Screening for Higher Grain Yield and Biomass among Sixty Bread Wheat Genotypes Grown under Elevated CO2 and High-Temperature Conditions

Natural genetic variation underlying the negative effect of elevated CO2 on ionome composition in Arabidopsis thaliana

The elevation of atmospheric CO2 leads to a decline in plant mineral content, which might pose a significant threat to food security in coming decades. Although few genes have been identified for the negative effect of elevated CO2 on plant mineral composition, several studies suggest the existence of genetic factors. Here, we performed a large-scale study to explore genetic diversity of plant ionome responses to elevated CO2, using six hundred Arabidopsis thaliana accessions, representing geographical distributions ranging from worldwide to regional and local environments. We show that growth under elevated CO2 leads to a global decrease of ionome content, whatever the geographic distribution of the population. We observed a high range of genetic diversity, ranging from the most negative effect to resilience or even to a benefit in response to elevated CO2. Using genome-wide association mapping, we identified a large set of genes associated with this response, and we demonstrated that the function of one of these genes is involved in the negative effect of elevated CO2 on plant mineral composition. This resource will contribute to understand the mechanisms underlying the effect of elevated CO2 on plant mineral nutrition, and could help towards the development of crops adapted to a high-CO2 world.

Combinatorial impacts of elevated CO2 and temperature affect growth, development, and fruit yield in Capsicum chinense Jacq

Hot chilli ('Bhut Jolokia') (Capsicum chinense Jacq.) is the hottest chilli widely grown in the North-Eastern region of India for its high pungency. However, little information is available on its physiology, growth and developmental parameters including yield. Therefore, the present research was undertaken to study the physiological responses of Bhut Jolokia under elevated CO2 (eCO2) and temperature. Two germplasms from two different agro-climatic zones (Assam and Manipur) within the North-East region of India were collected based on the pungency. The present study explored the interactive effect of eCO2 [at 380, 550, 750 ppm (parts per million)] and temperature (at ambient, > 2 °C above ambient, and > 4 °C above ambient) on various physiological processes, and expression of some photosynthesis and capsaicin related genes in both the germplasms. Results revealed an increase (> 1-2 fold) in the net photosynthetic rate (Pn), carbohydrate content, and C: N ratio in 'Bhut Jolokia' under eCO2 and elevated temperature regimes compared to ambient conditions within the germplasms. Gene expression studies revealed an up-regulation of photosynthesis-related genes such as Cs RuBPC2 (Ribulose biphosphate carboxylase 2) and Cs SPS (Sucrose phosphate synthase) which, explained the higher Pn under eCO2 and temperature conditions. Both the germplasm showed better performance under CTGT-II (Carbon dioxide Temperature Gradient Tunnel having 550 ppm CO2 and temperature of 2 °C above ambient) in terms of various physiological parameters and up-regulation of key photosynthesis-related genes. An up-regulation of the Cs  capsaicin synthase gene was also evident in the study, which could be due to the metabolite readjustment in 'Bhut Jolokia'. In addition, the cultivar from Manipur (cv. 1) had less fruit drop compared to the cultivar from Assam (cv. 2) in CTGT II. The data indicated that 550 ppm of eCO2 and temperature elevation of > 2 °C above the ambient with CTGT-II favored the growth and development of 'Bhut Jolokia'. Thus, results suggest that Bhut Jolokia grown under the elevation of CO2 up to 550 ppm and temperature above 2 °C than ambient may support the growth, development, and yield.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-023-01294-9.

Assessing performance and stability of yellow rust resistance, heat tolerance, and agronomic performance in diverse bread wheat genotypes for enhancing resilience to climate change under Egyptian conditions

