Evidence and opportunities for developing non-transgenic genome edited crops using site-directed nuclease 1 approach.

The innovations and progress in genome editing/new breeding technologies have revolutionized research in the field of functional genomics and crop improvement. This revolution has expanded the horizons of agricultural research, presenting fresh possibilities for creating novel plant varieties equipped with desired traits that can effectively combat the challenges posed by climate change. However, the regulation and social acceptance of genome-edited crops still remain as major barriers. Only a few countries considered the site-directed nuclease 1 (SDN1) approach-based genome-edited plants under less or no regulation. Hence, the present review aims to comprise information on the research work conducted using SDN1 in crops by various genome editing tools. It also elucidates the promising candidate genes that can be used for editing and has listed the studies on non-transgenic crops developed through SDN1 either by Agrobacterium-mediated transformation or by ribo nucleoprotein (RNP) complex. The review also hoards the existing regulatory landscape of genome editing and provides an overview of globally commercialized genome-edited crops. These compilations will enable confidence in researchers and policymakers, across the globe, to recognize the full potential of this technology and reconsider the regulatory aspects associated with genome-edited crops. Furthermore, this compilation serves as a valuable resource for researchers embarking on the development of customized non-transgenic crops through the utilization of SDN1.

CRISPR-based genome editing in wheat: a comprehensive review and future prospects.

CRISPR technology has vividly increased its applications in last five years for genome editing in a wide range of organisms from bacteria to plants. It is mostly applied in the field of mammalian research. This emerging versatile tool can be utilized in crop improvement by targeting various traits to increase economic value and adaptability of the crop species under changing climate. In plants, Arabidopsis and rice are the most studied plant species in genome editing through CRISPR technology. Wheat is lagging behind in the utilization of CRISPR based genome modifications. The hexaploid, large genome size and the recalcitrant nature in terms of tissue culture are the major obstacles for CRISPR utilization in wheat. Recently, the IWGSC released the high quality of reference genome for wheat which will greatly accelerate the application of CRISPR-based genome engineering in wheat and helps to resolve the global issue of food security in coming decades. The exogenous DNA-free improved mutants with CRISPR technology having desired traits will increase the productivity under biotic and abiotic stress conditions. To address complex traits involving multigene, recently developed multiplex genome editing toolkits can be used. This is a first review of its kind in which the practical utilization and updates on CRISPR validation in wheat along with its future prospects for use of this technology in wheat improvement are comprehensively discussed. Thus, the compiled information will immensely benefit the researchers for utilization of CRISPR system in wheat improvement across the globe.

Physiological traits associated with heat tolerance in bread wheat (Triticum aestivum L.).

Field experiments for evaluating heat tolerance-related physiological traits were conducted for two consecutive years using a mapping population of recombinant inbred lines (RILs) from the cross RAJ4014/WH730. Chlorophyll content (Chl) and chlorophyll fluorescence (CFL) were recorded under timely sown (TS) and late sown (LS) conditions. Late sowing exposes the terminal stage of plants to high temperature stress. Pooled analysis showed that CFL and Chl differed significantly under TS and LS conditions. The mean value of CFL (Fv/Fm) and Chl under both timely and late sown conditions were used as physiological traits for association with markers. Regression analysis revealed significant association of microsatellite markers viz., Xpsp3094 and Xgwm131 with coefficients of determination (R (2)) values for CFL (Fv/Fm) and Chl as 12 and 8 %, respectively. The correlation between thousand grain weight (TGW) with Chl and CFL were 14 and 7 % and correlation between grain wt./spike with Chl and CFL were 15 and 8 %, respectively. The genotypes showing tolerance to terminal heat stress as manifested by low heat susceptibility index (HSI = 0.43) for thousand grain weight, were also found having very low Chl, HSI (-0.52). These results suggest that these physiological traits may be used as a secondary character for screening heat-tolerant genotypes.

