Studies On Self Cross Characteristics And Breeding Utilization Of Intergeneric Hybrids Between Chrysanthemum And Allied Genera

In allied genera of chrysanthemum, many wild species possess elite attributes such as resistance to to disease, insect, virus and environment, Crossostephium chinense is one of them. It is mostly found in the coastal forest, mainly distributed in the cracks of bed rock, and possesses high salt tolerance. But it is usually difficult to obtain hybrids between these allied genera species and chrysanthemum cultivars. Bridge parent is an effective way to overcome distant hybridization and transfer useful genetic variation to elite germplasm. Here, self cross has been made in3intergeneric hybrids, including (C. nankingense×T. vulgare)F1(JJ),(C. crassum×A. myriantha) F1(DD),(C. crassum×C. chinense) F1(DF), to study seed set characteristics of self cross and genetic characteristics of self cross offsprings; threse3intergeneric hybrids, as bridge parent, were hybrided with chrysanthemum to study the possibility of transfer useful genetic variation to chrysanthemum cultivars and innovate chrysanthemum germ plasm; salt tolerance inheritance was investigated to find the genetic mechanism of salt tolerance in relative genera species of chrysanthemum. The main results and conclusion are listed as follows:(1) No selfed seed was obtained in JJ. Only one first self cross offspring was obtained in DD; seed set of second self cross was lower, and no second self cross offspring was obtained.10first self cross offsprings and38second self cross offsprings were generated in DF, and compared toDF, seed set per flower of line2of the first self cross offsprings was higher. The chromosome number of first self cross offspring of DD was54. The chromosome number of3first self cross offsprings of DF were58,63,68, respectively, and were aneuploidy. Traits of selfed offsprings were observed. Some traits of selfed offspings of2intergeneric hybrids were inbreedingly depressed, especially inflorescence diameter, flower disc diameter, tubular florets number; variation of leaf length/leaf width was no significant, showing stable inbreeding inheritance. There is no variation between the first self cross offspring and DF in the flower type; the flower color of line2of the first self cross offspring is non-white. The second self cross offsprings of DF differentiated obviously in the flower color.(2) No seed was obtained between C. morifolium’Xiumandaihua’,’6045-7’and JJ. The seed set of cross and backcross between D. morifolium’Maoyan’and DD was very low, only one cross hybrid and three single backcross hybrids using C. morifolium’Maoyan’as paternal parent were obtained. The seed set of cross between C. morifolium’T1012’,’Han2’(both female parent) and DF was comparatively high, and single backcross hybrids using C. morifolium’T1012’as paternal parent were successfully obtained. The cross hybrids and backcross hybrids differentiated obviously from their parents in many morphological characters and chromosome number and salt tolerance, and there existed transgressive individuals and aneuploids. The results of salt tolerance identification showed that using intergenneric hybrids as bridge parent can successfully introduce the salt tolerance of A. myriantha and C. chinense into chrysanthemum cultivars, and improve its salt tolerance.(3) Progenies were obtained between C. morifolium’Han2’and DF. Based on salt harm index, salt tolerance inheritance of F1population was investigated by single generation segregation analysis method of the mixed major gene plus polygene mixed inheritance model of quantitative traits. The results showed that the transgressive segregation of salt tolerance commonly existed in F1progenies; salt harm index ranged from3.33%to96.67%, the phenotypic coefficient of variability was53.63%. Based on salt harm index, F1population could be divided into high salt tolerant, salt tolerant, middle tolerant, sensitivity, and high sensitivity grade, respectively; in which14.52%are high salt tolerant,38.70%are salt tolerant,30.65%are middle tolerant,9.68%are sensitive,6.45%are high sensitive. Salt tolerance of relative genera species of chrysanthemum accorded with B-2model with additive-dominant effect, additive and dominant effect of the first major gene were18.06,-17.99; additive and dominant effect of the second major gene were19.13,-1.44, respectively. The heritability of major genes for salt tolerance was61.14%. All those indicated that, as bridge parent, using the intergeneric hybrids to innovate salt tolerant chrysanthemum germ plasm is practicable. Two major genes with dominantly additive gene effects were detected for salt tolerance in relative genera species of chrysanthemum. The heritability of major genes was high, the salt tolerance fit to earlier choice.