New hybrid rice technology results from

grower�RiceTec partnership

RiceTec invested over 12 years in developing the first commercial hybrid rice cultivar for the US. Hybrid XL6 was released in 2000. It increased yield potential by 20% over conventional varieties while reducing Nitrogen fertilizer requirements by nearly 50%. XL6 had several drawbacks such as lodging and poor grain quality. US rice growers have been very patient with the hybrid technology, allowing RiceTec to improve on those traits with newer hybrid releases. Grower confidence continues to fuel hybrid improvements.

Hybrids have a proven track record of yield increase across cropping systems

0

2000

4000

6000

8000

10000

12000

CLEARFIELD Conventional

Yiel

d (lb

/A)

Cropping System

Hybrid advantage

Variety

1960 lb/A2140 lb/A

The incorporation of herbicide tolerance into hybrids has expanded the high yielding opportunity to the CLEARFIELD system. This system has depended on older, lower yielding varieties. Long term yield trial data collected in more than 200 trials, conducted by independent parties have confirmed hybrid high yields. Grower testimonials also support the hybrid yield advantage.

However questions persist on hybrid tolerance to herbicide within the CLEARFIELD system

The hybrid system brought a new genetic constitution to US rice fields, sometimes with patterns of response to environmental and agronomic factors different from conventional varieties. Early plant response following the application of the herbicide used within the CLEARFIELD system (Newpath) have generated concerns over herbicide tolerance.

The concern is based in hybrids having a non�herbicide tolerant parent

Parent 1: Non-tolerant

Parent 2: Tolerant

Hybrid: Tolerant

X

Some have argued that hybrids have half the tolerance of varieties because their female parent is non�tolerant to Newpath herbicide. However, the gene controlling herbicide tolerance is dominant over non�tolerance; meaning that only one copy is needed to provide sufficient tolerance. Plants carrying only one copy of the herbicide�tolerant gene react the same as those carrying two copies under herbicide rates below 4X of recommendation.

CLEARFIELD hybrids constantly deliver high yields irrespective of herbicide rate

0

2000

4000

6000

8000

10000

4oz + 4 oz 8oz + 8oz 12oz + 12oz

Yiel

d (l

b/A

)

Newpath herbicide rate

AVG Yield 4 hybrids over 2 years

Long term herbicide tolerance trials show no statistical difference in hybrid yields across herbicide rates, similar to the response of CL varieties. Yields of hybrids CLXL729, CLXL730, CLXP746, and CLXL745 were not affected by herbicide rates as high as 12 oz/acre of Newpath followed by 18 oz/acre (Table); this is way beyond current recommendation of 6 oz/acre followed by 6 oz/acre .

CLXL729 CLXL730 CLXL745 CLXP746 CL161 CL1714+4 221.3 208.3 239.1 224.0 172.1 165.58+8 205.4 200.7 224.8 216.4 173.1 157.912+12 201.3 205.3 232.0 213.7 166.6 166.64+6 212.7 216.6 240.7 223.9 183.2 157.48+12 199.5 208.0 239.8 217.9 170.5 159.812+18 197.9 198.1 230.4 209.5 172.1 156.2LSD 23.7 18.5 22.1 23.5 17.1 20.7

CL VarietiesNewpath rate (oz+oz)/A

CL Hybrids

CLEARFIELD XL745: 12oz/A at 1-2 leaf & 12oz/A at 4-5 leaf

May 15th June 5th July 6th

Even though early plant response to herbicide rates is possible in certain conditions

High rates can result in early plant response, especially under cool wet conditions; however no evidence of plant response remains 3 weeks later. Farmers are already aware of hybrids’ ability to recover. They continue with recommended herbicide application and crop management practices. RiceTec technical advice is to always complete the 2 recommended Newpath applications even when early plant response is observed.

CLEARFIELD stewardship guide designed to prevent development of herbicide tolerant red rice

The rice CLEARFIELD production system is built around a gene for tolerance to a non�selective herbicide. The system allows for control of all other rice not carrying the tolerance gene. This is the only available chemical control of red (weedy) rice in a commercial rice crop as long as the tolerance gene is not transferred to this noxious rice. A way to avoid this transference and maintain the viability of the system is to reduce the chances of cross�fertilization between the two types of rice. The CLEARFIELD stewardship guide lists management recommendations to prevent cross�fertilization. Key stewardship recommendations are:

�Consecutive applications of Newpath to minimize the chances of any un�wanted rice plants growing along with the rice crop.

�If there is any doubt that both Newpath applications failed to control red rice 100%, a Beyond application should be scheduled within 2 wk of application of the permanent flood.

�Use of Beyond herbicide as a rescue treatment to get rid of any escapes from the pre�flood herbicide applications.

There are stewardship concerns over herbicide application to red rice growing in hybrid fields

Red rice escapes are easier to notice when the crop is at or nearing the flowering stage. Therefore, application of the herbicide Beyond as a rescue treatment depends on field observations at that time. The labeled cut�off for Beyond applications is PI+14 days on CL varieties and PI on CL hybrids. Multi�year data indicates that if Beyond is applied past PI on CL hybrids there is a potential for yield reduction. In some cases, the reduction has been high enough to reduce the CL hybrid yield to the same level as the CL variety. It is believed that growers could:

�Consciously skip the Beyond application to protect hybrid yields, and or

�Miss some escapes by not noticing their presence during the application window for hybrids.

To reduce the potential for outcrossing, fields should be scouted for red rice escapes and a Beyond application made within the label guidelines.

