Photoperiod Insensitivity Research Articles

Photoperiod-1 regulates the wheat inflorescence transcriptome to influence spikelet architecture and flowering time

Photoperiod insensitivity has been selected by breeders to help adapt crops to diverse environments and farming practices. In wheat, insensitive alleles of Photoperiod-1 (Ppd-1) relieve the requirement of long daylengths to flower by promoting expression of floral promoting genes early in the season; however, these alleles also limit yield by reducing the number and fertility of grain-producing florets through processes that are poorly understood. Here, we performed transcriptome analysis of the developing inflorescence using near-isogenic lines that contain either photoperiod-insensitive or null alleles of Ppd-1, during stages when spikelet number is determined and floret development initiates. We report that Ppd-1 influences the stage-specific expression of genes with roles in auxin signaling, meristem identity, and protein turnover, and analysis of differentially expressed transcripts identified bZIP and ALOG transcription factors, namely PDB1 and ALOG1, which regulate flowering time and spikelet architecture. These findings enhance our understanding of genes that regulate inflorescence development and introduce new targets for improving yield potential.

Is the time of anthesis in rice (Oryza sativa) influenced by photoperiod?

Photoperiod sensitivity in rice cultivars is defined when the cultivar begins anthesis on a relatively invariant date, varying by < 7days, regardless of the date of sowing or germination. While the date of flowering in photoperiod sensitive (PPS) rice cultivars is characteristically determined by the day length, especially during the short-day season (September-December), the response of the flower opening time (FOT) to photoperiod remains hitherto unexplored. This paper examines whether day length restrains year-to-year variation in FOT in PPS cultivars. We examined 105 PPS and 173 photoperiod insensitive (PPI) cultivars grown in different years and estimated their year-to-year FOT difference (or FOTD) and the year-to-year difference of sunrise to anthesis duration (or SADD). Wilcoxon signed rank test and bootstrap test were then performed to test whether these descriptors significantly differed between PPS and PPI groups of cultivars. The means of FOTD and SADD were detected to be significantly less in the PPS group than in the PPI group of cultivars, indicating significantly lesser variability of FOT in PPS than in PPI cultivars. This is the first report of a strong restraining influence of photoperiod on FOT variability in PPS cultivars.

Registration of indeterminate and photoperiod‐insensitive IIPG‐7 and IIPG‐11 pigeonpea germplasm

AbstractPigeonpea [Cajanus cajan (L.) Mill.] breeding lines (BL) IIPG‐7 (Reg. no. GP‐326, PI 704909) and IIPG‐11 (Reg. no. GP‐327, PI 704910) were developed at the University of Puerto Rico. Both BL were bred to have indeterminate flowering habit and photoperiod insensitivity. The agronomic performance of IIPG‐7, IIPG‐11, and checks was tested during different growing seasons in Isabela and Lajas, Puerto Rico. IIPG‐7 and IIPG‐11 were early maturing and initiated flowering at 73–84 days after planting (DAP), reaching harvest maturity at 121–127 DAP. This was in comparison to indeterminate cultivars ‘Ariel’, ‘Blanco Yauco’, ‘Kaki’, ‘Pinto Berrocales’, and ‘Super Pinto’, which initiated flowering at 91–102 DAP, reaching maturity at 138–148 DAP in short‐day conditions that occurred in October in both locations. These cultivars had seed yield values of over 1000 kg ha−1, whereas IIPG‐7 and IIPG‐11 produced 721–1010 kg ha−1. In contrast, IIPG‐7 and IIPG‐11 were the only indeterminate genotypes that initiated flowering at 42–88 DAP and reached maturity at 88–172 DAP under long‐day conditions (February, March, and May) in both locations. Seed yields of IIPG‐7 and IIPG‐11 varied from 626 to 2449 kg ha−1 in Isabela and were close to 2000 kg ha−1 in Lajas. IIPG‐7 has tan seed with reddish spots; IIPG‐11 has reddish seed with an average weight of 14 and 15 g per 100 seeds, respectively. The IIPG‐7 and IIPG‐11 BL can be used directly by growers or breeders to develop pigeonpea cultivars that can be planted year‐round.

