Muhammad Sajjad

The low down on association mapping in hexaploid wheat ( Triticum aestivum L.)

The past few decades have witnessed hundreds of family-based linkage studies mapping for numerous traits but only a limited number of QTLs were actually cloned, tagged, or used for marker-assisted selection. Although providing valuable information, this conventional approach cannot be scaled up to underpin the incredible amount of phenotypic variation in the form of 266, 589 hexaploid wheat accessions maintained in public germplasm collections. Association mapping has recently emerged as an alternative and more powerful mapping approach where a natural population is surveyed to determine marker-trait associations using linkage disequilibrium (LD). After its first application for milling quality in 2006, association mapping studies in hexaploid wheat are being extended to tag yield traits, protein quality, and tolerance to biotic and abiotic stresses. Advances in genotyping technology and statistical approaches greatly accelerated the shift from conventional linkage-based mapping to LD-based association mapping. Association mapping stands out because of simultaneous utilization of a large number of ex situ-conserved natural variation due to historical recombination events accumulated over centuries.

Patterns of trait associations in various wheat populations under different growth environments

Five wheat populations were investigated for two years to explore the pattern of trait associations and their contribution to grain yield. The correlation pattern between two traits and their association with grain yield was similar in CIMMYT and Pakistani germplasm. Indian germplasm had different pattern of trait association from those of CIMMYT and Pakistani germplasm. The number of kernels per plant, number of spikes per plant, spike length and spike dry weight were the major yield contributing traits in CIMMYT, Pakistani and ICARDA genotypes. In Indian and miscellaneous genotypes, the number of kernels per plant and number of spikes per plant were the only traits with a positive effect on grain yield. Furthermore, three traits, the number of kernels per plant, the number of spikes per plant and the spike dry weight appeared to have positive effect on grain yield and other major yield traits. Spike density had a negative effect on grain yield in CIMMYT germplasm in dry season. Chlorophyll contents showed no correlation with grain yield in all populations.

Morphological and chemical characteristics of tomato foliage as mechanisms of resistance to Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) larvae

Morphological characters and chemical composition of tomato ( Lycopersicon esculentum Miller) leaves were measured and compared among nine tomato varieties (Roma VFN, NARC-1, Fs-8802, Tommy, Pant Babr, Rio Grande, Nova Mecb, Pakit and Sahil) exhibiting varying levels of host plant resistance to Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) as based on fruit infestation. The variety, Sahil, was resistant, whereas Roma VFN was the susceptible variety. Hair length and hair density on lower leaf surface, as well as thickness of leaf lamina significantly correlated with larval population and fruit infestation. Leaf hair density accounted for 92.0% of the variation in fruit infestation and 77.0% of the variation in larval population. Ferrous (Fe 2+ ) and phosphorous content in the leaves were negatively correlated with fruit infestation and larval population; whereas, nitrogen, calcium, magnesium, manganese and zinc content were positively correlated with fruit infestation and larval population. The resistant variety, Sahil, produced the maximum yield as compared to susceptible variety, Roma VFN. Keywords: Helicoverpa armigera , tomato fruit borer, host plant resistance, Lycopersicon esculentum

Evaluating the Intercropping of Millet with Cowpea for Forage Yield and Quality

A field study was scheduled to estimate the impact of intercropping of pearl millet with cowpea on forage yield and quality at Agronomy Research Farm, University of Agriculture, Faisalabad. It was done in kharif season 2016. Randomized complete block design was used to conduct this experiment. It has three replications. The size of net plot is 3.6 m × 6 m. It comprised of five treatments (T1 = one row of millet alternating with one row of cowpea (1M:1C), T2 = two rows of millet alternating with one row of cowpea (2M:1C), T3 = one row of millet alternating with two rows of cowpea (1M:2C), T4 = sole millet, T5 = sole cowpea). We found that intercropping significantly effected the yield and quality of forage. Intercropping system had significant effects on nutritive value of forage crop. Within various treatments of intercropping, it is evident that treatment T2 (two rows of millet alternating with one row of cowpea) gives maximum total dry matter yield (9.68 t ha-1). It was then tracked by treatment T1 (one row of millet alternating with one row of cowpea) and treatment T3 (one row of millet alternating with two rows of cowpea) producing dry matter yield (9.07 t ha-1 and 8.33 t ha-1, respectively). Based on high grain and suitable environmental condition, intercrop productivity compared to sole crop could be selected for improving the productivity of millet/cowpea mixture in the Punjab.

Disruption of Phytoene Desaturase Gene using Transient Expression of Cas9: gRNA Complex

Engineered nucleases have emerged as a powerful tool for site specific gene manipulation in plants. Based on Clustered Regularly Interspersed Short Palindromic Repeats/CRISPR associated (CRISPR/Cas) system, engineered Cas9:gRNA complex can be used to cleave specific DNA sequences in the genome. In the present study, Nicotiana benthamiana Phytoene Desaturase (NbPDS) gene was targeted by CRISPR/Cas9 system. The plant codon optimized (pcoCas9) along with guided RNA (gRNA) was cloned in plant expression vector pGreen0029, to target NbPDS gene. The NbPDS gene was disrupted transiently by agroinfiltration of pcoCas9-gRNA complex. Visible albino spots were observed on agro-infiltrated leaves of N. benthamiana plants after 7 days of infiltration. The observed albino spots were analyzed through PCR amplification of gRNAtarget, fluorescent microscopy and chlorophyll contents measurements. Our results support the notion that CRISPR/Cas9 system is a swift, robust and useful tool for targeted gene disruption, deletion and editing.