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Reciprocal recurrent selection in populations of Zea mays L. will be of great value if the increase in mean performance is accompanied by a corresponding increase in performance of hybrids found in the upper tail of the genotypic distribution. We examined the frequency distributions for yields of two populations of single‐cross hybrids. A population of 192 intercultivar single crosses among inbreds was derived from two cultivars, ‘Jarvis Golden Prolific’ and ‘Indian Chief’, after six cycles of reciprocal recurrent selection. This population of single crosses was compared with a control population of 185 single crosses among unselected inbreds from the original cultivars. Frequency distribution of average single‐cross yields over replications and locations showed no significant deviations from normal distributions. A small but statistically significant estimate of skewness was found for average yields of single crosses from the selected cultivar. Mean yields of single crosses from the selected cultivars averaged 12.5% greater than those from the unselected cultivars. Variances among the selected single crosses were smaller than among the unselected single crosses, but the differences were small and not statistically significant. Reciprocal recurrent selection apparently had little effect on the distribution of single‐cross yields other than an increase in mean performance. This implied that the shape of the distribution had not changed but that the distribution had been shifted to the right, with an increased probability of outstanding hybrids in the upper tail. The best 10 single crosses from the selected population averaged 8.6% more yield than the 10 best single crosses from the original population. Five single crosses from the selected population exceeded the yield of the best single cross from the control population.

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In order to examine application of various herbicides for controlling weeds in wheat crop, a field trial was conducted at the Agronomic Research Area, Faculty of Agriculture, Gomal University, Dera Ismail Khan, Khyber Pakhtunkhwa (KPK) during the year 2015-2016. The experiment was laid out in a randomized complete block design (RCBD) with split-plot arrangements having three replications. The main plot was comprised application time of herbicides while the use of herbicides was assigned to sub-plots. The data revealed that most of the weed parameters, physiological traits and agronomic attributes of crop plants were significantly affected by weed management practices including the use of herbicides at different time intervals over the weedy check. Hand weeding technique excelled all other weed management practices in almost all the parameters studied. This technique was found to be the most effective treatment against all prevailing weeds and obtained the highest grain yield of wheat under climatic conditions of Dera Ismail Khan.

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