A FLOWERING LOCUS T ortholog is associated with photoperiod-insensitive flowering in hemp (Cannabis sativa L.).

Hemp (Cannabis sativa L.) is an extraordinarily versatile crop, with applications ranging from medicinal compounds to seed oil and fibre products. Cannabis sativa is a short-day plant, and its flowering is highly controlled by photoperiod. However, substantial genetic variation exists for photoperiod sensitivity in C. sativa, and photoperiod-insensitive ("autoflower") cultivars are available. Using a bi-parental mapping population and bulked segregant analysis, we identified Autoflower2, a 0.5 Mbp locus significantly associated with photoperiod-insensitive flowering in hemp. Autoflower2 contains an ortholog of the central flowering time regulator FLOWERING LOCUS T (FT) from Arabidopsis thaliana which we termed CsFT1. We identified extensive sequence divergence between alleles of CsFT1 from photoperiod-sensitive and insensitive cultivars of C. sativa, including a duplication of CsFT1 and sequence differences, especially in introns. Furthermore, we observed higher expression of one of the CsFT1 copies found in the photoperiod-insensitive cultivar. Genotyping of several mapping populations and a diversity panel confirmed a correlation between CsFT1 alleles and photoperiod response, affirming that at least two independent loci involved in the photoperiodic control of flowering, Autoflower1 and Autoflower2, exist in the C. sativa gene pool. This study reveals the multiple independent origins of photoperiod insensitivity in C. sativa, supporting the likelihood of a complex domestication history in this species. By integrating the genetic relaxation of photoperiod sensitivity into novel C. sativa cultivars, expansion to higher latitudes will be permitted, thus allowing the full potential of this versatile crop to be reached.

Loss of daylength sensitivity by splice site mutation in Cannabis pseudo-response regulator.

Photoperiod insensitivity (auto-flowering) in drug-type Cannabis sativa circumvents the need for short day (SD) flowering requirements making outdoor cultivation in high latitudes possible. However, the benefits of photoperiod insensitivity are counterbalanced by low cannabinoid content and poor flower quality in auto-flowering genotypes. Despite recent studies in cannabis flowering, a mechanistic understanding of photoperiod insensitivity is still lacking. We used a combination of genome-wide association study and genetic fine-mapping to identify the genetic cause of auto-flowering in cannabis. We then used gene expression analyses and transient transformation assays to characterize flowering time control. Herein, we identify a splice site mutation within circadian clock gene PSEUDO-RESPONSE REGULATOR 37 (CsPRR37) in auto-flowering cannabis. We show that CsPRR37 represses FT expression and its circadian oscillations transition to a less repressive state during SD as compared to long days (LD). We identify several key circadian clock genes whose expression is altered in auto-flowering cannabis, particularly under non-inductive LD. Research into the pervasiveness of this mutation and others affecting flowering time will help elucidate cannabis domestication history and advance cannabis breeding toward a more sustainable outdoor cultivation system.

Incorporation of Photoperiod Insensitivity and High-Yield Genes into an Indigenous Rice Variety from Myanmar, Paw San Hmwe

Paw San Hmwe (PSH) is an indigenous rice variety from Myanmar with a good taste, a pleasant fragrance, and excellent elongation ability during cooking. However, its low yield potential and strong photoperiod sensitivity reduce its productivity, and it is vulnerable to climate changes during growth. To improve the photoperiod insensitivity, yield, and plant stature of PSH, the high-yield genes Grain number 1a (Gn1a) and Wealthy Farmer’s Panicle (WFP), together with the photoperiod insensitivity trait, were introgressed into PSH via marker-assisted backcross breeding and phenotype selection. For the photoperiod insensitivity trait, phenotypic selection was performed under long-day conditions during the dry season. After foreground selection of Gn1a and WFP via simple sequence repeat genotyping, genotyping-by-sequencing was conducted to validate the introgression of target genes and determine the recurrent parent genome recovery of the selected lines. The improved lines were insensitive to photoperiod, and the Gn1a and WFP introgression lines showed significantly higher numbers of primary panicle branches and spikelets per panicle than the recurrent parent, with comparative similarity in cooking and eating qualities. This study successfully improved PSH by decreasing its photoperiod sensitivity and introducing high-yield genes via marker-assisted selection. The developed lines can be used for crop rotation and double-season cropping of better-quality rice.

