JWSS - Journal of Water and Soil Science

---

Seven Iranian and foreign cultivars of rice were crossed in a half-diallel. Parents with F2-generations were transplanted in a randomized complete blocks design with 3 replications and evaluated for length to breath ratio of paddy and brown rice, head rice and crust, grain yield, percent of head rice and broken rice, amylose content, gelatinization temperature and gel consistency. The ANOVA table showed significant differences among genotypes, general combining ability effects for all traits and specific combining ability effects for length to breath ratio of paddy and brown rice, percent of head rice and broken rice, so representing additive and non-additive effects in genetic control of the traits involved, respectively. The graphical analysis of the results showed partial dominance for length to breath ratio of paddy and brown rice, grain yield, amylose content, gelatinization temperature and gel consistency. Because of additive gene effects, genetic advance from selection would be high for these traits. The genetic control of brown rice weight is complete dominance, and for weight of head rice and rice crust weight over dominance involved. So, genetic advance by selection for these traits would be poor. In the genetic control of higher length to breath ratio of paddy and brown rice, brown and head rice weight, grain yield and amylose content recessive genes are involved. Domsiah for higher to breath ratio of paddy and brown rice and Sepidrud for brown and head rice weight had the most recessive genes. IR28 for higher grain yield and Sepidrud for less crust weight had the most recessive genes.

---

In order to analyze the genetics of tobacco cultivars’ resistance to blue mould (Peronospora tabacina A.) and to estimate the combining ability of the four resistant and susceptible tobacco cultivars (Bel 61-10, Bergerac C, Samsoun and Trumpf) received from CORESTA, these cultivars were crossed in 1997 in a half-diallel crossing system and in 1998 their parents and their progenies were sowed. Also to estimate gene effects controlling resistance and susceptibility of cultivars and to obtain F₂, BC₁ and BC₂ generations, F₁ generation was selfed and backcrossed with their parents. In 1999, the six generations (P₁, P₂, F₁, F₂, BC₁ and BC₂) from six families were evaluated in a complete block design with 3 replications and the resistance of genotypes against Peronospora tabacina were evaluated by the standard method of CORESTA and the parents with their F₁ and F₂ progenies were analyzed as a 4×4 half-diallel crossing system.

The ANOVA showed significant differences among genotypes concerning resistance to Peronospora tabacina and the generation means analysis indicated fit of families Bel 61-10 x Bergerac C and Bel 61-10 x Trumpf with additive-dominance model. The rest of the families showed non-allelic digenic interactions (epistasis) and were fit to 6-parameter model of Mather and Jinks. Because of moderate to high narrow sense heritability of resistance to Peronospora tabacina (from 34 to 85% for different families), the selection of resistant lines may be successful. The results showed significant GCA of parents for the resistance to Peronospora tabacina. So, the role of additive effects of genes concerning resistance to Peronospora tabacina was recognized and the estimated heritability (in the narrow sense) was from 72% to 75% for this trait.

---

The results of diallel analysis of 7 parents and 21 F2 progenies of Burley tobacco cultivars, which were transplanted in 2002 as RCBD with 3 replications in the Tobacco Research Center, Rasht, Iran, showed significant genetic differences among genotypes and high GCA and SCA for most of the traits. Therefore the role of additive and non-additive (dominant) effects of genes on the formation of the corresponding characteristics was important. The graphical analysis of progenies of diallel crosses showed partial dominant effect for nicotine percentage in leaves. The distribution of parents around regression line showed most dominant genes in cultivars B.CDL 28, B.Banket, and B.21 while cultivars B.14 and B.TN 86 hade most recessive genes for this characteristic. Also the low and high percentages of nicotine were controlled by dominant and recessive genes, respectively. Estimated simple (phenotypic) relationships between characteristics showed significant correlation between dry leaf yield of tobacco cultivars and its components such as leaf area index (LAI) (r = 0.482**), time to flowering (r = 0.440*), appearance of leaves (r = 0.648**) and percent age of dry matter of leaves. The path coefficient analysis showed very high direct influence of dry matter percent age of leaves, appearance of leaves, and LAI in dry leaf yield. These characteristics would be a favorite selection index for increasing tobacco yield, since characteristics such as leaves per plant, plant height and time to flowering have no significant direct influence on dry leaf yield of tobacco cultivars. These yield components explain 82% of variance of tobacco yield. Results of factor analysis, using principal Component Analysis (PCA) with Varimax rotation showed that characteristics such as leaves per plant, LAI, and plant height with high positive and significant factor loading as a morphological factor explain 44% of data variance. The second factor including such traits as time to flowering, appearance, and percent of dry matter of leaves with high positive and significant factor loading, form a physiological factor. These two factors together explains 65% of variance of dry leaf yield of tobacco cultivars.

