Laelia anceps Lindl. (Orchidaceae) adaptation on phorophytes within an anthropized landscape, Amatlán de los Reyes, Veracruz, Mexico

Objective: To determine the best phorophyte species for the adaptation of the Laelia anceps Lindl orchid. (Orchidaceae) in an anthropized landscape. Design/methodology/approach: A completely randomized experimental design with four treatments (phorophytes) was used: Swietenia macrophylla King., Fraxinus sp., Persea schiedeana Nees. and Tecoma stans. (L.) Juss. ex Kunth), with five repetitions per phorophyte and with three L. anceps orchid plants in each phorophyte. The following variables were measured: day to emergence, root length and thickness, and survival at 28 weeks after tying them in phorophytes. Results: Root emergence of L. anceps occurred in less time in S. macrophylla and in Fraxinus sp. at 52 and 54 days respectively; the longest root length (19.11 cm) and number of roots (32.45) were observed in S. macrophylla. However, the root thickness was greater in Fraxinus sp. (0.28 cm). After 28 weeks of establishing the L. anceps plants; 100% survival was obtained in the phorophytes S. macrophylla and Fraxinus sp., 77% in P. schiedeana and 33% in T. stans. Study limitations/implications: The amount of light received by L. anceps in each phorophyte was not measured. Findings/Conclusions: The best phorophytes for the establishment of L. anceps were S. macrophylla and Fraxinus sp. observed, the best development and strength of the roots and 100% survival at 28 weeks.

Influence of Nano Silicon and Nano Selenium on Root Characters, Growth, Ion Selectivity, Yield, and Yield Components of Rice (Oryza sativa L.) under Salinity Conditions

Rice production under salinity stress is a critical challenge facing many countries, particularly those in arid and semi-arid regions. This challenge could be handled by applying novel approaches to overcome yield limiting factors and improve resource use efficiency. The usage of nanoparticles (NPs) could be a beneficial approach to managing the growing problem of soil salinity. The aim of our study was to investigate the advantageous effects of soaking and foliar application of silicon (Si) and selenium (Se), (NPs-Si at 12.5 mg L−1 and NPs-Se at 6.25 mg L−1) on root characteristics, moropho-physiological traits, and yields of two rice varieties (i.e., Giza 177 as a salt sensitive and Giza 178 as a salt tolerant) grown in saline soil compared to untreated plants (control treatment). Results showed that soaking NPs-Se resulted in the highest value of root thickness for Giza 178 (0.90 mm, 0.95 mm) and root volume (153.30 cm3, 154.30 cm3), while Giza 177 recorded 0.83 mm, 0.81 mm for root thickness and 143.30 cm3, 141.30 cm3 for root volume in the 2018 and 2019 seasons, respectively. Soaking NPs-Se, NPs-Si and foliar application of NPs-Se at BT resulted in the highest relative water content and dry matter, while foliar application of NPs-Si at BT gave the highest leaf area index of rice plants compared to the other treatments. Giza 178 (i.e., salt tolerant variety) significantly surpassed Giza 177 (i.e., salt sensitive variety) in the main yield components such as panicle number and filled grains/ panicle, while Giza 177 significantly exceeded Giza 178 in the panicle weight, 1000-grain weight, and unfilled grains number/ panicle. Soaking NPs-Se and foliar application of NPs-Si at BT resulted in the highest grain yield of 5.41 and 5.34 t ha−1 during 2018 and 5.00 and 4.91 t ha−1 during 2019, respectively. The salt sensitive variety (Giza 177) had the highest Na+ leaf content and Na+/K+ ratio as well as the lowest K+ leaf content during both seasons. Applying nano nutrients such as NPs-Si and NPs-Se improved the yield components of the salt sensitive variety (Giza 177) by enhancing its ion selectivity. Both NPs-Si and NPs-Se had almost the same mode of action to mitigate the harmful salinity and enhance plant growth, and subsequently improved the grain yield. In summary, the application of NPs-Si and NPs-Se is recommended as a result of their positive influence on rice growth and yield as well as minimizing the negative effects of salt stress.

Genetic effects of yield and root parameters in rice (Oryza sativa L.) at reproductive stage drought stress as apportioned by generation mean analysis

The nature of gene action governing important quantitative traits viz.yield and drought tolerance in rice were studied through six parameter model of generation means analysis using six generations (viz., P1, P2, F1, F2, BC1 and BC2) of five crosses by imposing drought stress at reproductive stage. Additive gene action was noticed for the traits like days to flowering, panicle length, 100 grain weight and root thickness in majority of the crosses while the yield characters like productive tillers / plant, filled grains / panicle, harvest index and grain yield / plant and the drought tolerant characters like spikelet fertility, root length and root / shoot ratio were governed by dominance gene action. Both additive and dominance effects were found in panicle length in the cross Kallurundaikar / Moroberekan; spikelet fertility, dry root weight, root/shoot ratio and grain yield / plant in the cross Norungan / Moroberekan and 100 grain weight and root thickness in the cross PMK 2 / Moroberekan. Interaction effects mainly of additive x additive was noticed in panicle length, filled grains /panicle, dry root weight and root/shoot ratio in most of the crosses while dominance x dominance gene action was predominant in 100 grain weight and both additive x dominance and dominance x dominance in days to flowering and plant height.