Sense in sensitivity: difference in the meaning of photoperiod insensitivity between wheat and barley.

The description of long photoperiod sensitivity in wheat and barley is a cause of confusion for researchers working with these crops, usually accustomed to free exchange of physiological and genetic knowledge of such similar crops. Indeed, wheat and barley scientists customarily quote studies of either crop species when researching one of them. Among their numerous similarities, the main gene controlling the long photoperiod sensitivity is the same in both crops (PPD1; PPD-H1 in barley and PPD-D1 in hexaploid wheat). However, the photoperiod responses are different: (i) the main dominant allele inducing shorter time to anthesis is the insensitive allele in wheat (Ppd-D1a) but the sensitive allele in barley (Ppd-H1) (i.e. sensitivity to photoperiod produces opposite effects on time to heading in wheat and barley); (ii) the main 'insensitive' allele in wheat, Ppd-D1a, does confer insensitivity, whilst that of barley reduces the sensitivity but still responds to photoperiod. The different behaviour of PPD1 genes in wheat and barley is put in a common framework based on the similarities and differences of the molecular bases of their mutations, which include polymorphism at gene expression levels, copy number variation, and sequence of coding regions. This common perspective sheds light on a source of confusion for cereal researchers, and prompts us to recommend accounting for the photoperiod sensitivity status of the plant materials when conducting research on genetic control of phenology. Finally, we provide advice to facilitate the management of natural PPD1 diversity in breeding programmes and suggest targets for further modification through gene editing, based on mutual knowledge on the two crops.

Genetic variation in four maturity genes and photoperiod insensitivity effects on the yield components and on the growth duration periods of soybean

Soybean (Glycine max (L.) Merr.) is a typical short-day and thermophilic crop. Absence of or low sensitivity to photoperiod is necessary for short-day crops to adapt to high latitudes. Photoperiod insensitivity in soybeans is controlled by two genetic systems and involves three important maturity genes: E1, a repressor for two soybean orthologs of Arabidopsis FLOWERING LOCUS T, and E3 and E4, which are phytochrome A genes. The aim of this work was to investigate the role of four maturity genes (E1 through E4) on the yield components, seed quality and on phasic development of near isogenic by E genes lines of soybean: short-day (SD) lines with genotype e1E2E3E4e5E7, e1E2E3e4e5E7, E1e2e3E4e5E7 and photoperiodic insensitive (PPI) lines with genotype e1e2E3E4e5E7, e1e2e3E4e5E7 under a long photoperiod (the natural day length of 50 latitude) conditions and short day conditions. The results of the study showed that soybean development processes under conditions of different day lengths depend on the dominant/recessive state of the main maturity genes. In addition, the response to the photoperiod depends on certain combinations of genes. SD lines began flowering on average 16.9% later under the conditions of a natural long photoperiod. Dominant alleles of genes E1 and E3 extended the pre- and post-flowering phases under conditions of exposure to long and short photoperiods. The dominant allele of the E1 gene delayed the onset of flowering by an average of 26.9%, and the period of full maturity by 39.8% compared to the recessive e1. The dominant allele of the E3 gene, compared to the recessive e3, lengthened the transition to flowering by an average of 16.1%, and the period of full ripeness by 27.1%. The dominant allele of the E2 gene lengthened the duration of the vegetative phase by 20% under the conditions of a long photoperiod. No significant influence of the dominant E4 allele on the duration of the vegetative and generative phases of soybean development was found in our study. PPI lines begin flowering under the conditions of a long and short photoperiod at the same time, but the phases of flowering and full seed maturity in the line with genotype e1e2e3E4e5E7 occurred earlier, due to the loss of the photoperiod sensitivity of the E3 gene. PPI line with genotype e1e2e3E4e5E7 proved to be the most insensitive line to the effect of different photoperiod durations among the studied lines. It was shown that the dominant alleles of E1–E4 maturity genes reduced the parameters of seed weight per plant and the weight of 1000 seeds under the conditions of a natural long photoperiod in comparison with recessive alleles of these genes. The maximum weight of seeds per plant and the weight of 1000 seeds were recorded in the PPI line with genotype e1e2e3E4e5E7. It should be noted that the dominant alleles E1 and E3 increased yield under conditions of a short photoperiod. Maturity genes had different effects on the biochemical composition of seeds. It was shown that soybean lines with dominant E1, E2 and E4 genes showed a higher content of starch and a lower content of total nitrogen and oil in seeds under natural photoperiod conditions compared to lines with recessive alleles of these genes. The dominant E3 allele reduced the oil content and did not affect the starch and total nitrogen content of seeds under long day conditions compared to the recessive e3 allele. The analysis of the effect of photoperiod on the timing of phenophases, yield structure indicators and biochemical composition of seeds in soybean plants with different sensitivity to photoperiod showed that the PPI line with the genotype e1e2e3E4e5E7 was the most adapted to the natural conditions of 50 degrees latitude. The PPI line with the genotype e1e2e3E4e5E7 was characterized by the shortest phases of days from sowing to flowering and full maturity. As a result, this line had the shortest growing season without reducing the yield and seed quality. Clearly, photoperiod had strong effects on all stages of plant reproduction and often acted indirectly, as shown by delayed responses expressed in later phases of development. The obtained results can be useful for the selection of soybean cultivars adapted to the climatic conditions of cultivation of Kharkiv region.

