Abstract Drought limits wheat production in the Brazilian Cerrado biome. In order to search for candidate genes associated to the response to water deficit, we analyzed the gene expression profiles, under severe drought stress, in roots and leaves of the cultivar MGS1 Aliança, a well-adapted cultivar to the Cerrado. A set of 4,422 candidate genes was found in roots and leaves. The number of down-regulated transcripts in roots was higher than the up-regulated transcripts, while the opposite occurred in leaves. The number of common transcripts between the two tissues was 1,249, while 2,124 were specific to roots and 1,049 specific to leaves. Quantitative RT-PCR analysis revealed a 0.78 correlation with the expression data. The candidate genes were distributed across all chromosomes and component genomes, but a greater number was mapped on the B genome, particularly on chromosomes 3B, 5B and 2B. When considering both tissues, 116 different pathways were induced. One common pathway, among the top three activated pathways in both tissues, was starch and sucrose metabolism. These results pave the way for future marker development and selection of important genes and are useful for understanding the metabolic pathways involved in wheat drought response.

Resumo O objetivo deste trabalho foi analisar a resposta androgênica de genótipos brasileiros de trigo a diferentes pré-tratamentos das espigas, antes da cultura de micrósporos isolados, e ao efeito de um agente gelificante no meio de cultura de indução. Cinco genótipos foram avaliados quanto à formação de embriões, regeneração de plantas verdes e à duplicação espontânea dos cromossomos. Espigas de trigo foram submetidas a dois pré-tratamentos: frio, a 4ºC por 21 dias; e ácido 2-hidroxinicotínico, a 32ºC por dois dias. Os meios de cultura foram avaliados com ou sem Ficoll como agente gelificante. O frio produziu mais embriões e plantas verdes do que o pré-tratamento químico, em quatro dos cinco genótipos testados. Apenas dois genótipos tratados com ácido 2-hidroxinicotínico foram capazes de produzir plantas, e um deles produziu uma única planta albina. O meio com Ficoll produziu mais embriões do que o meio líquido e gerou maior número de plantas. A duplicação espontânea dos cromossomos varia entre os genótipos e os pré-tratamentos e apresenta alta variabilidade.

Abstract The objective of this work was to analyze the androgenic response of Brazilian wheat genotypes to different pretreatments of the spikes, prior to the culture of isolated microspores, and to the effect of a gelling agent in the induction culture medium. Five genotypes were evaluated for embryo formation, green plant regeneration, and spontaneous chromosome duplication. Wheat spikes were subjected to two pretreatments: cold, at 4ºC for 21 days; and 2-hydroxynicotinic acid, at 32ºC for two days. Culture media were evaluated with or without Ficoll as a gelling agent. Cold produced more embryos and green plants than the chemical pretreatment in four out of five genotypes. Only two genotypes treated with 2-hydroxynicotinic acid were able to produce plants, and one of them produced a single albino plant. Medium containing Ficoll produced more embryos than liquid medium and promoted a higher number of plants. Spontaneous chromosome duplication varies between genotypes and pretreatments, and shows high variability.