A look at Aluminium Toxicity in Tomato and how to genetically control it
Aluminium toxicity has been recognized as a major limiting factor for plant productivity on acid soil, which comprises about 40% of the arable land in the world.
The problem of aluminium toxicity is particular serious in low pH acidic soils (pH<5.5) that is difficult to reclaimed with lime. At low pH, dissolution of Al-containing compounds is enhanced and the release of toxic Al3+ ions into the soil solution that can rapidly inhibit root growth.
The major symptom of aluminum toxicity is rapid inhibition of root growth. Some plant species have developed different mechanisms to minimize the harmful effects of Al-toxicity. The most documented mechanisms of Al3+ resistance is the secretion of anions of organic acids from the roots.
It is possible to detoxify Al3+ in surface soil by liming to pH 5.5 or above. However, liming is not a remedy for subsoil acidity and it is not always economically feasible. Therefore, the most appropriate strategy to overcome Al-toxicity is to select or breed genotypes with tolerance to aluminium toxicity. For this, sources of tolerance and pattern of inheritance need to be identified.
In order to investigate the genetic mechanism of tolerance it is necessary to screen and measure the tolerance of aluminium toxicity in large number of genotypes by using rapid, effective and reproducible screening techniques. Several screening techniques have been employed in evaluating Al3+ tolerance in plants such as root length, root re-growth, staining of roots with hematoxylin, root re-growth after staining.
Score of hematoxylin staining is effective technique in wheat, pea, chickpea, pigeonpea and okra. However, score of hemotoxylin staining is failed to discriminate aluminium tolerant genotypes in tomato and lentil. Root re-growth after hematoxylin staining has been suggested as the best method to discriminate genotypes for aluminium tolerance at seedling stage in tomato and lentil.