Preponderant alleles at Hd1 and Ehd1 lead to photoperiod insensitivity in japonica rice varieties

Preponderant alleles at Hd1 and Ehd1 lead to photoperiod insensitivity in japonica rice varieties

GWAS analysis to elucidate genetic composition underlying a photoperiod-insensitive rice population, North Korea.

Heading date (Hd) is one of the main factors determining rice production and regional adaptation. To identify the genetic factors involved in the wide regional adaptability of rice, we conducted a genome-wide association study (GWAS) with 190 North Korean rice accessions selected for non-precocious flowering in the Philippines, a low-latitude region. Using both linear mixed models (LMM) and fixed and random model circulating probability unification (FarmCPU), we identified five significant loci for Hd in trials in 2018 and 2019. Among the five lead single nucleotide polymorphisms (SNPs), three were located adjacent to the known Hd genes, Heading date 3a (Hd3a), Heading date 5 (Hd5), and GF14-c. In contrast, three SNPs were located in novel loci with minor effects on heading. Further GWAS analysis for photoperiod insensitivity (PS) revealed no significant genes associated with PS, supporting that this North Korean (NK) population is largely photoperiod-insensitive. Haplotyping analysis showed that more than 80% of the NK varieties harbored nonfunctional alleles of major Hd genes investigated, of which a nonfunctional allele of Heading date 1 (Hd1) was observed in 66% of the varieties. Geographical distribution analysis of Hd allele combination types showed that nonfunctional alleles of floral repressor Hd genes enabled rice cultivation in high-latitude regions. In contrast, Hd1 alleles largely contributed to the wide regional adaptation of rice varieties. In conclusion, an allelic combination of Hd genes is critical for rice cultivation across wide areas.

Genetic Analysis of Mutagenesis That Induces the Photoperiod Insensitivity of Wild Cotton Gossypium hirsutum Subsp. purpurascens.

