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The spikelet number per spike (SNS) and spike length (SL) are key traits of interest for improving grain yields. Photoperiod-1 (Ppd-1) is a key regulator of inflorescence architecture and paired spikelet development in wheat. In this study, 170 recombinant inbred lines (RILs) derived by crossing synthetic hexaploid wheat (SHW-L1) with a commercial cultivar (Chuanmai 32) were evaluated for the number of days to heading (DTH), SNS and SL in four different years. Eight PPD1 combination homoeologs were also identified in the RILs by using genetic marker analysis. DTH had highly significant or significant positive correlations with SNS and SL, while SL also had a highly significant positive correlation with SNS. As a single factor, the photoperiod-sensitive ppd-D1b alleles had the largest effect on delaying heading, and these results showed that SL and SNS can eventually be increased. These findings confirmed that photoperiod-sensitive ppd-D1b is a potential means of increasing wheat yields. [ABSTRACT FROM AUTHOR]

Spikelet number and grain number per spike are two crucial and correlated traits for grain yield in wheat. Photoperiod-1 (Ppd-1) is a key regulator of inflorescence architecture and spikelet formation in wheat. In this study, near-isogenic lines derived from the cross of a synthetic hexaploid wheat and commercial cultivars generated by double top-cross and two-phase selection were evaluated for the number of days to heading and other agronomic traits. The results showed that heading time segregation was conferred by a single incomplete dominant gene PPD-D1, and the 2 kb insertion in the promoter region was responsible for the delay in heading. Meanwhile, slightly delayed heading plants and later heading plants obviously have advantages in grain number and spikelet number of the main spike compared with early heading plants. Utilization of PPD-D1 photoperiod sensitivity phenotype as a potential means to increase wheat yield potential. [ABSTRACT FROM AUTHOR]

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As one of the important spike components, spikelet number is closely related to wheat yield. In the present study, a major stable QTL for spikelet number per spike (SNPS), qSnps-7D, was identified using a recombinant inbred line mapping population derived from the cross between Kenong 9204 (KN9204) and Jing 411 (J411) (KJ-RILs). To decipher its genetic effects on yield-related traits and selection effects in wheat breeding process, phenotype data together with genotype data from KJ-RILs and a natural mapping population were collected. qSnps-7D was mapped to the interval of 1.63 Mb on chromosome 7D in the KN9204 genome assembly in 4 of the 6 datasets. The favored alleles from KN9204 could significantly increase SNPS, kernel number per spike (KNPS). The diagnostic markers for SNPS were further developed and validated. The selection utilization rate of the favored haplotype in foreign varieties was lower than that in China, and it showed an increasing trend with time passage, with the ratio reaching more than 50% since the 1990s. In addition, loci for yield-related traits co-located with qSnps-7D were sorted out. Meanwhile, the relationship between SNPS and its components as well as other important yield-related traits were also discussed. Taken together, the studies will lay foundation for gene cloning and molecular breeding utilization of qSnps-7D. [ABSTRACT FROM AUTHOR]

Spikelet number and grain number per spike are two crucial and correlated traits for grain yield in wheat. Photoperiod-1 (Ppd-1) is a key regulator of inflorescence architecture and spikelet formation in wheat. In this study, near-isogenic lines derived from the cross of a synthetic hexaploid wheat and commercial cultivars generated by double top-cross and two-phase selection were evaluated for the number of days to heading and other agronomic traits. The results showed that heading time segregation was conferred by a single incomplete dominant gene PPD-D1, and the 2 kb insertion in the promoter region was responsible for the delay in heading. Meanwhile, slightly delayed heading plants and later heading plants obviously have advantages in grain number and spikelet number of the main spike compared with early heading plants. Utilization of PPD-D1 photoperiod sensitivity phenotype as a potential means to increase wheat yield potential.

Summary: The AGAMOUS‐LIKE6 (AGL6)‐like genes are ancient MADS‐box genes and are functionally studied in a few model plants. The knowledge of these genes in wheat remains limited. Here, by studying a 'double homoeolog mutant' of the AGL6 gene in tetraploid wheat, we showed that AGL6 was required for the development of all four whorls of floral organs with dosage‐dependent effect on floret fertility. Yeast two‐hybrid analyses detected interactions of AGL6 with all classes of MADS‐box proteins in the ABCDE model for floral organ development. AGL6 was found to interact with several additional proteins, including the G protein β and γ (DEP1) subunits. Analysis of the DEP1‐B mutant showed a significant reduction in spikelet number per spike in tetraploid wheat, while overexpression of AGL6 in common wheat increased the spikelet number per spike and hence the grain number per spike. RNA‐seq analysis identified the regulation of several meristem activity genes by AGL6, such as FUL2 and TaMADS55. Our work therefore extensively updated the wheat ABCDE model and proposed an alternative approach to improve wheat grain yield by manipulating the AGL6 gene. [ABSTRACT FROM AUTHOR]

