No abstract
Marker-assisted selection (MAS) helps to shorten breeding time as well as reduce breeding resources and efforts. In our MAS program, we have targeted one of previously reported LD-blocks with its simple sequence repeat (SSR) marker(s), putatively associated with, at least, four different fibre quality QTLs such as fibre length, strength, micronaire and uniformity. In order to transfer targeted QTLs from a donor genotype to a cultivar of choice, we selected G. hirsutum donor genotypes L-141 and LN-1, possessing a fibre quality trait-associated LD-block from the chromosome 7/16. We crossed the donor lines with local elite G. hirsutum cultivars ‘Andijan-35’ and ‘Mekhnat’ as recipients. As a result, two segregating populations on LD-block of interest containing fibre QTLs were developed through backcrossing (BC) of F1 hybrids with their relative recipients (used as recurrent parents) up to five generations. In each BC and segregating BC1-5F1 populations, a transfer of targeted LD-block/QTLs was monitored using a highly polymorphic SSR marker, BNL1604 genotype. The homozygous cultivar genotypes with superior fibre quality and agronomic traits, bearing a targeted LD-block of interest, were individually selected from self-pollinated BC5F1 (BC5F2–5) population plants using the early-season PCR screening analysis of BNL1604 marker locus and the end-of-season fibre quality parameters. Only improved hybrids with superior fibre quality compared to original recipient parent were used for the next cycle of breeding. We successfully developed two novel MAS-derived cotton cultivars (named as ‘Ravnaq-1’ and ‘Ravnaq-2’) of BC5F5 generations. Both novel MAS cultivars possessed stronger and longer fibre as well as improved fibre uniformity and micronaire compared to the original recurrent parents, ‘Andijan-35’ and ‘Mekhnat’. Our efforts demonstrated a precise transfer of the same LD-block with, at least, four superior fibre QTLs in the two independent MAS breeding experiments exploiting different parental genotypes. Results exemplify the feasibility of MAS in cotton breeding.
Background and Objective: Soil salinity is a major abiotic stress factor affecting cotton production worldwide. This study aimed to deal with the morpho-biological traits of cotton affected by chloride-sulfate salt during the germination stage. Materials and Methods: About 21 cotton genotypes were obtained from Uzbekistan germplasm. Plant materials were grown in a greenhouse under optimum and soil salinity (mainly strong sulfate salinity) conditions. Data on plant morpho-physiological traits including germination rate, plant length and plant fresh and dry weight were collected at the seedling stage. The greenhouse experiments lasted 30 days. Results: Namangan-77, considered to be susceptible to salinity, was highly damaged by salinity stress. Salt-resistant KK-1795, Hapicala 19, Zangi Ota and An-Boyovut-2 varieties showed better morpho-biological characteristics than other varieties. A PCR test with the salinity-associated BNL-3140 marker proved that these varieties are molecularly resistant to salinity. Conclusion: Results on the plantsʼ germination rate and biomass as well as salinity-associated primer testing resulting from highly sulfated saline soil serve to identify genes that respond to salinity.
Background and Objective: A supramolecular complex of glycyrrhizic and salicylic acids has been established as one of the potential plant growth promoters. In this study, the impact of the complex on the root growth of grapes, grown from the apical meristem was studied. Materials and Methods: The 1-2 mm conical meristems were isolated from the terminal and lateral buds and kept in special containers.The obtained tissues were cleaned from excessive parts and sterilized in special conditions. Further apical meristems were rooted in modified MS and WPM nutrient media. The effects of the complex on the number and length of roots of four grape varieties, widely grown in Uzbekistan, showed its potential as a root growth regulator. Results: The complex in 0.15 and 0.17 mg LG 1 doses together with benzyl amino purine in MS medium or with meta-topolin and naphthalene acetic acid in WPN culture media led to several-fold increases in root growth in all grape varieties in vitro. The effects of the complex at 0.15 mg LG 1 dose resulted in at least twice the longer root length of all selected grape varieties compared to the control of both culture media. A higher 0.17 mg LG 1 dose led to several-fold increases in root length. Besides, significant increases were observed in root numbers in explants, grown in a culture medium holding 0.17 mg LG 1 of the complex. Conclusion: These results could determine a new discipline in plant hormones utilized to grow plants from the apical meristem.
Background and Objective: Stimulation of plant growth by rhizobacteria is a part of agricultural practice. Its enhancement leads to significant improvement in plant biology. In this study, we studied the effect of a mixture of salt-tolerant rhizobacteria containing strains KY041889, KY041694, KY041978 and KY041979 on the growth of two cotton varieties: Porloq-4 and Ravnaq-1. Materials and Methods: Experimental plants were grown in three different places in a plot and their agronomic traits, as well as fibre traits, were compared following the seed treatment with bacterial strains. Results: Indicators such as plant height, number of sympodia, buds and bolls and seed weight significantly improved after treatment. Bacterial treatment accelerated plant germination and flowering. No negative effects were determined on fibre quality in both varieties. Enhancement was defined in seed weight following the treatment with rhizobacteria but not in the total weight of fibre. Conclusion: Isolated rhizobacteria were found to stimulate plant growth which was explained by enhanced levels of agronomic traits such as several buds, flowers, bolls and sympodia.
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