Cotton genus Gossypium L., especially its wild species, is rich in genetic diversity. However, this valuable genetic resource is barely used in cotton breeding programs. In part, due to photoperiod sensitivities, the genetic diversity of Gossypium remains largely untapped. Herein, we present a genetic analysis of morphological, cytological, and genomic changes from radiation-mediated mutagenesis that induced plant photoperiod insensitivity in the wild cotton of Gossypium hirsutum. Several morphological and agronomical traits were found to be highly inheritable using the progeny between the wild-type G. hirsutum subsp. purpurascens (El-Salvador) and its mutant line (Kupaysin). An analysis of pollen mother cells (PMCs) revealed quadrivalents that had an open ring shape and an adjoining type of divergence of chromosomes from translocation complexes. Using 336 SSR markers and 157 F2 progenies that were grown with parental genotypes and F1 hybrids in long day and short night conditions, five quantitative trait loci (QTLs) associated with cotton flowering were located on chromosomes At-05, At-11, and Dt-07. Nineteen candidate genes related to the flowering traits were suggested through molecular and in silico analysis. The DNA markers associated with the candidate genes, upon future functional analysis, would provide useful tools in marker-assisted selection (MAS) in cotton breeding programs for early flowering and maturity.

The Association of Grain Yield and Agronomical Traits with Genes of Plant Height, Photoperiod Sensitivity and Plastid Glutamine Synthetase in Winter Bread Wheat (Triticum aestivum L.) Collection.

The reduction in plant height caused by mutations in Rht-B1 or Rht-D1 (Reduced height-1) genes in combination with day-length-independent early flowering associated with the Ppd-D1 (Photoperiod-D1) gene were the main factors of the drastic yield increase in bread wheat in the 1960s. Increasing nitrogen use efficiency as well as maintaining high yields under conditions of global climate change are the modern goals of wheat breeding. The glutamine synthetase (GS) enzyme plays a key role in ammonium assimilation in plants. In previous studies, the TaGS2-A1 gene, coding the plastid isoform of GS, was shown to be connected with nitrogen use efficiency in wheat. Using the polymerase chain reaction (PCR) markers, the association of yield and agronomical traits with haplotypes of Rht-B1, Rht-D1, Ppd-D1 and TaGS2-A1 genes was studied in a diverse collection of winter bread wheat cultivars grown in Krasnodar (Russia). In the three-year experiment, semidwarfism and photoperiod insensitivity were confirmed to be highly favorable for the grain yield. The TaGS2-A1b haplotype had a tendency for increased grain yield and lodging resistance, but mainly in plants not possessing the ‘green revolution’ alleles. Thus, TaGS2-A1b may have potential in breeding wheat cultivars with alternative dwarfing genes or tall cultivars, which may be optimal for growing under certain environments.

Identification of the &lt;i&gt;eam8&lt;/i&gt; allele associated with photoperiod insensitivity in barley accessions from Japan

BACKGROUND: Cultivated plants grown in the northern regions of Russia are subject to strict requirements in terms of their ability to produce a high yield during short growing season. Important adaptive traits that affect crop yield are early maturity and insensitivity to photoperiod. The search and involvement in breeding programs of new sources of these valuable traits is a necessary step for the creation of new ecologically plastic varieties.&#x0D; THE AIM: To identify alleles of the Eam8 gene, which determine weak photoperiodic sensitivity, among Japanese barley accessions from the N.I. Vavilov All-Russian Institute of Plant Genetic Resources (VIR) collection.&#x0D; MATERIALS AND METHODS: Screening of 200 barley accessions from Japan was carried out in a climatic chamber in order to identify plants with yellow color of seedlings a marker sign of the influence of the eam8 allele, which controls early maturity and low sensitivity to the photoperiod. The presumably photoperiod-insensitive accession was studied under conditions of long and short photoperiods and was studied by molecular methods.&#x0D; RESULTS: Phenotypic screening identified a presumably photoperiod-insensitive accession k-17545 (Jap.456). The photoperiodic sensitivity of the accession and the variety Mari (carrier of the recessive eam8 allele) were similar. Using molecular analysis, the eam8.k allele, occurred naturally in the cultivars Kinai 5 and Kagoshima Gold from Japan, was found in the k-17545 line. The Jap.456 was polymorphic by srorage proteins (hordein) patterns and RAPD profiles. In addition, previously undescribed SNPs in the eam8.k sequence were identified in individual plants.&#x0D; CONCLUSIONS: As a result of the study of 200 accessions of barley from Japan, accession k-17545 (Jap.456) was found, in which the eam8.k allele was identified, which controls weak sensitivity to the photoperiod.

