have also been described in Deepa Sankar et al., 2011, Research in Biotechnology 2(2), 1-10.

The hybrid rice plants suitable for the present invention may also contain additional traits making them tolerant or resistant to a variety of biotic or abiotic stresses, and may be transgenic or non-transgenic hybrid varieties. Such traits may include traits providing resistant to insects, e.g. brown-plant hopper, or to fungal diseases, e.g. blast diseases. Example of transgenic traits include for example Cry genes or VIP genes from the bacteria Bacillus thuringiensis, or genes imparting tolerance to certain herbicides.

The invention is illustrated by the examples below. However, the invention is not limited to the examples.

Example 1: Effect of hybrid rice in a rice-shrimp rotation system on water and sediment physico- chemical parameters

1.1. Experimental design

The experiment was conducted in the Ca Mau province, in the south of Vietnam.

An area of 10.000 m² was divided in two equal units, each unit being of 5,000 m².

One unit has been used for carrying out the experiment with a hybrid rice variety (B-TE1 hybrid variety), and other unit has been used as control with a local inbred rice variety (1 Bui Do variety, also known as "one red hill" variety).

All activities on the two units were exactly the same during the experiment. The rice field is designed with a surrounding dyke for keeping water. Rice cultivation:

The rice field was washed to remove saline water and replace it by fresh water to reach the standard for growing rice, and prepared for transplanting rice. 1 kg of rice seed for each variety has been sown on area of 40 m², which was then transplanted in the rice field for the experiment after 20 days. The two rice varieties have been grown about 3 months in the rice fields before being harvested.

Shrimp cultivation:

Saline water was entered in the field after the rice harvest. The saline water was kept and treated with lime before pumping to the rice field for experimental conduct. Tiger shrimps (Panaeus monodon) were released in the field at the post-larvae stage PL12. Salinity of water in the rice field at releasing of post-larvae was 19 %c, and the water level was 0.4 m.

Samplings were made six times over the whole experiment, two times during the rice cultivation and four times during the shrimp cultivation.

1.2. Results

Several physico-chemical parameters of the water were measured both in the control (inbred rice) and in the experimental units (hybrid rice). The parameters measured were temperature, pH, salinity, dissolved oxygen, chemical oxygen demand, alkalinity, hardiness, total suspended solids, total amonium nitrate, nitrite, total nitrate, total phosphate, total sulfide. The sediments were also analyzed for total organic matter, total nitrate, total phosphate, aluminium and ferric Fe.

The main parameters of the water like temperature, pH, and salinity fluctuated in the same manner (i.e. no differences) between the control and the experimental units. Similar fluctuations in the water were also observed between control and experimental units for the dissolved oxygen, chemical oxygen demand, alkalinity, total suspended solid, total nitrates.

In water, lower levels of total amonium nitrate, nitrite and sulfide were obersved in the experimental unit (hybrid rice) than in the control unit (inbred rice). In the sediments, total phosphate and aluminium fluctuated in a similar manner. However, lower levels of total organic matter, total nitrate and ferric Fe were observed in the experimental unit (hybrid rice) compared to the control unit (inbred rice).

Example 2: Effect of hybrid rice in a rice-shrimp rotation system on phytoplankton composition Water composition in phytoplankton was analyzed both during the rice cultivation (two samplings) and during the shrimp cultivation (four samplings).

The experimental design is the same as described in Example 1.1.

2.1. Phytoplankton during rice cultivation

No significant variation in the number of species and density of phytoplankton was observed between the experimental unit (hybrid rice) and the control unit (inbred rice) during the rice cultivation phase.

