Study On Crossbreeding Of WRKY-transgenic Chrysanthemum Results In Hybrids With Improved Resistance To Aphids

Chrysanthemum?Chrysanthemum morifolium?,is among the ten traditionally famous flowers in China and the four leading cut-flowers worldwide,possessing great ornamental and commercial values.Aphid infestation causes serious damage to chrysanthemum,which has become a bottleneck in chrysanthemum production.Thus,it is of fundamental importance to develop new cultivars with strong aphid resistance.The present study made three cross combinations between 'Finch',CmWRKY53-and CWRKY33-transgenic and non-transgenic?wild type?chrysanthemum 'Jinba'.The targeted WRKY genes,aphid resistance,and some ornamental traits were investigated for the F₁ seedlings,aiming to verify the transmission of WRKY genes in sexual progeny and their influences on the phenotypic traits,and to obtain some original plant resources with both excellent ornamental traits and aphid resistance.Findings from this study will provide an important germplasm for breeding programs focusing on aphid resistance in chrysanthemum,and will be of great importance for other resistance/tolerance breeding method combining transgenic technique and conventional hybridization.The main results are as following:1.Crossing non-transgenic?wild type?,CmWRKY53-and CmWRKY33-transgenic chrysanthemum 'Jinba' with wild type 'Finch' resulted in 30 F₁ seedlings.Of which,two?numbered B-5 and B-7?with CmWRKY53 and five?numbered C-1,C-2,C-3 C-6 and C-9?with CmWRKY33 were identified,thus indicative of the possibility of transmission of CmWRKYs through sexual hybridization.2.Artificial aphid inoculation indicated that the F₁ seedlings?i.e.C-1,C-3,C-6,C-9?with CmWRKY33,compared with those without CmWRKYs,had an increased aphid resistance,with the maximum inhibition rate of aphid population density up to 30.59%;whereas,the F₁ seedlings?B-5,B-7?with CmWRKY53 had an increased aphid sensitivity.This suggests that the expression of CmWRKYs influence the performance of aphid resistance in hybrid progeny,and the pattern of aphid resistance of F₁ individuals are concordant with their male parents with corresponding CmWRKYs.3.The transgenic hybrids all grew normally,and most flower-related traits were maternally inherited in either CmWRKYs-transgenic or non-transgenic hybrid progeny and the difference were not significant.As for plant height and basal stem diameter,however,the F₁ hybrids w:ith CmWRKY33 had an increasing trend for these two traits in comparison with the hybrids without CmWRKY33.This suggests that the F₁ hybrids with CmWRKY33 possess a stronger survival ability,and consequently a larger probability of evolutionary success.