Shade Tolerance Evaluation Of Chinese Wild Paeonia And Preliminary Study Of Cultivation Of Shade-tolerant Varieties

At present,most of the Chinese mainstream cultivars of herbaceous peony need sufficient light in their growth,and the main mode of production is field cultivation.In recent years,the cut flower market of Paeonia lactiflora has developed rapidly at home and abroad.In order to meet the market demand and improve the industrialization ability of Paeonia lactiflora,facility cultivation should be developed.Weak light is one of the main limiting factors of Paeonia lactiflora facility cultivation.There are few Paeonia lactiflora species adapting to the weak light environment of facility cultivation,so cultivating shade-tolerant varieties of Paeonia lactiflora has become an important way to solve this problem.Chinese wild Paeonia resources show shade tolerance in their native areas,but they are not fully involved in cross breeding research.In this study,the biological characteristics of P.internedia and P.emodi seeds were introduced in Beijing by seed introduction method,and the growth characteristics of P.anomala,P.internedia,P.anomala var.veitchii plants were introduced in Beijing by plant introduction method,and the shade tolerance was evaluated comprehensively from the aspects of morphological characteristics and photosynthetic physiology.Subsequently,hybrid breeding was carried out using Chinese wild Paeonia resources in China.Cytological mechanism of low compatibility was discussed,high compatibility hybrid combinations were screened and shade tolerance of hybrid offspring was evaluated.The results are as follows:1.The seedling emergence rate of P.internedia seeds introduced from Beijing is as high as 68.8%,and the effect of seed introduction is good.The seedling emergence rate of P.emodi seeds is only 0.05%,and the effect of seed introduction is poor.P.anomala,P.internedia and P.anomala var.veitchii plants introduced from Beijing were observed for two consecutive years.P.anomala plants grew well,but did not blossom.P.intermedia and P.anomala var.veitchii normally grow and blossom in Beijing area without special management and maintenance,showing the same morphological and ornamental characteristics as the original origin.Flowering period is about 1 month ahead of the original origin,and introduction is successful.2.70%shading treatment of P.anomala,P.internedia and P.anomala var.veitchii plants was carried out before germination.(1)The growth and flowering of Three Wild Peony plants and chlorophyll content were counted at full flowering stage.The results showed that under shading conditions,chlorophyll a and chlorophyll b contents increased,the leaf area of Three Wild Peony Species increased,and the plant width,branch length,stem diameter were basically the same as under full light.Flowering rate,amount of flowers and flower diameter of P.intermedia and P.anomala var.veitchii were basically the same under full light,and single flowering period was significantly prolonged for more than one day.Three kinds of wild Paeonia lactiflora showed strong adaptability and high shade tolerance under 70%shading conditions.(2)The diurnal changes of photosynthesis of P.anomala,P.internedia and P.anomala var.veitchii plants under full light and 70%shade conditions were measured at budding stage,20 days after flowering and 40 days after flowering.The results showed that the diurnal changes of net photosynthetic rate of three wild peony leaves under full light showed a "double peak" curve.Shading could alleviate the phenomenon of "noon rest" under full light,and the diurnal changes of net photosynthetic rate showed a "single peak" curve.The diurnal variation of stomatal conductance,intercellular CO2 concentration and transpiration rate showed that the net photosynthetic rate of three wild Paeonia Species was limited by non-stomatal factors.(3)The photosynthetic parameters and chlorophyll fluorescence parameters of P.anomala,P.internedia and P.anomala var.veitchii plants under full light and 70%shade conditions were measured at budding stage,20 days after flowering and 40 days after flowering.The results showed that apparent quantum efficiency,maximum photochemistry efficiency of PSII,potential activity of PSII,electron transfer rate of three wild Paeonia under shading conditions.The dark respiration rate,light compensation point and light saturation point decreased with the increase of photosynthetic rate,which showed the photosynthetic physiological characteristics of shade-tolerant plants.The comprehensive evaluation of shade tolerance by membership function method showed that the shade tolerance of three wild Paeonia species was close and significantly higher than that of cultivated Paeonia species.3.With P.lactiflora,P.internedia,P.anomala var.veitchii,P.emodi and P.sterniana as male parents,16 cross combinations were designed,552 flowers were pollinated,1352 seeds were obtained and 514 seedlings emerged.The distant hybridization of P.internedia,P.anomala var.veitchii,P.emodi and P.sterniana with cultivated varieties showed incompatibility in varying degrees.The Pollination Compatibility of two non-fruitful hybrid combinations P.lactiflora ’Fen Yunu’ × P.internedia and ’Qiao Ling’ ×P.intermedia was observed by fluorescence.The results showed that callose reaction of papillary cells occurred in both combinations after pollination,and the pollen tube of germination was distorted and stopped growing,which was the obstacle before fertilization.4.Before germination,the seedlings of 31 ’Qiao Ling’ ×P.anomala var.veitchii hybrid progenies were shaded by 70%,and 15 of them grew well after 40 days.The chlorophyll fluorescence parameters of 15 hybrid progenies were measured.The results showed that the number of shade-tolerant progenies of ’Qiao Ling’ × P.anomala var.veitchii was significantly higher than that of the progenies of interspecific crossing of Paeonia lactiflora,indicating that using P.anomala var.veitchii to participate in the crossing of Paeonia lactiflora could improve shade-tolerance of progenies.This study was the first to evaluate shade tolerance of Chinese wild Paeonia.The hybrid offspring with better shade tolerance were obtained by crossing wild Paeonia lactiflora,which laid a foundation for shade tolerance cultivation of Paeonia lactiflora and was of great significance for the development of protected cultivation and production of Paeonia lactiflora.