Atributos da arquitetura radicular como indicadores na seleção de plantas de trigo submetidas à deficiência de fósforo e toxidez por alumínio

Abstract

Phosphorus (P) deficiency and aluminum (Al3+) toxicity are two of the main constraints on achieving high crop yields and, often, those conditions coexist in soils. The selection of more adapted materials through easily assessed phenotype traits has a huge potential in the plant breeding. Thus, this work aimed to evaluate the response of traits of root system architecture to P deficiency and Al3+ toxicity, alone or in interaction, in nutritive solution and the potential of use of them in the plant selection of wheat. It were carried out four experiments, in a greenhouse, with the following treatments combination: [1] bifactorial experiment with four P levels ( 25, 50, 100 and 200 μM) in the main plot and four cultivars (Anahuac, IAC-5, Onix e Quartzo) in the subplot; [2] bifactorial experiment with four Al3+ levels ( 0, 37.5, 75 and 150 μM) in the main plot and four cultivars (Anahuac, IAC-5, Onix e Quartzo) in the subplot; [3] bifactorial experiment with four P vs. Al3+ combinations (-P -Al; +P -Al; -P +Al e +P +Al) in the main plot and four cultivars (Anahuac, IAC-5, Onix e Quartzo) in the subplot; and [4] trifactorial experiment with two P levels (25 and 125 μM), two Al3+ levels (0 and 74 μM) and two cultivars (IAC-5 and Onix). The experiment 4 was carried out in pots with sand until the anthesis while the others were carried out in pots with an inert substrate (expanded polystyrene) during 15 days. In all the experiments it was evaluated shoot (length, dry weight, foliar area), root dry weight and root system architecture (dry weight, length, superficial area, volume, diameter) growth, being in the assays 2, 3 and 4 the root variables were evaluated individually for root orders 0, 1 and 2. There was a wide variability among the cultivars for the tested conditions, which allows the use of root system architecture characterization in the selection of more adapted plants to P deficiency and Al3+ toxicity in wheat. P deficiency reduced both root and shoot growth, having the cv. IAC-5 showed the best response. The presence of Al3+ reduced the growth of plants, being cv. IAC-5 to more tolerant. This cultivar had higher growth of lateral roots of first and second order, while the sensitive one (Anahuac) had thickening of these types of root. The experimental system allowed a rapid evaluation of the alterations in the root system architecture in response to P deficiency and Al3+ toxicity, and the responses of short-term experiments are similar to those of the long-term.