Item No. 1 of 2

INVESTIGATOR: Dunand, R. T.

PERFORMING INSTITUTION:
RICE RESEARCH CENTER
LOUISIANA STATE UNIVERSITY
BATON ROUGE, LOUISIANA 70893

IMPROVEMENT OF RICE PRODUCTION WITH PLANT GROWTH REGULATORS

OBJECTIVES: To determine the ability of plant growth regulators (PGRs) to improve seedling vigor, facilitate water management, increase grain yield, and aid in pest control in rice and improve forage biomass in crawfish production.

APPROACH: Small plot field research would include drill- and water-seeded rice. Plant growth regulators would be applied to seeds and at various stages of growth between emergence and early grain filling. Various pesticides and pesticides plus PGR combinations varying rate and time of application would also be made. Effects on emergence, stand density, root density and length, plant height, canopy closure, water use efficiency, pest control, crop injury, panicle density and weight, and grain production would be documented. Increasing the ratio of vegetative to reproduction development through PGR application would involve monitoring leaf, stem, and panicle weights during the winter and spring of crawfish season.

PROGRESS: 1994/03 TO 1998/12
The effects of gibberellic acid (GA) and maleic hydrazide (MH) on rice production were consistent over the last 5 years. With 2 to 5 g GA/ha, the semidwarf varieties, Cypress, Jefferson, Bengal, and Lafitte, had greater improvements in seedling vigor with 25 to 50% increases in stand and 3- to 5-inch increases in seedling height compared with the tall varieties, Drew, Kaybonnet, LaGrue, and Maybelle, which had 10 to 25% increases in stand and 1- to 3-inch increases in seedling height. Similar results were noted in several experimental lines currently being considered as varietal releases. Increases in seedling vigor in March plantings required 2- to 3-fold higher rates of GA compared with April and May plantings. In the last 2 years, GA was equally effective in water- and drill-seeded rice. All commercial formulations of GA performed similarly whether used alone or in combination with the numerous commercial and experimental agricultural chemicals in rice production. Mild phytotoxic effects from certain herbicides were reduced by 20%, and the efficiency of low herbicide rates was improved by 25% with GA, resulting in significant 500 to 800 lb/A increases in yield. With 1.67 kg MH/ha, red rice seedhead production was controlled by 80 to 95%, increasing grain grade (reducing red rice seed in harvested grain by 90 to 100%), increasing grain quality (up to an 11% percentage point increase in milling yield), and reducing red rice populations by 50 to 75% in subsequent years. All rice varieties were tolerant to MH applied no earlier than the milk stage. Maleic hydrazide applied earlier than milk stage caused 20% floret sterility and decreased rice yields by 1000 kg/ha. Injury from MH in the first crop caused earlier heading and a 20% increase in yield in the ratoon crop. The impact on total crop yield was negligible. In drift studies, MH reduced soybean yields by 20%.

PUBLICATIONS: 1994/03 TO 1998/12
1. Saichuk, J.K., Dunand, R.T., et al. 1998. Plant growth regulators. In: 1998 rice varieties and management tips. La. Coop. Extn. Serv. Pub. 2270. 27 pp.
2. Dunand, R.T. et al. 1997. Rice Physiology Reports. Ann. Res. Rpt., Rice Res. Stn., La. Agri. Exp. Stn., LSU Agricultural Center, 89:231-333.
3. Dunand, R.T. 1998. Gibberellic acid and phytotoxic rates of propanil and thiobencarb in rice. Proc. S. Weed Sci. Soc. 51:35.
4. Dunand, R.T. 1998. Influence of booting applications of gibberellic acid on shoot growth and crop production in rice. Pl. Growth Reg. Soc. of Am. Quarterly. 26(2):48.
5. Linscombe, S.D. and Dunand, R.T. 1998. Genetic means for controlling growth in rice. Pl. Growth Reg. Soc. of Am. Quarterly. 26(2):63.
6. Dunand, R.T. 1998. Influence of booting applications of gibberellic acid on shoot growth and crop production in rice. Proc. Pl. Growth Reg. Soc. of Am. 25:60.
7. Linscombe, S.D. and Dunand, R.T. 1998. Genetic means for controlling growth in rice. Proc. Pl. Growth Reg. Soc. of Am. 25:76.
8. Dunand, R.T. 1998. Influence of gibberellic acid seed treatment timing and micronutrient in water-seeded rice. Proc. Western P. Growth Reg. Soc. 10:55-58.
9. Dunand, R.T. and Dilly, R.R. 1998. Using gibberellic acid to reduce herbicide costs in rice. Louisiana Agriculture 41(3):25.

