Expression (Lodging Resistance):
an evaluation method to determine the percentage of erect stems (> 45°).
David Johnson, David Miller, Debra Sharpee, Mark Darling, Gary Hoard, Doug Miller, and Dan Undersander
Nurseries should be managed to allow plants to reach early to mid bloom stage during each regrowth cycle. Susceptible plants generally lodge by late bud to early bloom in the spring and early to mid bloom during the summer.
Rating can be taken once the susceptible check is uniformly lodged, generally during flowering. A 0 to 9 scale is used to rate standability (lodging resistance). This scale can be used to estimate percentage of erect stems (>45°) on individual spaced transplanted plants or seeded rows/plots. In practice, alfalfa is grown in solid seeded stands and is not spaced transplanted. Seeded rows/plots are preferred compared to spaced transplanted plants because neighboring plants within a canopy help support each other. Spaced transplanted plants score slightly lower for standability compared to seeded rows or plots. A single rating often provides accurate description of varietal differences. Multiple ratings will enhance classification.
9 Resistant . 91 to 100% erect stems
7 Resistant . 71 to 90% erect stems
5 Moderately Resistant 51 to 70 % erect stems
3 Moderately Resistant 31 to 50% erect stems
1 Susceptible 11 to 30% erect stems
0 Susceptible 0 to 10% erect stems
Alfalfa populations can be characterized for standability (lodging resistance) by calculating an average standability index (SI) and percentage of lodging resistant plants (combined percentage of plants rated as class 7 and 9)
1 54H11 contains proprietary germplasm. As such, seed will only be made available to evaluators from Pioneer. Prior to seed shipment, requestors must agree to use the seed exclusively for the testing purposes defined above; the Pioneer materials transfer/use agreement is available from Pioneer (address below); no other agreement is required.
2 CW 14032 and CW 75046 contain proprietary germplasm. As such, seed will only be made available to evaluators from Cal West Seeds. Prior to seed shipment, requestors must agree to use the seed exclusively for the testing purposes defined above; the Cal West Seeds materials transfer/use agreement is available from Cal West Seeds (address below); no other agreement is required.
3 Only include the varieties Europe and/or Mercedes as comparison to European standards for lodging resistance. In France, the variety Europe is considered resistant to lodging and the variety Mercedes is considered moderately resistant to lodging. Europe and Mercedes are not adapted to North American field environments and may not persist for duration of test.
A successful test must show a significant difference (p=0.95) between the resistant class check cultivar and the susceptible class check cultivar. The resistant class check must have an SI of 6.0 or higher. The susceptible class check must have an SI of 1.0 or lower. Readings taken too early may overestimate lodging resistance.
Irrigation and/or high soil nitrogen levels may increase degree of lodging severity. Standability expression (lodging resistance) is not known to vary by synthetic generation of seed. Seed yield is genetically correlated with lodging resistance (Bolaρos-Aguilar, et al., 2002).
1. Bolaρos-Aguilar, E.D., C. Huyghe, C. Ecalle, J. Hacquet, and B. Julier. 2002. Effect of Cultivar and Environment on Seed Yield in Alfalfa. Crop Sci. 42:45-50.