Muhammad Iqbal

Molecular characterization of vernalization response genes in Canadian spring wheat

Vernalization response (Vrn) genes play a major role in determining the flowering/maturity times of spring-sown wheat. We characterized a representative set of 40 western Canadian adapted spring wheat cultivars/lines for 3 Vrn loci. The 40 genotypes were screened, along with 4 genotypes of known Vrn genes, using previously published genome-specific polymerase chain reaction primers designed for detecting the presence or absence of dominant or recessive alleles of the major Vrn loci: Vrn-A1, Vrn-B1, and Vrn-D1. The dominant promoter duplication allele Vrn-A1a was present in 34 of 40 cultivars/lines, whereas the promoter deletion allele Vrn-A1b was present in only 1 of the western Canadian cultivars (Triticum aestivum L. Rescue) and 2 of its derivative chromosomal substitution lines. The intron deletion allele Vrn-A1c was not present in any line tested. Only 4 of the western Canadian spring wheat cultivars tested here carry the recessive vrn-A1 allele. The dominant allele of Vrn-B1 was detected in 20 cultivars/lines. Fourteen cultivars/lines had dominant alleles of Vrn-A1a and Vrn-B1 in combination. All cultivars/lines carried the recessive allele for Vrn-D1. The predominance of the dominant allele Vrn-A1a in Canadian spring wheat appears to be due to the alleles vernalization insensitivity, which confers earliness under nonvernalizing growing conditions. Wheat breeders in western Canada have incorporated the Vrn-A1a allele into spring wheats mainly by selecting for early genotypes for a short growing season, thereby avoiding early and late season frosts. For the development of early maturing cultivars with high yield potential, different combinations of Vrn alleles may be incorporated into spring wheat breeding programs in western Canada.

Flowering time in wheat (Triticum aestivum L.): a key factor for global adaptability

Wheat is one of the most widely cultivated crops and, being the staple diet of more than 40 countries, it plays an imperative role in food security. Wheat has remarkable genetic potential to synchronize its flowering time with favourable environmental conditions. This ability to time its flowering is a key factor for its global adaptability and enables wheat plant to produce satisfactory grain yield under very diverse temperature and soil moisture conditions. Vernalization (Vrn), photoperiod (Ppd) and earliness per se (Eps) are the three genetic systems controlling flowering time in wheat. The objective of this review is to provide comprehensive information on the physiological, molecular and biological aspects of the three genetic constituents of flowering and maturity time in wheat. Reviews written in the past have covered either one of the aspects; and generally focused on one of the three genetic constituents of the flowering time. The current review provides (a) a detailed overview of all three gene systems (vernalization, photoperiod and earliness per se) controlling flowering time, (b) details of the primer sequences, their annealing temperatures and expected amplicon sizes for all known markers of detecting vernalization and photoperiod alleles, and (c) anxa0up to date list of QTLs affecting flowering and/or maturity time in wheat.

Surface-induced alkene oligomerization: does thermal hydrosilylation really lead to monolayer protected silicon nanocrystals?

Surface functionalization of hydride-terminated silicon nanocrystals (SiNCs) with dodecene via thermal hydrosilylation has been reexamined. We observed the formation of dodecyl oligomers (n ≤ 4) during the reaction under an argon atmosphere at various predesigned temperatures (100-190 °C). In a comparative study, surface hydrosilylation and ligand oligomerization were found to be more pronounced under air (n ≤ 7) at the same temperatures. These observations strongly suggest that hydrogen abstraction by oxygen accelerates hydrosilylation and generates sufficient silyl radical as initiator to interact with unsaturated bonds, promote chain propagation, and generate ligand oligomers. We further propose that, to inhibit ligand oligomerization and obtain monolayer coverage on SiNC surfaces, it is feasible to apply comparatively low temperatures, inert atmosphere, and dilute ligand concentration during thermal hydrosilylation.