Spikelet number per spike (SNS) is the primary factor that determines wheat yield. Common wheat breeding reduces the genetic diversity among elite germplasm resources, leading to a detrimental effect on future wheat production. It is, therefore, necessary to explore new genetic resources for SNS to increase wheat yield. A tetraploid landrace "Ailanmai" × wild emmer wheat recombinant inbred line (RIL) population was used to construct a genetic map using a wheat 55K single- nucleotide polymorphism (SNP) array. The linkage map containing 1,150 bin markers with a total genetic distance of 2,411.8 cm was obtained. Based on the phenotypic data from the eight environments and best linear unbiased prediction (BLUP) values, five quantitative trait loci (QTLs) for SNS were identified, explaining 6.71–29.40% of the phenotypic variation. Two of them, QSns.sau-AM-2B.2 and QSns.sau-AM-3B.2 , were detected as a major and novel QTL. Their effects were further validated in two additional F2 populations using tightly linked kompetitive allele-specific PCR (KASP) markers. Potential candidate genes within the physical intervals of the corresponding QTLs were predicted to participate in inflorescence development and spikelet formation. Genetic associations between SNS and other agronomic traits were also detected and analyzed. This study demonstrates the feasibility of the wheat 55K SNP array developed for common wheat in the genetic mapping of tetraploid population and shows the potential application of wheat-related species in wheat improvement programs. [ABSTRACT FROM AUTHOR]

Spikelet number per spike (SNS) is the primary factor that determines wheat yield. Common wheat breeding reduces the genetic diversity among elite germplasm resources, leading to a detrimental effect on future wheat production. It is, therefore, necessary to explore new genetic resources for SNS to increase wheat yield. A tetraploid landrace “Ailanmai” × wild emmer wheat recombinant inbred line (RIL) population was used to construct a genetic map using a wheat 55K single- nucleotide polymorphism (SNP) array. The linkage map containing 1,150 bin markers with a total genetic distance of 2,411.8 cm was obtained. Based on the phenotypic data from the eight environments and best linear unbiased prediction (BLUP) values, five quantitative trait loci (QTLs) for SNS were identified, explaining 6.71–29.40% of the phenotypic variation. Two of them, QSns.sau-AM-2B.2 and QSns.sau-AM-3B.2, were detected as a major and novel QTL. Their effects were further validated in two additional F2 populations using tightly linked kompetitive allele-specific PCR (KASP) markers. Potential candidate genes within the physical intervals of the corresponding QTLs were predicted to participate in inflorescence development and spikelet formation. Genetic associations between SNS and other agronomic traits were also detected and analyzed. This study demonstrates the feasibility of the wheat 55K SNP array developed for common wheat in the genetic mapping of tetraploid population and shows the potential application of wheat-related species in wheat improvement programs.

The efficiency of donors in plant breeding depends on the degree of knowledge of the physiological and genetic background of agronomic characters. The research is aimed to assess quantitative agronomic traits (1000-grain weight, grain weight, grain number per spike and spikelet number per spike) in soft spring wheat varieties with different maturation timing in order to identify genotypes that show the best adaptation to the regional environment, high yield and resistance to stress. Agronomic traits were studied in 139 soft spring wheat varieties in contrasting years. The cultivars were divided into the following maturation groups: mid-early and early (31 plants), middle (94 plants) and mid-late (14 plants). In the mid-early and early group, Leningradskaya 97 and Rosinka 1 had three measures of maturation (grain weight per spike, grain number per spike, and spikelet number per spike) higher than the group average. In the middle group, Baganskaya 51, Prokhorovka, Omskaya kormovaya, Amir and Lada each had two or more measures significantly higher than the group average. In the midlate group, the winners were Omskaya 24 (grain weight per spike, grain number per spike and spikelet number per spike), Sibirskaya 16 (grain weight per spike and spikelet number per spike) and Ishimskaya 98 (1000-grain weight and spikelet number per spike). Varieties identified and characterized in this way can be used in the selection process as a source of higher 1000-grain weight, grain number per spike, spikelet number per spike and grain weight per spike. A tendency towards increase has been demonstrated for 1000-grain weight, spikelet number per spike and grain weight per spike depending on the length of the growing season. No reduction in vegetation period was observed in epiphytotic years in susceptible varieties as compared to resistant varieties.

