Genetics, Variety Selection and Variety Testing

Transcription

1 Genetics, Variety Selection and Variety Testing Presentation by Dan Undersander A. Genetics 1. Centers of Origin Alfalfa first cultivated +9,000 yrs ago 2. Alfalfa Genetics a. Alfalfa is a pollinating plant b. Medicago sativa Species contains nearly 100 subspecies Variation in chromosome number is from 2n=16 up to 2n=48 Medicago sativa, subspecies sativa Medicago sativa, subspecies falcata c. Alfalfa is a tetraploid

2 d. Genetics of reproduction 2n = 16 Pollen or eggs 2n = 32 1n = 16 = = = = = == = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = e. Crossing to transfer genetic traits Crossing Diploids A A A AA Aa a Aa aa Crossing Tetraploids AA Aa Aa aa AA AAAA AAAa AAAa AAaa Aa AAAa AAaa AAaa Aaaa Aa AAAa AAaa AAaa Aaaa aa AAaa Aaaa Aaaa aaaa

3 3. Alfalfa Breeding methods a. Genotype vs phenotype Genotype is Phenotype is b. Recurrent selection Repeated selection for desired phenotype within the same population c. Crossing Cross pollinate Select plants and collect seed plant seed repeat process Var Balebuster x Var Haymaster = Variety Alpha High multileaf no multileaf High multileaf no fusarium res high fusarium res High fusarium res d. Backcrossing Repeated crossing back to one parent d. Hybrid Cross between two inbred lines resulting in hybrid vigor (or heterosis, an increase in the performance of hybrids over that of purebreds from linebred families) Two types Greater than 95% hybrid 75 to 95% hybrid e. Bio-engineering Introducing genetic material not normally found in alfalfa An events is f. Current forage varieties are synthetics varieties Derived from multiple clones Each plant not genetically identical

4 B. Variety Selection 1. Value of New Varieties Return per Acre vs Alfalfa Yield a. Yield single factor most related to profitability. Dollar Return per Acre $1,000 $500 $0 ($500) Yield (t/a) 2. Selection of Alfalfa Variety Yield (DM t/a) Yield difference between top and bottom entries in UW Alfalfa Variety Trials Average yield difference between top and bottom entries in UW alfalfa variety trials over last 20 years has been 2.40 t/a The yield of the top 5 varieties has averaged 0.43 t/a in the seeding year and 1.0 t/a more than Vernal at Arlington, WI in the last 25 years. Yields of top 5 varieties have averaged about 0.6 t/a higher than Vernal at Rosemount, MN. Yield (t/a) Yield of top five alfalfa varieties over Vernal at Rosemount, MN and Arlington, WI 1980 to 2004 MN WI Stand age (1=seeding year)

5 b. Persistence Consider value of short rotations Older stands yield less Increased weed problems in old stands Nitrogen credits when alfalfa is plowed down Rotational benefit to corn 10% greater corn yield Reduced root worm on corn c. Disease Resistance Total Income per acre Fig 3. Whole farm Income per acre from rotations with three or five-year alfalfa stands $350 $330 $310 $290 $270 $250 three year five year increased alfalfa yield increased corn silage yield increased corn grain yield legume credits (120lbs) base profit per acre Resistance Measured by % of resistant plants in population for diseases Susceptible = 0 to 5 % resistant plants Low Resistance = 6 to 14% resistant plants Moderate Resistance = 15 to 30% resistant plants Resistance = 31 to 50 % resistant plants High Resistance = > 50% resistant plants Resistance scores are relative to checks for Potato Leaf Hopper Resistance 1) Assess likelihood of occurrence for each disease 2) Determine severity of each disease 3) Select multiple pest resistance in accordance with above c. Winterhardiness 1) What is it? 2) How to measure

6 d. Fall Dormancy d. Forage Quality e. Special use (special needs) 1) grazing grazing tolerant bloat safe 2) short rotation 3) green manure 4) energy source to replace fossil fuels C. Alfalfa Variety Testing 1. Environment x Variety Interaction Variety test results are an estimate of a variety s performance in a given environment. Example: Yields (t/a) in Wisconsin Variety Trials Variety Arlington Marshfield Spirit Rushmore

7 2. Statistics Frequency µ Standard Deviation = range to include 2/3 of estimates LSD (Least Significant Difference) = estimate difference of means in a range Coefficient of Variation = Standard Deviation * 100 Trial mean 3. Finding Variety Trial Results A. Regional Publication of Results B. North American Alfalfa Improvement Conference listing of variety trial results C. Alfalfa variety Comparer for multisite comparisons Available at