Abstract
The challenge in tetraploid cotton cultivars is the narrow genetic base and therefore, the bottleneck is how to obtain interspecific hybrids and introduce the germplasm directly from wild cotton to elite cultivars. Construction of genetic maps has provided insight into understanding the genome structure, interrelationships between organisms in relation to evolution, and discovery of genes that carry important agronomic traits in plants. In this study, we generated an interspecific hybrid between two wild diploid cottons, Gossypium davidsonii and Gossypium klotzschianum, and genotyped 188 F2:3 populations in order to develop a genetic map. We screened 12,560 SWU Simple Sequence Repeat (SSR) primers and obtained 1000 polymorphic markers which accounted for only 8%. A total of 928 polymorphic primers were successfully scored and only 728 were effectively linked across the 13 chromosomes, but with an asymmetrical distribution. The map length was 1480.23 cM, with an average length of 2.182 cM between adjacent markers. A high percentage of the markers on the map developed, and for the physical map of G. raimondii, exhibited highly significant collinearity, with two types of duplication. High level of segregation distortion was observed. A total of 27 key genes were identified with diverse roles in plant hormone signaling, development, and defense reactions. The achievement of developing the F2:3 population and its genetic map constructions may be a landmark in establishing a new tool for the genetic improvement of cultivars from wild plants in cotton. Our map had an increased recombination length compared to other maps developed from other D genome cotton species.
Highlights
Wild cotton species have been well studied in terms of their variation in desired traits, such as chemical defenses [1], oil content [2], and fibre production [3,4]
Plant germplasm resources originate from a number of historical genetic events as a response to environmental stresses and selection; wild progenitors are important reservoirs of natural genetic variation that can be exploited to increase the genetic base of the elite cultivars
Our map is the first map developed from wild progenitors of the D genome; it covers a total map size of 1480.23 cM, with 728 mono-markers
Summary
Wild cotton species have been well studied in terms of their variation in desired traits, such as chemical defenses [1], oil content [2], and fibre production [3,4]. The production of cotton is ever-declining due to abiotic and biotic stress: currently the loss in cotton production is estimated to stand at 30% as a result of stress effects [7] This is projected to continue further due to available lands being highly polluted with increased salinity, and is estimated to cover more than 6% of the world’s arable land [8]. Wild cotton species have immense genetic diversity with great potential to improve many important agronomic traits, such as resistance to disease, fibre qualities, and abiotic stress tolerance [11,12,13]. The valuable agronomic traits in wild cotton progenitors can be exploited effectively to improve cultivated cotton cultivars and solve many problems associated with fibre quality, resistance to insects, pathogens, and tolerance to abiotic stress [11,14]
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