Screening Wheat Genotypes for Coleoptile Length: A Trait for Drought Tolerance

Abstract

The study was conducted during Rabi season of 2013-14 at the Wheat Research Centre (WRC), Bangladesh Agricultural Research Institute (BARI), Dinajpur. Thirty wheat genotypes including local control BARI Gom 26 were evaluated in split-split plot design having two replications with irrigation in the main plot, seeding depth in a sub-plot and genotype was in sub-sub-plot. The main objective of this study was to evaluate new exotic lines against drought, with emphasis on coleoptile length under Bangladeshi conditions, and to identify drought tolerant germplasm. To measure potential coleoptile length (CL), disease free, healthy, uniform seeds were sown in wooden trays with sandy soil in a temperature controlled room at 200 degree days (20 o c X 10 days). The genotypes were evaluated for yield, and yield components i.e., plant establishment, plant height (cm), spikes per m 2 , grains per Spike, 1000-grain weight (g) and visual grain quality. Selection of genotypes was based on Schneider's stress severity index (SSSI), yield under drought condition and coleoptiles length. Deep seeding over normal seeding had a significant effect on yield and the yield components, as did water stress. The interaction of the two factors showed that seeding depth causes more yield loss than irrigation. More traits showed significant relationships in deep seeding conditions than normal conditions, meaning that there is greater scope for screening wheat using sowing depth. Based on higher negative value of SSSI and higher yield in deep sowing conditions the genotypes G 16, G 13, G 12, G 24, G 2, G 18, G 19 and G 3 were primarily selected for drought tolerance and will be evaluated further for advanced studies. These genotypes also have longer coleoptiles ranging from 7.4 to 10.5 cm.

A Physio-Morphological Trait-Based Approach for Breeding Drought Tolerant Wheat

“…The coleoptile of wheat is a pointed protective sheath, which covers the emerging shoot or the first leaf during germination (Farhad et al, 2014). When a seed germinates, the coleoptile pushes through the soil and protects the young shoot.…”

“…The concept of deep planting is more subjective as the depth seeding may be defined based on the soil moisture availability. Although coleoptile length may not be the sole factor responsible for emergence after deep sowing (Mohan et al, 2013), the frequency of emergence under these conditions, when combined with the threat of surface desiccation, is greater in genotypes with longer coleoptiles than those with shorter coleoptiles (Rebetzke et al, 2005(Rebetzke et al, , 2007Farhad et al, 2014). Poor plant establishment can, therefore, result from shorter coleoptiles under stressed conditions (Schillinger et al, 1998), especially in dry environments.…”

Expansins: roles in plant growth and potential applications in crop improvement

“…Wheat breeders for example have been screening for genotypes with longer coleoptile lengths. The coleoptile is essential for successful emergence and early plant vigour (Farhad 2014 ). Plants with longer coleoptiles can be sown deeper and this allows growers to exploit soil moisture lying below the drying topsoil.…”

“…Plants with longer coleoptiles can be sown deeper and this allows growers to exploit soil moisture lying below the drying topsoil. Deeper sowing also assists in reducing removal of seeds by birds and rodents and in avoiding phytotoxicity associated with some pre-emergent herbicides (Farhad 2014 ). Overexpression of OsEXP4 was shown to significantly increase coleoptile and mesocotyl length by a massive 31 and 97 %, respectively (Choi et al 2003 ) as described above.…”

Phenotyping and Identification of Reduced Height (Rht) Alleles (Rht-B1b and Rht-D1b) in a Nepali Spring Wheat (Triticum aestivum L.) Diversity Panel to Enable Seedling Vigor Selection

“…Longer coleoptiles allow deep sowing, which helps in the exploitation of soil moisture [5][6][7] and facilitates early establishment as well as weed suppression [8]. Therefore, wheat accessions having longer coleoptiles are better suited to areas with drought stress or drought at the early growth stage of the crop [4,5,9]. In this context, breeding wheat for longer coleoptiles is a strategy to cope with these challenges [4,[9][10][11].…”