Physiological determination of oats yield: thoughts on promissory traits for further genetic gains Daniel Calderini Universidad Austral de Chile International Oat Conference Minneapolis, 2008

This presentation has the objective of: 1.Review few aspects of the effect of plant breeding on oat grain yield and associated traits 2.Analyze major grain yield components (i.e., grain number and grain weight) 3. Propose traits that could be useful to continue increasing yield potential 4. Propose a model of GW determination for temperate cereals

Introduction Grain crops are facing important challenges: - Expected increase of food demand - Alternative uses (biofuels) - Little opportunities for expanding arable land and irrigated areas - High grain production with low environmental impact

Grain yield (Mg ha) Grain yield (Mg ha -1 ) Oat 8595 YearsWheat Barley Rye Slafer and Peltonen-Sainio (2001) In addition, some evidences are showing that grain yield of temperate cereals are leveling off Introduction

Plant breeding is the most cost effective, and environmentally safe, way of increasing grain yield The knowledge of physiological bases of grain yield determination could provide useful tools to plant breeding programs aimed at increasing yield potential

MinnesotaFinlandItaly Grain yield (Mg ha -1 ) Year of release y = 0.036x – 67.4 (r = 0.71; p<0.01) y = 0.099x – 15.7 (r = 0.66; p<0.05) y = 0.018x – 31.9 (r = 0.96; p<0.001) Oat breeding effect on grain yield Breeding Adapted from Wych and Stuthman (1983); Peltonen-Sainio (1990); Redaelli et al. (2008)

Grain yield (Mg ha -1 ) Harvest index (%) MinnesotaFinland y = 0.099x – 0.36 (r = 0.90; p<0.001) Relationship between grain yield and harvest index y = 0.114x – 2.2 (r = 0.54; p<0.05) Breeding Adapted from Wych and Stuthman (1983); Peltonen-Sainio (1990)

Oat Wheat Harvest index (%) Grain yield (Mg ha -1 ) Theoretical maximum HI Relationship between grain yield and harvest index in wheat and oat Breeding

DDSD SH Plant height (cm) Grain yield Plant height optimum Richards (1992) Miralles and Slafer (1995) Breeding

Grain yield Grains m -2 = Grain Weight x Grain yield will be increased by improving major yield components

Argentina Australia India Italy Mexico UK Relationship between grain yield and grain number Calderini et al. (1999)

Variability of grain number, grain weight and grain yield (comparison between years) Spring barley Spring oat Spring wheat Winter wheat Winter rye Grain Number Grain Weight Yield Standard deviation/mean Adapted from Peltonen-Sainio et al. (2007)

Grain yield Grain weight Grains m -2 Sowing Emergence Anthesis Physiological Maturity Booting Harvest Tillering Adapted from Slafer and Rawson (1994) Major yield components and crop cycle

Emergence Anthesis Physiological Maturity Booting Harvest Tillering Adapted from Slafer and Rawson (1994) Grain number under stress Grain number Growth of reproductive organs

How to improve the growth of reproductive organs aimed at increasing grain number? 1.Higher partitioning of crop biomass to reproductive organs at pre-heading 2. Higher biomass production 3. Longer duration of the period when reproductive organs are growing Grain number

1.Higher partitioning of crop biomass to reproductive organs at pre-heading Gonzalez et al. (2005) Grain number

Year of release Grain yieldStem weight (g m -2 ) (g m -2 ) Difference Calderini et al. (1995) 1. Higher partitioning of crop biomass Grain number

Muurinen & Peltonen-Sainio (2006) Radiation interception Radiation use efficiency RUE at pre-heading ab bc JamaAslakSuomi Cultivar Radiation use efficiency (g MJ -1 m -2 ) 2. Higher biomass production Grain number

Wheat RUE at pre-anthesis Amador & Calderini (unpublished) Radiation use efficiency (g MJ -1 m -2 ) OttoQuijote b a Cultivar Grain number

OttoQuijote a b b a Wheat Cultivar RUE RI Amador & Calderini (unpublished) Grain number

