Salt Tolerance Improvement in Rice through Efficient SNP Marker-Assisted Selection Coupled with Speed-Breeding

Abstract

Salinity critically limits rice metabolism, growth, and productivity worldwide. Improvement of the salt resistance of locally grown high-yielding cultivars is a slow process. The objective of this study was to develop a new salt-tolerant rice germplasm using speed-breeding. Here, we precisely introgressed the hst1 gene, transferring salinity tolerance from “Kaijin” into high-yielding “Yukinko-mai” (WT) rice through single nucleotide polymorphism (SNP) marker-assisted selection. Using a biotron speed-breeding technique, we developed a BC3F3 population, named “YNU31-2-4”, in six generations and 17 months. High-resolution genotyping by whole-genome sequencing revealed that the BC3F2 genome had 93.5% similarity to the WT and fixed only 2.7% of donor parent alleles. Functional annotation of BC3F2 variants along with field assessment data indicated that “YNU31-2-4” plants carrying the hst1 gene had similar agronomic traits to the WT under normal growth condition. “YNU31-2-4” seedlings subjected to salt stress (125 mM NaCl) had a significantly higher survival rate and increased shoot and root biomasses than the WT. At the tissue level, quantitative and electron probe microanalyzer studies indicated that “YNU31-2-4” seedlings avoided Na+ accumulation in shoots under salt stress. The “YNU31-2-4” plants showed an improved phenotype with significantly higher net CO2 assimilation and lower yield decline than WT under salt stress at the reproductive stage. “YNU31-2-4” is a potential candidate for a new rice cultivar that is highly tolerant to salt stress at the seedling and reproductive stages, and which might maintain yields under a changing global climate.

Alleviation of Detrimental Effects of Salt Stress on Date Palm (Phoenix dactylifera L.) by the Application of Arbuscular Mycorrhizal Fungi and/or Compost

“…may directly limit or exclude sodium uptake (Munns, 2005;Liu et al, 2015;Rana et al, 2019). Another important aspect of root systems compared to shoots is their anatomy.…”

Physiological Basis of Salt Stress Tolerance in a Landrace and a Commercial Variety of Sweet Pepper (Capsicum annuum L.)

“…Plants may cope, within certain limits, with salt stress by activating a series of physiological responses. These include the control of water and ion homeostasis [ 7 , 8 ], the regulation of sodium and chloride uptake/accumulation via exclusion and compartmentalization mechanisms [ 6 , 9 ], the detoxification of stress-induced reactive oxygen species (ROS) and the hormonal control of multiple stress responses [ 10 , 11 ]. Most research suggests that these mechanisms are less efficient in domesticated plants compared to wild relatives, as well as in commercial cultivars compared to landraces, which were not bred for commercial traits [ 12 , 13 , 14 , 15 ].…”

Advances and Challenges in the Breeding of Salt-Tolerant Rice

“…Their offspring, YNU31-2-4, had agronomic traits similar to Yukinko-mai under normal growth conditions. Under salt stress, the yield of YNU31-2-4 was significantly higher than that of Yukinko-mai [99]; Bimpong et al used marker-assisted selection to develop salt-tolerant rice cultivars through introgressing Saltol into the lowland cultivar, Rassi, and obtained 16 introgression lines for further African-wide testing prior to release in six West African countries [100]. Pauyawaew et al introgressed Saltol into KDML105 by two rounds of marker-assisted backcrossing, and introgression lines with positive Saltol alleles are being tested for salinity tolerance in the salt-affected areas in the northeast of Thailand [101].…”

“…Moreover, traditional breeding methods are time-consuming and inefficient. SNP marker-assisted selection and genetic engineering technology will greatly improve the molecular breeding process [99,104]. Therefore, efforts should be made to capture useful salt tolerance genes as possible genetic markers to introgress into elite rice varieties.…”