Use of Path Coefficient Analysis in Identification of Traits Associated with Water use Efficiency in Drought Tolerant Wheat Genotypes

Abstract

About one third of the developing world’s wheat area is located in environments that are regarded as marginal for wheat production because of drought, heat and soil problems. Nearly one-third of the area planted to bread wheat and about three fourths of the area planted to durum wheat suffer from drought stress during the growing seasons. Despite these limitations, the world’s dry and difficult cropping environments are increasingly crucial to food security in the developing world. Worldwide, investment in irrigation infrastructure has been reported to fall continually, while population growth and demand for wheat are rising. Gains in wheat productivity in marginal environments are important because it is unlikely that increased productivity in the favourable environments will be sufficient to meet the projected growth in demand for wheat from the present to 2020. In this regard, this study was aimed at establishing an indirect selection method for drought tolerance in wheat genotypes through traits associated with water use efficiency (WUE). An experiment was conducted under rain shelter for two seasons (2001-2002) with six cultivars (Duma, Ngamia, Chozi, Kwale, Mbuni and Pasa) tested under two moisture regimes (High and low moisture regimes). The experiment was a randomized complete block design (RCBD) with split arrangement of the treatments. Moisture regime was assigned as the main plot and cultivars as the sub-plot. An analysis of variance was carried out on combined season data. The data was further subjected to correlation and path coefficient analyses. The key parameters measured during the study included evapo-transpiration (ET), WUE, grain yield. Measurements for ET involved the summation of the change in soil moisture storage and the amount of irrigation applied during the season, whereas WUE was determined as a ratio of grain yield to ET. The genotypes tested significantly differ in their water use efficiency (WUE) under both low and high moisture condition. Drought tolerant wheat cultivars (Duma, Ngamia and Chozi) had significantly higher WUE under moisture stress than the drought susceptible cultivars (Kwale, Mbuni and Pasa). The WUE of drought tolerant wheat cultivars (Duma, Ngamia and Chozi) was decreased (by 14%) under high moisture but increased (by 30%) for drought susceptible cultivars (Kwale, Mbuni and Pasa). Number of tillers/plant was positively correlated to WUE of Duma, Kwale and Pasa but negatively correlated to WUE of Ngamia, Chozi and Mbuni under high moisture situation. However, under low moisture the tillers/plant was positively correlated to the WUE of all the genotypes. Many of the traits studied (tiller/plant, plant height, seeds/spike) had direct positive effect on WUE of drought tolerant cultivars. Although biomass although had a low positive direct effect on WUE but it had a strong indirect positive effect via tillers/plant. This therefore makes biomass a viable indirect selection trait for drought tolerance in wheat genotypes. However, there is need to establish the optimum crop stage at which dependable information would be achieved.