Abdul Mujeeb-Kazi

High-molecular-weight (HMW) glutenin subunit composition of the Elite-II synthetic hexaploid wheat subset ( Triticum turgidum × Aegilops tauschii ; 2 n = 6 x = 42; AABBDD)

Characterization of high-molecular-weight (HMW) glutenins is an important criterion for identifying genotypes with good bread-making quality. In synthetic hexaploids (SHs), the D-genome encodes several allelic variants of HMW glutenins that require proper identification prior to their utilization for bread wheat (BW) improvement. In this study, SHs with promising agronomic features were characterized for HMW glutenin composition. Seven different allelic variants were observed at the Glu-D t 1 locus, three of which (1Dx1.5 þ 1Dy10, 1Dx1.5 þ 1Dy12.2 and 1Dx2.1 þ 1Dy10) have not been previously reported in existing BW germplasm. The results also showed a variety of D-genome-encoded subunits along with superior glutenin alleles in the B-genome (1Bx7 þ 1By8, 1Bx6 þ 1By8 and 1Bx13 þ 1By16). About 63% of these SHs encoded favourable allelic variants of HMW glutenins, which make them a good choice for improvement in wheat bread making. Glu-D t 1 encoded favourable allelic variants (1Dx5 þ 1Dy10 and 1Dx1.5 þ 1Dy10) that are frequently observed in SHs can be easily incorporated into BW through recombination breeding.

Karnal bunt resistance in synthetic hexaploid wheats (SH) derived from durum wheat × Aegilops tauschii combinations and in some SH × bread wheat derivatives

Bridge crosses utilizing the D genome synthetic hexaploids (SH), Triticum turgidum / Aegilops tauschii (2n = 6x = 42, AABBDD), are a potent means of improving bread wheat ( T. aestivum ) for biotic and abiotic stresses. The synthetic germplasm enables incorporation of the genetic diversity of T. turgidum cultivars together with the attributes of the Ae. tauschii accessions. In this research, SH wheats were screened for karnal bunt in Obregon, Mexico over six crop cycles and several SHs were earlier identified with an immune response. These SHs have unique Ae. tauschii accessions as parents. Phenologically descriptors and additional trait evaluations led us to develop a sub-set of the most desirable combinations for wheat breeding. The SH wheats are generally tall, late to mature, have good agronomic type, and are non-free threshing with a high 1000 kernel weight. All have a spring growth habit with several possessing multiple stress resistances. The resistance exhibited by SH wheats has been transferred i...

Allelic variation and composition of HMW-GS in advanced lines derived from d-genome synthetic hexaploid / bread wheat ( Triticum aestivum L.)

The objective of this study was to identify allelic variations at Glu-1 loci of wheat (Triticum aestivum L.) advanced lines derived from hybridization of bread wheat and synthetic hexaploid wheats (2n = 6x = 42; AABBDD). Locally adapted wheat genotypes were crossed with synthetic hexaploid wheats. From the 134 different cross combinations made, 202 F8 advanced lines were selected and their HMW-GS composition was studied using SDS-PAGE. In total, 24 allelic variants and 68 HMW-GS combinations were observed at Glu-A1, Glu-B1, and Glu-D1 loci. In bread wheat, the Glu-D1 locus is usually characterized by subunits 1Dx2+1Dy12 and 1Dx5+1Dy10 with the latter having a stronger effect on bread-making quality. The subunit 1Dx5+1Dy10 was predominantly observed in these advanced lines. The inferior subunit 1Dx2+1Dy12, predominant in adapted wheat germplasm showed a comparative low frequency in the derived advanced breeding lines. Its successful replacement is due to the other better allelic variants at the Glu-D1 locus inherited in these synthetic hexaploid wheats from Aegilops tauschii (2n = 2x = 14; DD).

