Choice of efficient breeding program depends on the knowledge of the genetic system controlling the character to be improved. To estimate the genetic parameters for yield, yield components and some other morphological traits in corn (Zea mays L.), B73×MO17 and B73×K74/1 crosses were studied by triple testcross method. The experiments were conducted at research field of Seed and Plant Improvement Institute (SPII) in 1999-2001. Significant differences were observed among means of F1 , P1 and P2 testcrosses for all of the traits in both crosses. The B73 testcrosses generally had greater means than MO17 and K74/1 testcrosses except for number of leaves in two crosses, cob weight in cross B73×MO17 and anthesis silking interval in cross B73×K74/1. B73 testcross seems to contribute significantly in the expression of positive epistatic effects. Epistasis effects were significant for all of the traits in both crosses. Partitioning of the epistasis effects into fixable and non-fixable components revealed that additive×additive effects (fixable) were not significant for the traits except for days to silking in both cross, anthesis silking interval and plant height in cross B73×MO17, but additive×dominance and dominance×dominance effects (non-fixable) were significant for all of the traits in both crosses.

In order to assess the heritability of short vegetation period (early maturity) of sugar beet hybrids, an experiment was carried out in randomized complete block (RCB) design with 4 replications in Abdolrasoul Motahari Agricaltural Research Station of Sugar Beet Seed Institute, Karaj, Iran in 2009. In this research, the heredity of the traits in testcrosses derived from crosses of 18 half sib families with a male sterile line accompanied by a short vegetation period check variety was evaluated under late sowing condition (about late June). ANOVA results showed that there were no significant differences among the testcrosses for most of the traits- Means comparison showed that the hybrids 3, 9, and 16 had slight difference with the check variety for most traits. The testcross 3 was considered suitable for short growth period which was comparable with the commercial check variety. For morphological traits (such as leaf number and crown height) and some impurity traits (such as sodium and extraction coefficient of sugar), narrow- sense heritability was high. Therefore, there is still possibility to improve the above- mentioned traits with respect to the short vegetation period in the half- sib families. For root yield, sugar yield, and white sugar yield, the heritability was about zero. Root yield had significant positive correlations with sugar yield, white sugar yield, root diameter, and crown height and significant negative correlation with sugar content.

The identification of parental inbred lines to develop superior hybrids is a rather costly and time-consuming step in maize breeding. In some cases, pedigree information has been used to select diverse parental lines. In the case of Iranian maize inbred lines, this information is not fully available. In this study we investigated the genetic distance (GD) based on Simple sequence Repeats (SSR) markers between pairs of five maize testers and 28 inbred lines and assessed the relationship between GD and F1 hybrid performance, specific combining ability (SCA) and midparent heterosis (MPH). One hundred and forty testcrosses were evaluated for grain yield in 2003, 2004 and 2005 at two locations, Karaj and Gorgan (only 2004), Iran. Significant positive but low correlations were found between GD and F1 performance, SCA and MPH (0.27**, 0.39** and 0.28**, respectively). Testers affected the magnitude of correlations, with relatively high values revealed in the Mo17 crosses (0.54**, 0.61** and 0.61** for F1, SCA and MPH, respectively) and lowest values in the B73 crosses. Although GD between parents correlated significantly with hybrid performance, the estimates of GD did not consistently identify the best crosses.

Breeding for QPM ear rot resistant cultivars could offer a reliable environmental and economic control of mycotoxins especially for the resource-poor communities that require inexpensive protein diets. This research aims at evaluating a testcross of QPM inbreds with ear rot resistant cultivars to develop resistant topcrosses with high grain protein quality and yield. Seven QPM inbreds (lines) and two open pollinated ear rot resistant varieties (testers) were crossed in a line × tester method (2 × 7). The 14 F1 topcrosses, 9 parents and 2 commercial hybrids (checks) were evaluated at the Lower Niger River Basin Authority, Oke-Oyi, Nigeria in 2014 and 2015 cropping seasons. The ear rot disease ratings in all topcrosses were low (

