No abstract

TaALMT1 and TaMATE1B promoter alleles are highly correlated with wheat growth in acidic soil with a high concentration of toxic aluminium. The aluminium (Al(3+)) resistance of 338 wheat genotypes with different geographic origins was correlated with morphological traits and TaALMT1 and TaMATE1B alleles. Both of these genes encode malate and citrate transporters associated with Al(3+) resistance mechanisms in wheat. Based on comparisons with the sensitive and resistant controls, the relative root growth was evaluated in hydroponic experiments and the plant performance was visually accessed in the field. The correlation between Al(3+) tolerance in the hydroponic and field tests was moderate (r = 0.56, P < 0.001). Higher selection pressure was observed in the field because a smaller number of genotypes was classified as resistant. The combination between the six TaALMT1 alleles and the two TaMATE1B promoters allowed the identification of 11 haplotypes that showed a high (r = 0.71, P < 0.001) correlation with Al(3+) resistance in the field, with the TaALMT1 alleles accounting for most of the correlation. The Brazilian wheat genotypes presented the best performance in soil, including eight cultivars with promoters usually associated with Al(3+) resistance and another six genotypes classified as moderately resistant but containing alleles usually associated with Al(3+) sensitivity. Although an increase in favourable alleles was observed over the past few decades, the average Al(3+) resistance in the field was not significantly different from that of older cultivars. The ease identification of the TaALMT1 and TaMATE1B alleles and their higher association with Al(3+) resistance along with the best genotypes identified here may be used for wheat-breeding programmes interested in increasing wheat Al(3+) resistance.

A gain in association was obtained by using a new multivariate index with alleles of TaALMT1 and TaMATE1B genes compared with a previously published index. Wheat is among the major grain crops. Its growth can be affected by aluminum toxicity, an important stress factor that limits plant productivity. Thus, an efficient means to select wheat genotypes that are resistant to this stress is required. Here, 172 wheat cultivars and 23 synthetic hexaploid wheat plants showing different alleles for TaALMT1 and TaMATE1B and different levels of Al resistance in field conditions (phenotyped in two crop seasons) were studied. The modified Lin and Binns method was applied to obtain the phenotype data in a multivariate manner aiming at a general identification of genotypes based on the multiple traits evaluated. The genotype × year interaction was significant for all traits that were evaluated in three growth stages (tillering, silking, and maturation). The top 20 Al‐resistant genotypes obtained by the multivariate method were highlighted as having the best combination of the main desirable traits. Correlation analysis showed a gain in the association of the multivariate index with alleles of TaALMT1 and TaMATE1B genes compared with a previously published index. The superior TaMATE1B allele (having an insertion in the promoter region) contributed a greater Al resistance independent of the TaALMT1 allele. The higher association with Al resistance qualifies the selection index described in this study to be used for wheat breeding programs with the aim of improving the performance of wheat when grown under Al stress. Core Ideas Wheat is among the major grain crops. Its growth can be affected by aluminum toxicity. Genotypes with high adaptability and stability were identified. A new multivariate index allowed greater association with Al resistance.

Resumo -O objetivo deste trabalho foi avaliar a colonização micorrízica arbuscular em pupunha (Bactris gasipaes Kunth) e cupuaçu (Theobroma grandiflorum (Willd ex Spring) K. Schum) cultivados em sistema agroflorestal e em monocultivo na Amazônia Central, em duas épocas do ano, e também identificar características anatômicas da formação dessa simbiose nessas espécies. Foram realizadas coletas de solo e raízes em duas estações, seca e chuvosa. A colonização micorrízica arbuscular no cupuaçu e na pupunha é alterada pelo sistema de manejo adotado, com taxas maiores de colonização no monocultivo. A densidade total dos esporos de fungos micorrízicos arbusculares sob o cupuaçu não é alterada pelo sistema de manejo ou pela época do ano, ao contrário do que ocorre sob a pupunha. Nessa cultura, a densidade de esporos foi maior sob sistema agroflorestal no período seco. A colonização micorrízica na pupunha apresenta dois padrões anatômicos, Paris e Arum, enquanto no cupuaçu ocorre o padrão Arum.Termos para indexação: Bactris gasipaes, Theobroma grandiflorum, fungos micorrízicos arbusculares, simbiose, sistema de manejo de culturas. Arbuscular mycorrhiza in cupuaçu and peach palm cultivated in agroforestry and monoculture systems in the Central Amazon regionAbstract -The objective of this work was to evaluate the arbuscular mycorrhizal colonization in peach palm (Bactris gasipaes Kunth) and cupuaçu (Theobroma grandiflorum (Willd ex Spring) K. Schum), in agroforestry systems and monoculture in the Central Amazon region, and to identify anatomic characteristics of mycorrhizal colonization in these species. Soil and root samples were collected in the field, in the dry and rainy season. Mycorrhizal root colonization of cupuaçu and peach palm is affected by the management systems, with higher colonization rates in the monoculture system. Total spore density of the arbuscular mycorrhizal fungi under cupuaçu is not affected by management systems or season, but under peach palm this variation is season dependent. Mycorrhizal colonization of Arum and Paris types occur in peach palm, and only Arum type occurs in cupuaçu.