Photosynthetic Physiological Basis of Forage Mass Stability in a Progeny of Rhizome-Rooted ‘Qingshui’ Medicago sativa L.

Rhizome-rooted alfalfa (Medicago sativa L.) is an excellent forage for establishing grazing and ecological grasslands, requiring a high stable yield. Studying the genetic physiological basis of expression biomass traits essential improving production performance in rhizome-rooted alfalfa. We analyzed mass photosynthetic indices improved progenies (RSA−01, RSA−02, RSA−03), parental “Qingshui” (CK1), “WL168” (CK2) at ages one five years their relationships, then revealed heterotic stability. Moreover, we explored effects interannual dynamics differences on tested indices. The results compared with CK1, RSA−03 increased by 22.17% 19.72%, respectively, while RSA−01 RSA−02 varied from 1.40% to 8.65%, indicating obvious heterosis RSA−03. At year age, Gs value, Car content SS were higher than those CK1; CK2 RSA−02; Ci, Tr values RSA−01. Pn, Gs, WUE values, Sta Ci value Suc CK2; other progenies. mass; Chl(a/b) ratio; values; age 9.99%–44.24%. Through path analysis, NSC direct factors affecting year, both Pn SP affected indirectly through Gs; Chl(a+b) years, Gs. Interestingly, Chlb, Chl(a/b), Tr, Suc, SP, more influenced genetics, opposite was true Sta. Accordingly, showed physiology, recommending establishment pastures vegetation.