---

Relationship between grain filling rate , grain filling duration, yield components and other physiological traits of rice was investigated in 93 genotypes of rice at Rice Research Institute of Iran (Rasht, Iran) during the growing season of 2001-2002. The experiment was performed without any statistical design. Panicles of main stem were tagged and taken at 3- day intervals during the grain filling period. A cubic polynomial model was used to fit the grain dry weight data (mean of R²= 0.98 for all genotypes) and the grain filling rate and duration estimated for the genotypes. Traits related to sink capacity such as grain weight, grain size and grain number per panicle correlated with grain filling rate but source -capacity- related traits except chlorophyll content of flag leaf and secondary leaf did not correlate with grain filling rate. Stepwise regression showed that final grain weight, grain filling duration and flag leaf angle contributed to grain filling rate, however, path analysis showed that only final grain weight and grain filling duration had the greatest effect on grain filling rate. The results of stepwise regression irrespective of final grain weight showed that chlorophyll content of flag leaf, grain width, grain filling duration and grain length contributed to grain filling rate. Path analysis results showed that the final grain weight had the greatest direct positive effect on grain filling rate, while grain filling duration had negative effect on grain filling rate.

---

Six Iranian rice cultivars (Binam, Domsiyah, Shahpasand, Sepidrud, Khazar and Valed 46) were crossed in 1989 in the Iranian Rice Research Institute in Rasht, Iran in a full-diallel design. The F1 progenies together with parents were transplanted in a CRBD in the 5 x 0.75 m plots at plant density of 25 x 25 cm (60 plantlets per plot) in 3 replications. Part of this research was published in 1994 as a half-diallel design and the data of full-diallel, using Griffing approach, is subject of this paper. The analysis of variance showed significant differences among genotypes. The mean of six parents, 15 crosses and 15 reciprocal crosses were analyzed using the four diallel crossing systems of the Griffing approach. The SS of genotypes were separated into GCA for each parent and SCA for each cross using corresponding formula. The additive variance (V_A) and dominance variance (V_D) values were estimated using the table of variance analysis. The heritability (h²_ns) was also estimated from V_A and V_D variances. The simple variance analysis of “grain yield per plant” and other agronomic traits using each of the 4 diallel crossing methods of Griffing showed significant differences (P < 1%) among genotypes, indicating a sufficient genetic potential of the investigated genotypes. The GCA variance analysis of the lines was significant for all the characteristics, indicating the importance of additive variance (V_A) by inheritance of these traits. Using Griffing’s diallel methods 1 and 3, SCA variances for all investigated traits showed significance, whereas in the methods 2 and 4, traits “1000 grain weight” and “tiller per plant” were not significant according to SCA. This also indicates the importance of dominant variance (V_D) in most of the traits, except for “1000 grain weight” and “tiller per plant”. The differences among the reciprocal crosses in diallel methods 1 and 3 were also examined where for all the characteristics (except for “deaf grains per panicle” and “length to breadth ratio of brown rice grain”) significant differences were observed, suggesting the possibility of cytoplasmic effect of mother line on the reciprocal crosses. The heritability (h²_ns), which indicates the ratio of additive variance (V_A) to phenotypic variance (V_P), was estimated to be equal to zero due to the absence of additive variance for grain per panicle and the number of days from transplanting to full maturity of grain. The heritability for other characteristics was estimated high or low according to additive variance. For example in all 4 diallel methods the heritability estimation for length to breadth ratio of brown rice grain was relatively high (65 – 71%) whereas for “panicle length” and “grain yield per plant” was relatively low (13 – 48%). The correlation among genetic parameters (V_A, V_D, D, h²_ns ) were generally high and significant.