A daylength-neutral winged bean (Psophocarpus tetragonolobus) for Southern Australian latitudes

Abstract. Eagleton GE. 2022. A daylength-neutral winged bean (Psophocarpus tetragonolobus) for Southern Australian latitudes. Asian J Agric 6: 68-78. In the summer of 2019, on the central coast of NSW, Australia (at Latitude 34°S), an early-maturing genotype of the tropical legume crop, winged bean (Psophocarpus tetragonolobus (L.) DC.), was detected among a range of late-maturing accessions. The performance of this accession, MY0-01 from Bago in Myanmar, was evaluated in staked plots alongside one other accession from Myanmar and two from the island of New Guinea planted on three successive occasions between October and late November 2020 in a split-plot experiment. Across the three planting dates, the mean number of days from planting to the first open flower for MYO-01 ranged from 68 to 82 + s.e. 3.2 compared with a range of 119 to 167 for the other three accessions. The mean accumulated seed yield of MYO-01 obtained from the October planting equated to 3.1 t ha-1, but by the third planting in late November, the yield was only half as much. Among the four accessions, MYO-01 was second in the amount of lower stem branching and tuber yield, with the smallest pods and hardest seeds. Hard seededness creates difficulties for germination and plant establishment and is a limitation in MYO-01, as are its small pods, which lowers its potential for vegetable production. Investigating genetic control of photoperiod insensitivity in MYO-01 and combining the ability for pod and seed characteristics is relevant to sub-tropical latitudes and for developing stable early maturity cultivars for the tropics.

Photoperiod Insensitivity in Pigeonpea Introgression Lines Derived from Wild Cajanus Species

Pigeonpea is a photoperiod-sensitive crop; therefore, the introgression of photoperiod insensitivity could increase its adaptability to new environments. We determined the effect of extended daylength (ED; 16 h light) on the phenotypical traits of extra-early, early, and mid-early maturing pigeonpea introgression lines (ILs) derived from wild Cajanus species belonging to secondary and tertiary gene pools. Plants were grown under natural daylength and extended daylength in a greenhouse. Comparisons of the time of floral bud initiation, days to flowering, plant height, number of branches, and number of leaf nodes on the main stem at flowering revealed photoperiod-insensitive lines. All traits varied widely among the ILs. Analyses of flowering traits revealed large genetic components with low genotype × treatment interactions and high broad-sense heritability. The photoperiod most strongly affected the number of primary branches, followed by plant height. The extended day advanced flowering by approximately four days in extra-early ILs, confirming that these ILs are quantitative, short-day plants. The photoperiod insensitivity index varied from 0.88 in ICPP 171541 (moderately photoperiod sensitive) to 0.99 in ICPP 171546 and ICPP 171561 (photoperiod insensitive). These photoperiod-insensitive extra-early flowering ILs can be used to enrich the genetic diversity of pigeonpea and to develop photoperiod-insensitive cultivars for cultivation in new environments.

Inheritance of growth habit under photoperiod insensitive genetic background in dolichos bean [Lablab purpureus (L.) Sweet

Development of high yielding cultivars with determinate growth habit in photoperiod insensitive (PIS) background is one of the major objectives of breeding grain legumes crops including dolichos bean [Lablab purpureus (L.) Sweet]. A thoroughly validated genetic basis is a prerequisite for breeding dolichos bean for determinate growth habit in PIS background. Based on the published reports by researchers of our laboratory and those by others, and our unpublished data, we hypothesized that the number and mode of action of genes controlling growth habit differ with degree of photoperiod sensitivity of the genetic material used to investigate the inheritance of growth habit in dolichos bean. To test this hypothesis, we compared the number and mode of action of genes controlling growth habit between segregating generations in Photoperiod sensitive (PS) and those in PIS genetic backgrounds. While indeterminate and determinate plants segregated in 15:1 ratio in F2 populations derived from crosses between determinate PIS and indeterminate PIS parents, they segregated in 9:7 ratio with indeterminacy being dominant in F2 populations derived from crosses between determinate PIS and indeterminate PS parents. These patterns of segregation (15:1 and 9:7) in favour of indeterminate and determinate plants, respectively in F2 populations were confirmed in F3 populations of PIS and PS genetic backgrounds based on good fit between observed and expected ratios (55:9 and 29:35, respectively) in favour of indeterminate and determinate plants, respectively. The patterns of segregation in F2 populations were further confirmed in F3 populations based on good fit between observed and expected ratios of 3:1 segregating and non-segregating families, and of 3:1 indeterminate and determinate non-segregating families, respectively.

