Tolerance To Chlorosis Research Articles

Evaluation of Advanced F4 Groundnut Breeding Lines for Chlorosis Tolerance, Morphological and Yield Parameters under Lime-induced Iron Chlorosis Condition

Iron deficiency chlorosis, a major physiological disorder affecting the groundnut production worldwide and is prevalent in alkaline and calcareous soils with a pH of 7.5 to 8.5. Identifying and developing a chlorosis tolerant genotype is the best solution to overcome this major abiotic stress in calcareous soils. Therefore, a field experiment was conducted at University of Agricultural Sciences, Dharwad, in June, 2019 under rainfed conditions to evaluate a set of sixteen advanced breeding lines along with three parents of groundnut checks for chlorosis tolerance, morphological and yield parameters. Associated traits like SPAD chlorophyll meter reading (SCMR) and visual chlorotic rating (VCR) were assessed to evaluate the chlorosis tolerance. Among the parents, lime induced iron chlorosis (LIIC) tolerant parent, ICGV 86031 had recorded higher SCMR value and lower VCR (35.62 and 2.40, respectively) at 60 DAS with lower plant height, higher number of branches per plant, total dry matter production and pod yield (19.27cm, 5.20, 9.34g and 9.21g, respectively) at harvest compared to LIIC susceptible parents. However, among the derived breeding lines, TIP 16-5 recorded higher SCMR value and lower VCR (28.82 and 1.72, respectively) at 60 DAS with higher plant height, number of branches and total dry matter (26.29 cm, 5.33 and 12.80g, respectively) at harvest over the respective susceptible parent TMV 2. Further, TIP 16-5 and JIP 29-14 recorded about 50.47 and 31.46 per cent increased pod yield over their susceptible parents. These results indicate introgression of dry matter production, pod yield and chlorosis tolerance from the tolerant parent.

Accumulation of resveratrol, ferulic acid and iron in seeds confer iron deficiency chlorosis tolerance to a novel genetic stock of peanut (Arachis hypogaea L.) grown in calcareous soils.

The online version contains supplementary material available at 10.1007/s12298-023-01321-9.

QTLs Identification for Iron Chlorosis in a Segregating Peach-Almond Progeny Through Double-Digest Sequence-Based Genotyping (SBG).

Linkage maps are highly appreciated tools for cultivar and rootstock breeding programs because they are suitable for genetic and genomic studies. In this study, we report on using sequence-based genotyping (SBG) approach to simultaneously discover and genotype SNPs from two peach-based rootstocks (“Adafuel” and “Flordaguard”) and their progeny (n = 118): from a initial mapping population composed of 131 seedlings. The plant material was developed at the EEAD–CSIC Prunus rootstocks breeding program, aiming to obtain a segregating progeny for a range of characters of agronomical interest to rootstock breeding (iron-chlorosis and root-asphyxia tolerance, nematode resistance, vigor traits, and other effects on scion cultivars). Sequence reads obtained from double-digest SBG were aligned to the P. persica reference genome (Peach v2.0). While eight linkage groups were constructed for “Adafuel,” only four linkage groups were constructed for “Flordaguard,” given the low heterozygosity of this last genotype. High synteny and co-linearity were observed between obtained maps and Peach v2.0. On the other hand, this work aimed to elucidate the genetic basis of leaf chlorosis tolerance using the phenotypic segregation of the progeny to iron-chlorosis tolerance, along with the QTLs responsible for leaf chlorosis. The F1 mapping population, composed initially of 131 seedlings, was growing in four field trials established on calcareous soils at the experimental field of the EEAD-CSIC in Zaragoza, Spain. From the initial mapping population, 131 individuals were selected for their phenotypical characterization with SPAD measurements of plants grown in the field, exhibiting a great variability. Significant QTLs associated with tolerance to iron chlorosis were found in LG1, LG5, LG7, and LG8. The significant QTLs detected in LG5 and LG7 have not been associated with this abiotic stress before in Prunus. Several candidate genes such as Prupe.1G541100, predicted as glutamyl-tRNA reductase 1, Prupe.1G468200, encoding a 2-oxoglutarate (2OG), and Fe(II)-dependent oxygenase superfamily protein or Prupe.1G577000 (ppa011050.m), a NIFU-like protein 2 (NIFU2) were detected. The exact biological function of some of these genes should be verified for the future development of marker-assisted selection for peach iron chlorosis tolerance.

