Impact of landrace germplasm, non-conventional habit and regional cultivar selection on forage and seed yield of organically grown lucerne in Italy

Abstract

SUMMARYOrganically grown lucerne (Medicago sativa L.) should ensure sufficiently high forage and seed yields to sustain the profitability of organic production chains. Twenty lucerne populations were evaluated for forage dry matter (DM) yield over 3 years (2005–7), and for seed yield and its components in the third year, under organic management and a mowing regime in Lodi (sub-continental climate with sandy-loam soil) and Perugia (sub-Mediterranean climate with silty-clay soil). The objectives were to assess the impact on lucerne forage and seed yield of: (i) type of germplasm (landrace or commercial cultivar); (ii) plant growth habit (erect or non-conventional); (iii) area of germplasm origin or selection (northern Italy north of the Po river, NI-N; northern Italy south of the Po river, NI-S; central Italy, CI). The populations included seven cultivars selected under conventional management and one selected under organic management, seven landraces and five breeding selections, of which one was semi-erect and one was semi-prostrate. On average, cultivar and landrace germplasm types did not differ for forage or seed yield in any geographic set of populations (NI-N, NI-S or CI), except for the higher seed yield of landraces in one set. Compared with erect germplasm, semi-prostrate germplasm exhibited distinctly lower forage and seed yield, especially where weed competition was severe (Lodi) because of poor competitive ability. Semi-erect germplasm tended to have lower forage yield across locations. Specific adaptation was the main determinant of forage and seed yield responses of landraces and cultivars. Erect populations originated in NI-N were high yielding in the test site similar to NI-N environments (Lodi) and low yielding in the location representing CI environments (Perugia). Populations that originated in CI, including the cultivar selected under organic management, displayed the opposite adaptive response. Populations that originated in NI-S, whose major environmental characteristics were somewhat intermediate between NI-N and CI, tended to be mid-ranking for forage and seed yield in each site. The large cross-over population×location interaction was confirmed by the lack of genetic correlation for forage yield (rg=−0·25, P>0·20) and the negative genetic correlation for seed yield (rg=−0·68, P<0·05) of populations across locations. No genetic correlation across locations was found for density of fertile tillers and pod fertility. The association of population seed yield with its component traits was site-specific. Cropping and seed multiplication of locally adapted erect cultivars have paramount importance for mown organically grown lucerne in Italy.