Iranian Journal of Crop Sciences
Year:2008 | Volume:10 | Issue:2 (38)|Papers Count:9

To evaluate the effect of drought stress on yield and its components in cotton and introduce the suitable cotton genotype for Darab region, four genotypes of cotton (Gossypium hirsutum) were studied in a filed experiment using split plot arrangement in a randomized complete blocks design (RCBD) with three replications. Main factor included four levels of irrigation (70, 100, 130 and 160 mm cumulative evaporation from class A pan) and four genotypes consisting of Siokra, 818-312, B-557 and Bakhtegan (control) assigned as sub-plots. Studied traits were plant height, length and numbers of monopodial (L.M.B and N.M.B) and sympodial branches (S.B), boll number, boll weight, yield and earliness. Also leaf area and water use efficiency were studied. Analysis of variance showed that the effect of irrigation interval on plant height, L.M.B, L.S.B, boll weight, and earliness were highly significant. Drought stress reduced boll weight, however, Bakhtegan cultivar had the biggest and heaviest bolls. The 70 and 100 mm irrigated treatments were in one group and 130 and 160 mm treatments grouped together. Therefore, there was high significant difference between them. The genotype 818-312 had the highest yield of 3322 Kg/ha in 100 mm (I2) irrigation treatment. Water used in this treatment was 9646 m3/ha in 13 times and irrigation intervals were approximately every 10 days.

Six advanced durum wheat lines with different levels of resistance to Russian wheat aphid (RWA) were crossed in half-diallel method. Seedlings of F1 and their parents were grown in greenhouse and artificially infected with RWA. Analysis of variance and diallel analysis using Griffing, and Jinks and Hayman methods were performed for leaf rolling and chlorosis (percentage of leaf rolling and chlorosis) traits. General and specific combining abilities for resistance to Russian Wheat Aphid were significant for both traits indicating the role of additive and non-additive gene effects in controlling these traits. Jinks and Hayman analysis revealed higher additive gene effect as compared to non-additive gene effects. Non-additive gene effects were of partial dominance type for both traits. Less leaf rolling and chlorosis (greater resistance) were under control of recessive and dominant alleles, respectively. Broad and narrow sense heritability for resistance to RWA based on leaf chlorosis damage were 58 and 45 percent and for leaf rolling were 86 and 62 percent, respectively implying potential for improving resistance to RWA based on leaf rolling as compared to leaf chlorosis trait.

Thirty six Medicago populations were collected from natural habitats across Iran. Number and size of chromosoms as well as karytypic formula of the populations was measured and studied-using their root tip meristems. This study showed that M. sativa consists of diploid (2n = 16) and teraploid (2n = 32) populations in Iran, while M. rugosa and M. scutellata were tetraploid (2n = 30) and M. ciliaris was diploid (2n = 18). In addition, M. radiate, M. lupolina, M. minima, M. coronata, M. laciniata, M. sauvagei, M. tornata, M. orbicularis, M. noeana, M. turbinata , M. truncatula, M. littoralis, M. arabica and M. aculeata were diploid possesing 16 chromosomes, while M. constricta, M. polymorpha, M. rigidula and M. rigiduloides were diploid possesing 14 chromosomes. Based on karyotypic formula, in these species most of the studied chromosomes were metacentric and sub-metacentric. This study also revealed that M. ciliaris has genotypes with n = 9 base chromosomes in Iran.

In order to investigate the effect of NaCl stress on Na+ and K+ distribution and compartmentation in salt tolerant (IR651) and sensitive(IR29) rice genotypes, a factorial experiment based on completely randomized design (CRD) with four replications was conducted in Agricultural Biotechnology Institute of Iran (ABRII) during 2006. Seeds of rice genotypes were grown in Yushida nutrient solution and treated with 0 and 100 mM NaCl, after full expansion of sixth leaves. Leaves were scored basipetally and samples were collected from root, leafsheath and leaves No. 3, 4, 5 and 6 at 0, 72, 120, 240 and 384 h after starting treatments. In addition, some attributes including, RWC, water and osmotic potentials, osmotic adjustment, total soluble sugars, Ca2+, Cl¯, and Mg2+ concentrations were measured only in leaf 6 until development of injury in this leaf (240 h after starting treatments). Results showed that salt stress declined dry weight (DW) of IR29 more than IR651 and had no significant effect on DW of older leaves while reduced DW of leaf 6 and root in both cultivars. Salt tolerant cultivar was able to compartmentize Na+ in lower leaves. Concentration of K+ reduced by salt stress in leafsheaths and roots, and had no changes in leaf 6 of both genotypes. However, osmotic adjustment was more in tolerant genotype (0.2 MPa) compare to sensitive genotype (0.03 MPa). Salinity stress increased the amount of Cl¯ and total soluble sugars, while reduced Ca2+ and Mg2+ concentrations in leaves of both genotypes. Our findings show that the IR651 has the ability to control Na+ transport to upper parts of plant, and compartmentize the Na+ in older leaves; hence it was able to reduce damage to younger leaves. This helps plant for up-regulation of other salinity tolerance mechanisms. Therefore, it is possible to use these attributes for selection of tolerant lines in rice breeding programs.

