Aluminium (Al) toxicity is an important limiting factor for wheat Trit
icum aestivum L. adaptation to acid soils in different regions of Braz
il. The purpose of this research was to classify the reaction of recom
mended wheat cultivars in Brazil in relation to Al toxicity. Seventy-f
ive cultivars were tested from 3 to 15 years under field conditions fr
om 1980 to 1995 in Passe Fundo, Brazil. Soils with pH between 4.2 and
4.9 contained from 2.50 to 4.27 cmol Al/l. The resistance to aluminium
in acid soil was evaluated visually before heading time in some years
and at maturity in all pears in three replications, using a score ran
ging from 0.5 (highly resistant) to 5 (highly susceptible). Using the
over-years mean index, 19 cultivars were classified as resistant, 33 a
s moderately resistant, 17 as moderately susceptible, and six as susce
ptible. The cultivars 'BH 1146','Embrapa 15','Embrapa 24','Embrapa 49'
, 'IAC 5-Maringa','IAC 18-Xavantes',`IAC 27-Pantaneiro', 'IAPAR 46, 'I
APAR 53','RS 8-Westphalen', Trigo BR 15', 'Trigo BR 20-Guato', 'Trigo
BR 25','Trigo BR 35', and 'Trigo BR 41-Ofaie' were the most Al resista
nt of the 75 tested. It is highly probable that all Brazilian Al-toler
ant cultivars have a major gene known to be on the long arm of chromos
ome 4D. Aluminium tolerance was traced by pedigree analysis to a small
number of landraces introduced and grown in Brazil in the early twent
ieth century. Breeding for resistance to Al is required because soil a
melioration by liming is effective only in the upper root zone and sus
ceptible or moderately susceptible cultivars do not develop extensive
root systems and suffer under drought or hear stress.