Iqbal Muhammad A, Rahman Mehboob-Ur-
Plant Genomics and Molecular Breeding Lab (PGMB), Agricultural Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE)Faisalabad, Pakistan; Department of Biotechnology, Pakistan Institute of Engineering and Applied Sciences (PIEAS)Nilore, Islamabad, Pakistan.
Front Plant Sci. 2017 Feb 6;8:86. doi: 10.3389/fpls.2017.00086. eCollection 2017.
Harvesting high quality lint, a long-awaited breeding goal-accomplished partly, can be achieved by identifying DNA markers which could be used for diagnosing cotton plants containing the desired traits. In the present studies, a total of 185 cotton genotypes exhibiting diversity for lint traits were selected from a set of 546 genotypes evaluated for fiber traits in 2009. These genotypes were extensively studied for three consecutive years (2011-2013) at three different locations. Significant genetic variations were found for average boll weight, ginning out turn (GOT), micronaire value, staple length, fiber bundle strength, and uniformity index. IR-NIBGE-3701 showed maximum GOT (43.63%). Clustering of genotypes using Ward's method was found more informative than that of the clusters generated by principal component analysis. A total of 382 SSRs were surveyed on 10 genotypes exhibiting contrasting fiber traits. Out of these, 95 polymorphic SSR primer pairs were then surveyed on 185 genotypes. The gene diversity averaged 0.191 and the polymorphic information content (PIC) averaged 0.175. Unweighted pair group method with arithmetic mean (UPGMA), principal coordinate analysis (PCoA), and STRUCTURE software grouped these genotypes into four major clusters each. Genetic distance within the clusters ranged from 0.0587 to 0.1030. A total of 47 (25.41%) genotypes exhibited shared ancestry. In total 6.8% ( ≥ 0.05) and 4.4% ( ≥ 0.1) of the marker pairs showed significant linkage disequilibrium (LD). A number of marker-trait associations (in total 75) including 13 for average boll weight, 18 for GOT percentage, eight for micronaire value, 18 for staple length, three for fiber bundle strength, and 15 for uniformity index were calculated. Out of these, MGHES-51 was associated with all the traits. Most of the marker-trait associations were novel while few validated the associations reported in the previous studies. High frequency of favorable alleles in cultivated varieties is possibly due to fixation of desirable alleles by domestication. These favorable alleles can be used in marker assisted breeding or for gene cloning using next generation sequencing tools. The present studies would set a stage for harvesting high quality lint without compromising the yield potential-ascertaining natural fiber security.
收获高品质皮棉，这一期待已久的育种目标已部分实现，可通过鉴定DNA标记来实现，这些标记可用于诊断具有所需性状的棉花植株。在本研究中，从2009年评估纤维性状的546个基因型中，共选出185个皮棉性状表现出多样性的棉花基因型。这些基因型在三个不同地点连续三年（2011 - 2013年）进行了广泛研究。发现平均铃重、轧花率（GOT）、马克隆值、纤维长度、纤维束强度和整齐度指数存在显著遗传变异。IR - NIBGE - 3701的轧花率最高（43.63%）。发现使用沃德法对基因型进行聚类比主成分分析生成的聚类更具信息性。在10个表现出不同纤维性状的基因型上共检测了382个简单重复序列（SSRs）。其中，95对多态性SSR引物随后在185个基因型上进行了检测。基因多样性平均为0.191，多态信息含量（PIC）平均为0.175。非加权算术平均法（UPGMA）、主坐标分析（PCoA）和STRUCTURE软件将这些基因型各自分为四个主要聚类。聚类内的遗传距离范围为0.0587至0.1030。共有47个（25.41%）基因型表现出共同祖先。总共6.8%（≥0.05）和4.4%（≥0.1）的标记对显示出显著的连锁不平衡（LD）。计算了许多标记 - 性状关联（共75个），包括平均铃重13个、轧花率百分比18个、马克隆值8个、纤维长度18个、纤维束强度3个和整齐度指数15个。其中，MGHES - 51与所有性状相关。大多数标记 - 性状关联是新发现的，而少数验证了先前研究中报道的关联。栽培品种中有利等位基因的高频率可能是由于驯化使理想等位基因固定。这些有利等位基因可用于标记辅助育种或使用下一代测序工具进行基因克隆。本研究将为在不影响产量潜力的情况下收获高品质皮棉奠定基础，确保天然纤维安全。
