Abstract
Identifying suitable salt stress-tolerant phenotypes based on their agronomic and physiological traits remains a herculean task in forage-type oat (Avena sativa L.) breeding. This study examined the responses of six forage-type oat cultivars under four levels of saline stress over the vegetative growth cycle. Crop growth, water status-related traits and nitrogen status-related traits were analyzed in different plant parts to evaluate effective approaches for identifying salt tolerance. Plant biomass, height, tiller number and culm thickness changed substantially during salinity, but they were not precise enough for use in estimating genotypic salinity tolerance during long-term stress. Genotypes bearing larger numbers of tillers showed greater sensitivity to salinity due to its effects on biomass loss. Tolerant genotypes exhibited higher relative shoot biomass together with higher water use efficiency. The concentrations of Na+, K+ and their ratio, combined with the δ13C in shoots and roots were effective indicators for estimating tolerant genotypes through better water maintenance. N concentrations of shoots were the most efficient for evaluating genotypic tolerance. Low nitrate reductase (NR) and glutamine synthetase (GS) activity might be key factors limiting N accumulation. Chlorophyll (Chl) content and net photosynthetic rate, as well as stomatal conductance and evaporation, were useful for identifying salinity tolerance physiological mechanisms, but the effectiveness was low for genotypic tolerance testing for forage type oats due to the interaction between genotypes and salinity levels. The selection of high salinity-tolerant genotypes should focus on genotypes with photosynthetic resilience to salt, followed by high N metabolism (higher NR and GS activities) to ensure accumulation of more N in the shoot dry matter.
Highlights
Oat (Avena sativa L.) is an important cereal and forage crop, making it a double-purpose crop, and is widely planted in low fertility or saline-alkaline soil
Salinity stress restricted the formation of shoot biomass due to the development of short plants, low tiller numbers and thin culm thickness
relative growth rate (RGR) and relative water content (RWC) were informative for separating the salinity tolerance according to genotype
Summary
Oat (Avena sativa L.) is an important cereal and forage crop, making it a double-purpose crop, and is widely planted in low fertility or saline-alkaline soil. Vast areas of low-fertility farmland, such as the Northeast China Plain and the Qinghai Tibet Plateau, with their high salinity and alkalinity (accounting for 6.62% of the total arable land), are restricted from large-scale cultivation of oats due to a lack of salt-tolerant varieties [2]. Breeding for salt-tolerant oats that could be widely planted across. Plants 2020, 9, 1025 large areas of low fertility would increase the production of fodder grasses and ensure fodder supplies to local livestock industries, but would increase soil cover in early spring in northern. An effective phenotyping approach remains a worthwhile exercise in breeding for salinity tolerance. Under traditional methods of breeding, salt-tolerant germplasm selection remains very slow, with the reality that breeders need to identify salt-tolerant germplasm with “experienced eyes” [3]
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