Dose-Response Study to Evaluate Dicamba Tolerance in Selected Wild Tomato Germplasm

A greenhouse dose-response study was conducted to determine the tolerance of three wild tomato accessions (TOM199, TOM198, TOM300) in comparison to a commercial cultivar (Better Boy) against the dicamba application at five rates (0, 70, 140, 210, and 280 g ae ha-1) at 14 and 28 days after treatment (DAT). Several physiological traits were evaluated at 0, 1, 3, 5, and 7 DAT. Wild accessions and cultivar were killed at all rates above 70 g ae ha-1 at 14 and 28 DAT, which is why differences between accessions and cultivar were only evident at 70 g ae ha-1. The GR50 (the herbicide rate that causes 50% reduction in dry weight) of Better Boy was 4.4 g ae ha-1 at 28 DAT, and this cultivar was approximately 11-fold more sensitive than wild accessions. At 7 DAT, the levels of H2O2 for wild accessions were lower than Better Boy up to 5 at 70 g ae ha-1 of dicamba. Furthermore, wild accessions showed lower herbicide absorption than Better Boy at all dicamba doses at 1, 3, and 7 DAT. All the three wild accessions expressed tolerance to the dicamba application at the dose of 70 g ae ha-1. At the same time, Better Boy and wild accessions were susceptible to dicamba application at rates of 140, 210, and 280 g ae ha-1.

Morphological, physiological, and biochemical responses of onion (Allium cepa L.) breeding lines to single and combined salt and drought stresses

Abiotic stresses deteriorate plant growth resulting in devastating yield losses. Salt stress solely cause ionic toxicity and disturbed homeostasis, whereas combined salt and drought stress has more pronounced effects on plants. Here we performed a pot experiment using 32 Turkish onion breeding lines and commercial cultivars for screening against salt, drought and combined salt and drought stress treatments initiated at the bulbification stage under greenhouse conditions. Physiological characteristics, such as gaseous exchange traits, chlorophyll index, leaf temperature, and morphological traits including number of leaves, length and diameter of leaf were measured during stress treatment and yield response of the onions was quantified by measuring bulb length, bulb diameter and bulb weight after harvest. Proline and malondialdehyde accumulation were estimated for biochemical effect of stress on onion genotypes. All genotypes responded differentially to the applied single and combined stresses. Overall results revealed that the breeding lines K25, U6, U17 and commercial cultivar K58, were grouped as sensitive across all stresses, whereas the breeding lines K41, U47, U49 and commercial cultivar K52, were found to be the most stable upon stress. These resilient genotypes can be used as breeding material for future abiotic stress studies.

Polyphasic OKJIP Chlorophyll a Fluorescence Transient in a Landrace and a Commercial Cultivar of Sweet Pepper (Capsicum annuum, L.) under Long-Term Salt Stress

In a soilless long-term salt-stress experiment, we tested the differences between the commercial sweet pepper cultivar “Quadrato d’Asti” and the landrace “Cazzone Giallo” in the structure and function of PSII through the JIP test analysis of the fast chlorophyll fluorescence transients (OKJIP). Salt stress inactivated the oxygen-evolving complex. Performance index detected the stress earlier than the maximum quantum yield of PSII, which remarkably decreased in the long term. The detrimental effects of salinity on the oxygen evolving-complex, the trapping of light energy in PSII, and delivering in the electron transport chain occurred earlier and more in the landrace than the cultivar. Performance indexes decreased earlier than the maximum quantum yield of PSII. Stress-induced inactivation of PSII reaction centers reached 22% in the cultivar and 45% in the landrace. The resulted heat dissipation had the trade-off of a correspondent reduced energy flow per sample leaf area, thus an impaired potential carbon fixation. These results corroborate the reported higher tolerance to salt stress of the commercial cultivar than the landrace in terms of yield. PSII was more affected than PSI, which functionality recovered in the late of trial, especially in the cultivar, possibly due to heat dissipation mechanisms. This study gives valuable information for breeding programs aiming to improve tolerance in salt stress sensitive sweet pepper genotypes.