Comparative transcriptome and physiological analyses reveal key factors in the tolerance of peach rootstocks to iron deficiency chlorosis.

The online version contains supplementary material available at 10.1007/s13205-021-03046-6.

Increase in root branching enhanced ferric-chelate reductase activity under iron stress in potato (Solanum tuberosum)

In response to Fe-deficiency, various dicots increase their root branching to improve ferric-chelate reductase activity. It still remains unclear, whether the response caused by Fe-deficiency ultimately improves the plant's ability to withstand Fe-deficiency. In this experiment conducted at ICAR-Central Potato Research Institute, Regional Station, Shillong during 2020, we demonstrated a substantial increase in the growth of the lateral root of potato genotype (CP 3443), when grown in the iron-stress, in relation to control plants, and the total lateral root number is well linked to ferric-chelate reductase (FCR) activity. These findings showed that FCR is involved in root Fe uptake in potato (Solanum tuberosum L.) and they suggest a role in Fe distribution throughout the plant. In view of these findings, the Fe-deficiency induced increases in the lateral roots suggested that these play a significant role in Fe-deficiency tolerance in potato, which can serve as useful trait for the identification of chlorosis tolerance and/or nutrient-deficiency stress.

Differential response of groundnut genotypes for iron (Fe) deficiency chlorosis tolerance and productivity traits under Fe-supplemented and Fe-non-supplemented conditions

Groundnut is sensitive to Fe deficiency under alkaline and calcareous soils and exhibits iron deficiency chlorosis (IDC) causing significant reduction in growth and yield. Genotypes were assessed for IDC related traits such as visual chlorosis rating, SPAD chlorophyll meter reading, chlorophyll and active iron (Fe2+) content across five growth stages and also for productivity traits viz., plant height, number of primary branches, number of pods per plant, pod yield, shelling per cent, 100 seed weight and haulm yield. Comparison between Fe-supplemented and Fe-nonsupplemented condition for IDC related traits showed not much difference among IDC tolerant genotypes across all five growth stages, while significant differences among IDC susceptible genotypes were observed. Maximum reduction in pod yield was observed among IDC susceptible genotypes compared to IDC tolerant and moderately tolerant genotypes. However, recently released variety G 2- 52 with moderate tolerance to IDC and higher yield potential recorded higher pod yield both under Fe applied (1754 kgha–1) and non-applied conditions (1544 kgha–1).

Analysis of contrast iron chlorosis tolerance in the pear cv. ‘Huangguan’ grafted onto pyrus betulifolia and quince A grown in calcareous soils

Quince (Cydonia oblonga Mill.) represents an examplar rootstock in modern training programmes to escalate pear production worldwide because of its dwarfing characteristic and precocity. However, iron deficiency often poses a hard hurdle to overcome for developing quince grafted pears in calcareous and alkaline soils. In North China, we observed that the high-quality pear cultivar Huangguan (Pynus bretschneideri Rehd.) grafted onto quince A (Hardy as interstock, defined as HG-QA) suffered iron deficiency chlorosis in calcareous soils in early spring, even more severe during late spring to early summer. In contrast, Huangguan grafted onto Pyrus betulifolia (Hardy as interstock, defined as HG-PB) did not suffer it. We were inspired to design this field experiment to figure out iron mobilization/uptake in the two rootstocks and the two scion-rootstock combinations. Our results showed that the soil plant analysis development (SPAD) values of quince A (24.7) and HG-QA (13.7) were much lower than that of Pyrus betulifolia (41.6) and HG-PB (36.1). The root length density and surface area density of quince A and HG-QA were more than 2-fold higher than those of Pyrus betulifolia and HG-PB. The rhizosphere pH of quince A and HG-QA was more than 0.20 units lower than that of Pyrus betulifolia and HG-PB respectively, whereas we didn’t detect any obvious differences in the root ferric-chelate reductase activity, iron concentrations in leaves and roots, and iron transport ratio. These results strongly suggest that the iron efficiency of HG-PB is attributed to an iron activation mechanism in leaves. The deciphering of the mechanisms that how rootstock influences the iron acquisition system inside the leaf of the scion and changes the efficiency of iron utilization will facilitate making effective solutions for iron deficiency induced chlorosis, popularizing and planting Huangguan grafted onto quince A in pear production.

