Evaluation of root traits and water use efficiency of different cotton genotypes in the presence or absence of a soil-hardpan

Cotton(Gossypium spp.) is an important fiber and oil crop grown worldwide. Water and nutrient stresses are major issues affecting cotton production globally. Root traits are critical in improving water and nutrient uptake and maintaining plant productivity under optimal as well as drought conditions.However, root traits have rarely been utilized in cotton breeding programs, a major reason being the lack of information regarding genetic variability for root traits. The objective of this research was to evaluate ten selected cotton genotypes for root traits and water use efficiency. The tested genotypes included germplasm lines(PD 1 and PD 695) and cultivars that are currently grown in the southeastern USA(PHY 499 WRF, PHY 444 WRF, PHY 430 W3 FE, DP 1646 B2 XF, DP 1538 B2 XF, DP 1851 B3 XF, NG5007 B2 XF, and ST 5020 GLT). Experiments were conducted under controlled environmental conditions in 2018 and 2019. A hardpan treatment was included in the second year to evaluate the effect of a soil hardpan on root traits and water use efficiency. Genotype PHY 499 WRF ranked at the top and NG5007 B2 XF ranked at the bottom for root morphological traits(total and fine root length, surface area,and volume) and root weight. PHY 499 WRF was also one of the best biomass producers and had high water use efficiency. PHY 444 WRF, PHY 430 W3 FE, and PD-1 were the other best genotypes in terms of root traits and water use efficiency. All genotypes had higher values for root traits and water use efficiency under hardpan conditions. This trend indicates a horizontal proliferation of root systems when they incur a stress imposed by a hardpan. The genotypic differences identified in this research for root traits and water use efficiency would be valuable for selecting genotypes for cotton breeding programs.

Application of near infrared spectroscopy in cotton fiber micronaire measurement

The term‘‘micronaire”describes an important cotton fiber property by characterizing both the fiber maturity and fineness.In practice,micronaire is regularly measured in laboratories with the well established high volume instrumentation(HVITM)protocol.In most scenarios,cotton breeders/geneticists sent cotton breeding line field trial samples to laboratories equipped to use the HVI^TM systems available for fiber micronaire determination.Researchers have previously investigated the use of NIR as an alternative means of measuring micronaire either at breeding sites or in standard laboratories.As a proof-of-concept investigation,this study collected both near infrared(NIR)spectra and HVI^TM micronaire from a total of 381 cottons harvested in the 2011 and 2012 crop years.Partial least square(PLS)calibration model relating NIR spectral information to fiber HVITM micronaire was developed and then applied to both a validation sample set from identical crop years and an independent test sample set from the 2014 crop year.Results indicated an acceptable bias(or differences between HVI^TM measured and NIR predicted micronaire)and an over 97%correctly predicted micronaire(within±0.30 micronaire unit)in an independent test set.Therefore,the development of a robust and effective NIR model for rapid laboratory micronaire assessment that would be applicable to remote/breeding locations is feasible.