Gul Sanat Shah Khattak

Triple test cross analysis for some morphological traits in mungbean (Vigna radiata (L.) Wilczek)

Thirty progenies of mungbean were produced by crossing 10 true-breeding genotypes with three testers (NM 92, 6601, and their F1) in a Triple Test cross (TTC) fashion and evaluated with parents in the kharif (July-October) and spring/summer (March-June) seasons. The data on parents and F1s were analysed for pod clusters on main stem, pod clusters on branches, node of the first peduncle, nodes on main stem and average internode length to detect epistasis and estimate additive and dominance components of genetic variation. Epistasis was observed for node of the first peduncle and nodes on main stem in the kharif season. Partitioning of total epistasis revealed that both additive × additive (i type), and additive × dominance, and dominance × dominance (j and l types) interactions were significant with prevalent influence of i type interactions on these traits. Both additive and dominance components of genetic variation were significant for all those traits not significantly influenced by epistasis in either or both seasons. The additive component was predominant for pod clusters on main stem, pod clusters on branches and average internode length in the kharif season, and for the node of the first peduncle and nodes on main stem in spring/summer season whereas dominance component was important for pod clusters on main stem, pod clusters on branches, and average internode length in spring/summer season. These results suggested that particular generation of segregating population and specific breeding method for selection might be adopted in each season for the improvement of these traits in mungbean.

Detection of epistasis, and estimation of additive and dominance components of genetic variation for synchrony in pod maturity in mungbean (Vigna radiata (L. ) Wilczek)

Abstract Genetics of days to first flowering, first pod maturity, 90% pod maturity, and duration of the period from first flower to 90% pod maturity (DDd1) and from first pod maturity to 90% pod maturity (DDd2) [degree of non-synchrony of pod maturity] were investigated in mungbean using the triple test cross (TTC) technique. Ten diverse genotypes were crossed with two true breeding testers (L1 and L2) and the F1 hybrid of the tester lines (L3). The resultant single and three-way crosses were evaluated in two seasons (kharif and spring/summer). Epistatic variation was found to be an integral part of inheritance of days to first flower in both seasons and days to first pod maturity only in kharif season. Further partitioning of total epistasis revealed that additive×additive (i type) interactions had a major role in the inheritance of these traits. In the absence of epistasis both additive and dominance genetic components were significant for days to 90% pod maturity, DDd1, and DDd2 in both seasons, and for days to first flower in spring/summer season. The additive genetic component was predominant for days to 90% pod maturity and DDd2 in both seasons and for DDd1 in spring/summer season, whereas the dominance component was important for days to first flower and DDd1 in the spring/summer season. The direction of dominance was towards early maturity of 90% pods and late maturity of the first pod. The significant additive genetic component in DDd1 and DDd2 could be exploited in later generations for developing mungbean genotypes with improved synchrony in pod maturity.

Genetic control of flag leaf area in wheat (Triticum aestivum) crosses

The results indicated that the trait was mostly under control of one major gene in combination with polygenes (model D-2) for the two crosses during the first year. However, it was controlled by mixed epistasis of two major genes plus polygenes (model E-1) in cross 2 during the second year. Transgressive segregate on both upper and lower extremity of the trait in B 1, B2 and F 2 indicated the presence of both favorable and reversed genes in the parents. Higher major gene heritability (9.6 to 71.0) for the trait was recorded than the polygenes heritability (4.8 to 38.9) in the segregating generations (B 1, B 2 and F 2). Moderate to high environmental variations (14.4 to 85.0) in the trait for segregating generations revealed that FLA is influenced by the environmental fluctuations. Predominant additive effect over all other types of genetic effects suggests the delay in selection for FLA until maximum favorable genes are accumulated in the individuals.

Selection of parents for crossing based on genotyping and phenotyping for stripe rust (Puccinia striiformis) resistance and agronomic traits in bread wheat breeding.

Bread wheat (Triticum aestivum L.) germplasm consisting of 45 genotypes were clustered phenotypically using ten morphological traits and Area Under Disease Progress Curve (AUDPC) as measure of stripe rust resistance. The clustering was ratified by using twenty three molecular markers (SSR, EST and STS) linked to stripe rust (Puccinia striiformis f. sp. tritici) resistant QTLs. The aim was to asses the extent of genetic variability among the genotypes in order to select the parents for crossing between the resistant and susceptible genotypes with respect to stripe rust. The Euclidian dissimilarity values resulted from phenotypic data regarding morphological traits and AUDPC were used to construct a dendrogram for clustering the accessions. Using un-weighted pair group method with arithmetic means, another dendrogram resulted from the similarity coefficient values was used to distinguish the genotypes with respect to stripe rust. Clustering based on phenotypic data produced two major groups and five clusters (with Euclidian dissimilarity ranging from 2.44 to 16.16) whereas genotypic data yielded two major groups and four clusters (with percent similarity coefficient values ranging from 0.1 to 46.0) to separate the gene pool into highly resistant, resistant, moderately resistant, moderately susceptible and susceptible genotypes. With few exceptions, the outcome of both type of clustering was almost similar and resistant as well as susceptible genotypes came in the same clusters of molecular genotyping as yielded by phenotypic clustering. As a result seven genotypes (Bakhtawar-92, Frontana, Saleem 2000, Tatara, Inqilab-91, Fakhre Sarhad and Karwan) of diverse genetic background were selected for pyramiding stripe rust lesistant genes as well as some other agronomic traits after hybridization.