Powdery mildew resistance in some new wheat amphiploids (2n 5 6x 5 42) derived from A- and S-genome diploid progenitors

Triticum urartu possesses the A u genome common to bread wheat. Similarly, Triticum monococcum contains the A m genome, which is closely related to the A-genome donor of bread wheat. Aegilops speltoides of the Sitopsis section has the S genome, which is most similar to the B genome of bread and durum wheat when compared with all other wild grasses. Amphiploids developed through bridge crossing between A m /A u and S-genome diploid resources and elite durum cultivars demonstrate enormous diversity to improve both bread and durum wheat cultivars. We evaluated such A-genome amphiploids (Triticum turgidum £ T. urartu and T. turgidum £ T. monococcum ,2 n ¼ 6x ¼ 42; BBAAA m A m /A u A u ) and S-genome amphiploids (T. turgidum £ Ae. speltoides ,2 n ¼ 6x ¼ 42; AABBSS) along with their durum parents (AABB) for their resistance to powdery mildew (PM) at the seedling stage. The results indicated that 104 accessions (53.6%) of A-genome amphiploids (AABBA m A m /A u A u ) were resistant to PM at the seedling stage. Of their 24 durum parents, five (20.83%) were resistant to PM and 16 (66.6%) were moderately tolerant. Similarly, ten (50%) accessions of S-genome amphiploids (BBAASS) possessed seedling PM resistance, suggesting a valuable source of major resistance genes. PM screening of the amphiploids and parental durum lines showed that resistance was contributed either by the diploid progenitors or durum parents, or both. We also observed the suppression of resistance in several cases; for example, resistance in durum wheat was suppressed in respective amphiploids. The results from this germplasm screening will facilitate their utilization to genetically control PM and widen the genetic base of wheat.

Cytological, Phenological and Molecular Characterization of B (S)-Genome Synthetic Hexaploids (2n = 6x = 42; AABBSS)

The B(S) genome diploids (2n = 2x = 14) are a unique reservoir of genetic diversity that can provide wheat breeders a rich source of allelic variation for stress traits that limit productivity. Restricted in practical use essentially due to their complex chromosomal behavior, these diploids have been in limited practical usage. The classic utilization example has been the suppression activity of the Ph locus and role in alien genetic transfer aspects that has been a standard in cytogenetic manipulation studies. For applied efforts focusing on Aegilops speltoides researchers in CIMMYT initiated an ambitious program to make AABBBB(SS) synthetics and made progress by generating over 50 such synthetics. Of these 20 were available for this study in which phenology and powdery mildew screening were evaluated. Four of these 20 synthetics appeared to be useful sources for further exploitation in breeding. These were entries 6, 9, 10 and 11 suited for exploitation in pre-breeding, with positive phenological characters particularly high thousand-kernel weight and are cytologically near euploid at 2n = 6x = 42. The subtle hyper (43) and hypoploid number would not negate their applied use potential. Preference however goes to genotypes 9 and 11.

An Overview of Omics for Wheat Grain Quality Improvement

Cereal grain quality aspects are integral aspects of a complex food chain, which assimilate outputs achievable by breeding, production and processing. In order to get better economic gains and be internationally competitive in diverse market scenarios, it is paramount to breed wheat cultivars with better grain quality. Higher grain quality demands are exponentially increasing due to novel processing technologies, environmental changes and change in consumer preferences due to striking demographic shifts. Advances in the genomic arena of grain quality are considered crucial for defining genes and their networks underpinning functional flour qualities. The complexities associated with the genes underlying these traits can be resolved by elucidating functional and comparative genomics information of relevant genes and the efficient transfer of such information across cultivars. Wheat, due to wider consumption as a staple food, has been a subject of intensive cytogenetic investigations which are now extended further in the genomics era using powerful tools of molecular biology and new genetic stocks. The recent progress in wheat genomics research particularly the use of molecular markers for a variety of purposes and advances in map based positional cloning of several genes has been remarkable. As a result we have been able to better understand the wheat genome and the mechanisms involved in the function of different quality encoding genes. Additionally, we have also utilized information generated from genomics research in producing better quality grains. The advances in the genomics of quality presented in this chapter provide ample information to the underlying gene networks controlling quality traits thereby addressing the challenges of the brisk changes prevalent within the wheat based food systems. Aiding the exploitation of novel genome diversity for quality value addition, research has benefitted from the unique germplasm resource generated by synthesizing wheat from genomic/allelic variability residing in the wheat progenitor accessional resource. These under-utilized diploid wheat progenitor accessions are a promising conduit to wheat productivity enhancement and the novel genomic resource contributing to wheat quality as elucidated here.