Breeding creeping-rooted lucerne for the subtropics

Abstract

A lucerne-breeding programme was undertaken at Lawes, south-eastern Queensland, to transfer the creeping-rooted habit from Heinrichs's Canadian strains to subtropical lucerne varieties. Before intensive selection commenced, the inheritance and association of three characters, summer yield, winter yield, and the number of extra crowns originating as adventitious shoots from roots, were determined in the F2 and F3 generations. The F2 genotypic variances for summer yield, winter yield, and number of extra crowns were predominantly additive and were respectively 81, 53, and 54% of their phenotypic variances. The genotypic correlation coefficient for winter yield and number of extra crowns was negative ( rG = –0.18), consisting of a negative additive correlation rg = –0.55 and a positive non-additive correlation rs = 0.50. In the F3 generation the approximate genotypic correlation for these two characters was small and positive and composed of a nearly zero additive correlation and a high positive non-additive correlation. Simultaneous mass selection for summer yield, winter yield. and creeping-rootedness was undertaken in the F3 generation, and the combining ability variances and covariances for these characters were studied in the F4 generation. All three variables were positively associated in their general and specific effects, and the majority of families did not differ significantly from Hunter River in winter and summer yield. The seed production of ten F4 families was studied and it was found that eight families were significantly lower seed producers than Hunter River, their seed yields ranging from 20 to 47% of the mean for Hunter River. Covariance analysis showed seed yield and number of extra crowns to be negatively associated in the F4 generation. The changes in creeping-rootedness in the successive generations F1 to F5 were 2, 9, 34, 19, and 59% compared with a mean of 4% for Heinrichs's Canadian strains at Lawes. Creeping-rooted individuals survived better than non-creeping-rooted plants of similar genotype and better than Hunter River, particularly in the F4 generation, where the respective survival rates were 75, 27, and 23% 19 months after transplanting in the field

Evaluation of a lucerne germplasm collection in relation to traits conferring grazing tolerance

“…sativa from northern Spain called "mielga" (Ben Chaabane, 1990) which are originating some interest in breeding programmes in the Mediterranean region (Prosperi et al ., 1990) . It is affirmed that spreading lucernes have usually long periods of dormancy in their growth cycle and, hence, low winter yield (Heinrichs, 1963 ;Edye & Haydock, 1967) . Nonetheless, this seems more attributable to their mainly northern origin than to the presence of the rhizomatous or creeping characters per se (Heinrichs, 1963) .…”

“…Breeding programmes have been undertaken with some success to combine the creeping-root or rhizomatous character with high winter yield ability of non-dormant, warm-climate varieties to extend the utilization of spreading lucernes in less cold-prone environments (e .g . Edye & Haydock, 1967 ;Daday, 1968 ;Bray, 1969 ;Cameron, 1974) .…”

Plant Traits Associated with Grazing‐Tolerant Alfalfa

“…Leach (10) and Piskovatski and Stepanova (14) postulated that deep crowns are important in tolerance. Further, the creeping-rooted trait has been implkated in grazing tolerance (2,4,5,7). However, the creepingrooted trait is inconsistently expressed, and success at incorporating this trait into alfalfa cultivars has lbeen limited (11 ).…”

Excess Soil Water and Phytophthora Root Rot Stresses of Phytophthora Root Rot Sensitive and Resistant Alfalfa Cultivars1

“…The impact of soil wetness has often been attributed to the development of Phytophthora root rot caused by Phytophthora megasperma f.sp. medicaginis (Pmm) (Edye and Haydock, 1967;Erwin, 1965). However, 437 there is evidence of a rapid response by alfalfa plants to excess soil water before sufficient time has elapsed for the development of disease or when disease is not present (Barta, 1980;Cameron, 1973; Thompson and Fick, 1981 ).…”

“…This is often referred to as "flooding injury" or "flooding damage". Plants suffering from excess soil water stress may be predisposed for the development of Phytophthora root rot (PRR) (Edye and Haydock, 1967) or they may be affected by inorganic chemical toxicities (especially Mn) resulting from the anaerobic conditions (Graven et al, 1965). Phytophthora root rot may predispose the plants to infection by weakly pathogenic organisms such as Fusarium spp.…”