The study consists of 15 varieties (Table 2, 10 from Mexico and 5 from India), which were grown in randomized block design with three replications. Eight rows were planted in a plot size of 5.5 x 1.6 m2 under flat condition. The crop was sown during the last week of November by plot drill into dry soil followed by irrigation to give about 300 viable seeds/m2 in rows, 20 cm apart. Prior to planting, a summer green manure crop (Sesbania aculeata) was incorporated by cultivation. At the time of planting, 100 kg N/ha was applied as Urea and 46 kg/ha phosphorous as Single Super Phosphate. Potash was not applied due to inherent high content of potassium (557 ppm) in soil (0-15 cm depth). Top dressing of 200 kg N/ha through Urea was done at DC 31 stage (Zadoks et al. 1974) followed by irrigation.
Netting (20 X 20 mesh) was imposed after first irrigation to facilitate easy growing of young plants and its height was adjusted with the growth of crop. This was done to avoid the crop from lodging, which generally occurs after anthesis during or after irrigation, so as to ensure uninterrupted supply of nutrients and continuous interception of solar radiation to achieve maximum possible yield. Irrigation was applied as per need of the crop by flat method. Herbicides, like Topik (Clodinafop-propargyl) @ 250 ml/ha and Brominal (Bromixinil @ 1.5 l/ha) + Harmony (Thiofensulfuron @ 25 g /ha) were used by Knap Sack sprayer at two leaves weed stage for control of grassy and non-grassy weeds, respectively. Fungicides were applied at every 15 days interval after heading to prevent diseases, which facilitated proper estimation of yield potential.
Net plot of 3.6 m2, excluding border rows and ends of the plot, was harvested manually after 7-10 days of physiological maturity. Dates of 75 % seedling emergence and 50 % anthesis, at which spikes extruded at least one anther and physiological maturity was recorded. Duration from emergence to anthesis and maturity was considered as anthesis and maturity period of different varieties, respectively. At the time of harvest, a sub sample of 100 culms was taken, which were weighed, dried at 70oC and again weighed and used for adjustment of constant moisture in biomass and calculations of spikes/m2. Remainder plot material was threshed after a week of sun drying and grain yield was recorded. Another sub sample of grain was taken, weighed (fresh and dry), for adjustment of grain yield at 12 % moisture, which was further used for determining thousand grain weight. All the yield and yield attributing characters were obtained by using methods as described by Bell and Fischer (1994).
The data of the experiment were analyzed on pooled basis by using MSTATC (Michigan State University), a statistical analysis package (Nissen 1983). Phenotypic correlation (r) between yield and other traits were calculated by using Pearsons Correlations. Calculation of genetic gain was done by regressing the mean grain yield and natural logarithm of yield with the year of release of varieties. The slope (b) in linear regression equation of grain yield and year gave an increase in grain yield in kg/ ha/year (absolute term). Similarly, natural logarithm of grain yield with year resulted in per cent per year (relative term) increase when b was multiplied by 100 (Ortiz Monasterio et al. 1997).