Co-silencing E1 and its homologs in an extremely late-maturing soybean cultivar confers super-early maturity and adaptation to high-latitude short-season regions

Soybean (Glycine max (L.) Merr.), a typical short-day plant, is sensitive to photoperiod, which limits the geographical range for its cultivation. In the flowering pathway regulated by photoperiod, E1, a flowering inhibitor in soybean, plays the dominant role in flowering time regulation. Two E1 homologs, E1-like-a (E1La) and E1-like-b (E1Lb), play overlapping or redundant roles in conjunction with E1. In the present study, E1 and E1La/b were simultaneously silenced via RNA interference (RNAi) in Zigongdongdou (ZGDD), an extremely late-flowering soybean landrace from southern China. As a result, RNAi lines showed a much earlier-flowering phenotype and obvious photoperiod insensitivity compared with wild-type (WT) plants. In RNAi transgenic plants, the expression levels of flowering inhibitor GmFT4 and flowering promoters GmFT2a/GmFT5a were significantly down- and up-regulated, respectively. Further, the maturity group (MG) of the RNAi lines was reduced from WT ZGDD's MG VIII (extremely late-maturity) to MG 000 (super-early maturity), which can even grow in the northernmost village of China located at a latitude of 53.5°N. Our study confirms that E1 and E1La/b can negatively regulate flowering time in soybean. The RNAi lines generated in this study, with early flowering and maturity traits, can serve as valuable materials and a technical foundation for breeding soybeans that are adapted to high-latitude short-season regions.

Changing times: Opportunities for altering winter wheat phenology

Social Impact StatementClimate change presents challenges to agricultural production systems. Wheat is a significant crop in the United Kingdom, occupying 40% of arable land area. Increased temperatures and drought risk are predicted to lead to future productivity losses. Plant breeders and researchers are working to develop more resilient wheat varieties although are often driven by different motivating factors compared to farmers. Here, we report on a dialog with agronomists working with farmers in wheat‐producing regions throughout the UK to gain greater understanding of the farm‐level importance of wheat flowering time and maturity along with the future opportunities and risks presented by earlier flowering varieties. Summary Optimized environmental adaptation is the cornerstone of regional crop breeding. Recent and predicted future instability for long‐standing adaptive response presents new challenges to selective breeding. Wheat is a long day plant, requiring extended daylength to initiate flowering, a response controlled by the Photoperiod‐1 (Ppd‐1) gene. Mutations conferring photoperiod insensitivity arose during domestication, allowing rapid flowering in both short and long days and extending wheat's adaptive range. In the United Kingdom, wheat production is dominated by photoperiod‐sensitive winter varieties which have a relatively narrow window of flowering time. Changing seasonal conditions alongside mounting logistics pressure as a result of loss of effective agrochemicals and increasing seasonal weather fluctuations mean that greater flexibility in varietal flowering time is likely required to sustain UK wheat productivity. In this Opinion piece, we present findings from a recent dialog with UK agronomists on the demand and likely potential for greater flowering time range in winter wheat varieties. This provides important insight connecting farmer priorities and demands with ongoing genetic research and breeding. Our findings highlight the farm‐level importance of wheat phenology and provide recommendations for future research and plant breeding.

Utilizing Wild Cajanus platycarpus, a Tertiary Genepool Species for Enriching Variability in the Primary Genepool for Pigeonpea Improvement.

