Improvement Of Amylose Content In Hybrid Rice Tianyou 3611 By Molecular Marker-assisted Selection

Rice is one of the most important food crops,and its grain quality will directly affect the commercial and cooking values.Starch is the main composition of the rice endosperm,and its composition and structure directly influences the rice grain quality.Normal cereal starch is made up of long-chain linear amylose with a few branches and large numbers of highly branched short-chain amylopectin.In rice,amylose content was thought to be the key components affecting rice eating and cooking qualit.In general,a higher AC is usually associated with a harder texture of cooked rice in indica rice.Expression levels of Wx and OsGBSSI activity in the endosperm are therefore used as key determinants of rice grain quality variation.In this study,in order to improve the grain quality of indica hybrid rice Tianyou 3611,the Wxin and Wxb alleles were introduced into the parents of hybrid rice Tianyou 3611 through backcross and marker-assisted selection method.The main results are as follows:(1)We developed a tetra-primer amplification refractory mutation system-PCR(ARMS-PCR)for detecting one single nucleotide polymorphism in extron 6 of Wx.This ARMS-PCR was used to detect Wxa and Wxin.Also the SSR marker QRM190 was used to detect Wxa and Wxb.Using this two markers,we constructed the near-isogenic lines(NILs)containing Wxin or Wxb using restore line 3611 as recurrent parent,9311 or IR64 as the donor parents by marker-assisted selection(MAS).The agronomic trait and the physicochemical properties of the NILs were analyzed.The results showed that the agronomic trait of the NILs was almost the same as the wiltd type except for the grain appearance quality.Further more,we found the different Wx alleles have significant effects on amylose content,and the lines with Wxa have a high amylose content of around 25%,while the case of Wxin have a medium one for 23.3%and Wxb have the minimum one of about 15.5%in the 3611 background.Besides,the gel consistency,viscosity and pasting properties were also changed according to the subsutitution of different Wx alleles.(2)Using the ARMS-PCR methord,we constructed the near-isogenic lines(NILs)containing Wxin using maintain line Tian feng B as recurrent parent,IR64 as the donor parents.We analyzed the agronomic trait and the physicochemical properties of the NILs.We found that the NILs showed similar agronomic characteristics compared with the wild type.For the grain physico-chemical quality,lines with Wxin showed a decreased amylose content and an increased gel consistency,also improved RVA profiles but no significant change for GT.(3)By using the improved parents,several hybrid lines were generated,including the cross combinations Tian feng A/3611?Tian feng A/3611-Wxin?Tian feng A/3611-Wxb?Tian feng B/3611?Tian feng B-Wxin/3611-Wxin?and Tian feng B/3611-Wxb.The agronomic trait and the physicochemical properties of the NILs were analyzed.The results showed that the different cross combinations have a similar agronomic trait except for the relative poor grain apparent quality in the cross combinations generated by the NILs.In terms of rice grain physicochemical properties,the cross combinations Tian feng B-Wxin/3611-Wxin,Tian feng A/3611-Wxb and Tian feng B/3611-Wxb exhibited a significant lower amylose content compared with the control cross combinations Tian feng A/3611 and Tian feng B/3611.More ever,these improved cross also showed an improved gel consistency and RVA profiles.However,the grain physicochemical properties of the cross combinations Tian feng A/3611-Wxin and Tian feng B/3611-Wxin showed no significant improvement.