The objective of this study was to correlate root length of wheat {Tri-ticum aestivum L.) genotypes grown in Al-containing, acidic hydroponic solutions, with root weights from acid-soil experiments and field scores from Brazilian acid-field trials. A total of 43 wheat genotypes, primarily from Brazil, were evaluated by growing seedhngs for 4 days in hydroponic solutions containing 0.0-4.0 mg/1 Al. The root growth rate of all the genotypes was reduced with the addition of Al to the solution and the Al-sensitive and Al-tolerant wheat genotypes were clearly identified. Genotypes with intermediate Al-tolerance levels showed variable root lengths in response to Al stress. Correlations between root length or a root tolerance index (RTI) in the Al solutions versus acid-soil experiments and acid-field trials were highly significant (r = 0.71-0.85, P < 0.01). The most significant correlation was observed among seedlings grown in 1 mg/1 Al. This study presents evidence that this short duration and simple screening technique provides a highly significant correlation with previous acid-soil Al-tolerance evaluations. Furthermore, the data obtained suggest that hydroponic screening of wheat seedlings for Al tolerance may be used in breeding programmes or in screening germplasm collections.

Acid soils containing high levels of aluminum (Al) are known to severely limit plant growth on over 1.6 billion hectares worldwide. In the United States, a gradual decline in the pR of many soils both in the Great Plains as weil as the Southeast, has caused many soils to become high in levels of free Al. This worldwide condition encouraged the analysis of wheat (Triticum aestivum L. em Thell.), triticale (X Triticosecale Wittmack), and rye (Secale cereale L.) germplasm from one of the major acid soi! regions of the world (Brazil) in order to evaluate and compare the genetic potential of Al genes for cereal improvement. The objectives were to compare Al-tolerance levels in wheats, triticales, and ryes by measuring root elongation responses in Al-containing hydroponic nutrient solutions. Root elongation was impaired for all species grown in Img/L concentrations of Al. Rye had the longest root regrowth and Al-sensitive wheats had the shortest root regrowth. The triticaies containing a 2D(2R) substitution developed in the mid-1970s bad the poorest root regrowth of all triticale types. The newly developed advanced triticaie lines (AABBRR) yet to be released for commercial production showed the highest degree of Al tolerance of all the triticaie types and approach or exceed the levels observed in rye. This indicated that progress is being made in improving triticaie's Al-tolerance in Brazil. Of all the old and new wheat varieties showing the highest degree of Al-tolerance, none ofthem were better than 'BR 1146' a variety that is at least 50 years old. This indicated that over the past 50 years, although Brazilian wheat breeders have made yield improvements in wheat production, they have not improved Al-tolerance. Rye showed a higher degree of Al-tolerance than the other cereals, when tested in 1 mg/L of al, but as expected some variation was noted.

RESUMO Na agricultura moderna, interessam sistemas de produção eficientes no uso da energia. Objetivou-se avaliar a conversão e o balanço energético de cinco sistemas de rotação de (I: 5,38, II: 5,02, IV: 8,12 e V: 7,37; I: 18.067 Mcal/ha, II: 13.790 Mcal/ha, IV: 19.875 Mcal/ha e V: 19.264 Mcal/ha, respectivamente (23.860 Mcal/ha), as compared to the othen studied systems (I: 5.38, II: 5.02, IV: 8.12 e V: 7.37; I: 18.067 Mcal/ha, II: 13.790 Mcal/ha, IV: 19.875 Mcal/ha e V: 19.264 Mcal/ha, respectivily). In this period, the climatic conditions were normal. On average, the period 1990 to 1991, there were no significant differences between energy conversion and balance means. In this period, climatic conditions were adverse.

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