Morpho-agronomic characterization and genetic divergence in lentil genotypes

ABSTRACT Lentil production has been increasing in Brazil, due to strong national and international demand. Despite the economic importance, few cultivars are available on the Brazilian market. The aim of this study was to evaluate 48 lentil inbred lines and one commercial cultivar (Silvina), based on morpho-agronomic traits and to identify genotypes which can be used in a plant breeding program. Twenty-one morpho-agronomic descriptors (nine qualitative and twelve quantitative) were used. The descriptors showed genetic variability among the genotypes. Clustering techniques using characterization data allowed to identify genetically divergent genotypes as well as identify superior genotypes in relation to agronomic traits: FLIP2010-8L and FLIP2010-12L (similarity group I), FLIP2010-99L, FLIP2010-20L and FLIP2010-106L (group II), FLIP90-25L and 6031 (group III), FLIP2007-16L (group IV) and the commercial cultivar Silvina (group V). We concluded that these genotypes have the potential to be used in lentil breeding programs.

Comparative Study of Drought Stress Effects on Traditional and Modern Apple Cultivars

Genotype-dependent responses of apples to drought stress were evaluated between commercial and traditional apple cultivars. The results indicate different mechanisms of tolerance to investigated drought stress conditions. Chlorophyll fluorescence induction (OJIP) parameters, chlorophyll and carotenoid content, malondialdehyde (MDA), hydrogen peroxide (H2O2), proline, phenols and leaf water content (WC) were measured. The traditional cultivar “Crvenka” confirmed the best tolerance to a drought stress condition, presenting higher photosynthetic efficiency, higher leaf water content, higher levels of chlorophyll content and lower lipid peroxidation with greater membrane stability. The commercial cultivar “Golden Delicious Reinders” showed decreased water content in leaves, increased lipid peroxidation levels and photoinhibition. Considering all results, the commercial cultivar “Golden Delicious Reinders” was adversely affected by drought, while traditional cultivars exhibited better tolerance to drought stress.

Characterization and fine mapping of a new dwarf mutant in Brassica napus

Background Plant height is an important plant characteristic closely related to yield performance of many crops. Reasonable reduction of plant height of crops is beneficial for improving yield and enhancing lodging resistance. Results In the present study, we described the Brassica napus dwarf mutant bnd2 that was isolated using ethyl methanesulfonate (EMS) mutagenesis. Compared to wild type (WT), bnd2 exhibited reduced height and shorter hypocotyl and petiole leaves. By crossing the bnd2 mutant with the WT strain, we found that the ratio of the mutant to the WT in the F2 population was close to 1:3, indicating that bnd2 is a recessive mutation of a single locus. Following bulked segregant analysis (BSA) by resequencing, BND2 was found to be located in the 13.77–18.08 Mb interval of chromosome A08, with a length of 4.31 Mb. After fine mapping with single nucleotide polymorphism (SNP) and insertion/deletion (InDel) markers, the gene was narrowed to a 140-Kb interval ranging from 15.62 Mb to 15.76 Mb. According to reference genome annotation, there were 27 genes in the interval, of which BnaA08g20960D had an SNP type variation in the intron between the mutant and its parent, which may be the candidate gene corresponding to BND2. The hybrid line derived from a cross between the mutant bnd2 and the commercial cultivar L329 had similar plant height but higher grain yield compared to the commercial cultivar, suggesting that the allele bnd2 is beneficial for hybrid breeding of lodging resistant and high yield rapeseed. Conclusion In this study, we identified a novel dwarf mutant of rapeseed with a new locus, which may be useful for functional analyses of genetic mechanisms of plant architecture and grain yield in rapeseed.

Distinctness, uniformity and stability and GT biplot tests for the selection of snap bean lines

ABSTRACT The lack of records about snap bean cultivars is one of the obstacles that has led to a yield gap and low prominence of the crop. This work aimed at indicating snap bean lines obtained by the Breeding Program of the Universidade Estadual do Norte Fluminense (UENF) to assess their performance and to apply for a certificate of plant variety protection. The study was managed using a randomized block design with three replicates in a greenhouse at the Research Support Unit of the UENF. Nine candidate lines were compared to the commercial cultivar “Topseed Blue Line” in accordance with 56 descriptors set by the National Plant Variety Rights. All lines presented themselves as homogeneous. The L31 line provided a total of 30 different descriptors of the commercial cultivar. For the quantitative data added to the Distinctness, Uniformity and Stability, (DUS) tests, the analysis of variance was performed and the GT biplot generated by the R software. Variability was noticed among the genotypes for all assessed traits, excepting days until germination and seed thickness. The lines that showed the best mean performance were L6, L7, L10, L11, and L13. Among those, the L6 and L11 lines provided higher stability.

