Comparison and Analysis on DUS Screening Traits of Two Lavender Species

Xiaoyu ZHUANG,Ling QIN,Pingsheng LENG,Man SHEN*

1.Plant Science and Technology College,Beijing University of Agriculture,Beijing 102206,China;

2.Landscape Architecture College,Beijing University of Agriculture,Beijing 102206,China

Responsible editor:Nanling WANG Responsible proofreader:Xiaoyan WU

Lavender (Lavandula spp.) is a kind of perennial herb or subshrub plant which belongs to Labiatae.It has beautiful shapes and leaves,and elegant flower color.Its whole plant has aromatic odor,so it is noted as a natural spiceberry and ornamental plant[1].

DUS(Distinctness,Uniformity and Stability)testing refers to the testing on distinctness,uniformity and stability for new varieties of plants which should be applied for the varieties right.Currently,main DUS testing method is field planting identification.In the testing process,quantitative traits are very important for completing the description of varieties’traits,with the continuous breeding of new varieties,the difference among varieties is smaller and smaller,so to assess the specificity using quantitative traits in DUS testing are increasing common,but human input and workload for the investigation of quantitative traits are the most,therefore,how to both lessen the workload and exactly reflect the accuracy of quantitative trait investigation is the urgent topic which needs to be solved at present.Xu Zhenjiang et al.[2]pointed out that statistical analysis was another significant identifying basis besides DUS testing.Combined with principal component analysis,information overlap[3]among different traits brought by correlations of varying degrees was solved effectively,making the analysis results more scientific and reasonable.Some foreign researchers[4-5]conducted in-depth discussions on the discriminated methods of specificity of quantitative traits of flower plants.Due to different observation periods and methods of each phenotypic character,these character data must be further sorted and analyzed.The previous methods are centesimal system method,fuzzy comprehensive evaluation method and analytic hierarchy process[6].

In this paper,based on the phenotypic characters in DUS testing of lavender,25 phenotypic characters therein were selected to observe and analyze the changes of different traits of Lavandula angustifolia and L.heterophylla in growth cycle,and analyze the correlations of traits within species population and between two species of lavender,as well as find out the differences between the two species of lavender and the growing laws of some characters in introduction areas,thereby providing some references for species (cultivar)identification,popularization and utilization in the introduction and breeding of lavender.

Materials and Methods

Plant materials

The tested two species of lavender were L.angustifolia and L.heterophylla from Lavandula and Hybrids strains,respectively.They were sowed in greenhouse in October of 2011; in March of 2012,the seedlings were transplanted to open field and planted in Tingzizhuang Test Base of Beijing University of Agriculture,the row spacing was 0.5 m×0.7 m,water and fertilizer were managed routinely.The two plants grew in open field for one year to ensure the stability of growth,data were collected during April and September in 2013.

Experimental methods

The partition of sampling areasReferring to the survey methods of Wan Nianfeng et al.[7],planting regions of each variety were classified as Sudoku according to north,south,east and west,nonadjacent three sampling areas were selected randomly,and 20 plants per area were chosen.

The discrimination of growth periodAccording to the division of flowering phase by Peng Guiqun[8],the whole growth period was divided into vegetative growth period (including earlier stage and later period) and reproductive growth period (including early flowering season,full-bloom stage and later flowering season).

The selection and observation of phenotypic characterConsulting the characters and observational methods recorded in Testing Guideline of New Lavender Variety issued by UPOV in 2002 and authorized by CPOV in 2004,25 phenotypic characters (including 10 quantitative traits and 15 qualitative traits)were selected and observed.From vegetative growth period to the end of flowering phase,observing once every 7 d,5 plants of each area were selected to investigate and count the 25 characters.

Data statistics and analysisAll experimental data were collected.Referring to Saudagar et al.[9]methods,the differences of same traits among different cultivars were analyzed using Duncan’s new multiple range method,and the correlations of different traits within species population were also researched using correlation coefficient method of matrix calculation.The analysis softwares were Microsoft Excel and DPS7.55.

Results and Analyses

Changes of each trait of vegetative growth stage

Changes of quantitative traitsAs seen in Table1,in vegetative growth stage,winter dormancy time of L.angustifolia was less than that of L.heterophylla (the time difference was 7 d according to the first observable time),thus L.angustifolia can better adapt to the introduction environment of Beijing.In total,the growth of L.angustifolia was superior to that of L.heterophylla,but the canopy of L.heterophylla was always greater than that of L.angustifolia during the vegetation process,the differences between two species and canopy were consistent with their growth habits:L.angustifolia exhibited an essentially vertical growth habit,and L.heterophylla showed a semi-erect or clumpy growth.At later stage of vegetative growth,there was no obvious difference in blade growing status of the two species,the blade length of L.heterophylla was slightly longer than that of L.angustifolia.

Changes of qualitative traitsAs shown in Table2,the plant morphology(including growth habit and compactness degree) of the two lavender species conformed to their characteristics and the observed results of contemporary plant height and canopy,indicating that the two lavender species kept the character stability during introduction planting period in Beijing area.Blade colors were the main phenotypic characters of that growth stage,gray and green degree of the blades of L.angustifolia changed in May and then began to stabilize,that was the same as that of L.heterophylla.As recorded in related data,blades of the two species had no incision.

