Stability analysis and selection of sugar beet (Beta vulgaris L.) genotypes using AMMI, BLUP, GGE biplot and MTSI.

The methods utilized to analyze genotype by environment interaction (GEI) and assess the stability and adaptability of genotypes are constantly changing and developing. In this regard, often instead of depending on a single analysis, it is better to use a combination of several methods to measure the nature of the GEI from various dimensions. In this study, the GEI was investigated using different methods. For this purpose, 18 sugar beet genotypes were evaluated in randomized complete block design in five research stations over 2 years. The additive effects analysis of the additive main effects and multiplicative interaction (AMMI) model showed that the effects of genotype, environment and GEI were significant for root yield (RY), white sugar yield (WSY), sugar content (SC), and extraction coefficient of sugar (ECS). The multiplicative effect's analysis of AMMI into interaction principal components (IPCs) showed that the number of significant components varies from one to four in the studied traits. According to the biplot of the mean yield against the weighted average of absolute scores (WAAS) of the IPCs, G2 and G16 for RY, G16 and G2 for WSY, G6, G4, and G1 for SC and G8, G10 and G15 for ECS were identified as stable genotypes with optimum performance. The likelihood ratio test showed that the effects of genotype and GEI was significant for all studied traits. In terms of RY and WSY, G3 and G4 had high mean values of the best linear unbiased predictions (BLUP), so they were identified as suitable genotypes. However, in terms of SC and ECS, G15 obtained high mean values of the BLUP. The GGE biplot method classified environments into four (RY and ECS) and three (WSY and SC) mega-environments (MEs). Based on the multi-trait stability index (MTSI), G15, G10, G6, and G1 were the most ideal genotypes.

Evaluation of resistance and determination of stability of different sugar beet (Beta vulgaris L.) genotypes in rhizomania-infected conditions.

Plant diseases are considered one of the main factors reducing yield and quality of crops, which are constantly developing and creating more virulent races and cause the resistance of more genes to break. Identifying resistance sources and including them in breeding programs will improve resistant genotypes. Rhizomania is the most common, widespread, and devastating disease of sugar beet in Iran and worldwide. Breeding genotypes with disease resistance genes is one of the most important ways to deal with this destructive disease. Twenty sugar beet genotypes along with five controls were evaluated in a randomized complete block design with four replications in rhizomania-infected conditions in four regions of Mashhad, Shiraz, Miandoab, and Hamedan for 2 years. The results of genotypic reaction to rhizomania showed that the genotypes with resistance reaction were much more frequent than those with susceptibility reaction. The analysis of multiplicative effects of the AMMI model showed that the first six components were significant and explained 98.80% of the interaction variations. The biplot obtained from the mean white sugar yield and the first interaction principal component confirmed the superiority of the RM5 genotype due to its high white sugar yield and stability in infected conditions. The results obtained from the first three principal components biplot showed that the RM9 genotype with a mean white sugar yield of 11.91 t. ha-1 was a genotype with vast general stability in all disease-infected environments. Based on the results of the MTSI index, RM3, RM17, RM9, RM13, and RM15 are introduced as stable genotypes under rhizomania-infected conditions. In conclusion, it seems that the studied genotypes have valuable and useful genes inherited from their parents to deal with rhizomania disease. Applying these genotypes in sugar beet breeding programs can effectively prevent the threat of rhizomania.

The potential of tebuconazole for mitigating oxidative stress caused by limited irrigation and improving sugar yield and root quality traits in sugar beet.

Water deficit is the main reason for sugar yield losses in semi-arid areas. Triazole derivatives may mitigate the harmful impacts of water stress. Therefore, this study aimed to assess the effect of tebuconazole (TEB) application on antioxidants, root quality traits, and sugar yield under drought stress conditions. The treatments included three levels of irrigation set according to crop evapotranspiration (ETC): 100%, 75%, and 50% ETC, as well as three levels of TEB (0, 25, and 50 mg L-1). While significantly increasing antioxidant and alpha-amino-nitrogen (α-amino-N) contents, limited irrigation decreased total chlorophyll content, net photosynthesis rate, leaf relative water content, the weight of roots, and sugar yield. In contrast, TEB treatment resulted in a marked rise in all biological and physiological traits as well as enzymatic antioxidants. Our findings indicated that the decline in α-amino-N content might be linked to increased NR activity in response to the TEB application. Our results also showed that the stress-ameliorating role of TEB cannot be associated with the increase of flavonols (quercetin and rutin). Overall, the results demonstrated that TEB has a high potential for ameliorating the negative impacts of limited irrigation.

Carbon isotopes and water use efficiency: sense and sensitivity.

We revisit the relationship between plant water use efficiency and carbon isotope signatures (delta(13)C) of plant material. Based on the definitions of intrinsic, instantaneous and integrated water use efficiency, we discuss the implications for interpreting delta(13)C data from leaf to landscape levels, and across diurnal to decadal timescales. Previous studies have often applied a simplified, linear relationship between delta(13)C, ratios of intercellular to ambient CO(2) mole fraction (C (i)/C (a)), and water use efficiency. In contrast, photosynthetic (13)C discrimination (Delta) is sensitive to the ratio of the chloroplast to ambient CO(2) mole fraction, C (c)/C (a) (rather than C (i)/C (a)) and, consequently, to mesophyll conductance. Because mesophyll conductance may differ between species and over time, it is not possible to determine C (c)/C (a) from the same gas exchange measurements as C (i)/C (a). On the other hand, water use efficiency at the leaf level depends on evaporative demand, which does not directly affect Delta. Water use efficiency and Delta can thus vary independently, making it difficult to obtain trends in water use efficiency from delta(13)C data. As an alternative approach, we offer a model available at http://carbonisotopes.googlepages.com to explore how water use efficiency and (13)C discrimination are related across leaf and canopy scales. The model provides a tool to investigate whether trends in Delta indicate changes in leaf functional traits and/or environmental conditions during leaf growth, and how they are associated with trends in plant water use efficiency. The model can be used, for example, to examine whether trends in delta(13)C signatures obtained from tree rings imply changes in tree water use efficiency in response to atmospheric CO(2) increase. This is crucial for predicting how plants may respond to future climate change.

A preliminary study on genotypic differences in transcript abundance of drought-responsive genes in sugar beet.

In this study, four sugar beet genotypes of differing responses to drought were selected from a field experiment conducted under well-watered and water-limited conditions in 2004. In addition, two candidate genes: 2-cysteine peroxiredoxin (2-cys prx) and Nucleoside Diphosphate Kinase (NDPK), thought to be associated with drought tolerance, were chosen from a previous proteomics study in sugar beet. An expression analysis of the two drought-regulated genes using semi-quantitative reverse transcription Polymerase Chain Reaction (RT-PCR) indicated that there were genotypic differences in the transcript abundance of the candidate genes with the differences in the expression level of 2-cys prx being likely associated with the drought responses of the genotypes in a two-year field study. However, the expression analysis of the genes has to be investigated at different stages of the stress period on more genotypes.