2.2. Phytoplankton during shrimp cultivation

Despite some fluctuations over the four samplings, the average number and composition of the phytoplankton species as well as their density appeared to be similar in the experimental unit (hybrid rice) and the control unit (inbred rice) over the shrimp cultivation phase. The only observed difference was in the late shrimp cultivation phase (last two samplings), where the dinoflagellate species (Dinophyta) appeared to be the dominant ones over the diatom species (Bacillariophyta) in the control unit, whereas the reverse situation was observed in the experimental unit, i.e. dominance of the diatom species (Fig. 1). The presence of dinoflagellates is generally known as being an indicator of poor water quality. Dinoflagellates are only present in limited densities in the inlet canal distributing both the experimental and the control units.

B-TE1 CossSfo! frctet sa^ai

Fig. 1: phytoplankton composition and density during shrimp cultivation

Example 3: Effect of hybrid rice in a rice-shrimp rotation system on zooplankton and zoobenthos composition

The composition of the cultivation area in zooplankton and zoobenthos was analyzed both during the rice cultivation (two samplings) and during the shrimp cultivation (four samplings).

The experimental design is the same as described in Example 1.1. 3.1. Zooplankton and Zoobenthos during rice cultivation

In a first experiment, no significant variation in the number of species and density of zooplankton and zoobenthos was observed between the experimental unit (hybrid rice) and the control unit (inbred rice) during the rice cultivation phase.

In a second experiment, the results showed a much higher density of zooplankton at the end of the rice cultivation phase in the experimental unit (hybrid rice) than in the control unit (inbred rice), on average 80.000 individuals/m³ and 27.000 individuals/m³.

3.2. Zooplankton and Zoobenthos during shrimp cultivation

No significant variation in the number of species of zooplankton was observed between the experimental unit (hybrid rice) and the control unit (inbred rice) during the shrimp cultivation phase. However, over the whole shrimp cultivation phase (4 samplings), the density of zooplankton appeared to be much higher in the experimental unit (hybrid rice) than in the control unit (inbred rice). It was on average 182.000 individuals/m³ in the experimental unit, and 65.000 individuals/m³ in the control unit (Fig. 2).

t»le« Caoai B-Tf ^■ Central

Fig. 2: zoobenplankton composition and density during shrimp cultivation

A second experiment confirmed this finding, showing on average a density of 375.000 individuals/m³ in the experimental unit, and 100.000 individuals/m³ in the control unit. No significant variation in the number of species and density of zoobenthos was observed between the experimental unit (hybrid rice) and the control unit (inbred rice) during the rice cultivation phase.

Example 4: Effect of hybrid rice in a rice-shrimp rotation system on beneficial bacteria composition

The composition of the cultivation area in beneficial bacteria was analyzed both during the rice cultivation (two samplings) and during the shrimp cultivation (four samplings).

The experimental design is the same as described in Example 1.1.

4.1. Density of bacteria in water

Over the whole experiment, the total density of bacteria in water was always higher in the experimental unit (hybrid rice) than in the control unit (inbred rice). More specifically, the density of bacteria of the Bacillus group, the Nitrosomas group and the Nitrobacter group was higher in the experimental unit (hybrid rice) than in the control unit (inbred rice).

4.2. Density of bacteria in sediments

Over the whole experiment, the total density of bacteria in the sediments was always higher in the experimental unit (hybrid rice) than in the control unit (inbred rice). More specifically, the density of bacteria of the Bacillus group, the Nitrosomas group and the Nitrobacter group was higher in the experimental unit (hybrid rice) than in the control unit (inbred rice). Example 5: Effect of hybrid rice in a rice-shrimp rotation system on pathogenic bacteria (genus Vibrio) composition

The composition of the cultivation area in pathogenic bacteria was analyzed both during the rice cultivation (two samplings) and during the shrimp cultivation (four samplings). The experimental design is the same as described in Example 1.1.

No significant variation in the number of Vibrio was observed between the experimental unit (hybrid rice) and the control unit (inbred rice) during the whole cultivation phase, either in the water or in the sediments.

