Variation in Root System Architecture among the Founder Parents of Two 8-way MAGIC Wheat Populations for Selection in Breeding

Root system architecture (RSA) is a target for breeding crops with effective nutrient and water use. Breeding can use populations designed to map quantitative trait loci (QTL). Here we non-invasively phenotype roots and leaves of the 16 foundation parents of two multi-parent advanced generation inter-cross (MAGIC) populations, covering diversity in spring (CSIRO MAGIC) and winter (NIAB MAGIC) wheats. RSA components varied after 16 days in the upgraded, paper-based imaging platform, GrowScreen-PaGe: lateral root length 2.2 fold; total root length, 1.9 fold; and seminal root angle 1.2 fold. RSA components total and lateral root length had the highest root heritabilities (H2) (H2 = 0.4 for CSIRO and NIAB parents) and good repeatability (r = 0.7) in the GrowScreen-PaGe. These can be combined with leaf length (H2 = 0.8 CSIRO; 0.7 NIAB) and number (H2 = 0.6 CSIRO; 0.7 NIAB) to identify root and shoot QTL to breed for wheats with vigorous RSA and shoot growth at establishment, a critical phase for crop productivity. Time resolved phenotyping of MAGIC wheats also revealed parents to cross in future for growth rate traits (fastest: Robigus–NIAB and AC Barrie–CSIRO; slowest Rialto–NIAB and G204 Xiaoyan54–CSIRO) and root: shoot allocation traits (fast growers grew roots, notably laterals, quicker than leaves, compared to slow growers).

Response of Hybrid Tomato (Solanum lycopersiucm L) for Calcium Nutrition: Growth, Root Traits and SPAD Index

Aims: To evaluate the effect of various sources and levels of calcium fertilisation in improving the growth and SPAD index of hybrid tomato at different growth stages. Study Design: Factorial randomized block design (FRBD) with three replications. Place and Duration of Study: A field experiment was conducted in the farmer’s field at Devarayapuram village, Thondamuthur block, Coimbatore from January to April, 2021. Methodology: A field experiment was conducted with hybrid tomato (Solanum lycopersiucm L) Shivam by using various organic and inorganic calcium sources viz., calcium sulphate, calcium nitrate, calcium silicate, poultry manure and pressmud applied at different levels (0, 20, 40, 60, 80 kg Ca ha-1) in a factorial randomized block design with three replications. The growth parameters such as plant height, root length, lateral root length, root volume and SPAD index were recorded as per standard protocols at different plant growth stages. Results: A linear increase in the plant growth, root traits and SPAD index of hybrid tomato was noted by the addition of organic and inorganic sources of calcium and the highest values were observed with the application of 80 kg Ca ha-1. Higher plant height (93.8 cm), root length (16.8 cm), lateral root length (13.3 g cc-1) and SPAD index (62.0) was registered with poultry manure applied at 80 kg Ca ha-1 which was followed by pressmud applied at the same level. Skipping of calcium in the fertiliser schedule registered the lowest growth response of hybrid tomato at all the growth stages. Conclusion: Inorganic Ca fertiliser sources though improved the growth, root traits and SPAD index of hybrid tomato at different growth stages, and it was comparatively lesser than the organic sources such as poultry manure and pressmud as calcium sources. The order of better growth performance was: Poultry manure > Pressmud > Ca silicate > Ca Nitrate > Ca sulphate. The lowest values of all the growth attributes were noted with NPK control. It was concluded that application of poultry manure at 80 kg Ca ha-1 would be effective in improving the growth, root traits and SPAD index of hybrid tomato.

Interactions between magnesium, calcium, and aluminum on soybean root elongation

Alleviation of Al rhizotoxicity by Ca and Mg can differ among species and genotypes. Root elongation of soybean [Glycine max (L.) Merr.] line N93-S-179 and cvs. Young and Ransom exposed to varying concentrations of Al, Ca and Mg were compared in two experiments using a vertically split root system. Roots extending from a surface compartment with limed soil grew for 12 days into a subsurface compartment with nutrient solution treatments maintained at pH 4.6 with either 0 or 15 µmol L-1 Al. Calcium and Mg concentrations in treatments ranging from 0 to 20 mmol L-1. Although an adequate supply of Mg was provided in the surface soil compartment for soybean top growth, an inclusion of Mg was necessary in the subsurface solutions to promote root elongation in both the presence and absence of Al. In the absence of Al in the subsurface solution, tap root length increased by 74 % and lateral root length tripled when Mg in the solutions was increased from 0 to either 2 or 10 mmol L-1. In the presence of 15 µmol L-1 Al, additions of 2 or 10 mmol L-1 Mg increased tap root length fourfold and lateral root length by a factor of 65. This high efficacy of Mg may have masked differences in Al tolerance between genotypes N93 and Young. Magnesium was more effective than Ca in alleviating Al rhizotoxicity, and its ameliorative properties could not be accounted for by estimated electrostatic changes in root membrane potential and Al3+ activity at the root surface. The physiological mechanisms of Mg alleviation of Al injury in roots, however, are not known.

