Growth Performance of Larval and Juvenile Manila Clam(Ruditapes philippinarum) from Divergently Selected Individuals of a Full-Sib Family

Abstract In this study, the method of divergent selection was employed to test the larval and juvenile growth performance within a full-sib family of Manila clam Ruditapes philippinarum. The 10% largest and 10% smallest clam individuals （on the basis of shell length） of a full-sib family were selected as parents for the fast and slow growing lines, respectively. The difference in shell length was significant among the three lines （fast, control, and slow） tested. The sequence of shell length were fast line 〉 control line 〉 slow line. The responses to selection, realized heritability, and genetic gain were 0.06%-0.81%, 0.04%-0.47% and 0.58%-18.89% in the fast direction, respectively; and were 0.14%-1.27%, 0.08%-0.73%, and 0.31%-49.03% in the slow direction, respectively. The re- suits suggested that there was a large portion of additive genetic variance affecting the growth in the full-sib family. Selection in the fast direction within the full-sib family would greatly improve the growth ofR. philippinarum.

Comparisons of Three Recurrent Selection Methods in the Improvement of Maize Populations

The maize population Csyn 4 was improved for three cycles with three recurrent selection methods MS1, MS1-HS, and MHSRRS in northern China. A total of 40 NC Ⅱ testcrosses were made by four testers with Csyn 4 and 10 improved populations, which were evaluated in four environments in the cropping season of 2005. Analysis of variance indicated a significant progress （P〈 0.05） in yield and other chief agronomic traits in the improved populations and testcrosses, demonstrating that the three recurrent selection methods were effective for increasing grain yield of testcrosses and improvement of general combining ability in maize population. The average grain yield increase of population Csyn 4 in MS1, MS1-HS, and MHSRRS recurrent selections was 266.7 kg ha^-1 （5.3%）, 288.0 kg ha^-1 （5.7%）, and 231.3 kg ha^-1 （4.6%） per cycle, while the grain yield of S 1 progeny of population for Csyn 4 was increased by 420.0 kg ha^-1 （10.9%）, 376.0 kg ha^-1 （9.8%）, and 414.7 kg ha^-1 （10.8%） per cycle in MS1, MS1-HS, and MHSRRS recurrent selections, respectively. Linear responses （b） in the MS1, MS1-HS, and MHSRRS recurrent selections were the same as the realized responses of the selection （G） for grain yield increase of Csyn 4 and S1 progeny of the populations. The grain yield of testcrosses increased by 3.3-5.2% on average per cycle. The value of heterosis did not display any differences amongst the different cycles of selections. The GCA for yield component traits of population Csyn 4 was improved significantly by means of three selection methods, whereas the GCA for plant height, ear height, days to silking, and days to pollen did not show significant increase in the recurrent selections. GCA for the number of tassel branches were decreased in the selections, while GCA for the number of plant leaves were increased, but the difference was not significant.

导入br-2温带矮生系的热带玉米种质利用研究

利用温带优良玉米自交系矮351中br-2基因致矮特性,将其导入热带血缘种质,并对组建的温热群体进行品系内全同胞群体轮回选择和表型评价,研究隐性单基因br-2矮源导入热带血缘玉米种质在改良异源种质资源中的效果。轮回选择结果显示,群体产量平均每轮增益6.4%;倒伏率平均每轮增益达5.6%。成功选育出两个优良自交系南381和南387,囊括了热带和温带种质的主要优良特性。组配的杂交种南玉8号、惠玉537和隆单9号通过四川省玉米品种审定并被大面积推广应用。

Study of Autosomal Short Tandem Repeat Loci Using ITO Method in Full‑Sibling Identification

This study aimed to investigate the application of autosomal short tandem repeat(STR)loci using the ITO method and discriminant function algorithm for full‑sibling(FS)identification.A total of 342 pairs of full siblings(FSs)and 3900 pairs of unrelated individuals(UIs)were genotyped at 51 STR loci.The groups were in accordance with discrimination power(DP)values and the number of loci,and the values of FS index(FSI)of FSs and UIs were calculated by the ITO method.The discriminant functions of FS–UI were established using the Fisher’s discriminant analysis method with SPSS 19.0 software.All the lgFSI values in the FS and UI groups followed a normal distribution,and there were significant differences between the two pairs.A higher average DP value was associated with a more significant difference,as was a greater number of STR loci detected.Receiver operator characteristic curves showed that the accuracy of FS identification can be affected by both locus polymorphism and the number of loci detected.Comparing the rate of false positives and false negatives of discriminant function between the two groups,a higher average DP value and larger number of loci detected were associated with a lower rate of miscarriage of justice and were more helpful for FS–UI identification.The ITO‑based discriminant analysis method has high applicability in FS–UI tests.Testing of a greater number of STR loci promotes FS identification.