Also, no shrimp have been found to be infected with Vibrio harveyi using a PCR detection method. Example 6: Effect of hybrid rice in a rice-shrimp rotation system on viral pathogens in shrimps

The presence of the following shrimp pathogenic viruses has been analyzed with specific PCR-based detection methods in shrimp samples:

- Whitespot Syndrome Baculo virus virus (WSSV)

- Infectious Hypodermal and Hematopoietic Necrosis virus (IHHNV)

- Monodon Baculovirus (MBV),

- Yellowhead virus/ Gill- Associated virus (YHV/GAV)

The experimental design is the same as described in Example 1.1.

No significant difference in the presence of the IHHNV, MBV and YHV/GAV viruses has been observed in shrimp samples grown in the experimental unit (hybrid rice) or in the control unit (inbred rice).

However, although the presence of WSSV was detected in shrimps of the control unit (inbred rice) over the whole growing period, it was not detected in two out of four samplings in shrimps of the experimental unit (hybrid rice). Moreover, in some additional similar experiments, a trend is observed of finding much less prevalence of at least one, sometimes two or three, of these monitored viruses in the experimental unit (hybrid rice) than in the control unit (inbred rice).

Example 7: Effect of hybrid rice in a rice-shrimp rotation system on yield of shrimp production

In a similar experiment, the yield of shrimp production was measured both in the experimental unit (hybrid rice) or in the control unit (inbred rice). The experimental design is the same as described in Example 1.1.

The shrimps has been harvested eight times in each unit, and the total yield calculated out of the eight harvests.

Table 1 : yield of shrimp production As can be seen from Table 1, the yield in shrimp production is much higher (+ 19 %) when shrimps have been grown in the experimental unit (hybrid rice) than when grown in the control unit (inbred rice).

In a second similar experiment, the following yields have been observed in the shrimp and in the rice production (Table 2).

Table 1 : yield of shrimp and rice production

As can be seen from Table 2, the yield in shrimp production is much higher (+ 16 %) when shrimps have been grown in the experimental unit (hybrid rice) than when grown in the control unit (inbred rice).

This is a significant advantage, which translates into additional income for the farmers.

Claims

1. Method for growing both rice and an aquatic animal suitable to be grown in rice paddy fields, wherein the rice is a hybrid rice variety.

2. Method for increasing the yield of production of an aquatic animal suitable to be grown in rice paddy fields in a mixed aquaculture and rice growing system, wherein the rice is a hybrid rice variety.

3. Method for increasing the density of phytoplankton in fields grown in a mixed aquaculture and rice growing system, wherein the rice is a hybrid rice variety.

4. Method for increasing the density of beneficial bacteria in fields grown in a mixed aquaculture and rice growing system, wherein the rice is a hybrid rice variety.

5. Method for avoiding the development of phytoplankton species of the Dinophyta group (i.e. dinoflagellates) in fields grown in a mixed aquaculture and rice growing system, wherein the rice is a hybrid rice variety.

6. Method for decreasing the level of infestation by Whitespot Syndrome Baculovirus virus (WSSV) of an aquatic animal suitable to be grown in rice paddy fields in a mixed aquaculture and rice growing system, wherein the rice is a hybrid rice variety.

7. Method according to anyone of claims 1 to 6, wherein the mixed aquaculture and rice growing system is a cultivation system taking place in a field, where a rice crop is grown either concomitantly, i.e. at the same time, or consecutively, i.e. in alternate consecutive growing cycles (in rotation), with the growth of one or more aquatic animals suitable to be grown in rice paddy fields.

8. Method according to anyone of claims 1 to 7, wherein the aquatic animal suitable to be grown in rice paddy fields is a crustaceans like e.g. freshwater or marine prawns or shrimps, crabs or crawfish.

9. Method according to claim 8, wherein the aquatic animal suitable to be grown in rice paddy fields is shrimp.

10. Method according to anyone of claims 1 to 9, wherein the hybrid rice variety is a variety having the capacity to grow in soils and water containing salt

11. Method according to anyone of claims 1 to 10, wherein the hybrid rice variety is a variety having the denomination B-TEl