Studies On Biological Characteristics Of The Twin-Embryo Seedling Rice

In the marram, the phenomenon of multiple embryo or seedling is the important embryological and morphological characteristics of apomictic species.Screening polyseedling materials from autotetraploid rice will help to find apomixes reproductive germplasm, thereby fix crop heterosis.These studies were made from the twin seedlings of autotetraploid rice mutant lines (D07-04-01),close lines (D07-02-01 and 01-04-01)and Ion Beam offspring (DP07-04-01).Seed vigor, seedling position and embryo position of these four tested materials were observed and calculated;By using plant tissue culture technology, we have did a comparative study on dedifferentiation and re-differentiation of rice seed and established a high-frequency plant regeneration system; Agronomic traits, pollen fertility, flower organ traits, differences in grain traits were compared among D07-04-01 and its tissue regeneration and the F1 progeny of tissue regeneration;With the help of chalky analysis software chalkiness 1.0, scanning electron microscopy and X-ray diffractometer, the appearance and eating quality of four materials were comparative determined.The results of these studies were included four parts as follows:1.Seed vigor, seedling position and embryo position of four tested materials were observed and identified.D07-04-01 has high seed vigor, its two-seedlings can be tranmitted,0.74% of the balance-power-same-sheath of seedlings and 0.59% of the unbalance-power-same-sheath of seedlings were observed, in addition, four kinds of unusual embryo positions including the top-located embryo, the radicle-free germ embryo, the germ-free radicle embryo, the germ-free radicle-free embryo have not been seen;Seedling position and embryo position of D07-02-01 are the most abundant,some rare three seedlings have been observed.2.Rice seed callus induction and regeneration system were built. The results show that the optimum concentration of 2,4-D is different for distinct rice genotypes. The concentration of 2.5mg/L is the most suitable for autotetraploid rice; Half-endosperm treatment is more easy to operate than non-endosperm treatment. With the half-endosperm treatment, embryo is not easy hurt, callus induction rate is high and callus quality is good;Callus differentiation rate can be improved by dried-treatment.3.Major agronomic traits of four test materials were compared.Compared with D07-04-01,TCD07-04-01has no significant difference in five major agronomic traits; its normal pollen rate is lower; floral organ traits are quite different;single-shell mutation is the most, comparatively D07-04-01 has more three-shell mutation;grain traits is quite different. Concludingly, greatly somaclonal variation of rice plants were happened at different levels through tissue culture. Compared with TCD07-04-01, F1TCD07-04-01 has no significant difference in five major agronomic traits;its normal pollen rate is higher; Distinction of floral organ traits is quite little; The mutations of glume number is much less than TCD07-04-01;grain traits has little difference. We can conclude that seeding propagation of this material can maintain parental traits at a maximum degree.4.Grain characteristics of four test materials were observed and identified.By the determination of chalkiness, the microscopic observation of cross-sectional and rice starch grains, and the X-ray diffraction analysis of starch crystal,we found that there are different degrees of cross-sectional radial and cracks, hypoplastic endosperm cells and unsufficient accumulated starch which loosely arranged, and the amylose content is high of three autotetraploid rice strains, while the chalkiness of diploid rice strain D07-02-01 is the best, there is no radial grain cross section, its cracks is small and shallow, the overall development of starch is better, those starch is showing a typical crystal structure, the appearance of the whole grain is glassy and transparent, and its amylose content is low. Although compared with the traditional diploid, grain quality of the autotetraploid rice is slightly inferior, this shortage has pointed out a direction and challenge for future breeding of autotetraploid rice.