Lodging Resistance In Wheat Research Articles

Haplotype Analysis and Linkage Disequilibrium at Five Loci inEragrostis tef

Eragrostis tef (Zucc.), a member of the Chloridoideae subfamily of grasses, is one of the most important food crops in Ethiopia. Lodging is the most important production problem in tef. The rht1 and sd1 dwarfing genes have been useful for improving lodging resistance in wheat and rice, respectively, in what has been known as the “Green Revolution.” All homologs of rht1 and sd1 were cloned and sequenced from 31 tef accessions collected from across Ethiopia. The allotetraploid tef genome was found to carry two rht1 homologs. From sequence variation between these two putative homologs, an approximate ancestral divergence date of 6.4 million years ago was calculated for the two genomes within tef. Three sd1 homologs were identified in tef, with unknown orthologous/paralogous relationships. The genetic diversity in the 31 studied accessions was organized into a relatively small number of haplotypes (2−4) for four of these genes, whereas one rht1 homeologue exhibited 10 haplotypes. A low level of nucleotide diversity was observed at all loci. Linkage disequilibrium analysis demonstrated strong linkage disequilibrium, extending the length of the five genes investigated (2−4 kb), with no significant decline. There was no significant correlation between haplotypes of any of these genes and their recorded site of origin.

Relationship between Lignin Metabolism and Lodging Resistance in Wheat

As a component of cell wall,lignin is believed to be relevant to mechanical intensity of culm.In this study,we investigated the dynamic changes of lignin content and activities of four enzymes involved in lignin metabolism in culm as well as the snapping resistance and lodging index of wheat(Tritcum aestivum L.) to disclose the relationship between lignin content and lodging resistance.The lignin content and activities of phenylalanine ammonia-lyase(PAL),tyrosine ammonia-lyase(TAL),cinnamyl alcohol dehydrogenase(CAD),and 4-coumarate:CoA ligase(4CL) were tested with the second internode of six cultivars with different lodging resistance.The snapping resistance and culm lodging index were determined at anthesis,milking,and maturity stages.The lignin content varied significantly among cultivars.Jimai 22 and Jimai 20,which showed high resistance to culm snapping and loging,had higher lignin content and the activities of PAL,TAL,CAD,and 4CL than other cultivars.The lignin content was negatively correlated with the actual lodging ratio(r = -0.83,P 0.05),and positively correlated with the snapping resistance of culm(r = 0.86,P 0.05).The activities of PAL,TAL,and CAD were positively correlated with lignin content with correlation coefficients of 0.78(P 0.05),0.77(P 0.05),and 0.85(P 0.05),respectively.Based on these results,we conclude that high activities of PAL and CAD are the enzymatic basis of increased lignin content,and the lignin content in culm can be used as an important indicator to evaluate lodging resistance of wheat.

Microsatellite Markers for Culm Wall Thickness and Anatomical Features of Solid Stem Wheat 86-741

Lodging is a big problem in further increasing yield of wheat(Triticum aestivum L.) . Development of variety with thickwall of basal internodes is an effective way to improve lodging resistance in wheat. A solid stem line "86-741" has been developed from the cross between hexaploid Triticale and common wheat,and acted as parent in lodging resistance breeding. To detect the gene(s) of culm wall thickness in 86-741,we made a cross between 86-741 and a stem hollow wheat line "Xinjiang Daomai" [Triticum petropavlovskyi Udacz. et Migusch] in 2004–2005 growth season,and developed its F2 population in 2005–2006 growth season. The F2 population was used for bulked segregation analysis(BSA) of the gene related to culm wall thickness by SSR markers. Anatomical analysis revealed that 86-741 had very smaller stem pith cavity with pith,thicker mechanical tissue and more vascular bundles than Xinjiang Daomai. The F1 progeny of the cross showed some tendencies to its parent 86-741:culm with smaller diameters of pith cavity than the parent Xinjiang Daomai. The percentage of mechanical tissue in F1 was smaller than that in 86-741,and the number of vascular bundles in F1 was less than that in 86-741,but more than that in Xinjiang Daomai. Two recessive genes relating to pith and a single dominant gene on 3BL relating to culm wall thickness were detected in 86-741,respectively. The gene controlling culm wall thickness was temporarily designated as Cwt-1. We found 3 microsatellite(SSR) markers Xgwm-247,Xgwm-340,and Xgwm-547 linking to Cwt-1,in which Xgwm-247 was the closest to the gene with genetic distance of 5.3 cM. Our results indicated that Xgwm-247 can be used in marker-assisted selection(MAS) for lodging resistance breeding by selecting culm wall thickness trait in wheat.

GENOTYPIC AND PHENOTYPIC CORRELATION AND PATH ANALYSIS FOR LODGING RESISTANCE TRAITS IN BREAD WHEAT (Triticum aestivum L.)