In order to study the effect of agronomic research findings on increasing grain yield in farmer fields, a study was carried out in 150 farmers' fields in East Azarbaijanin in 2004-2005 cropping season. Fields in Maragheh, Mianeh, Hashtrood, Charoimagh, Sarab and Ahar regions were surveyed. There were 77 questions related to the crop planting, soil fertility management and harvesting and 14 questions were designed for recommended research findings. Farmers' answers were collected. These data were analyzed by SPSS software using t- test and stepwise regression analysis. The results indicated that differences between application of recommended research findings by Dryland Agriculture Research Institute (DARI) with common farmer management practices, except using fertilizers, were significant (P<0.01). In addition, regression analysis showed that fertilizer placement, stubble management, date of planting, depth of planting, secondary tillage system and fertilizer significantly increased grain yield. The differences in grain yield were 20.69, 16.44, 18.18, 16.61, 13.17, and 9.99 percent, respectively. It can be concluded that application of research findings by farmers through technology transfer procedures can increase dryland bread wheat grain yield.

To study the relationship between some quantitative and qualitative traits in red bean, 15 red bean genotypes were studied in experimental field of Faculty of agriculture, the University of Tehran in 2004 cropping season using a randomized complete block design with three replications. Necessary scores and measurements were made and multivariate statistical analyses were performed for different quantitative and qualitative traits. Analysis of variance of data revealed high genetic variation for concerned traits among red bean genotypes. Seven quantitative traits were used in stepwise regression model which included quantitative attributes of seed and plant morphological traits. Among these attributes pod weight in plant and length of internode with highest correlation coefficients had direct effects of 1.605 and -1.302, respectively. In factor analysis, 89% of total variation was explained by eight factors which were divided in two sets: The primary factors included; seed yield related; quantitative morphological and physiological traits and the secondary factors comprised; cooking quality related traits and plant type. Cluster analysis grouped the 15 red bean genotypes in three distinctive groups. KS31169 genotype had the least similarities with the other genotypes; therefore, it would be expected that crosses made between this genotype and genotypes of the first group will develop desirable variation in segregating populations for breeders.

In order to screen sorghum germplasm in National Plant Gene Bank of Iran for salinity tolerance, 142 sorghum accessions from five different types were planted in two different field growing conditions. Electronic conductivity (EC) of irrigation water was 2.12 and 14.8 ds/m in non-stress and salinity stress conditions, respectively. Experimental design was Balanced Group Blocks with two replications. The grouping in each block was based on sorghum types (wild, grass, grain, forage, and broom sorghums). This experimental design allowed us to compare sorghum types in order to differentiate and identify the most tolerant and susceptible germplasm. Stress susceptibility index (SSI) and stress tolerant index (STI) based on single plant biological yield and plant height traits were used in the analysis. Based on these indices the tolerant accessions were identified within and between sorghum types. The distribution of tolerant and susceptible accessions in each type was determined by using biplot for SSI and STI. These analyses facilitated the identification of the tolerant germplasm in both local and introduced accessions. These germplasm can be used in sorghum breeding programs for tolerance to salinity. Passport data showed that there was no correlation between the tolerance to salinity and the origin of germplasm. However, the correlation coefficients of STI, SSI, yield and plant height showed a high relationship between STI and the first cutting yield (r = 0.695**), implying that STI is the most suitable index for screening sorghum germplasm for tolerance to salinity stress.