Changes of each trait in the reproductive growth stage

Changes of quantitative traitsAs shown in Table3,in the reproductive growth stage,height and canopy of L.angustifolia were greater than these of contemporaneous L.heterophylla,that was,in the flowering phase,the whole plant of L.angustifolia had higher ornamental value.Since early flowering season,the growth of blades oftwo lavender species has changed compared to vegetative growth stage,in detail,blade length of L.heterophylla has tended to become stable,however,blade of L.angustifolia further grew lengthways and reached a stable state in middle full-bloom stage; blade width of the two lavender species basically has not changed,and blade width of L.angustifolia was slightly larger than that of L.heterophylla.

Table1 Changes of major quantitative traits of two lavender species during their vegetative growth stages

Table2 Changes of major qualitative traits of two lavender species during their vegetative growth stages

For the inflorescence,the inflorescence height (namely spray length)of L.angustifolia was generally higher than that of L.heterophylla,however,the inflorescence length and that above the second round between the two lavender species had not much difference,showing that the inflorescence of L.heterophylla occupied a larger proportion in the whole spray,thus from inflorescence of view,L.heterophylla had higher ornamental value.Furthermore,the bracteole of L.heterophylla was generally greater than that of L.angustifolia,and the withering degree in the later full-bloom stage was lower,but the bracteole of the two lavender species both dropped at the end of full-bloom stage.

Table3 Changes of major quantitative traits of two lavender species during their reproductive growth stages

Table4 Changes of major qualitative traits of two lavender species during their reproductive growth stages

Changes of qualitative traitsAs seen in Table4,from the whole shape,the plant and outer pedicel of L.angustifolia both showed en erect growth habit,which was more beautiful than L.heterophylla which had a semi-erect or loose growth habit.From the blade,resolution degree of blade color of L.angustifolia was superior to that of L.heterophylla,moreover,there was no incision in the blade edge of the two lavender species during their reproductive growth stages,thereby keeping the stability of the characters.

From the florescence,the florescence traits of the two lavender species were both planate cone,but in flower color,the corolla color of L.heterophylla in the alternative stage between early flowering season and fullbloom stage changed,making it more abundant in ornamental value than L.angustifolia.

Analysis on the differences of traits between L.angustifolia and L.heterophylla

From the statistical data of Table5,the differences of plant height and canopy in major quantitative traits between L.angustifolia and L.heterophylla were the highest,and correlation rates were 0 and 14.29%,respectively,these were entirely in line with the observed results of qualitative traits(plant:growth habit)corresponded by plant height and canopy of the previous vegetative phase and reproductive stage.In terms of the inflorescence,there were bigger differences in inflorescence height (pedicel length),inflorescence length above the second round,bracteole width and length,andthe corresponding correlation rates were 14.29%,21.43%,30.00% and 20.00%,respectively.

Table5 Analysis on the differences among main quantitative traits of two lavender species

Based on the difference analysis,we drew the conclusion that,on main ornamental traits of two lavender species,there were greater differences in plant parts and inflorescence parts,only few traits like long and narrow fade specific to lavender had small difference.

Analysis on the correlations among main quantitative traits of L.angustifolia and L.heterophylla

L.heterophyllaThe correlation coefficients among tested quantitative traits of L.heterophylla within growth cycle were indicated in Table6.From Table6,plant canopy showed extremely significant positive correlation with leaf length,number of flowering,inflorescence length above the second round,bracteole length and width; leaf length was highly correlated to number of flowering,inflorescence length above the second round,bracteole length and width; leaf width had extremely significant positive correlation with number of flowering and inflorescence length above the second round;inflorescence height showed extremely significant positive correlation with inflorescence length,bracteole length and width; number of flowering had extremely significant positive correlation with inflorescence length above the second round; bracteole length showed extremely significant positive correlation with its width.

L.angustifoliaThe correlation coefficients among tested quantitative traits of L.angustifolia within growth cycle were indicated in Table7.From Table7,plant height showed extreme-ly significant positive correlation with leaf width,number of flowering and inflorescence length above the second round; plant canopy had extremely significant positive correlation with leaf length,inflorescence height,total inflorescence length,bracteole length and width;leaf length was highly correlated to inflorescence height,total inflorescence length,bracteole length and width;leaf width had extremely significant positive correlation with total inflorescence length,bracteole length and width; inflorescence height showed extremely significant positive correlation with total inflorescence length,bracteole length and width; number of flowering had extremely significant positive correlation with inflorescence length above the second round; total inflorescence length showed extremely significant positive correlation with bracteole length and width; bracteole length showed extremely significant positive correlation with its width.

Table6 Correlation coefficients among each trait of L.heterophylla

Table7 Correlation coefficients among each trait of L.angustifolia

Conclusions and Discussions

In the study,taking 25 traits of lavender in DUS testing as the object,the change rules of different traits of L.angustifolia and L.heterophylla in growth cycle and the correlations of traits within species population and among different species of lavender were analyzed.The results showed that there was correlation among each phenotypic character of lavender,and the correlations among different phenotypic characters were different.The correlation coefficients of different traits of L.angustifolia and L.heterophylla were higher,reflecting the stability and consistency of the growth of two lavender species in introduction areas.

In addition,the further research should focus on principal component analysis on some traits with higher correlations.In evaluation,the importance of each trait as indicator was different,meanwhile,multiple traits may cause information overlap because of gene linkage or pleiotropism.Principal component analysis can transform numerous character indexes into relative independent principal components by dimension reduction,not only achieving information consolidation,but also avoiding falsity caused by information overlap; the weight of each integrated factor should be determined by its rate of contribution,and this was objective and reasonable[10-12].

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