Skip to main content
ARS Home » Research » Publications at this Location » Publication #137574
Title: SELECTION FOR ALUMINUM AND ACID-SOIL RESISTANCE IN WHITE CLOVER

Author
item Voigt, Paul
item Staley, Thomas

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/12/2003
Publication Date: 1/5/2004
Citation: Voigt, P.W., Staley, T.E. 2004. Selection for aluminum and acid-soil resistance in white clover. Crop Science. 44(1):38-48.

Interpretive Summary: Despite relatively high resistance to acid-soil stresses, white clover is not found on some acid soils. New germplasm with increased acid-soil resistance should be better adapted to those sites. We selected for (i) seedling Al resistance, (ii) seedling Al susceptibility, and (iii) seedling Al resistance and mature-plant acid-soil resistance. A total of 12 populations were developed and evaluated for seedling Al resistance and mature plant acid-soil resistance. In response to Al stress, root growth of populations developed for Al resistance and Al susceptibility differed. Progress from selection was made towards both increased seedling Al resistance and susceptibility. In response to acid-soil stress, populations selected for acid-soil resistance had greater relative root growth than the parent (unselected) germplasm. However, populations selected only for seedling Al resistance were usually no more acid-soil resistant than the original parent germplasm. Selection for acid-soil resistance was successful, but selection for seedling Al resistance was not an effective way to develop acid-soil resistance white clover germplasm. Potential scientific uses of this new germplasm include determination of: (i) the relationship between seedling and mature plant Al resistance and susceptibility, (ii) the effect of acid-soil resistance on root and root hair development, (iii) the effect of acid-soil resistance on nodulation capacity in acid soils, and (iv) the value of acid-soil resistant rhizobia for effective nodulation of acid-soil resistant white clover grown in acid soil. Impact of this white clover germplasm on producers depends upon further experimentation to determine if production and persistence of acid-soil resistant white clover exceeds that of the parent germplasm in field environments.

Technical Abstract: Despite relatively high resistance to acid-soil stresses, white clover, Trifolium repens L., is not found on some acid soils. Our objectives were to develop Al resistant and acid-soil resistant populations of white clover and to validate the soil-on-agar procedure as a selection technique. Results from this technique, based on primary root growth of very-young seedlings, are closely related to toxic levels of soil Al. We used a two-stage selection procedure. For Stage 1 we used the soil-on-agar technique to select seedling Al resistant and Al susceptible populations. For this work we used Brown Loam Synthetic No. 2 and `Grasslands Huia' as base populations. For Stage 2 we used conventional pot studies with two soil pH treatments, 4.2 and 5.2, and stem tip cuttings of Al resistant selections from Brown Loam. The acid-soil resistance selections were made by calculating a resistance index (RI), root weight at pH 4.2 / root weight at 5.2 × 100, and then selecting for high RI and average root weight at pH 5.2. A second cycle of selection for Al resistance, Al susceptibility, and acid-soil resistance was done only in Brown Loam. A total of 12 experimental populations and the two parents were evaluated for seedling Al resistance and mature plant acid-soil resistance in studies using techniques similar to those used in Stage 1 and Stage 2 selection. Both Brown Loam and Huia Al resistant and Al susceptible populations diverged. For Brown Loam, progress was made towards both increased Al resistance and Al susceptibility. For Huia, progress appeared more towards Al susceptibility than towards Al resistance. Populations developed from two-stage selection were more acid-soil resistant than their parent. However, populations selected only for seedling Al resistance or Al susceptibility were usually no more acid-soil resistant than their parent. We were able to select for improved acid-soil resistance in Brown Loam using the two-stage procedure. We were able to select divergent populations using the soil-on-agar procedure, but soil-on-agar selection did not appear useful for increasing acid-soil resistance of white clover.