| Potato(Solarium tuberosum L.)is one of the world's most important staple crops,ranked fourth after maize,rice,and wheat in terms of total production.Potato starch is of superior quality,and its unique properties make it attractive for food and industrial applications.Potato starch bioengineering has been an extensive subject of study over the past three decades.The characteristics of starch such as amylose content,thermal properties,pasting properties,mean diameter,size,and chain length distribution of amylopectin are considered as important traits to describe the quality of starch for various applications.The functionalities of potato starches for food and non-food applications are dependent on the starch structures and their properties,which are affected by genetics as well as environment.The main objectives of this study were to investigate the genetic diversity in potato germplasm and their relation with physicochemical and functional properties.1-Genetic diversity of 29 potato genotypes was estimated by their starch physicochemical properties.The AAC of potato starches averaged 25.3%,ranging from 18.8-29.1%.Significant differences were observed in pasting and gel texture properties among potato accessions.A wide range of diversity was found in the onset temperature,peak temperature,conclusion temperature,enthalpies of gelatinization,retrogradation and retrogradation percentage,which had a range of 58.7-62.5 0C,62.5-66.1 0C,68.7-72.3 0C,15.1-18.4 J/g,1.95-4.41 J/g,and 10.5-21,4,respectively.The AAC had a significant and positive correlation with the pasting viscosities and gel hardness but had no correlation with thermal and retrogradation properties.The genetic diversity of these 29 potato accessions were also investigated by microsatellite markers.The grouping of the potato genotypes using microsatellite markers was not completely corresponding to that drawn using the starch physicochemical properties.2-Chain length distribution is one of the fine structural parameters of starch,playing significant roles in determining starch physicochemical properties.Six pigmented potato cultivars were used to explore the relationship between starch structural properties and starch functional properties.It was found that the amylose content,the peak height of amylose and the first peak height of amylopectin significantly differed,whereas the other structure parameters had small variations among the potato starches.The average length of amylopectin side chains varied from 24.8-26.4 degree of polymerization(DP),and fractions fa,fb1,fb2 and fb3 of amylopectin showed no significant difference.A wide variation in the starch pasting and thermal properties was observed The correlation analysis indicated that the pasting properties were affected by the fine structures of both amylose and amylopectin,while the thermal properties were only affected by the amylopectin fine structure.These results contribute to our understanding regarding the structure-function relationships among potato starches.3-Seven potato accessions were planted at two different locations in Zhejiang province,E1(Yiwu)and E2(Jinhua),to assess the effects of growing locations on the starch fine structure and physicochemical properties.Potato starches showed significant differences in starch properties among cultivars and between two locations.The amylose content of debranched potato starches ranged from 18.3-20.9%and 19.0-21.6%in El and E2 respectively.Significant differences were found for XAM(the DP at the peak maxima of the amylose peak)in all potato cultivars growing in different locations,showing an obvious environmental effect.The mean value of fa(DP 6-12)was significantly affected by environment.A wide variation in the starch pasting and thermal properties was observed.The AAC of potato starches were ranged between 23.6-30.2%and 26.8-31.1%in El and E2 respectively.The lowest AAC was observed for Zhongshu-3 in both locations,whereas Favorita and N108 displayed the highest AAC values(30.2%,30.1%)in E1 and E2 respectively.The correlation analysis indicated that the pasting and thermal properties were affected by the fine structures of both amylose and amylopectin.These results further contribute to our understanding regarding the structure-function relationships among potato starches.4-The selection of superior clones from a large set of a population(more than 1000 clones)derived from the two parents(Zhongshu-3 and Favorita)for quality breeding was conducted.Initial screening was done on the basis of yield performance and 206 accessions(HP01-HP206)were selected.All 206 potato accessions were planted along with their parent plants at Jinhua as spring(2017)crop.Twenty breeding lines were selected and planted again at Hangzhou as an autumn(2017)crop to continue breeding work and analysis was done on the basis of starch physiochemical indices to check the quality.Although we had not found that a single genotype was superior in all of the analyzed traits,certain genotypes excelled in specific attributes.For example,HP206 line performed consistently in both locations and showed relatively higher AAC values(32.6%and 29.2%)in spring and autumn seasons respectively.While HP37 line performed consistently for peak viscosity in both locations and gave high values(478.0 RVU&486.8 RVU)in both seasons respectively.These genotypes may be useful parents in a breeding program to improve starch characteristics,producing cultivars containing all desirable traits.The variation which we have identified in our germplasm for different starch physiochemical indices is used for the development of new improved varieties with the desired quality traits.The results from this study will be very useful in the potato breeding program to obtain the ideal potato required for a region. |
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