Chances of red escapes in hybrids are 40% lower than varieties in the absence of herbicide use

0.0

0.1

0.2

0.3

0.1 0.2 0.3Red

Ric

e Pl

ants

/ft2

rea

chin

g m

atur

ity

Red Rice Seeds in Soil (seeds/sq ft)

CL Variety

CL Hybrid

However, the hybrids can naturally reduce the chances of red rice plant escapes by outcompeting them. Work conducted by the University of AR during 2002 and 2003 comparing red rice survival in variety CL161 and hybrid CLXL8 plots provided evidence of higher competitive ability of hybrids versus varieties.

Does cross pollination of hybrid parents affect CLEARFIELD stewardship within a hybrid system?

Hybrid systems originated in cross�pollinated crops such as corn with separate female and male flowers. The separation of sexes and the resulting wind pollination facilitates hybrid seed production . Development of a hybrid system in a naturally self�pollinated crop such as rice, which has both sexes in the same flower, requires careful selection of traits that facilitate cross pollination. Such selection includes a male sterile and a good pollen receptor female parent. How much of that ability to receive pollen from other flowers is transferred to the resulting hybrid? What effect if any would it have on the ability of the hybrid to preserve the CLEARFIELD trait?

Foreign pollen was twice as successful in fertilizing hybrid than variety when applied to intact flowers

Red Rice CL Hybrid 12% Red Rice CL Variety 5%

CL Hybrid Red Rice 2%CL Variety Red Rice 2%

Foreign Pollen source

Applied to intact flowers of

Foreign Pollen fertilization success

We went to the extreme to simulate natural out�crossing in 2003. We dusted red rice pollen as soon as flowers began to open occurred in intact panicles of plants of CL XL8 and CL161. The same procedure was followed using CL XL8 and CL161 pollen over open red rice flowers. Pollen was applied daily between 11 AM and noon until the last flower opened, or about 10 consecutive days. DNA of 250 seeds was assessed for the presence of red rice traits. The resulting data suggests red rice pollen was more effective in fertilizing CL cultivars, especially hybrids, than the cultivar pollen fertilizing red rice. This indicates the most likely mechanism of transferring the CL trait to red rice is the planting of seed of CL cultivars resulting from fertilization with red rice pollen. Since hybrid grain is not planted again, the likelihood of transference would be restricted to plants growing from dropped seed (volunteers).

However hybrids reduce the potential of transferring the CLEARFIELD trait to red rice by one half

Red rice non-CL

CL Hybrid

100% CL 50% non-CL50% CL

CL Variety

All CL 50% CL 50% non-CL

If outcrossing with red rice occurs, all resulting progeny from red rice cross pollination with a variety would carry the CL trait; whereas, only one half of the progeny of a cross between a CL hybrid and red rice would carry the CL trait. Therefore, the higher outcrossing potential of hybrids would be neutralized. The outcrossing potential of hybrids as pollen source is the same as varieties. The net result is that hybrids are better stewards of the CLEARFIELD technology because no matter the direction of the cross they only transfers the trait half of the time:

Non-CL pollen

CL Variety

50% 50%100%

CL pollen

CL Hybrid

CL pollen

Other stewardship concerns focus on the potential effects of hybrid grain on the ground

An increased potential of developing volunteer CL rice from hybrids due to shattering has recently been proposed . The higher shattering potential of current hybrids was evident under the high winds of the hurricanes of the 2008 season. The concern has merit and deserves careful analysis.

Hybrid grain does NOT have higher survival rate once it falls to the ground

CL Variety CL HybridGrain positionIncorporate into soil 1.5% 1.0%

Left on top of ground 0.0% 0.0%

Spring Stand Established

Although existing hybrids may drop more grain than varieties, survival rate is very similar. Survival can even be eliminated if grain is left on top of the ground

A quarter of the plants coming from dropped hybrid grain would be susceptible to Newpath

Grain incorporated into soil

% plant death after Newpath application

CL Variety 0.0

CL Hybrids 25.9

Additionally, as hybrids carry a single copy of the CL trait, 25% of the volunteer plants that could potentially germinate are expected to be non�CL (left table); therefore, killed by Newpath. Two years of research with 4 hybrids confirm the expected proportion of herbicide�susceptible F2 plants (right table).

% volunteer plant death

after 6oz+6oz Newpath

CLXP746 F2 grain 29.3

CLXP745 F2 grain 23.8

CLXL730 F2 grain 21.8

CLXL729 F2 grain 28.8

Average 25.9

CL

Hybrid as female

Non-CLCL

Non-CL

CL

CL

CL

Non�CL

Hybrid as

male

Latest hybrid release shows RiceTec is continually improving grain retention

0

5

10

15

20

25

30

2006 (CL XL730) 2007 (CL XL729) 2008 (CL XL745)

Gra

in d

rop

afte

r hu

rric

ane

(bu/

A)

CLEARFIELD hybrid

The risk of hybrid shattering is higher than both RiceTec and its customers would like. The latest hybrid release is an indication of the Company’s commitment to deal with the issue.

Seeds/sq ft Bu Actual Yield % Yield LossCL161 49 2 163 -1.9%CL171 153 8 154 -5.3%CLXL745 293 15 193 -8.2%CLXL729 538 27 173 -14.3%CLXL730 562 28 163 -16.0%

Average of 7 observations over 4 locations after hurricane force winds

The Hybrid platform offers safe & efficient

mechanisms to preserve CLEARFIELD technology