Recent progress in drought and salt tolerance studies in Brassica crops

Abstract

Water deficit imposed by either drought or salinity brings about severe growth retardation and yield loss of crops. Since Brassica crops are important contributors to total oilseed production, it is urgently needed to develop tolerant cultivars to ensure yields under such adverse conditions. There are various physiochemical mechanisms for dealing with drought and salinity in plants at different developmental stages. Accordingly, different indicators of tolerance to drought or salinity at the germination, seedling, flowering and mature stages have been developed and used for germplasm screening and selection in breeding practices. Classical genetic and modern genomic approaches coupled with precise phenotyping have boosted the unravelling of genes and metabolic pathways conferring drought or salt tolerance in crops. QTL mapping of drought and salt tolerance has provided several dozen target QTLs in Brassica and the closely related Arabidopsis. Many drought- or salt-tolerant genes have also been isolated, some of which have been confirmed to have great potential for genetic improvement of plant tolerance. It has been suggested that molecular breeding approaches, such as marker-assisted selection and gene transformation, that will enhance oil product security under a changing climate be integrated in the development of drought- and salt-tolerant Brassica crops.

Keywords: Brassica; drought; genetic study; salinity; tolerance.

Fig. 1

Evaluation of drought tolerance for Brassica napus at germination stage. Uniformly germinated seeds (2 d) were transferred into petri dishes, which contained 3 layers of filter paper soaked with 10 ml of 10% polyethylene glycol 6000 (PEG6000) solution to simulate drought stress (10% PEG) or water as a control (CK), and allowed for additional 7 d of growth. Biological traits were then recorded to determine the tolerance level of each genotype (Yang et al. 2007).

Fig. 2

Comparison of QTLs mapped using different populations for salt tolerance in Arabidopsis. The QTLs in RIL populations Ler-0 × Col-4 (black) were detected by Quesada et al. (2002), those of Sha × Col-0 (green) and Sha × Ler (purple) were by Galpaz and Reymond (2010), and those of Col × Ler(blue) and Cvi × Ler(red) were by DeRose-Wilson and Gaut (2011).