Item No. 2 of 2

INVESTIGATOR: Dunand, R. T.

PERFORMING INSTITUTION:
RICE RESEARCH STATION
LOUISIANA STATE UNIVERSITY
BATON ROUGE, LOUISIANA 70893

IMPROVEMENT OF RICE PRODUCTION WITH PLANT GROWTH REGULATORS

OBJECTIVES: To determine the ability of plant growth regulators (PGRs) to improve seedling vigor, interact with pesticides, and alter plant growth and development for the general benefit of rice production.

APPROACH: Small plot field research would include drill- and water-seeded rice. Plant growth regulators would be applied to seeds and at various stages of growth between emergence and maturity. Pesticide and PGR combinations would be evaluated for interactions. Effects on emergence, stand density, root density and length, plant height, canopy closure, pest control, crop injury, panicle density and weight, and grain production would be documented. The influence of PGRs on both main and ratoon crop production systems would be studied.

PROGRESS: 2001/01 TO 2001/12
Plant growth regulators improved seedling vigor, increased tolerance to herbicides, reduced height, and increased yield of rice. Seed treatment with gibberellic acid in 14 varieties and experimental lines resulted in 3 to 4 days earlier emergence, had no effect on stand density, and increased seedling height by 50%. Long-grain varieties and experimental lines were more responsive than medium-grain types and semidwarf types were more responsive than tall types. At lower than recommended seeding rates, drill-seeded imidazolinone tolerant (Clearfield) rice treated with gibberellic acid seed treatment was more tolerant to imazethapyr, resulting in 50% less injury, twice the vigor, and 8% higher yields. Grain yield in Jefferson, a semidwarf, early season variety, was increased 500 kg/ha by gibberellic acid applied at the beginning of the reproductive phase of growth. Experimental plant growth regulators containing natural and synthetic gibberellins, auxins, and cytokinins produced yield increases ranging from 0 to 500 kg/ha and had no effect on premature abscisin layer in grain induced by panicle blight (Pseudomonas glumeae). Suboptimal rates of prohexadione-calcium (0.1 kg/ha) reduced mature plant height by 1 to 2 cm with no effect on lodging resistance, maturity, and grain production. In a simulated weed resistance management system with transgenic rice, maleic hydrazide affected seed production on 100% of the panicles of a crop compatible weed substitute. Maleic hydrazide applied during the late grain filling stages of the first crop increased grain yield by 30% in the subsequent ratoon crop.

IMPACT: 2001/01 TO 2001/12
Plant growth regulator use in rice can have a direct, positive impact on crop vigor, weed control, lodging tolerance, and grain production. Also, improving crop growth and development with plant growth regulators facilitates crop management, which decreases production costs and increases overall productivity.

PUBLICATIONS: 2001/01 TO 2001/12
1. Saichuk, J.K., Dunand, R.T., et al. 2001. Plant growth regulators. In: 2002 Rice Varieties and Management Tips. La. Coop. Extn. Serv. Pub. 2270. 36 pp.
2. Dunand, R.T. et al. 2001. Rice physiology reports. Ann. Res. Rpt., Rice Res. Stn., La. Agri. Exp. Stn., LSU Agricultural Center, 92:154-283.
3. Dunand, R.T. 2001. Plant growth regulators in rice. Proc. Western Pl. Growth Reg. Soc. 13:57-61.
4. Dunand, R.T., Webster, E.P., Linscombe, S.D., and Masson, J.A. 2001. Impact of gibberellic acid on crop tolerance of imidazolinone tolerant rice. Proc. S. Weed Sci. Soc. 54:44.
5. Dunand, R.T. 2001. Primo, nitrogen fertility, and stature reduction in rice. Proc. Rice Tech. Wrkg. Group. 28:152.
6. Dunand, R. 2001. A comparison of mefluidide and prohexadione-calcium on plant growth and crop production in semidwarf rice. Proc. Pl. Growth Reg. Soc. of Am. 28:64.
7. Linscombe, S.D., Jodari, F., Bollich, P.K., Groth, D.E., White, L.M., Chu, Q.R., and Dunand, R.T. 2001. Registration of `Earl' Rice. Crop Science 41(6):2003-2004.