(Slafer et al., 1996) Adapted from Slafer and Rawson (1994) Growth of reproductive organs 3. Longer duration of the period when reproductive organs are growing Grain number

Whitechurch et al., (2007) In wheat and barley, clear differences between duration of pheno-phases have been found Grain number

Relative duration of pheno-phases in oat (14 cultivars and 6 lines from Finland) Vegetative / whole crop cycle Generative / whole crop cycle Range of relative duration (%) 14.3 – – 36.5 Phenological phases Peltonen-Sainio & Rajala (2007) Grain number

Major yield components: Grain Weight Although more conservative than GN, GW could be a useful trait for continuing increasing yield potential of temperate cereals, especially if future plant breeding programs set more grains with lower GW potential Due to higher stability of GW, the knowledge of physiological bases of GW determination can help breeding programs to increase grain yield by improving GW

Major yield components: Grain Weight In oat, there are clear evidences that this trait has been increased by plant breeding (e.g., Wych and Stuthmann, 1983; Peltonene-Sainio, 1994)

Grain yield Grain weight Grains m -2 Sowing Emergence Anthesis Physiological Maturity Booting Harvest Tillering Adapted from Slafer and Rawson (1994) Assumptions on GN and GW determination

Temperature was increased (5.5°C) at different developmental phases in wheat, barley and triticale S Em Anthesis PM Heading Harvest Time DR TS Booting B-A H-A SE-B Ugarte et al. (2007) Effect of temperature on major yield components Grain weight

Effect of increased temperature on GN and GW Averaged across crops and experiments (3 years) H-A -7% B-A -15% SE-B -7% GNGW GN GW -8% -42%

Grain yield S Em Anthesis PM Head Harvest Time DR FI TE Grain weight Grains m -2 Booting This has important consequences for the study of grain weight determination

All these evidences are showing that flowers, which grow at the pre-anthesis period, are involved in GW determination Grain weight

New evidences of the involvement of the pre- anthesis period in GW determination gives support to promising molecular traits for increasing GW in temperate cereals

spikelet Different traits associated with GW were measured at central spikelets of the wheat spike G1 G2 G3 G4 rachis Grain weight

Huayun Pandora Huanil Pandora Kambara Bacanora Kambara Bacanora Kambara Bacanora11 G4G3G2G1 Grain weight (mg)CultivarSeasonExperiment Grain weight in two experiments Grain weight

y = 86.18x R 2 = ,00,20,40,60,81,0 y = x – 5.93 R 2 = ,00,20,40,60,81,0 Carpel weight at pollination, W10 (mg) Grain weight (mg) year 2006 year 2007 Relationship between grain weight and carpel weight Grain weight

Dynamic of grain dimensions PM days after anthesis Grain dimensions (mm) Length Width Height Grain weight

y = 1.12x R 2 = Grain volume (mm 3) 3)3) 3) Grain weight (mg) y = 17.89x R 2 = Grain length (mm) Grain volume (mm 3 ) Relationship between grain weight, grain volume and grain length Grain weight

days after anthesis Grain dry matter and water content (mg) Dynamic of dry matter and water content of grains Dry matter Water Maximum water content Grain weight

Relationship between grain weight and maximum water content of grains Grain weight (mg) Maximum water content (mg) Experiment 1 Experiment 2 y = 1,39x - 2,45 R 2 = 0, y = 0,93x + 15,89 R 2 = 0, Grain weight

Dynamics of water content and enlargement of grains Grain weight

Grain length (mm) Grain weight or Maximum Water Content (mg) Relationship between grain weight or maximum water content and grain length GW MWC (r= 0.91; p<0.001) (r= 0.95; p<0.001) Grain weight

Grain length is associated with carpel weight r = 0.75; p<0.01 Carpel weight at pollination (mg) Grain length (mg) year 2007 year 2006 Grain weight

Recurrent selection for grain yield in oat increased GW, grain area, grain length and grain width (De Koeyer et al., 1993) In the poster session of this conference, Hu et al. (2008) show data of GW and grain dimensions Relationship between GW and grain length: r 2 = 0.74; p<0.05 Grain weight

