Selection for salinity tolerance in an international rice collection at vegetative stage

Abstract

Water and soil salinity as the main abiotic stresses decrease crop yield and restrict the use of agricultural lands. In order to assess salt stress effect on seedling growth of rice and to select more tolerant rice genotypes, a factorial experiment was performed at two levels of NaCl namely non-stress (EC 1.2 dS m −1 ) and salt-stress (EC 10 dS m −1 ) in hydroponics with an international rice collection consisted of 155 varieties. Seven stress tolerance indices including STI, SSI, HM, RDI, SSPI, ATI and TOL were used to identify salt tolerant genotypes. The results of variance analysis showed that the effect of genotypes (G), Salt treatment (T) and G×T interaction were significant for all investigated traits (except for the effect of genotypes on shoot length). Under salt stress most genotypes showed similar trend of salt response, i.e. reduction in all traits. The results also revealed that dry weight (DW) was less affected than fresh weight (FW), and the shoot weight (SW) was affected more than the root weight (RW), indicating that shoot growth is more sensitive than root growth to salt stress. The Na + , K + and Na + :K + ratio were increased more than 713%, reduced 22% and increased more than 996% under salt stress, respectively. Four stress tolerance indices including MP, HM, GMP and STI showed highest correlation with each other and also with plant performance (Z-scores) under both normal and stress conditions; thus each of these indices can be used as the suitable indicators for screening salt tolerant genotypes. Based on the results, genotypes #84, #30 and #48 showed the highest performance and STI under salinity condition, so they have considerable potential to improve salt tolerance in rice breeding programs. In addition, genotypes #178, #198 and #6 with the lowest values of STI were found to be intolerant genotypes to salt stress.

Genome-Wide Association Study (GWAS) to Identify Salt-Tolerance QTLs Carrying Novel Candidate Genes in Rice During Early Vegetative Stage

“…The position of QTL qRFWs6.1 on chromosome 6 (4.58–4.61 Mbp) is similar to the position of q06_02 for leaf area reported by Frouin et al ( 2018 ). The positions of 2 co-located QTLs qRLs6.1 and qRFWs6.3 on chromosome 6 (29.76–30.92 Mbp interval) are comparable to QTL #2098 for relative seminal root length reported by Prasad et al ( 2000 ). Also, the location of QTLs qRLs8.1 on chromosome 8 (0.06–0.12 Mbp interval) co-locates to a08_04 for tiller number reported by Frouin et al ( 2018 ), and the location of QTL qRLs8.2 on the same chromosome (2.33 Mbp) is comparable to QTL #2175 for leaf water content detected by Ul Haq et al (2010).…”

“…In the present study, the expression pattern of several new genes involved in salt tolerance of rice was investigated by real-time PCR in two sensitive (ARC6578 and Shoemed) and one tolerant (Bombilla) rice accessions that were selected based on previous work (Nayyeripasand et al 2019). RNA samples were extracted from 20day-old seedlings treated with NaCl (100 mM) at three times after salt stress (24, 48 and 72 h).…”

“…A lot of studies show that salinity tolerance is a complex trait which is controlled by quantitative trait loci (QTL) (Roy et al 2011 ), and using QTL mapping in segregating populations many QTL regions were reported for different traits under salinity stress in rice. Prasad et al ( 2000 ) using a DH population identified a QTL for seminal root length under salt stress on chromosome 6 which explained 18.9% of phenotypic variation. Using a RIL population and AFLP markers, Koyama et al ( 2001 ) identified a QTL for dry mass under salt stress on chromosome 6 explaining 9.7% of phenotypic variation.…”

Genome-Wide Association Study of Salinity Tolerance During Germination in Barley (Hordeum vulgare L.)

“…Yu et al (2018) reported that salttolerance levels in rice (O. sativa) were not strongly correlated with rice subgroups, which was confirmed in a maize population the following year (Luo et al, 2019). Tolerance indices do not accurately distinguish cultivars under severe stress (Mardeh et al, 2006;Mohammadi, 2019), but can be used as indicators for high-yielding, salt-tolerant lines in stress, and non-stress environments or for traits like germination (Nayyeripasand et al, 2019;Sedri et al, 2019).…”

“…Traits with low rates of variation are not suitable for selecting tolerant barley genotypes using tolerance indices under stress (Jamshidi and Javanmard, 2017). Nayyeripasand et al (2019) reported a positive correlation among stress tolerance indices, including STI, SSI, and TOL, but not in the subgroups. Yu et al (2018) reported that salttolerance levels in rice (O. sativa) were not strongly correlated with rice subgroups, which was confirmed in a maize population the following year (Luo et al, 2019).…”