Yellow rust and heat stress adversatively impact the growth and production of bread wheat in particular under rising adverse environmental conditions. Stability of grain yield is a pivotal purpose of plant breeders to improve wheat production and ensure global food security especially under abrupt climate change. The objective of this study was to assess the performance and stability of diverse bread wheat genotypes for yellow rust resistance, heat stress, and yield traits. The studied genotypes were evaluated in two different locations under two sowing dates (timely and late sowing) during two growing seasons. The obtained results displayed significant differences among the tested locations, sowing dates, and genotypes for most measured traits. The yellow rust measurements evaluated under the field conditions including final rust severity (FRS), the average coefficient of infection (ACI), and area under disease progress curve (AUDPC) revealed that Giza-171, Misr-1, Gemmeiza-12, Shandweel-1, Sids-13, Line-1, Line-2, and Line-55 had better resistance. Based on heat sensitivity measurements, Line-1 and Line-2 followed by Line-35, Shandweel-1 and Line-55 were classified as more tolerant to heat stress compared with the remaining genotypes. The genotypes Line-55, Gemmeiza-12, Giza-171, Line-1, Line-2, and Misr-1 were able to maintain acceptable agronomic performance under timely and late sowing dates in all evaluated environments. Different statistical procedures were employed to explore the adaptability and stability of tested genotypes i.e., joint regression, stratified ranking, Wricke's Ecovalence values, cultivar superiority, additive main effects, and multiplicative interaction (AMMI), AMMI stability value, and genotype plus genotype-by-environment interaction (GGE). The applied stability parameters were quite similar for describing the stability of the evaluated wheat genotypes. The results indicated that Gemmeiza-12, Giza-171, Sids-12, Sids-13, Misr-1 Shandweel-1, Line-1, Line-2, and Line-55 were desirable and stable. The heatmap and hierarchical clustering were exploited for dividing the evaluated bread wheat genotypes into different clusters based on yellow rust resistance measurements, heat tolerance indices, and agronomic performance. Line-1 and Line-2 had the best performance for all rust resistance, heat tolerance, and agronomic performance followed by Giza-171, Line-55, Line-35, Gemmeiza-12, Shandweel-1, Misr-1, and Sids-13. In conclusion, our findings provide evidence of utilizing promising genotypes in rust resistance, heat tolerance, and agronomic performance in breeding programs for improving wheat grain yield stability mainly under climate change.

Insights into breeding history, hotspot regions of selection, and untapped allelic diversity for bread wheat breeding

Breeding has increasingly altered the genetics of crop plants since the domestication of their wild progenitors. It is postulated that the genetic diversity of elite wheat breeding pools is too narrow to cope with future challenges. In contrast, plant genetic resources (PGRs) of wheat stored in genebanks are valuable sources of unexploited genetic diversity. Therefore, to ensure breeding progress in the future, it is of prime importance to identify the useful allelic diversity available in PGRs and to transfer it into elite breeding pools. Here, a diverse collection consisting of modern winter wheat cultivars and genebank accessions was investigated based on reduced-representation genomic sequencing and an iSelect single nucleotide polymorphism (SNP) chip array. Analyses of these datasets provided detailed insights into population structure, levels of genetic diversity, sources of new allelic diversity, and genomic regions affected by breeding activities. We identified 57 regions representing genomic signatures of selection and 827 regions representing private alleles associated exclusively with genebank accessions. The presence of known functional wheat genes, quantitative trait loci, and large chromosomal modifications, i.e., introgressions from wheat wild relatives, provided initial evidence for putative traits associated within these identified regions. These findings were supported by the results of ontology enrichment analyses. The results reported here will stimulate further research and promote breeding in the future by allowing for the targeted introduction of novel allelic diversity into elite wheat breeding pools.

From source to sink: mechanistic insight of photoassimilates synthesis and partitioning under high temperature and elevated [CO2]

Photosynthesis is the vital metabolism of the plant affected by abiotic stress such as high temperature and elevated [CO₂] levels, which ultimately affect the source-sink relationship. Triose phosphate, the primary precursor of carbohydrate (starch and sucrose) synthesis in the plant, depends on environmental cues. The synthesis of starch in the chloroplasts of leaves (during the day), the transport of photoassimilates (sucrose) from source to sink, the loading and unloading of photoassimilates, and the accumulation of starch in the sink tissue all require a highly regulated network and communication system within the plant. These processes might be affected by high-temperature stress and elevated [CO₂] conditions. Generally, elevated [CO₂] levels enhance plant growth, photosynthetic rate, starch synthesis, and accumulation, ultimately diluting the nutrient of sink tissues. On the contrary, high-temperature stress is detrimental to plant development affecting photosynthesis, starch synthesis, sucrose synthesis and transport, and photoassimilate accumulation in sink tissues. Moreover, these environmental conditions also negatively impact the quality attributes such as grain/tuber quality, cooking quality, nutritional status in the edible parts and organoleptic traits. In this review, we have attempted to provide an insight into the source-sink relationship and the sugar metabolites synthesized and utilized by the plant under elevated [CO₂] and high-temperature stress. This review will help future researchers comprehend the source-sink process for crop growth under changing climate scenarios.

