GENES CONTROLLING COLEOPTILE LENGTH AND SEEDLING EMERGENCE IN WHEAT AND THEIR ROLE IN  PLANT HEIGHT

Khalid A. Elbudony

Seedling emergence in wheat is a complex trait that plays an important role in stand establishment especially after deep planting in low-precipitation regions. The genetic mechanism and its relationship with coleoptile length, plant height, peduncle length and spike length were investigated. A diverse doubled-haploid population derived from a cross between an ancient tall wheat cultivar ‘Indian’ and a super dwarf red spring cultivar ‘Perigee’ was used in this study. A set of 343 doubled-haploid lines along with parental lines (Indian and Perigee) was evaluated phenotypically in the field as well as in a controlled laboratory setting. Data were obtained on coleoptile length, seedling emergence, plant height, and peduncle length. All phenotypic traits showed strong positive correlations. Whole genome-genetic linkage maps were constructed using 83 simple sequence repeat (SSR) markers, which were eventually used to identify QTLs controlling genetic variation for the above-mentioned traits. Two major QTLs controlling plant height (Rht1 and Rht2) were co-localized with coleoptile length, seedling emergence, peduncle length, and spike length on 4B and 4D chromosomes. To nullify the influence of Rht1 and Rht2 mutants, four sub-population maps were constructed, which were used for the identification of new QTLs controlling variation other than dwarfing genes (Rht1 and Rht2) for different traits. Finding alternate dwarfing gene system by modulating auxin distribution, a ‘true’ wheat ortholog (TaABCB19) of the Arabidopsis ABCB19 has shown to be involved in regulating plant height via modulating auxin transport in the stem. True ortholog of AtPGP19 has been identified in various monocots and dicots species. The smallest genomic copy of PGP19 is present in barley and quite largely in Soybean, the variation in gene size ranged from7496 bp to 6628 bp. The gene structure showed similarities between monocots and dicots, with highly conservative exonic region 1 and 8. The TaABCB19 RNAi plant resulted in reduced height up to 48%, and more than doubled spikelet number. This studies furthers the scientific understanding of the genetic relationship of plant height with other growth related traits for selecting and combining desirable traits for wheat improvement.

GENES CONTROLLING COLEOPTILE LENGTH AND SEEDLING EMERGENCE IN WHEAT AND THEIR ROLE IN PLANT HEIGHT

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