NaCl salinity affects lateral root development in Plantago maritima

Root growth and morphology were assessed weekly in hydroponically-grown seedlings of the halophyte Plantago maritima L. during exposure to 0, 50, 100 and 200 mm NaCl for 21 d. Relative growth rate was reduced by 25% at 200 mm NaCl. The lower NaCl treatments did not affect relative growth rates. Primary and lateral roots responded differently to NaCl. While primary-root length increased at all NaCl concentrations, total lateral-root length increased at 50 and was not affected at 100 mm but was considerably reduced at 200 mm NaCl. NaCl concentrations of 50 and 100 mm, which had no effect on relative growth rate or total lateral-root length, severely affected root branching pattern in that the number of first, second and third order laterals was reduced. At 200 mm NaCl third order laterals were not formed at all. However, mean lateral-root length was increased at all NaCl concentrations and was highest at 200 mm NaCl. We conclude that the increase in total lateral-root length in plants at 50 and 100 mm NaCl was mainly caused by increased length growth, while the decrease in total lateral-root length at 200 mm was the consequence of inhibition of lateral root primordia and / or the activation of apical meristems rather than reduced length growth.

Response of Selected Soybean (Glycine max) Cultivars to Dimethenamid and Metolachlor in Hydroponic Conditions

Soybean cultivars were grown in a hydroponic culture to evaluate tolerance to dimethenamid and metolachlor. Root length was reduced in 7 of the 32 cultivars with 50 ppb dimethenamid. ‘Asgrow 5403’ and ‘Bryan’ root lengths were reduced more than 20%. ‘Asgrow 6297’ was the only cultivar with greater than 12% root length reductions with 83 ppb metolachlor. The longest lateral root of all cultivars was shortened with dimethenamid. ‘NK-1460’ and Bryan expressed the most lateral root length reduction, at 73 and 62%, respectively. Asgrow 6297 was tolerant to dimethenamid, but lateral roots were reduced 16%. Metolachlor reduced the lateral root lengths of 12 cultivars, with Asgrow 5403, ‘Coker 6955,’ and Bryan reduced more than 20%. Bryan was the most sensitive cultivar to both herbicides, while ‘Brim’ was the most tolerant of cultivars evaluated.

Greenhouse Irrigation Systems Affect Growth of `TAM-Mild Jalapeño-1' Pepper Seedlings

Two studies were conducted to determine how greenhouse irrigation systems alter root elongation, root morphology, shoot growth, and water status of `TAM-Mild Jalapeño-1' pepper (Capsicum annuum L.) seedlings. Transplants were grown in containerized trays for 48 days in a greenhouse. Irrigation systems were 1) flotation (FI), 2) 28 days FI plus 14 days overhead (OI; FI + OI), 3) alternate OI and FI (OI–FI), and 4) OI. FI and OI–FI transplants maintained a uniform lateral root length increase between 20 and 41 days after seeding (DAS). In FI + OI and OI transplants, lateral root elongation tended to plateau at ≈31 DAS; however, by increasing the number and length (33%) of basal roots, OI transplants had a total root growth compensation during the remaining growth period. At 41 DAS, OI transplants had a higher shoot: root ratio (S: R = 5) and maintained a higher shoot water potential (Ψstem = –0.58) than FI transplants (S: R = 3; Ψstem= –0.69 MPa, respectively). In the second study, OI transplants maintained higher Ψstem than FI transplants. The latter had a lower stomatal conductance and photosynthesis rate than OI and FI + OI transplants. FI may be used to lower the S: R ratio and promote hardiness in jalapeño transplants.

MINIMIZING CORKY ROOT DESTRUCTION OF LETTUCE ROOT SYSTEMS BY THE USE OF TRANSPLANTS

Corky root (CR) of lettuce (Lactuca sativa L.) is caused by the bacterium Rhizomonas suberifaciens. Current management strategies involve the use of resistant cultivars and crop rotation. The use of transplants as a method to grow CR-susceptible cultivars in CR-infested fields was recently demonstrated. The objective of this study was to evaluate corky root destruction of root systems of direct-seeded and transplanted lettuce. Direct seeded, and three and five week old transplants of CR susceptible `Shawnee' and CR resistant `South Bay' crisphead lettuce were grown in a naturally CR-infested field. Root systems were evaluated at head harvest maturity. When direct seeded, South Bay developed 104% more total lateral root length than did Shawnee. When transplanted at three and five weeks, South Bay developed 50% and 61% more total lateral root length than Shawnee, respectively. Total lateral root length for Shawnee transplanted at five weeks was 100% greater than direct seeded Shawnee. Comparatively, total lateral root length for South Bay transplanted at five weeks was 58% greater than direct seeded South Bay. Tap root lengths and dry weights were not different among planting systems. Transplanting is a possible method for reducing the impact of CR on lettuce lateral root development.