The efficiency of donors in plant breeding depends on the degree of knowledge of the physiological and genetic background of agronomic traits. This research aims to assess the quantitative agronomic traits (1000-grain weight, grain weight, grain number, and spikelet number per spike) in soft spring wheat varieties with different ripening period in order to identify genotypes that show the best adaptation to the regional environment, a high yield, and resistance to stress. The agronomic traits were studied in 139 soft spring wheat varieties grouped according to the length of the vegetation period: mid-early and early (31 plants), mid-ripening (94 plants), and mid-late (14 plants). In Leningradskaya 97 and Rosinka 1 varieties from mid-early and early groups indices for grain weight per spike, grain number per spike, and spikelet number per spike were higher than the group average. In the middle group, Baganskaya 51, Prokhorovka, Omskaya kormovaya, Amir, and Lada had two or more indices significantly higher than the group average. In the mid-late group, the following cultivars were distinguished: Omskaya 24 (grain weight per spike, grain number per spike, and spikelet number per spike), Sibirskaya 16 (grain weight and spikelet number per spike), and Ishimskaya 98 (1000-grain weight and spikelet number per spike). The varieties identified and characterized based on several traits can be used in the breeding process as a source for increasing 1000-grain weight, grain number per spike, spikelet number per spike, and grain weight per spike. An increasing tendency was demonstrated for the 1000-grain weight, spikelet number per spike, and grain weight per spike depending on the length of the maturation. The reduction in the vegetation period was not observed during the epiphytotic years in the susceptible varieties compared to the resistant varieties. [ABSTRACT FROM AUTHOR]

Grain number per spike of wheat is lower in early sowing than in the conventional standard cultivation in Yamaguchi, Prefecture, Japan. Components of the grain number per spike in five cultivars were analyzed with respect to temperature during the spike development period throughout three growing seasons 2001/2002, 2002/2003 and 2003/2004 to find the cause of the problem of early sowing cultivation. The plants sown in early-October and late-November were called the early sown group and the standard group, respectively, in the following. Three of the five cultivars, Hokushin, Akitakko and Nanbukomugi, showed a strong winter habit, which requires very cold temperatures for spike differentiation. The other two cultivars, Iwainodaichi and Airakomugi, had a moderate winter habit. Grain number per spike and grain yield were decreased by early-sowing (compare with the standard group) in almost all cultivars throughout the three growing seasons. The three cultivars which had a strong winter habit had fewer spikelets per spike in the early-sown group than in the standard group. The other two cultivars which had a moderate winter habit had fewer grains per spikelet in the early-sown group. The higher the temperature during the spikelet formation phase, which is from flag leaf initiation to terminal spikelet initiation, the higher the number of spikelets per spike in the standard group. The spikelet number per spike in the early-sown group increased with the increase in productive tillers under fertile conditions. Such conditions also increased the grain number per spike.

The major vernalisation genes of VRN1 are well understood at the molecular level. However, their quantitative contributions to flowering time and grain yield related traits are not clear. In this study, we used a double haploid population (225 lines) of Westonia × Kauz in which the Vrn- A1a (Westonia), Vrn- B1a (Westonia) and Vrn- D1a (Kauz) were segregating, and a high resolution genetic map of 1,159 loci, to determine the quantitative contributions of Vrn- A1a, Vrn- B1a and Vrn- D1a for the days to anthesis and grain yield related traits in diverse environments. The major quantitative trait loci (QTL) of spikelet number per spike and days to anthesis were contributed by the winter alleles of VRN1. The QTL of the time of grain filling were contributed by the spring alleles of VRN1. The wild genotype ( vrn- A1vrn- B1vrn- D1) showed the latest flowering, the highest spikelet number per spike, lowest peduncle proportion and thousand grain weight in three environmental analyses, and the largest spikelet number per spike, which resulted in high kernel number per spike (KN) and grain weight (GW) in well-watered environments. One QTL of KN was located on 5B, contributed by winter allele of vrn- B1 in three environmental analyses, and one GW QTL was detected on 5A, contributed by the spring allele of Vrn- A1a in a drought environment. The results indicated that the genotype Vrn- A1avrn- B1Vrn- D1a would shorten the time to anthesis and give high GW and KN in drought environments. The early anthesis associated phenotype, peduncle proportion would provide an indicator in breeding programs. [ABSTRACT FROM AUTHOR]