جستجوی مقالات مرتبط با کلیدواژه « backcrossing » در نشریات گروه « زراعت »

Green Revolution which occurred by introducing dwarfing genes into bread wheat varieties had a great impact on the global wheat production. Nevertheless, these genes decrease grain yield under rain-fed conditions. In general, semi-dwarf genes may not have any advantage in heat and drought stress conditions. In rain-fed conditions, the combination of Rht-D1b and Rht-B1b genes causes a decrease in the grain yield and coleoptile length. It should be noted that the genes Rht4, Rht5, Rht7, Rht8, Rht9, Rht12, Rht13 and Rht14, which are sensitive to gibberellic acid, do not affect coleoptile length.

In the present research, wild type genes which cause higher plant height were transferred from Roshan to Excalibur variety using backcrossing. Similarly, in the F3 generation of a cross between Roshan and Mahdavi, a semi-dwarf plant was observed. This plant was backcrossed with Roshan to have semi-dwarf isogenic lines of this cultivar. Development of isogenic lines for plant height in two genetic backgrounds made it possible to study the effect of the plant height on yield and yield components. Isogenic lines and their parents were evaluated in two successive years (2020-2021 and 2021-2022) under Sepidan rain-fed conditions.

On average, plant height of Roshan and its semi-dwarf isogenic lines were 90.84 and 51.22 cm, respectively. Also, the average plant height of Excalibur and its tall isogenic line were 47.61 and 65.36 cm, respectively. Results showed that breeding for higher plant height had a positive and significant effect on wheat grain yield under rain-fed conditions. On average, tallness increased grain yield by 375.43 and 177.94 kg.ha in Roshan and Excalibur genetic backgrounds, respectively. In addition, the effect of plant height on yield components under rain-fed conditions was investigated. The findings of this research show that breeding for higher plant height indirectly increase grains number per spike and 1000 grain weight to improve grain yield. While, spikes number per meter square was not affected with plant height. Considering the high heritability of plant height and its significant correlation with grain yield, it is suggested that this trait be considered in breeding programs under rain-fed conditions.

In the present research, it was found that tallness improve grains yield of bread wheat under rain-fed conditions via increasing grains number per spike. Two other yield components were also investigated and it was found that the plant height had no effect on spikes number per meter square. 1000-grains weight did not affected by plant height in the first year, although in the second year, the taller genotypes had higher 1000-grains weight. Considering that plant height has high heritability and response to selection, it is recommended to pay special attention to this trait in breeding programs for rain-fed conditions. It should be mentioned that as narrow sense heritability of plant height is very high, selection for this trait based on single plant is very effective. Consequently, selection for plant height in backcrossing and pedigree breeding methods could be extremely successful.

Fusarium wilt (FW) caused by F. oxysporum f. sp. ciceris causes extensive damage to chickpea in many parts of the Iran. The technique of Marker-assisted backcrossing (MABC) is one of the effective and accurate methods in transferring specific genes such as disease resistance genes in a short time in self-pollination plants. Hashem is one of Iranian chickpea cultivars with high yield, plant height and tall stems which its cultivation is limited due to susceptibility to the fusarium wilt. Therefore, Purpose of this study was to introgression resistance to fusarium wilt from Ana cultivar, as a donor, to Hashem as a recurrent and susceptible cultivar using molecular marker-assisted backcrossing.

This research was conducted during five cropping seasons (2018-2023). Crossing was done between the selected parents of chickpea cultivar Ana (as a donor parent) and Hashem (as a recurrent parent) and the F1 progeny was backcrossed with Hashem to produce the BC1F1 generation. By using three backcrosses and one rounds of selfing, BC3F2 progeny was obtained. Foreground selection (FGS) was conducted with four markers (TA59, TA96, TR19, and CaM1402) linked to FW resistance genes. Background selection (BGS) was employed with evenly distributed 16 (Ana × Hashem) SSR markers in the chickpea genome to select plant(s) with higher recurrent parent genome (RPG) recovery. Finally, the selected lines of BC3F2 generation were phenotypically evaluated in terms of Fusarium disease resistance.

In first year, from the crossing of two parents, 20 real F1 plants were obtained and backcrossed with Hashem to produce BC1F1 plants. Based on results of foreground selection (FGS), was undertaken using four markers (TA59, TA96, TR19, and CaM1402) linked to resistance genes, 6 BC1F1 plants contained 4 resistant alleles and participated in the second backcrossing to produce BC2F1 plants. In the following, from a total of 52 BC2F1 plants 12 BC2F1 plants contained 4 resistant alleles, for background selection (BGS) to observe the recovery of recurrent parent genome using 16 SSRs, At this stage based on the BGS results 5 plant, with the highest background recovery, selected and backcrossed with recurrent parent to produce BC3F1 plants. Followed by cycles of, 6 plants in BC3F1 containing resistant genes and most similar to the recurrent parent were selected. The identified plants were selfed to obtain 6 BC3F2 lines which were screened phenotypically for resistance to fusarium wilt. Finally, 12 BC3F2 lines were obtained which led to identification of 3 highly resistant lines of Hashem with FWR gene introgressed in them. Also, in this study using Meta-QTL analysis region associated with genetic resistance to different race of fusarium wilt were identified on chromosomes 2, 4, 5 and 6.

Sweet corn, Zea mays Var. Saccharata is the youngest form of corn that arose after an accidental mutation in the common corn, and the Native Americans and Indian tribes began to cultivate it after becoming aware of the differences. The first registered variety of sweet corn was named Black Iroquois by European settlers in 1779. In the 19th century, white OP (open pollination) cultivars became popular in the United States. Two varieties of this type that are still cultivated and consumed are the Country Gentleman variety (with elongated and small seeds and irregular rows, also called Shoepeg corn) and the 'Stowell's Evergreen' variety. Scientific developments in the field of plant breeding, including the hybridization technology by inducing traits such as ripening at the same time and improving the quality of cobs and resistance to diseases, created tremendous changes in the production of sweet corn in the 20th century. This article with an overview of the successes achieved in creating new cultivars and improving the quality and marketability traits of sweet corn, its genetic differences from common corn, and the role of hybridization as one of the common tools of classical breeding to achieve superior genotype qualities are emphasized in sweet corn. Classification of sweet corn hybrid cultivars based on factors such as genes affecting carbohydrate metabolism and endosperm sugar percentage, planting time until harvest, seed color (yellow, white, pink, purple, and black), cob shape, and type of consumption (freshly eaten, Freezing, canning and exporting) forms another part of this article. Examining sweet corn breeding methods shows that despite the use of a number of specific techniques and theories, due to the different results of each method, the effect of external pollination, and the high perishability of the final product, Sweet corn breeding is very different in practice. The most important methods in sweet corn breeding have been reviewed in another part of this article. These methods include pedigree breeding, production of synthetic and composite masses, backcrossing and breeding with the help of molecular markers, as well as selection for some special traits such as edible quality, seed production, improved germination in Sh2 seeds, and resistance to pests and pathogens. In the final part, all kinds of sweet corn varieties, including commercial hybrids for fresh consumption and hybrids suitable for processing, have been introduced according to the genetic changes that have taken place in sweet corn cultivars since long ago.