Variation for Root Aerenchyma Formation in Flooded and Non-Flooded Maize and Teosinte Seedlings

Morphological and anatomical factors such as aerenchyma formation in roots and the development of adventitious roots are considered to be amongst the most important developmental characteristics affecting flooding tolerance. In this study we investigated the lengths of adventitious roots and their capacity to form aerenchyma in three- and four-week-old seedlings of two maize (Zea mays ssp. mays, Linn.) inbred accessions, B64 and Na4, and one teosinte, Z. nicaraguensis Iltis & Benz (Poaceae), with and without a flooding treatment. Three weeks after sowing and following a seven day flooding treatment, both maize and teosinte seedlings formed aerenchyma in the cortex of the adventitious roots of the first three nodes. The degree of aerenchyma formation in the three genotypes increased with a second week of flooding treatment. In drained soil, the two maize accessions failed to form aerenchyma. In Z. nicaraguensis, aerenchyma developed in roots located at the first two nodes three weeks after sowing. In the fourth week, aerenchyma developed in roots of the third node, with a subsequent increase in aerenchyma in the second node roots. In a second experiment, we investigated the capacity of aerenchyma to develop in drained soil. An additional three teosinte species and 15 maize inbred lines, among them a set of flooding-tolerant maize lines, were evaluated. Evaluations indicate that accessions of Z. luxurians (Durieu & Asch. Bird) and two maize inbreds, B55 and Mo20W, form aerenchyma when not flooded. These materials may be useful genetic resources for the development of flooding-tolerant maize accessions.