Crop Breeding Journal
Volume:1 Issue: 2, Summer-Autumn 2011

Based on principal component analysis (PCA), GGE biplot analysis is an effective method to fully assess multi-environmental yield trials (METs). Additive main effects and multiplicative interaction (AMMI) is an alternative method for assessing phenotypic stability and adaptability. In this research, MET data of 14 maize inbred lines were used to perform AMMI and GGE biplot analyses. These genotypes were evaluated under diverse climatic conditions in five Iranian locations during two cropping cycles (2007 and 2008). A genotype (inbred line) by location table was used for performing the analyses. Based on both mean grain yield and yield stability, inbred lines K3615/2, K19/1, K166B and K18 proved to be superior and also had greater mean performance among the test inbred lines. Graphic analysis was used to identify the most suitable inbred lines for each test environment. Inbred lines K3615/2, K19/1, K166B, K18, K3653/2 and K3547/5 were identified as suitable in all locations. The AMMI and GGE biplot graphics revealed three separate groups of environments, i.e., three mega-environments. Group one included three sites, Karaj, Kabootar Abad and Zarghan, while group two included only Islam Abad-e-Gharb and group three only Miandoab. Islam Abad Gharb and Miandoab were more discriminative for genotypes. The inbred lines that were most responsive to the environment were K3615/2, K166B, K19/1 and K18; the least responsive line was K3547/5.

Iran, with a yearly production of 147,000 tons of plums, is one of the most important plum producers in the world. This study was conducted to compare the phenological and pomological characteristics of 18 plum cultivars. An experiment was conducted using a randomized complete block design with three replications at the Khorasan Razavi Agricultural and Natural Resource and Agricultural Research Center during the 2003-2008 growing seasons. Phenological and pomological traits were scored and recorded following IPGRI and UPOV instructions and methods. Flowering extended from 21 March (Ghermez Damavand and Queen Rosa) to 6 April (Regina d' Italia) and fruit ripening from 10 August (Black Amber) to 20 September (Angelono). Fruit weight ranged from 16.9 g (Tee Blue) to 105.8 g (Queen Rosa). Results revealed that harvest date differed among plum cultivars. Plum cultivars were divided into three groups based on days after full bloom: early (<110 days), medium (110 to 150 days), and late (> 150 days) ripening. President, Simka, Zuccella, No.17, No.16, Angelono, Stanley and Queen Rosa were better adapted to Mashhad conditions and are thus recommended for plum growing areas in northeastern Iran.

The occurrence of genotype × environment (GE) interaction has led to the development of several stability parameters that can be used to estimate the stability of cultivar performance. Repeatability of 20 parametric and non-parametric stability measures across years and yield subsets as well as their association with mean seed yield and interrelationship among them in safflower (Carthamus tinctorius L.) were studied. Seed yields of 14 safflower advanced breeding lines were evaluated in 46 environments (10 locations in the 2000-2005 growing seasons, with some missing combinations) under rainfed conditions in semi-arid areas of Iran. A wide range of stability statistics, including 12 parametric and 8 non-parametric stability measures, were calculated for seed yield. The repeatability of stability measures, the interrelationships among them and their association with mean yield were estimated using Spearman’s rank correlation over environments. A combined analysis of variance revealed highly significant environmental and G × E effects over all years and yield subsets. The AMMI analysis showed that in most of the years and subsets, three first interaction principal component axes (IPCA1, IPCA2 and IPCA3) explained G × E interaction. Rank correlation between stability measures and mean yield was repeatable for four parametric measures including superiority index (Pi), geometric adaptability index (GAI), regression coefficient (bi) and environmental variance (S2xi), as well as five non-parametric stability statistics including Nassar and Huehn (1987) stability statistics (Si(3), Si(6)) and Thennarasu (1995) measures (NPi(2), NPi(3) and NPi(4)). Rank correlations among stability measures showed that non-parametric statistics were more correlated than parametric statistics over years and yield subsets. For example; Si(3) can be used instead of Si(2), Si(6), NPi(1), NPi(2) and NPi(3). Repeatability of the stability measures obtained in consecutive single years was low but moderate for bi and GAI in subsets, and highly repeatable for Pi, GAI, NPi(3) and NPi(2) in year/subsets versus the remaining environments. Superiority measure (Pi) and geometric adaptability index (GAI), along with two Thennarasu non-parametric stability measures (NPi (2) and NPi (3)), displayed strong rank correlations with seed yield, and high repeatability. Therefore, these statistics can be used simultaneously with seed yield to select genotypes with high yield and high yield stability in safflower breeding programs.