Relationships between the traits associated with lodging resistance in wheat were studied within the period of 1999-2002 at Wheat Research Center, Dinajpur in both F1 and F2 generations of a 9 × 9 diallel cross without reciprocal. The genotypic and phenotypic correlation coefficients studied in F1 and F2 generations were similar with some exceptions. In both F1 and F2 generation, the second internode breaking strength was positively correlated with diameter, wall thickness and unit-stem weight of second internode, and main shoot weight but negatively with plant height and second internode length at both genotypic and phenotypic levels. It was observed from path coefficient analysis in both F1 and F2 generations that the second internode unit-stem weight had high positive direct effect on it’s breaking strength. Main shoot weight, second internode diameter and wall thickness positively influenced breaking strength through its unit-stem weight. Simultaneous selection for the traits contributing to lodging resistant in semi-dwarf wheat might be effective in the improvement of lodging resistance in bread wheat.DOI: http://dx.doi.org/10.3329/bjpbg.v20i2.17036

Correlação de acamamento com rendimento de grãos e outros caracteres de interesse agronômico em plantas de trigo

A seleção indireta visando ao incremento no rendimento de grãos pelos seus componentes primários bem como a resistência ao acamamento podem representar estratégias eficientes a serem adotadas para otimização do ganho genético em trigo. Nesse sentido, o objetivo do trabalho foi evidenciar caracteres que possibilitem identificar genótipos de elevado rendimento de grãos e resistentes ao acamamento através de seleção indireta. O experimento foi conduzido no Centro Agropecuário da Palma, em Capão do Leão/RS, utilizando dezenove genótipos de trigo em delineamento de blocos ao acaso, com três repetições. Nas condições deste estudo, o peso hectolítrico pode ser empregado de maneira eficiente na seleção indireta, visando ao incremento no rendimento de grãos, no peso médio de grãos, número de grãos por espiga e no peso de espiga. O caráter peso de espiga evidenciou elevado efeito indireto sobre o rendimento de grãos, podendo ser empregado na seleção indireta pela facilidade de mensuração. A linhagem TB 951 é indicada como excelente fonte de resistência ao acamamento em trigo, podendo contribuir para elevar o comprimento de espiga, o número de espigueta por espiga, o peso de espiga e o número de grãos por espiga.

Genetics of lodging-resistance in wheat

Knowledge on the inheritance of lodging-resistance is of great value for the development of new wheat varieties (Triticum aestivum L.). Crosses among four different bread wheat genotypes were evaluated in the field. The analysis was based on three fixed (P 1, P2 and F1) and three segregant (F 2, BC1F1 and BC2F1) generations. Means and variances were computed for each generation in all crosses and the gene effects estimated. The lodging-resistance factor method (cLr) was measured. Partial or complete dominance of the lodging-susceptible over the lodging-resistant parent in each cross was evident. Results showed a large genetic variability among the genotypes.

Quantitative trait loci (QTL) of stem strength and related traits in a doubled-haploid population of wheat (Triticum aestivum L.)

Scoring for lodging resistance is difficult under natural field conditions. The stem strength of wheat has been used as an index of lodging resistance. However, this is a complex trait comprised of two characters, i.e. stem mechanical elasticity and rigidity. Therefore it is closely associated with stem morphological and anatomical features. A study of the genetics of stem strength and related traits of basal stem internodes is very important for genetic improvement of lodging resistance in wheat. In this study, a doubled-haploid (DH) population derived from anther culture of the cross CA9613/H1488 was used. Stem strength and related basal internode traits were measured at the milk stage. A molecular map of the DH population was constructed using 189 SSR markers, and quantitative trait loci (QTL) for each trait were analyzed based on this molecular linkage map. A total of six QTL for stem strength, culm wall thickness, pith diameter and stem diameter were identified: 1) Two QTL (QSs-3A and QSs-3B) for stem strength were detected on chromosomes 3A and 3B, exhibiting 10.6 and 16.6% phenotypic variance, respectively. 2) Two QTL (QPd-1A and QPd-2D) associated with pith diameter were detected on chromosomes 1A and 2D, respectively, jointly explaining about 30% of phenotypic variance. 3) As far as stem diameter and culm wall thickness were concerned, one QTL was detected on chromosomes 3B and 2D, respectively; QSd-3B explained 8.7% of the phenotypic variance of stem diameter, whereas QCwt-2D explained 9.6% of the phenotypic variance of culm wall thickness. In addition, among the QTLs detected, two with pleiotropic effects were observed. Correlated traits are usually associated with the pleiotropic effects of the same QTL(s) or linkage of different QTLs. But this was not true in some cases. The results of QTL mapping showed that stem strength can be improved by breeding for wider stems with a higher stem diameter/pith diameter ratio. This can be facilitated by using the markers linked to QSd-3B and QCwt-2D. Combining stem strength, stem diameter and culm wall thickness may be used as a selection index for lodging resistance with marker-assisted selection (MAS) to improve lodging resistance in this population.

Screening for lodging resistance in spring wheat breeding programmes

AbstractSelection for lodging resistance in Canadian hard red spring wheat under natural conditions is difficult due to the sporadic and often random nature of lodging events. We conducted field trials in Edmonton AB Canada (2000–2002) to determine if either a high seeding rate, or artificially inducing lodging (by dragging a weighted apparatus across plots at the early milk stage), would be an effective screen for determining genetic lodging resistance in wheat breeding programmes. For the 25 genotypes tested, applying artificial lodging at the experimental mean early milk stage was a suitable method to screen and identify lodging tolerant and susceptible genotypes. Tolerance to artificially induced lodging was mainly found within semi‐dwarf genotypes, and susceptibility was mainly found within Canadian bread wheat genotypes. Severe lodging resulted in yield losses as high as 40%. Lodging tolerant genotypes identified in this study are now being crossed into elite western Canadian bread wheat in an effort to increase genetic lodging resistance within Canadian breeding lines.

Spread of the Root System as Indicator for Evaluating Lodging Resistance of Wheat1

A technique for estimating the spreading angle of wheat roots is described and various methods of testing and sampling are discussed. The use of gravel beds with 3 or 4 replicates consisting of a single 1‐m row per variety or line and samples of 5 to 10 plants per row is recommended. High correlations were found between varietal means of spreading angles and lodging rates from a series of field trials grown under various environmental conditions. Spreading angle estimates may serve as a method of selecting for lodging resistance.