Identification of ecogeographical gaps in the Spanish Aegilops collections with potential tolerance to drought and salinity

Climate change conditions the selection of rust-resistant candidate wild lentil populations for in situ conservation

Crop Wild Relatives (CWR) are a valuable source of genetic diversity that can be transferred to commercial crops, so their conservation will become a priority in the face of climate change. Bizarrely, in situ conserved CWR populations and the traits one might wish to preserve in them are themselves vulnerable to climate change. In this study, we used a quantitative machine learning predictive approach to project the resistance of CWR populations of lentils to a common disease, lentil rust, caused by fungus Uromyces viciae-fabae. Resistance is measured through a proxy quantitative value, DSr (Disease Severity relative), quite complex and expensive to get. Therefore, machine learning is a convenient tool to predict this magnitude using a well-curated georeferenced calibration set. Previous works have provided a binary outcome (resistant vs. non-resistant), but that approach is not fine enough to answer three practical questions: which variables are key to predict rust resistance, which CWR populations are resistant to rust under current environmental conditions, and which of them are likely to keep this trait under different climate change scenarios. We first predict rust resistance in present time for crop wild relatives that grow up inside protected areas. Then, we use the same models under future climate IPCC (Intergovernmental Panel on Climate Change) scenarios to predict future DSr values. Populations that are rust-resistant by now and under future conditions are optimal candidates for further evaluation and in situ conservation of this valuable trait. We have found that rust-resistance variation as a result of climate change is not uniform across the geographic scope of the study (the Mediterranean basin), and that candidate populations share some interesting common environmental conditions.

Searching for Abiotic Tolerant and Biotic Stress Resistant Wild Lentils for Introgression Breeding Through Predictive Characterization

Crop wild relatives are species related to cultivated plants, whose populations have evolved in natural conditions and confer them valuable adaptive genetic diversity, that can be used in introgression breeding programs. Targeting four wild lentil taxa in Europe, we applied the predictive characterization approach through the filtering method to identify populations potentially tolerant to drought, salinity, and waterlogging. In parallel, the calibration method was applied to select wild populations potentially resistant to lentil rust and broomrape, using, respectively, 351 and 204 accessions evaluated for these diseases. An ecogeographic land characterization map was used to incorporate potential genetic diversity of adaptive value. We identified 13, 1, 21, and 30 populations potentially tolerant to drought, soil salinity, waterlogging, or resistance to rust, respectively. The models targeting broomrape resistance did not adjust well and thus, we were not able to select any population regarding this trait. The systematic use of predictive characterization techniques may boost the efficiency of introgression breeding programs by increasing the chances of collecting the most appropriate populations for the desired traits. However, these populations must still be experimentally tested to confirm the predictions.

Response of Three Greek Populations of Aegilops triuncialis (Crop Wild Relative) to Serpentine Soil

A common garden experiment was established to investigate the effects of serpentine soil on the photosynthetic and biochemical traits of plants from three Greek populations of Aegilops triuncialis. We measured photosynthetic and chlorophyll fluorescence parameters, proline content, and nutrient uptake of the above plants growing in serpentine and non-serpentine soil. The photochemical activity of PSII was inhibited in plants growing in the serpentine soil regardless of the population; however, this inhibition was lower in the Aetolia-Acarnania population. The uptake and the allocation of Ni, as well as that of some other essential nutrient elements (Ca, Mg, Fe, Mn), to upper parts were decreased with the lower decrease recorded in the Aetolia-Acarnania population. Our results showed that excess Ni significantly increased the synthesis of proline, an antioxidant compound that plays an important role in the protection against oxidative stress. We conclude that the reduction in the photosynthetic performance is most probably due to reduced nutrient supply to the upper plant parts. Moreover, nickel accumulation in the roots recorded in plants from all three populations seems to be a mechanism to alleviate the detrimental effects of the serpentine soil stress. In addition, our data suggest that the population from Aetolia-Acarnania could be categorized among the nickel excluders.

Addition of Aegilops biuncialis chromosomes 2M or 3M improves the salt tolerance of wheat in different way

Aegilops biuncialis is a promising gene source to improve salt tolerance of wheat via interspecific hybridization. In the present work, the salt stress responses of wheat-Ae. biuncialis addition lines were investigated during germination and in young plants to identify which Aegilops chromosomes can improve the salt tolerance of wheat. After salt treatments, the Aegilops parent and the addition lines 2M, 3M and 3M.4BS showed higher germination potential, shoot and root growth, better CO₂ assimilation capacity and less chlorophyll degradation than the wheat parent. The Aegilops parent accumulated less Na in the roots due to an up-regulation of SOS1, SOS2 and HVP1 genes, while it contained higher amount of proline, fructose, glucose, galactose, maltose and raffinose. In the leaves, lower Na level was accompanied by high amount of proline and increased expression of NHX2 gene. The enhanced accumulation of sugars and proline was also observed in the roots of 3M and 3M.4BS addition lines. Typical mechanism of 2M addition line was the sequestration of Na into the vacuole due to the increased expression of HVP1 in the roots and NHX2 in the leaves. These results suggest the Aegilops chromosomes 2M and 3M can improve salt tolerance of wheat in different way.