The Use of Phytohormones in Production of Fruit Tree Rootstocks in Nursery Without Irrigation

The most commonly used phytohormone to reduce the impact of drought is 24‑epibrassinolide (EBR). In this study, EBR was applied over two years on young rootstocks of peach (B‑VA‑1) and myrobalan (Vanovice myrobalan) seedlings. Young rootstocks were treated by EBR at different concentrations, IAA and a mixture of EBR with IAA. The best results in seedling height of Vanovice myrobalan in both years had the treatment of 0.05% IAA, 549.69 mm (2016) and 553.77 mm (2017). On the other hand, on the crown root thickness was affected the most in 2016 by treatment of EBR 0.06 ppm (5.5 mm) and in 2017 by EBR 0.01 ppm (7.5mm). At B‑VA‑1 rootstock, the highest seedlings in 2016 were measured after EBR + IAA treatment (1573.18 mm) and in 2017 after IAA treatment (682.75 mm). The highest thickness of the crown root was recorded in 2016 after EBR and IAA (17.76 mm) and in 2017 after EBR 0.1 ppm (8.08 mm) treatments. At more than half of the treatments the control variant was evaluated as a variant with the least satisfying results. According to the results EBR and IAA are possibly increasing the quality of the rootstocks in conditions of a nursery without an irrigation.

Combining ability and heterosis analysis for drought tolerant traits in rice (Oryza sativa L.)

Rice is the most important staple food for more than half of the world’s population and also for most of the countries. A Line x Tester analysis was undertaken to study the nature of gene action for yield and drought tolerant traits. The ratio of SCA and GCA was less than unity for all the characters which revealed that the preponderance of non- additive gene action governing the traits concerned. The lines viz., ADT 43, ADT (R) 49, CO (R) 50 and the testers viz., PMK (R) 3, Chandikar and Anna (R) 4 were adjudged as the best general combiners for drought tolerant traits. The cross combinations viz., ADT 39 x Vellaichitraikar had exhibited significant values for dry root weight (9.66), root/shoot ratio (0.31), root length (3.82), number of roots per plant (37.08), root thickness (0.11), root volume (4.27) and root length density (0.03) ADT (R) 49 x Chandikar for 70 percent relative water content (8.85), dry root weight (18.03), dry shoot weight (40.55), root length (3.10), number of roots per plant (140.16) root thickness (0.38) and root volume (23.14) were found to be specific combiners for most of the drought tolerant traits. The cross combinations, viz., ADT 43 x Anna (R) 4, ADT (R) 49 x Chandikar and ADT 43 x PMK (R) 3 had highly significant standard heterosis. Breeding for drought tolerance in rice would be of immense value to the farmers economic health, family well-being and harmony in the society.

The minimum residual root thickness after using ProTaper, RaCe and Gates-Glidden drills: A cone beam computerized tomography study

ABSTRACT Objective: The aim of this study was to evaluate the minimum residual root thickness (MRRT) of the danger zone after preflaring of the mesio-buccal (MB) canal of mandibular first molars using ProTaper, RaCe and Gates-Glidden (GG) drills as coronal shapers by cone beam computerized tomography (CBCT). Materials and Methods: In this experimental study, the initial CBCT scans of 75 MB canals of mandibular first molars were provided within 1, 2, 3 and 4 mm of the furcation level. The samples were divided into three groups. The samples of ProTaper and RaCe groups were prepared up to F2 and #25.04 as the master apical file (MAF), respectively. The coronal preparation of the samples in the GG group was done using GG drills #2, #3 and #4 and canals were prepared till MAF # 25. After obtaining the postinstrumentation images, the MRRT and the amount of removed dentin were analyzed by t-test and ANOVA statistical analyses. Results: The GG drills removed significantly more dentin than RaCe at all the sections (P < 0.05) and more than ProTaper at 3 mm from the furcation. Statistically there was no significant difference between ProTaper and RaCe groups (P > 0.05). There was no significant difference in MRRT between the groups (P > 0.05). The mean MRRT was not < 0.75 mm at all sections. Conclusion: Based on the results of this study, when an appropriate root thickness is initially present, all of the instruments that were investigated may safely be used as coronal shapers in MB canals of mandibular first molars.