Zhi-hua Yuan

Genome-Wide Association Study of Grain Appearance and Milling Quality in a Worldwide Collection of Indica Rice Germplasm

Grain appearance quality and milling quality are the main determinants of market value of rice. Breeding for improved grain quality is a major objective of rice breeding worldwide. Identification of genes/QTL controlling quality traits is the prerequisite for increasing breeding efficiency through marker-assisted selection. Here, we reported a genome-wide association study in indica rice to identify QTL associated with 10 appearance and milling quality related traits, including grain length, grain width, grain length to width ratio, grain thickness, thousand grain weight, degree of endosperm chalkiness, percentage of grains with chalkiness, brown rice rate, milled rice rate and head milled rice rate. A diversity panel consisting of 272 indica accessions collected worldwide was evaluated in four locations including Hangzhou, Jingzhou, Sanya and Shenzhen representing indica rice production environments in China and genotyped using genotyping-by-sequencing and Diversity Arrays Technology based on next-generation sequencing technique called DArTseq™. A wide range of variation was observed for all traits in all environments. A total of 16 different association analysis models were compared to determine the best model for each trait-environment combination. Association mapping based on 18,824 high quality markers yielded 38 QTL for the 10 traits. Five of the detected QTL corresponded to known genes or fine mapped QTL. Among the 33 novel QTL identified, qDEC1.1 (qGLWR1.1), qBRR2.2 (qGL2.1), qTGW2.1 (qGL2.2), qGW11.1 (qMRR11.1) and qGL7.1 affected multiple traits with relatively large effects and/or were detected in multiple environments. The research provided an insight of the genetic architecture of rice grain quality and important information for mining genes/QTL with large effects within indica accessions for rice breeding.

Effects of Different Culture Conditions to Middle-season Rice "Feng-liang-you-xiang -1"

To study the impact of different culture conditions to the growth and yield, an orthogonal experiment was conducted with four factors ¡X sowing date, basic seedling, nitrogen rate and water depth and three levels (L934)about Mid-season Hybrid Rice Feng-liang-you-xiang-1 for three years ( 2009 ~ 2011). The results showed that: ?The effect of the climatic conditions in different years on the growth duration and yield of mid-season rice is very significant, ?The effect of sowing date on the growth duration and yield of mid-season rice is very significant. As the sowing date is delayed, the growth duration is shortened. (y =-0.2222x +132.98; R =0.9983*, y represents growth duration, and x represents sowing date). When the sowing date was May 1, the yield was the highest, ?The effect of nitrogen rate on the growth duration and yield of mid-season rice is also very significant. As the nitrogen rate increases, the growing duration and yield shows an increasing trend. The overall conclusion was that the yield was the highest when planting on May 1, with a basic seeding number of 480000/hm2, a nitrogen rate of 135kg+120kg+105kg/hm2 and a water depth just casing the surface of field when transplanting.

A Cultivation Technique of Direct Seeding Rice Adapted to Cold Soaked Mud Field in the Mountains Southwest Hubei

The S-W Hubei area is located in the southwest of Hubei, with high-elevation terrain, unique climate, and lots of cold soaked fields. On account of the environmental characteristics of cold soaked mud fields, the procedure of direct seeding cultivation within ridging and plastic film mulching was introduced. The application of this technique can exalt the tiller node, increase the available soil nutrients of cold soaked mud fields, and improve the economic structure and the technical effect of yield, and the corresponding recommendations on the application of mechanical support, economic cost and technical standard were made.

Application of Direct Seeding Cultivation within Ridging and Plastic Film Mulching to Cold Soaked Mud Fields in Southwest of Hubei

Southwest of Hubei, a mountain with high-elevation (1500 m above sea level), distributed lots of cold soaked fields which have a low productivity of rice. In order to raise its productivity, a method of cultivation was tested that is direct seeding cultivation within ridging and plastic film mulching. The results showed that the technique can play a bit to exalt tiller node, increase the effective soil nutrients in cold soaked mud fields, improve economic structure, and develop the technical effect of rice yield. Finally, for its best application in agricultural practice, it gave some suggestion relevant to agricultural machinery use, economic cost and technical standards.