As a consequence of the relationship between final grain weight and carpel weight at anthesis, is proposed that the pericarp of grains is involved in grain weight determination. In other words, the final size of the pericarp is setting the potential weight of grains Pericarp growth is the result of the number of pericarp cells and the enlargement of these cells. Plant cell enlargement is controlled by proteins called expansins, which are involved in cell wall loosening (McQueen-Mason et al., 1992) Recently, expansin expression has been found in growing grains of wheat (Calderini et al., 2006; Liu et al, 2007) Grain weight

Preliminarily, we found the expression of 6 expansins in pericarp of grains at 10 days after anthesis from the experiment 2 - ExpA 2 - ExpA 4 - ExpA 6 - ExpA 8 - Exp novel 1 (similar to Festuca pratensis) - Exp novel 2 (similar to Oriza sativa) After this first step, ExpA 6 has been separated in 3 different goups: ExpA 6 a, ExpA 6 b and ExpA 6 c Expansins Grain weight

Days after anthesis Grain lenght (mm) 1,0 1,2 1,4 1,6 1,8 2,0 Expression of EXPA 6c (ID) Lenght Expansin Dynamics of grain length and ExpA 6c expresion in cultivar Bacanora Grain weight

AntisenseSenseNegative control Hybridization of Expansin A 6c in grains at 5 days after anthesis Grain weight

AntisenseSenseNegative control Hybridization of Expansin A 6c in grains at 10 days after anthesis Grain weight

Proposed Model of Potential Grain Weight Determination Carpels growth Lag Phase Carpel weight at pollination Endosperm cell number Physiological Maturity PollinationBooting Pericarp cells Water in grain Maximum water content Pericarp elongation Expansin expression

Conclusions - The overlapping of both GN and GW determination in temperate cereals is determination in temperate cereals is longer than generally assumed longer than generally assumed - The sensitivity of major yield components to environmental constraints during this to environmental constraints during this overlapping has been similar overlapping has been similar - There is not evidences of trade-off between GN and GW as a consequence of the GN and GW as a consequence of the overlapping between booting and anthesis overlapping between booting and anthesis

Conclusions - There are opportunities for increasing GN of temperate cereals. Differences between of temperate cereals. Differences between pheno-phases found in oats is a starting point pheno-phases found in oats is a starting point for using this trait in plant breeding programs for using this trait in plant breeding programs - The involvement of expansins in grain enlargement could be used for increasing enlargement could be used for increasing GW in temperate cereals GW in temperate cereals

Mrs. Carolina LizanaPh.D. Student (U. Austral de Chile) Dr.Ricardo RiegelAdjunt Professor (U. Austral de Chile) Dr. Simon McQueen-Mason Professor (U. of York)

Thank you!

Time (days after anthesis) Grain weight (mg) Grain growth rate Grain filling duration Usual approach for studying GW Grain weight

Response of sunflower yield components to shading Cantagallo et al. (2004)

Pre-anthesis temperature (°C) Kernel weight (mg) Wardlaw (1994) Wheat Other evidences of the involvement of the pre- anthesis period in grain weight determination Grain weight

Relationship between GW and carpel weight at anthesis in wheat (data from different experiments) Calderini & Reynolds (2000) Grain weight

Grain number reduction relative to the control H-A +1% B-A -13% Wheat SE-B -40% Exp. 1 Exp. 2 H-A +3% B-A +4% -18%Barley SE-B -36% H-A -2% B-A -15% -16%Triticale SE-B -48% Ugarte et al. (2007)

Grain weight reduction relative to the control H-A -9% B-A -14% -19%Wheat SE-B -7% Exp. 1 Exp. 2 H-A -8% B-A -13% -21%Barley SE-B -8% H-A -9% B-A -15% -23%Triticale SE-B -6% Ugarte et al. (2007) Grain weight

y = 1.12x R 2 = Grain volume (mm 3) 3)3) 3) Grain weight (mg) Relationship between grain weight and grain volume Grain weight