The use of crop wild relatives in the breeding program has been well recognized to diversify the genetic base along with introgression of useful traits. Cajanus platycarpus (Benth.) Maesen, an annual wild relative belonging to the tertiary genepool of pigeonpea, possesses many useful traits such as early maturity, high protein content, photoperiod insensitivity, and pod borer tolerance for the genetic improvement of cultivated pigeonpea. Using this cross incompatible wild Cajanus species, an advanced backcross population was developed following the embryo rescue technique. In the present study, a pre-breeding population consisting of 136 introgression lines (ILs) along with five popular varieties (used as checks) was evaluated for important agronomic traits during 2016 and 2017 rainy seasons and for grain nutrient content during 2016, 2017, and 2018 rainy seasons. Large genetic variation was observed for agronomic traits such as days to 50% flowering, number of pods per plant, pod weight per plant, grain yield per plant, and grain nutrients [protein content, grain iron (Fe), zinc (Zn), calcium (Ca), and magnesium (Mg)] in the pre-breeding population. Significant genotype × environment interaction was also observed for agronomic traits as well as grain nutrients indicating the sensitivity of these traits to the environments. No significant correlations were observed between grain yield and grain nutrients except grain Zn content which was negatively correlated with grain yield. Overall, 28 promising high-yielding ILs with high grain nutrient content were identified. These ILs, in particular, ICPP # 171012, 171004, 171102, 171087, 171006, and 171050 flowered significantly earlier than the popular mega variety, ICPL 87119 (Asha) and thus hold potential in developing new short-duration cultivars. The comprehensive multi-site assessment of these high-yielding, nutrient-rich accessions would be useful in identifying region-specific promising lines for direct release as cultivars. Moreover, these ILs are expected to replace the popular existing cultivars or for use as new and diverse sources of variations in hybridization programs for pigeonpea improvement.

Allelic Variation at the Vernalization Response (Vrn-1) and Photoperiod Sensitivity (Ppd-1) Genes and Their Association With the Development of Durum Wheat Landraces and Modern Cultivars.

Wheat adaptability to a wide range of environmental conditions is mostly determined by allelic diversity within genes controlling vernalization requirement (Vrn-1) and photoperiod sensitivity (Ppd-1). We characterized a panel of 151 durum wheat Mediterranean landraces and 20 representative locally adapted modern cultivars for their allelic composition at Vrn-1 and Ppd-1 gene using diagnostic molecular markers and studied their association with the time needed to reach six growth stages under field conditions over 6 years. Compared with the more diverse and representative landrace collection, the set of modern cultivars were characterized by a reduction of 50% in the number of allelic variants at the Vrn-A1 and Vrn-B1 genes, and the high frequency of mutant alleles conferring photoperiod insensitivity at Ppd-A1, which resulted on a shorter cycle length. Vrn-A1 played a greater role than Vrn-B1 in regulating crop development (Vrn-A1 > Vrn-B1). The results suggest that mutations in the Vrn-A1 gene may have been the most important in establishing the spring growth habit of Mediterranean landraces and modern durum cultivars. The allele Vrn-A1d, found in 10 landraces, delayed development. The relative effects of single Vrn-A1 alleles on delaying the development of the landraces were vrn-A1 = Vrn-A1d > Vrn-A1b > Vrn-A1c. Allele vrn-B1 was present in all except two landraces and in all modern cultivars. The null allele at Ppd-A1 (a deletion first observed in the French bread wheat cultivar ‘Capelle-Desprez’) was found for the first time in durum wheat in the present study that identified it in 30 landraces from 13 Mediterranean countries. Allele Ppd-A1a (GS105) was detected in both germplasm types, while the allele Ppd-A1a (GS100) was found only in modern North American and Spanish cultivars. The relative effect of single Ppd-A1 alleles on extending phenological development was Ppd-A1(DelCD) > Ppd-A1b > Ppd-A1a (GS105) > Ppd-A1a (GS100). Sixteen Vrn-1+Ppd-1 allelic combinations were found in landraces and six in modern cultivars, but only three were common to both panels. Differences in the number of days to reach anthesis were 10 days in landraces and 3 days in modern cultivars. Interactive effects between Vrn-1 and Ppd-1 genes were detected.