This study was carried out to investigate the genetic variation of sugar beet testcrosses for drought tolerance in the lab (faculty of Tabriz Islamic Azad University) and field conditions (Khorasan Agriculture and Natural Recourses Research Center) in 2010. In the lab study, two factors including 49 genotypes (44 test cross hybrids and 5 control treatments) and 5 drought stress levels (0, -2.5, -5, -7.5 and -10 bar) were analyzed using a factorial experiment based on completely randomized design with three replications. The field study was conducted based on a square lattice design (7 x 7) with three replications. The results showed that genotypes and different stress levels had significant differences for germination percent, radicle, plumule length, and fresh and dry weight of radicle and plumule. Drought tolerant genotypes under lab conditions (genotypes number 1, 10, 22, 23, 32, 41 and 49) were superior to other groups with mean traits of germination percent, and dry weight of plumule and radicle of 43.29%, 4.22 µg and 2.75 µg. In terms of field traits, the drought tolerant group (genotypes number 11, 15, 19, 21 and 43) with white sugar yield of 10.18 t ha-1 was superior to the sensitive group with 5.84 t ha-1 of white sugar yield. The cluster analysis showed the sugar beet genotypes were subdivided into 5 and 4 groups based on traits studied in the lab and field, respectively. These results emphasis on genetic variation for drought tolerance amongst the studied genotypes. Percent of germination and radicle dry weight under stress conditions can be employed as traits that are effective for selection of drought tolerant genotypes under field conditions.

To assess the combining ability of lines derived from tropical and subtropical CIMMYT germplasm with temperate region lines and to determine their heterotic groups, twenty eight crosses of four temperate maize testers (MO17, K18, K166B and A679) with seven lines originated from CIMMYT germplasm were evaluated along with two hybrid checks (SC704 and SC705) using randomized complete block design with three replications, in Moghan, Iran, in two years 2012-13. The results of line×tester analysis to estimate gene action showed that both additive and non-additive effects played an important role in controlling grain yield and other traits. The estimation of general combining ability showed that there was the possibility of direct improvement of grain yield via lines No. 3, 5 and 7. Also, positive significant specific combining ability were only found for L3×MO17 testcross. In order to learn more about lines derived from various sources of CIMMYT germplasm and to assign lines to heterotic groups, HSGCA effects were calculated. According to the HSGCA, the reaction of line 1 was similar to Lancaster-Sure-Crop’s heterotic group, lines 3 and 4 had similar reaction to Reid-Yellow-Dent’s heterotic group and line 6 had similar reaction to K166B’s heterotic group (a tester extracted from none-temperate CIMMYT originated materials in Iran) and the other lines showed no similar reaction to the heterotic groups of the studied testers. These results showed that using more testers as well as more than one tester from each heterotic group, is necessary to identify appropriate sources of the tropical and subtropical germplasm to facilitate the success in development of adapted maize germplasm.

Sugar beet cultivation faces significant challenges from diseases such as rhizomania and cyst nematode, both in Iran and globally. The most effective and straightforward approach to mitigate the damage caused by these diseases is the use of resistant varieties. The Hosna cultivar was developed after extensive preliminary and advanced research. This variety was produced by crossing a pollinator inbred line from the SB27 population, which carried resistance genes for both rhizomania and cyst nematode, with a monogerm single cross maternal line. A value-for-cultivation and use (VCU) test was conducted in Hamadan, Mashhad, Shiraz, and Miandoab under rhizomania-infected conditions and in Karaj under non-infected conditions to evaluate this variety's performance. Simultaneously, the resistance of the hybrids to cyst nematode was evaluated in another experiment under controlled conditions (greenhouse). The results showed the superior performance of Hosna cultivar, which produced an average white sugar yield of 11.52 tha-1, outperforming the foreign control variety Azare (11.36 tha-1) and the domestic control varieties Shokoufa and Arta (10.19 and 10.12 tha-1, respectively). However, no significant difference was found between Hosna and the foreign control Rosier (12.02 tha-1). Hosna is a diploid monogerm cultivar, resistant to both rhizomania and cyst nematode, and suitable for spring cultivation across various regions of the country. In addition to its disease resistance, this cultivar has a high potential for sugar yield.