Physiological and Antioxidant Response to Different Water Deficit Regimes of Flag Leaves and Ears of Wheat Grown under Combined Elevated CO2 and High Temperature

Triticum aestivum L. cv. Gazul is a spring wheat widely cultivated in Castilla y León (Spain). Potted plants were grown in a scenario emulating the climate change environmental conditions expected by the end of this century, i.e., with elevated CO₂ and high temperature under two water deficit regimes: long (LWD) and terminal (TWD). Changes in biomass and morphology, the content of proline (Pro), ascorbate (AsA) and glutathione (GSH), and enzymatic antioxidant activities were analyzed in flag leaves and ears. Additionally, leaf gas exchange was measured. LWD caused a decrease in biomass and AsA content but an increase in Pro content and catalase and GSH reductase activities in flag leaves, whereas TWD produced no significant changes. Photosynthesis was enhanced under both water deficit regimes. Increase in superoxide dismutase activity and Pro content was only observed in ears under TWD. The lack of a more acute effect of LWD and TWD on both organs was attributed to the ROS relieving effect of elevated CO₂. Gazul acted as a drought tolerant variety with anisohydric behavior. A multifactorial analysis showed better adaptation of ears to water deficit than flag leaves, underlining the importance of this finding for breeding programs to improve grain yield under future climate change.

Co-expression network analysis of genes and networks associated with wheat pistillody

Crop male sterility has great value in theoretical research and breeding application. HTS-1, whose stamens transformed into pistils or pistil-like structures, is an important male sterility material selecting from Chinese Spring three-pistil (CSTP) wheat. However the molecular mechanism of pistillody development in HTS-1 remains a mystery. RNA-seq data of 11 wheat tissues were obtained from the National Center for Biotechnology Information (NCBI), including the stamens of CSTP and the pistils and pistillodic stamen of HTS-1. The Salmon program was utilized to quantify the gene expression levels of the 11 wheat tissues; and gene quantification results were normalized by transcripts per million (TPM). In total, 58,576 genes were used to construct block-wise network by co-expression networks analysis (WGCNA) R package. We obtained all of modules significantly associated with the 11 wheat tissues. AgriGO V2.0 was used to do Gene Ontology (GO) enrichment analysis; and genes and transcription factors (TFs) in these significant modules about wheat pistillody development were identified from GO enrichment results. Basic local alignment search tool (BLAST) was used to align HTS-1 proteins with the published pistillody-related proteins and TFs. Genes about wheat pistillody development were analyzed and validated by qRT-PCR. The MEturquoise, MEsaddlebrown, MEplum, MEcoral1, MElightsteelblue1, and MEdarkslateblue modules were significantly corelated to pistillodic stamen (correlation p < 0.05). Moreover, 206 genes related to carpel development (GO:0048440) or gynoecium development (GO:0048467) were identified only in the MEturquoise module by Gene Ontology (GO) analysis, and 42 of 206 genes were hub genes in MEturquoise module. qRT-PCR results showed that 38 of the 42 hub genes had highly expressed in pistils and pistillodic stamens than in stamens. A total of 15 pistillody development-related proteins were validated by BLAST. Transcription factors (TFs) were also analyzed in the MEturquoise module, and 618 TFs were identified. In total, 56 TFs from 11 families were considered to regulate the development of pistillodic stamen. The co-expression network showed that six of HB and three of BES1 genes were identified in 42 hub genes. This indicated that TFs played important roles in wheat pistillody development. In addition, there were 11 of ethylene-related genes connected with TFs or hub genes, suggesting the important roles of ethylene-related genes in pistillody development. These results provide important insights into the molecular interactions underlying pistillody development.

Crop Adaptation to Elevated CO2 and Temperature

There is no ambiguity about the fact that both atmospheric CO₂ levels and air temperatures are continuing to increase [...].