Selection of white clover ( Trifolium repens L.) using root traits related to dinitrogen fixation

Abstract

A synthetic population of white clover was developed during three cycles of phenotypic recurrent selection in plants of two varieties, which were in second and third cycles crossed and in all cycles inoculated by Rhizobium. The plants were grown in sand hydroponics with and without mineral nitrogen. The selection criteria were aerial matter, root system size and volume of the pink (active) root nodules. The content of nitrogen in aerial matter of 21 developed and randomly chosen clones was higher by 5.5% than in the four varieties compared, due to higher concentration of nitrogen and due to higher yield. The developed synthetic population 1 The synthetic population was registered in the Czech Republic and OECD as Nivel. 1 consisting of 51 clones proved similar yield of dry matter as two standard varieties in 33 environments for 5 years on eight locations. However, it was adapted to more fertile environments as proved by regression analysis, since the regression coefficient of the yield in the environments amounted 1.121 and 1.144, when the basis of comparison of the new synthetic was average yield of two standard varieties, or yield of one of the parental varieties, respectively. It means that increased yield due to environmental influence by 1 t ha −1 proved increasing of yield in the new synthetic by 1.121 and 1.144 t ha −1, respectively. The overall averaged yield of the standard varieties from the 33 environments amounted 9.47 t ha −1, but in one-third of the most fertile environments 12.50 t ha −1 and of the new synthetic 12.97 t ha −1 (i.e. more by 3.8%).