Wheats developed for high yield on stored soil moisture have deep vigorous root systems.

Many rainfed wheat production systems are reliant on stored soil water for some or all of their water inputs. Selection and breeding for root traits could result in a yield benefit; however, breeding for root traits has traditionally been avoided due to the difficulty of phenotyping mature root systems, limited understanding of root system development and function, and the strong influence of environmental conditions on the phenotype of the mature root system. This paper outlines an international field selection program for beneficial root traits at maturity using soil coring in India and Australia. In the rainfed areas of India, wheat is sown at the end of the monsoon into hot soils with a quickly receding soil water profile; in season water inputs are minimal. We hypothesised that wheat selected and bred for high yield under these conditions would have deep, vigorous root systems, allowing them to access and utilise the stored soil water at depth around anthesis and grain-filling when surface layers were dry. The Indian trials resulted in 49 lines being sent to Australia for phenotyping. These lines were ranked against 41 high yielding Australian lines. Variation was observed for deep root traits e.g. in eastern Australia in 2012, maximum depth ranged from 118.8 to 146.3cm. There was significant variation for root traits between sites and years, however, several Indian genotypes were identified that consistently ranked highly across sites and years for deep rooting traits.

Differential Activity and Expression Profile of Antioxidant Enzymes and Physiological Changes in Wheat (Triticum aestivum L.) Under Drought.

Wheat crop may experience water deficit at crucial stages during its life cycle, which induces oxidative stress in the plants. The antioxidant status of the plant plays an important role in providing tolerance against the water stress. The objective of this study was to investigate the impact of water stress on physiological traits, antioxidant activity and transcript profile of antioxidant enzyme related genes in four wheat genotypes (C306, AKAW3717, HD2687, PBW343) at three crucial stages of plants under medium (75% of field capacity) and severe stress (45% of field capacity) in pots. Drought was applied by withholding water for 10 days at a particular growth stage viz. tillering, anthesis and 15 days after anthesis (15DAA). For physiological traits, a highly significant effect of water stress at a particular stage and genotypic variations for resistance to drought tolerance was observed. Under severe water stress, the malondialdehyde (MDA) content increased while the relative water content (RWC) and chlorophyll index decreased significantly in all the genotypes. The drought susceptibility index (DSI) of the genotypes varied from 0.18 to 1.9. The drought treatment at the tillering and anthesis stages was found more sensitive in terms of reduction in thousand grain weight (TGW) and grain yield. Antioxidant enzyme activities [superoxide dismutase (SOD) and peroxidase (POX)] increased with the decrease in osmotic potential in drought tolerant genotypes C306 and AKAW3717. Moreover, the transcript profile of Mn-SOD upregulated significantly and was consistent with the trend of the variation in SOD activity, which suggests that Mn-SOD might play an important role in drought tolerance.

Leaf cuticular wax amount and crystal morphology regulate post-harvest water loss in mulberry (Morus species).

Mulberry leaves are the sole source of food for silkworms (Bombyx mori), and moisture content of the detached leaves fed to silkworms determines silkworm growth and cocoon yield. Since leaf dehydration in commercial sericulture is a serious problem, development of new methods that minimize post-harvest water loss are greatly needed. In the present study, variability in moisture retention capacity (MRC, measured as leaf relative water content after one to 5 h of air-drying) was examined by screening 290 diverse mulberry accessions and the relationship between MRC and leaf surface (cuticular) wax amount was determined. Leaf MRC varied significantly among accessions, and was found to correlate strongly with leaf wax amount. Scanning electron microscopic analysis indicated that leaves having crystalline surface waxes of increased facet size and density were associated with high MRC accessions. Leaf MRC at 5 h after harvest was not related to other parameters such as specific leaf weight, and stomatal frequency and index. This study suggests that mulberry accessions having elevated leaf surface wax amount and crystal size and density exhibit reduced leaf post-harvest water loss, and could provide the foundation for selective breeding of improved cultivars.