Root and shoot attributes of indigenous perennial accessions of the wild mungbean (Vigna radiata ssp. sublobata)
G. J. Rebetzke A and R. J. Lawn B CA Department of Agriculture, University of Queensland, St Lucia, Qld 4072; present address: CSIRO Plant Industry, PO Box 1600, Canberra, ACT 2601, Australia.
B School of Tropical Biology, James Cook University, Townsville, Qld 4811 and CSIRO Sustainable Ecosystems, Davies Laboratory, Townsville, Qld 4814, Australia.
C Corresponding author. Email: robert.lawn@jcu.edu.au
Australian Journal of Agricultural Research 57(7) 791-799 https://doi.org/10.1071/AR05363
Submitted: 17 October 2005 Accepted: 2 March 2006 Published: 14 July 2006
Abstract
Root and shoot attributes of 12 indigenous perennial accessions of the wild mungbean (Vigna radiata ssp. sublobata) were evaluated in early and late summer sowings in the field in SE Queensland. All but one of the accessions were obtained from the Townsville–Charters Towers region of NE Queensland. In both sowings, the accessions developed thickened tap and lateral roots, the taproot thickening extending to a depth of 0.20–0.30 m below the soil surface, depending on accession. The thickened lateral roots emerged from the taproot within 0.10 m of the soil surface, and extended laterally up to 1.10 m, remaining close to the soil surface. Differences among the accessions in gross root morphology and phenology were relatively small. There were differences among the accessions in the production of seed, tuberised root, and recovered total plant biomass. Depending on accession and sowing date, the tuberised roots accounted for up to 31% of recovered plant biomass and among accessions, the root biomass was positively correlated with total plant biomass. In contrast, seed biomass represented only a small proportion of recovered plant biomass, up to a maximum of 14%, depending on accession and sowing date. Among accessions, the proportion of seed biomass tended to be negatively correlated with that of tuber biomass. The perennial trait appears to be unique to Australian accessions of wild mungbean obtained from coastal-subcoastal, speargrass-dominant woodlands of NE Queensland. Although the ecological significance of the trait remains conjectural, field observation indicates that it facilitates rapid plant re-growth following early summer rainfall, especially where dry-season fire has removed previous-season above-ground growth.
Additional keywords: bush tucker, environmental adaptation, legume germplasm, root tubers.
Acknowledgments
The research reported here was supported by the Grains Research and Development Corporation and the CSIRO Division of Tropical Crops and Pastures, and was undertaken in partial fulfillment of the requirements of the MAgrSc degree awarded to GJR by the University of Queensland.
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