The combining ability of quantitative and qualititative traits has been studied quite frequently in rapeseed (Brassica napus L.), but rarely at different nitrogen levels. Twenty-one genotypes, including 6 parents and their 15 F2 diallel progenies, were evaluated at two nitrogen rates, N0 and N150. A combined analysis of variance revealed significant mean squares of general (GCA) and specific (SCA) combining abilities for all of the traits. The nitrogen × GCA mean square was not significant for all of the traits, indicating the stability of additive genetic effects in different environments. Days to end of flowering, days to maturity, oil content and oil yield had significant nitrogen × SCA mean squares, which showed significant variation of SCA effects on these traits at different nitrogen levels. Days to flowering, days to end of flowering and days to maturity showed high narrow-sense heritability at two nitrogen levels, but plant height and seed yield had high narrow-sense heritability estimates at N0. Most of the crosses had significant positive or negative SCA effects for seed yield at N0; however, at N150 only two crosses had significant SCA effects. Therefore, selection of hybrids based on SCA effects at N0 would be more effective.

To determine the association between genetic parameters and traits in chickpea (Cicer arietinum L.) genotypes, a field experiment was conducted with 17 chickpea genotypes using a randomized complete block design with four replications at the Ilam Agricultural and Natural Resources Research Center in the 2004 growing season. Genetic parameters including genetic, environmental and phenotypic variances; coefficients of variation; heritability; genetic advances; correlation coefficients and path coefficients were estimated, and cluster analysis was performed. Heritability values were greater for number of days to 50% maturity (98.43%), number of days to 50% flowering (98.19%), plant height (58.87%), number of secondary branches (45.81%), number of primary branches (42.03%) and number of seeds per plant (35.42%), indicating that these traits are controlled mainly by additive genes and that selection of such traits may be effective for improving seed yield. Number of seeds per plant and 100-seed weight had a positive direct effect on seed yield. Number of seeds per plant, number of secondary branches, 100-seed weight, number of pods per plant, number of primary branches and plant height also had positive and highly significant phenotypic correlations with seed yield. Stepwise regression analysis indicated that number of seeds per plant and 100-seed weight explained 96% of total yield variation. It can be concluded that seed yield in chickpea can be improved by selecting an ideotype having greater number of secondary and primary branches, as well as higher number of pods per plant, number of seeds per plant and 100-seed weight.

Seven maize inbred lines were crossed in a complete diallel cross design at the Seed and Plant Improvement Institute, Karaj, Iran, during the 2006 growing season. The parents and 42 F1 hybrids were grown in the research field of Islamic Azad University of Firoozabad, Firoozabad, Iran, using a Randomized Complete Block Design (RCBD) with three replications, during the 2007 growing season. The Hayman method was used for data analysis. Results indicated over-dominance gene effects for days from silking to physiological maturity, days from anthesis to physiological maturity, plant height, kernel depth, number of rows per ear and grain yield. The most appropriate strategy for the exploitation of these effects is to obtain hybrid cultivars and evaluate these characteristics in hybrid combinations. The gene effect for days from emergence to physiological maturity and number of kernels per row was complete dominance, suggesting that reciprocal recurrent selection would be effective. Ear leaf area and ear length were controlled by partial dominance, indicating that additive gene effects were more important than non-additive gene effects for controlling the inheritance of these traits. Therefore, improvement of these traits through selection of breeding materials is highly feasible. Broad-sense heritability ranged between 47.4% and 89.4% for days to physiological maturity and number of rows per ear; however, narrow-sense heritability varied between 7.3% and 50.6% for days from anthesis to physiological maturity and ear leaf area, respectively. Non-additive gene effects were predominant for controlling the majority of traits.

Oilseed rape is economically affected by stem rot caused by Sclerotinia sclerotiorum worldwide. Glucosinolates are the specific secondary metabolites of Brassica plants that appear in different profiles of each species. Their hydrolysis products have biocidal activity and may play a role in resistance against plant pathogenic fungi. The resistance of oilseed rape (Brassica napus) cultivars and two other Brassica species (B. nigra and Sinapis alba) was evaluated employing leaf disc inoculation, and oxalic acid and fungal inoculums on leaves of intact plants under controlled conditions. By using leaf disc inoculation, three plant ages were used to compare their reactions against the pathogen. No significant differences between genotypes were observed in this method. However, results demonstrated significant differences in main effects of wounding and plant age. The two intact plant inoculation techniques (oxalic acid and fungal mycelium) resulted in significant differences between genotypes in reaction to the disease. Furthermore, the oxalic acid assay followed the same pattern as fungal inoculations. Among the oilseed rape cultivars, AV-Sapphire and AG-Castle were the most resistant and susceptible genotypes, respectively. Brassica species differed significantly in their reaction to disease, in both wounded and non-wounded leaves with fungal mycelium inoculation and oxalic acid. Overall, non-significant differences between Brassica genotypes showed the unreliability of the leaf disc assay, whereas leaf inoculation of intact plants by means of either oxalic acid or fungal mycelium demonstrated significant differences in lesion size among Brassica cultivars and species.