Characterization and Fine Mapping of a New Dwarf Mutant in Brassica Napus

Background: Plant height is an important plant architecture character closely related to yield performance of many crops. Reasonable reduction of plant height of crops is beneficial for enhancing lodging resistance and improving yield. Results: In the present study, we described a Brassica napus dwarf mutant bnd2 induced by ethyl methanesulfonate (EMS) mutagenesis. Compared to wild type, bnd2 showed shorter stature, shorter hypocotyl, as well as shorter petiole leaves. We crossed the bnd2 mutant with its wild type and found that the ratio of the mutant to the wild type in the F2 population was close to 1:3, indicating that bnd2 is a recessive mutation of a single locus. Following bulked segregant analysis (BSA) by resequencing, BND2 was located into the 13.77 Mb-18.08 Mb interval of chromosome A08, with a length of 4.31 Mb. After fine mapping with SNP and InDel markers, the gene was narrowed to a 140-Kb interval ranging from 15.62 Mb to 15.76 Mb. According to reference genome annotation, there are 27 genes in the interval, and one of them BnaA08g20960D has a SNP type variation in the intron between the mutant and its parent, which may be the candidate gene conferring to BND2. The hybrid line derived from a cross between the mutant bnd2 and a commercial cultivar L329 has similar plant height but higher grain yield than the commercial cultivar, suggesting that the allele bnd2 is benefit for hybrid breeding of lodging resistance and high yield in rapeseed.Conclusion: In this study, we found a fresh resource and a new locus for dwarf in rapeseed, which may be benefit for functional analysis of genetic mechanism of plant architecture and grain yield in rapeseed.

Resilience Capacity Assessment of the Traditional Lima Bean (Phaseolus lunatus L.) Landraces Facing Climate Change

Agriculture is highly exposed to climate warming, and promoting traditional cultivars constitutes an adaptive farming mechanism from climate change impacts. This study compared seed traits and adaptability in the germinative process, through temperature and drought response, between a commercial cultivar and Mediterranean Phaseolus lunatus L. landraces. Genetic and phylogenetic analyses were conducted to characterize local cultivars. Optimal germination temperature, and water stress tolerance, with increasing polyethylene glycol (PEG) concentrations, were initially evaluated. Base temperature, thermal time, base potential and hydrotime were calculated to compare the thermal and hydric responses and competitiveness among cultivars. Eight molecular markers were analyzed to calculate polymorphism and divergence parameters, of which three, together with South American species accessions, were used to construct a Bayesian phylogeny. No major differences were found in seed traits, rather different bicolored patterns. A preference for high temperatures and fast germination were observed. The ‘Pintat’ landrace showed marked competitiveness compared to the commercial cultivar when faced with temperature and drought tolerance. No genetic differences were found among the Valencian landraces and the phylogeny confirmed their Andean origin. Promoting landraces for their greater resilience is a tool to help overcome the worldwide challenge deriving from climate change and loss of agrobiodiversity.

Correlations between fruit yield and sensory and nutritional quality of pumpkin (Cucurbita moschata Duch.)

Traits related to fruit yield and physical and chemical fruit quality are being evaluated by Embrapa pumpkin breeding program. Path and Pearson's correlation analysis are necessary to allow the knowledge of the relation between the variables of interest for this program. The objective of the present study was to determine the genetic correlations between yield- and sensorial and nutritional quality attributes-associated variables in pumpkin progenies to support the selection process. Twelve genotypes were evaluated for 10 yield-related traits, and 8 sensory and nutritional quality traits of fruit, including the commercial cultivar Jacarezinho. A path analysis considered the fruit weight (FrW) was as basic variable and the others as explanatory. The FrW had 98% of its total variation available in a function of the explanatory variables. The highest variations were observed in the fruit-shape related traits. In addition, the variables internal median cavity diameter (IDmed), equatorial pulp thickness (EPT), apical pulp thickness (APT), and smallest fruit diameter (Dsm) are indicated for a direct selection of progenies targeting a higher FrW. The correlation analysis highlighted that color-related variables have the possibility of indirect selection aiming to increase total carotenoid content (TCC) and β-carotene content (β-car). The evaluated progenies showed notable soluble solids content (SSC), TCC and β-car contents compared to the commercial cultivar. Furthermore, the contribution of β-car to TCC is at least 50% higher in these progenies than in 'Jacarezinho' pumpkin.