Proceedings of the XLVI Italian Society of Agricultural Genetics - SIGA Annual Congress

Giardini Naxos, Italy - 18/21 September, 2002

ISBN 88-900622-3-1

Poster Abstract - 4.13

MAPPING QTLs FOR ROOT MORPHOLOGY IN MAIZE SEEDLINGS GROWN AT LOW TEMPERATURE

HUND A.*, BELLOTTI M.**, SOLDATI A.*, STAMP P.*, FRASCAROLI E.**

*) Institute of Plant Sciences, Agronomy and Plant Breeding, ETH Zurich, Switzerland

**) Dip. Scienze e Tecnologie Agroambientali, Università di Bologna, Italy

Supported by EU COST Action 828

root morphology, cold, maize, QTL, COST 828

Seedling root morphology traits of maize can be related with early field performance and yield (Crop Sci., 1997: 37[4], 1237-1241) but have not been used in breeding programs due to their difficult accessibility. In principle there are two contrasting types of seedling root systems in maize (I) extensive root systems where seminal roots are equal in size with the primary root and (II) intensive root systems with strong, highly structured primary roots compared with seminal roots. We use QTL mapping to elucidate genetic linkage of root morphological traits with shoot traits, and to link experimental results across environments. Once a clear understanding of the ecological function of a particular locus is achieved, map data can be used for marker assisted selection (MAS).

168 F_2:3 of the cross between two dent parents have been chosen, Lo964 with a very intensive, Lo1016 with a typical extensive root system. The population had already been studied for root traits in different conditions (PMB, 2002: 48, 697-712) and for cold tolerance at germination. Seedlings were grown for 21 days under controlled conditions in a sand-vermiculite substrate at temperatures of 15/13 °C day/night and 12 h photoperiod. Temperature conditions match early field conditions of Central Europe. Root morphology was measured with a root image analyses program (Root Detector, ETH).

The number of QTLs found for structural root traits ranged from 1 for the diameter of primary and seminal lateral roots to 8 for the diameter of primary axile roots, accounting for 9.3 and 92.0 % of the phenotypic variability, respectively. Most QTLs for root length were specific for a given root type. In only three out of 14 cases, co-location of QTLs for primary and seminal root length was found. The same was true for the length of axile and lateral roots. QTLs for root diameter were more frequently associated with length: 7 of 15 QTLs overlapped with QTLs for root length and most frequently this association was negative.

Major QTLs for root length, explaining about 20% of the phenotypic variability, were mapped to different locations: on chromosome 1, a QTL for seminal axile roots was found between 44 and 56 cM, one for primay axile roots between 118 and 128 cM. Both overlap with QTLs for root traits found in another study. Another major QTL for primary lateral root length was mapped on chromosome 5, from 108 to 118 cM. The latter overlaps with QTLs for other growth-related traits including leaf area, dry matter accumulation, and cold germination. Our data clearly show that root morphological traits are independently inherited and that key loci exist which can be utilised for MAS. The linkage of the detected QTLs to other traits and their stability across environments will be discussed.