Identification of a set of genes from genotypes of common bean tolerant and susceptible to water stress for a macroarray-based selection strategy

Abstract

Globally, drought is the main factor that reduces common bean yield. For this reason, breeding alternatives, such as molecular marker-assisted selection, that focus on various functional genes directly involved in the response to water stress, such as those encoding late embryogenesis abundant (LEA), early response to dehydration (ERD), and dehydrin proteins, have been implemented. The aim of this study was to identify differentially expressed genes of Phaseolus vulgaris in drought-tolerant cultivars Pinto Saltillo (PS) and Pinto Villa (PV), and drought-susceptible cultivars Bayo Madero (BM) and Canario 60 (C60) in vegetative and reproductive stages. Relative water content (RWC) in leaf tissue was measured. Twenty-eight P. vulgaris genes obtained from GenBank and from a subtractive suppressive library from the PS cultivar were analysed, and their expression profiles were examined by reverse transcription polymerase chain reaction (RT-PCR). Then, cDNA arrays were developed and hybridised to confirm expression which was finally validated by quantitative PCR (qPCR). The usefulness of the identified genes as selection criteria for the tolerance of different genotypes to drought was examined using cDNA arrays. Expression of 21 genes was induced by drought. The cDNA arrays confirmed that expression of 19 of these genes increased in the vegetative stage upon exposure to the drought, and a higher expression was observed in the reproductive stage compared with vegetative stage V4. Only five genes induced by the drought were found to have a lower expression in the susceptible cultivars compared with the tolerant ones. During recovery after the drought in the reproductive stage, 13 of the 21 induced genes remained transcriptionally active including LEA3 and dehydrin. The RWC during the drought in vegetative stage V4 decreased by about 55 % in all cultivars, but at the onset of flowering, it increased to 80 % in PV and PS. In contrast, in the susceptible cultivars, it remained at 55 %. Using qPCR validation, expression induction was confirmed in the drought-tolerant cultivars. Polyubiquitin2, LEA3, LEA4, and dehydrin were useful genes for selecting drought-tolerant genotypes under field conditions.