Ahsan Iqbal

Biodiversity in the sorghum (Sorghum bicolor L. Moench) germplasm of Pakistan.

Sorghum ranks fifth in worldwide economic importance among cereal crops and is one of the most important summer annual grasses of Pakistan. As it is a very diverse crop, sorghum genetic fingerprinting requires an efficient marker system. We estimated genetic divergence among 29 sorghum (Sorghum bicolor) genotypes, including approved varieties and local and exotic lines collected from different ecological regions of Pakistan, using random amplified polymorphic DNA (RAPD) markers. A total of 125 RAPD loci, with an average of 66 loci per genotype, were used to calculate genetic divergence among these genotypes, of which 119 were polymorphic, showing 95% overall polymorphism. Genetic similarity ranged from 0.36 to 0.92, indicating a relatively broad genetic base. RAPD analysis revealed maximum similarity between the Indian III and K-A-113 sorghum genotypes (both exotic lines), while the F-601 and F-606 were observed to be the most diverse genotypes. Mean band frequency revealed by these RAPD primers ranged from 0.17 to 0.56, with an average of 0.36. The data presented here support the findings that RAPDs can be effectively used for studying genetic diversity in sorghum.

Effect of high temperature on grain filling period, yield, amylose content and activity of starch biosynthesis enzymes in endosperm of basmati rice

BACKGROUND High temperature during grain filling affects yield, starch amylose content and activity of starch biosynthesis enzymes in basmati rice. To investigate the physiological mechanisms underpinning the effects of high temperature on rice grain, basmati rice was grown under two temperature conditions - 32 and 22 °C - during grain filling. RESULTS High temperature decreased the grain filling period from 32 to 26 days, reducing yield by 6%, and caused a reduction in total starch (3.1%) and amylose content (22%). Measurable activities of key enzymes involved in sucrose to starch conversion, sucrose synthase, ADP-glucose pyrophosphorylase, starch phosphorylase and soluble starch synthase in endosperms developed at 32 °C were lower than those at 22 °C compared with similar ripening stage on an endosperm basis. In particular, granule-bound starch synthase (GBSS) activity was significantly lower than corresponding activity in endosperms developing at 22 °C during all developmental stages analyzed. CONCLUSION Results suggest changes in amylose/amylopectin ratio observed in plants grown at 32 °C was attributable to a reduction in activity of GBSS, the sole enzyme responsible for amylose biosynthesis.

Molecular characterization of Pakistani wheat cultivars using random markers

The genetic diversity among fifteen varieties of wheat was studied by random amplified polymorphic DNA (RAPD) analysis. By applying 20 RAPD primers, 182 fragments were amplified, out of which 118 were polymorphic (64.84%). The number of fragments amplified per primer ranged from 10 to 24 with an average of 17 fragments per primer. Primer K-17 produced the maximum number of fragments (24) and all the fragments were polymorphic. Range of polymorphism percentage was from as low as 0% (I to 15) to as high as 100% (K-11). The number of fragments produced per wheat genotype varied from 36 to 56 with an average of 47.2 fragments per genotype. The variety Shahkar-95 produced maximum number of fragments (56). Cluster analysis classified fifteen varieties of wheat into two main groups; three varieties were placed in group I and the rest of the varieties were placed in group II. Second group (group II) was further divided into three subgroups; IIA, IIB and IIC. The pair wise similarity values ranged from 54.88 to 82.93% and showed that genotypes Kohinoor-83 and Pak-81 were the closest with highest similarity value (82.93%), while genotypes Kohinoor-83 and Kohistan-97 were most distinct with minimum similarity value (54.88%).