ITEMS FROM ROMANIA

S.C.A.-AGRICULTURAL RESEARCH STATION

Turda, 3350, str. Agriculturii 27 Jud Cluj, Romania.

Yield potential and performance stability of winter wheat cultivars under diverse ecological condition of Transylvania province, Romania. [p. 95-96]

V. Moldovan, Maria Moldovan, and Rozalia Kadar.

Transylvania is a Romanian province with varied agro-climatic conditions that include environmental factors such as temperature, rainfall, fertility status, and other soil characteristics that play an important role in the varietal performance of winter wheat. The adaptability of a cultivar over diverse environments is usually tested by the degree of its interaction with different environments under which it is grown. A cultivar is considered to be adaptive or stable if it has high mean yield but a low degree of fluctuation in yield ability when grown under diverse environments.

Previously (Ann Wheat Newslet 49:91-95), we suggested that one of the best techniques used to rank genotypes for yield stability is the statistical model of Eberhart and Russell (1966). In this study, the coefficient of variation (CV) for yield will be considerate as a measure of yield stability.

Data for grain yield of the recommended winter wheat cultivars for Transylvania were obtained from trials grown under nine diverse environmental conditions at three locations (Turda, Targu-Mures, and Brasov) for 3 years (2002, 2003, and 2004). For each location and year, the trial was conducted in a balanced squared lattice design with six replications and a repeated the basic scheme. Thus, the first three replications were fertilized at optimum rate of nitrogen and phosphorus, whereas the other three replications were unfertilized or had a low rate of nitrogen applied. The three experimental years were highly variable for the degree of favorable climate for wheat; 2002 was favorable, 2003 was fair to unfavorable, and 2004 was very favorable.

The mean grain yield, range, and coefficient of variation on the first three replications of the trials with optimum rates of nitrogen fertilizer of the recommended winter wheat cultivars for Transylvania province are given in Table 1. No large differences in mean grain yield of the analyzed cultivars were observed. The data for wheat grain yield showed that Ariesan had the highest average yield at 6,225 kg/ha, whereas Apullum had the lowest mean yield at 5,720 kg/ha. However, the range between minimum and maximum grain yield of each cultivar was very wide. Maximum grain yields were reached in 2004 at Targu-Mures, exceeding 10,000 kg/ha for all except Apullum, which only was 9,000 kg/ha. The minimum values for grain yield were obtained in 2003 at Turda. In this year, yield was determined by high temperatures in the spring and summer and severe drought stress during the growing season.

Yield stability is defined as the degree of a cultivars interaction with different environmental conditions under which it is grown. The large fluctuation in yield ability of the tested cultivars is reflected by relatively high CV values. Apullum seem to be a relatively stable cultivar (CV = 43.76). In this case, the relative advantage in stability is associated with a lower mean yield and more a reduced maximum grain yield. However, this conclusion is not supported by our data for some of the other cultivars. Ariesan, which has the highest mean yield (6,225 kg/ha), has a smaller CV (44.03) comparative to other cultivars.

These data show that the currently grown wheat cultivars in Transylvania reached high yield potential (> 10,000 kg/ha). On the other hand, the highly variable environmental conditions of Transylvania (given by high CV for yield) reflect powerful constraints that prevent the full expression of the genetic potential for yield of the cultivars.