Genetic analysis of flowering and maturity time in high latitude spring wheat

Due to the short growing season in the high northern latitudes, the development of early maturing spring wheat (Triticum aestivum L.) cultivars is important to avoid frost damage which can lower production and quality. We investigated earliness of flowering and maturity, and some associated agronomic traits, using a set of randomly selected high northern latitude adapted spring wheat cultivars (differing in maturity) and their F1 and F2 crosses made in a one-way diallel mating design. The parents, and their F1 and F2 crosses were evaluated under field conditions over 2xa0years. Anthesis and maturity times were controlled by both vernalization response and earliness per se genes, mainly acting additively. Non-additive genetic effects were more important in controlling grain fill duration, grain yield and plant height. Additivexa0×xa0additive epistatic effects were detected for all traits studied except time to anthesis. Segregation analyses of the F2 populations for time to anthesis indicated the presence of different vernalization response genes. Molecular genetic analyses revealed the presence of Vrn-A1 and Vrn-B1 genes in the parental cultivars. Narrow-sense heritability was medium to high (60–86%) for anthesis and maturity times but low to medium (13–55%) for grain fill duration, plant height and grain yield. Selection for early flowering/maturity in early segregating generations would be expected to result in genetic improvement towards earliness in high latitude spring wheats. Incorporation of the vernalization responsive gene Vrn-B1 in combination with vernalization non-responsive gene Vrn-A1 into spring wheats would aid in the development of early maturing cultivars with high grain yield potential for the high latitude wheat growing regions of the northern hemisphere.

Borane-catalyzed room-temperature hydrosilylation of alkenes/alkynes on silicon nanocrystal surfaces.

Room-temperature borane-catalyzed functionalization of hydride-terminated silicon nanocrystals (H-SiNCs) with alkenes/alkynes is reported. This new methodology affords formation of alkyl and alkynyl surface monolayers of varied chain lengths (i.e., C5-C12). The present study also indicates alkynes react more readily with H-SiNC surfaces than equivalent alkenes. Unlike other toxic transition-metal catalysts, borane or related byproducts can be readily removed from the functionalized SiNCs. The new method affords stable luminescent alkyl/alkenyl-functionalized SiNCs.

The relationship between lodging and plant height in a diverse wheat population

We examined the genetic variation for lodging tolerance in different plant height groups, within a diverse population of wheat (Triticum aestivum L.) genotypes (n = 14 0). Lodging was artificially induced by dragging a weighted apparatus across plots twice during the season at early and late milk stages. Grain yield was negatively correlated with lodging, while lodging scores were positively correlated with plant height. Although plant height appeared to be the major contributor to lodging tolerance, some variation was also observed in taller plants. This suggests that genetic gain in lodging tolerance can be obtained, to some extent, independent of plant height. Key words: Plant height, lodging tolerance, Triticum aestivum L., CIMMYT, Canada

A genetic examination of early flowering and maturity in Canadian spring wheat

Under short-season western Canadian growing conditions, vernalization non-responsiveness is generally considered a preferable spring wheat (Triticum aestivum L.) phenotype, to avoid inconsistent maturity and yield patterns. The objectives of this study were to investigate the genetic factors affecting early flowering and maturity, and related agronomic traits, in a set of five Canadian spring wheat cultivars. The cultivars were first studied under 10- and 16-h photoperiods and 0- and 42-d vernalization treatments. Thereafter, the parents and F1 hybrids from a one-way diallel mating design were grown with and without a 42-d vernalization treatment. Shorter photoperiod delayed flowering time in all cultivars, and increased final leaf number in AC Barrie. Vernalization hastened flowering and decreased final leaf number in AC Foremost and AC Taber. AC Foremost and AC Taber carry at least one different allele, from the rest of the cultivars studied, at the major loci governing vernalization response. Leaf and ...

Genetic variation for flowering time and height reducing genes and important traits in western Canadian spring wheat

