QTL mapping of root angle in F-2 populations from maize 'B73' x teosinte 'Zea luxurians'

We evaluated variation in nodal root angle in the genus Zea and performed quantitative trait locus (QTL) mapping for the trait. Angle (in degrees) of roots emerging from the second (2nd-root angle) and third (3rd-root angle) nodes from the bottom of shoot showed wide variation in nine accessions; relatively high repeatability was obtained. QTL analyses controlling root angle were performed in the two sets of F2 populations (127 individuals in Trial A and 123 in Trial B) developed from different crossings of maize ` B73' (deep-rooting) x teosinte ` Zea luxurians' (shallow-rooting). In Trial A, we used an SSR-based map with 107 markers, covering 1,329 cM throughout all ten chromosomes. By composite interval mapping analysis, four QTLs were identified, two on chromosome 10 for 2nd-root angle and one each on chromosomes 2 and 7 for 3rd-root angle. In Trial B, using a 1,397 cM SSR-based map with 92 markers, one QTL was located on chromosome 4 and two on chromosome 7 for 2nd-root angle and one each on chromosomes 2, 4 and 7 for 3rd-root angle. The QTL on chromosome 7 (identified as Qra2nd3rd7.04) was consistently found across the trials. A potential role of the Qra2nd3rd7.04 in controlling angles of nodal roots and thus flooding tolerance was discussed.