Genetic variation is prerequisite for wheat improvement. High grain yield and protein content and early maturity are some of the major objectives in global as well as Canadian wheat breeding programs. We investigated genetic diversity for earliness related and plant height reducing (Rht) genes in 82 spring wheat cultivars, registered in western Canada, through eight diagnostic DNA markers. Allelic variation was observed at the Vrn-A1, Vrn-B1, Vrn-D1 and Ppd-D1 loci but not at Ppd-A1 and Ppd-B1 loci in the 82 cultivars. Spring type allele of Vrn-A1 was present in 94xa0% cultivars, whereas only two cultivars carried spring allele of Vrn-D1. Among the four earliness related genes, the most frequent combination was Vrn-A1a, Vrn-B1, vrn-D1 and Ppd-D1b, which was found in 32 cultivars. As for the Rht genes, eight cultivars had Rht-B1b and 13 cultivars had Rht-D1b. All cultivars carrying dominant allele of Vrn-B1, photoperiod-insensitive allele of Ppd-D1 and height reducing allele of Rht-1 had shorter plants and higher grain yield but lower grain protein content. Days to heading and maturity showed positive genetic (rgxa0=xa00.65) and phenotypic (rpxa0=xa00.44) correlation, and were also positively correlated with grain yield and kernel weight but negatively correlated with test weight and protein content. Plant height was positively correlated with grain protein content (rgxa0=xa00.53; rpxa0=xa00.42), but negatively correlated with grain yield (rgxa0=xa0−0.47; rpxa0=xa0−0.14). Grain yield and protein content showed negative genetic correlation (rgxa0=xa0−0.57). Among the sixty cultivars from Canada Western Red Spring Class released over 100xa0years, the newest cultivar yielded 23xa0% more grain and had 15xa0% higher grain protein than the oldest cultivar ‘Red Fife’. Breeders in western Canada have incorporated vernalization and photoperiod insensitive and Rht genes in modern cultivars to promote early maturity, to make use of off-season nurseries abroad, and to improve lodging tolerance.

Earliness per se quantitative trait loci and their interaction with Vrn-B1 locus in a spring wheat population

In the spring wheat-growing regions of western Canada, early maturity is an important trait for timely harvest to avoid frost damage, and associated harvest and post-harvest problems. Earliness is genetically regulated by vernalization, photoperiod, earliness per se genes, and complex gene interactions. In this study, we explored the effect of these gene complexes on the expression of 11 agronomic traits in the CDC Tealxa0×xa0CDC Go Canadian western red spring wheat-mapping population. The population of 187 recombinant inbred lines was genotyped with 341 DArT polymorphic markers and a functional Vrn-B1 marker, and phenotyped over 3xa0years in replicated trials. The dominant allele of Vrn-B1 reduced the number of days to heading, flowering and maturity, and increased leaf color concentration and plant height, but did not affect grain yield in the presence of common genetic backgrounds with dominant Vrn-A1a and Ppd-D1 alleles at two epistatic loci, Vrn-A1 and Ppd-D1. A total of 21 QTLs were identified for all phenotypic traits recorded, except plant height and grain protein content. Two earliness per se QTLs were mapped on chromosomes 1A (QEps.dms-1A) and 4A (QEps.dms-4A) in all three growing seasons, contributing 15–27 and 8–10xa0%, respectively, to the total genetic variation in days to maturity. The two earliness QTLs and Vrn-B1 exhibited additive interaction. Lines carrying dominant alleles at these three loci headed, flowered and matured 1.7, 1.9 and 4xa0days earlier, respectively, but yielded 0.43xa0txa0ha−1 less than lines with recessive alleles.

Effect of Lr34/Yr18 on agronomic and quality traits in a spring wheat mapping population and implications for breeding

The locus Lr34/Yr18 plays an important role in conferring resistance to a number of fungal diseases and is thus an important component of global wheat breeding efforts. We investigated the differences in disease response and agronomic traits of the ‘CDC Teal’xa0×xa0‘CDC Go’ spring wheat population of 187 recombinant inbred lines (RILs) in relation to the presence/absence of the rust resistance gene Lr34/Yr18. Lines carrying the resistant allele of Lr34/Yr18 were taller, matured earlier, and yielded less grain with lower test weights than lines without Lr34/Yr18. Lines with or without the resistant allele of Lr34/Yr18 did not differ for grain protein content, SDS sedimentation volume, and for resistance to leaf spotting and common bunt. Lines with Lr34/Yr18 exhibited lower leaf and stripe rust infection than lines without it. We selected superior lines from the population based on high yield, protein content, SDS sedimentation, and the presence of the resistant allele of Lr34/Yr18 and grew them with continued selection in replicated yield trials over nine site-years. We attempted to combine Lr34/Yr18 with high yield, protein content, and SDS sedimentation suitable for the Canadian western red spring wheat class. Our results suggested that the population size we used was not large enough to obtain recombinants with high yield potential, high grain protein, and acceptable quality attributes. Moreover, selection for Lr34/Yr18 resulted in the elimination of lines with high yield potential. We therefore suggest using a population size of at least 310 to increase the potential of pooling Lr34/Yr18 with high grain yield and desirable agronomic and end-use quality attributes.