Deconstructing the genetic architecture of iron deficiency chlorosis in soybean using genome-wide approaches

BackgroundIron (Fe) is an essential micronutrient for plant growth and development. Iron deficiency chlorosis (IDC), caused by calcareous soils or high soil pH, can limit iron availability, negatively affecting soybean (Glycine max) yield. This study leverages genome-wide association study (GWAS) and a genome-wide epistatic study (GWES) with previous gene expression studies to identify regions of the soybean genome important in iron deficiency tolerance.ResultsA GWAS and a GWES were performed using 460 diverse soybean PI lines from 27 countries, in field and hydroponic iron stress conditions, using more than 36,000 single nucleotide polymorphism (SNP) markers. Combining this approach with available RNA-sequencing data identified significant markers, genomic regions, and novel genes associated with or responding to iron deficiency. Sixty-nine genomic regions associated with IDC tolerance were identified across 19 chromosomes via the GWAS, including the major-effect quantitative trait locus (QTL) on chromosome Gm03. Cluster analysis of significant SNPs in this region deconstructed this historically prominent QTL into four distinct linkage blocks, enabling the identification of multiple candidate genes for iron chlorosis tolerance. The complementary GWES identified SNPs in this region interacting with nine other genomic regions, providing the first evidence of epistatic interactions impacting iron deficiency tolerance.ConclusionsThis study demonstrates that integrating cutting edge genome wide association (GWA), genome wide epistasis (GWE), and gene expression studies is a powerful strategy to identify novel iron tolerance QTL and candidate loci from diverse germplasm. Crops, unlike model species, have undergone selection for thousands of years, constraining and/or enhancing stress responses. Leveraging genomics-enabled approaches to study these adaptations is essential for future crop improvement.

Identification and Fine-Mapping of a Soybean Quantitative Trait Locus on Chromosome 5 Conferring Tolerance to Iron Deficiency Chlorosis.

CORE IDEAS: 'Fiskeby III' harbors a combination of abiotic stress traits, including iron deficiency chlorosis (IDC) tolerance. An IDC quantitative trait locus on chromosome Gm05 was identified in genome-wide association studies and biparental populations. Fine-mapping resolved a 137-kb interval containing strong candidate genes. Iron deficiency chlorosis (IDC) is an important nutrient stress for soybean [Glycine max (L.) Merr.] grown in high-pH soils. Despite numerous agronomic attempts to alleviate IDC, genetic tolerance remains the most effective preventative measure against symptoms. In this study, two association mapping populations and a biparental mapping population were used for genetic mapping of IDC tolerance. Quantitative trait loci (QTLs) were identified on chromosomes Gm03, Gm05, and Gm06. Heterogenous inbred families were developed to fine-map the Gm05 QTL, which was uniquely supported in all three mapping populations. Fine-mapping resulted in a QTL with an interval size of 137 kb on the end of the short arm of Gm05, which produced up to a 1.5-point reduction in IDC severity on a 1 to 9 scale in near isogenic lines.

Relationships among iron deficit-induced potato callus growth inhibition, Fe distribution, chlorosis, and oxidative stress amplified by reduced antioxidative enzyme activities

Callus cultures were used to investigate and delineate responses of potato to iron (Fe) deficiency conditions over different culture durations. The morphological responses included chlorotic symptoms, reduced fresh weight and area of callus growth on Fe-deficient medium compared to calli grown under Fe sufficient conditions. Biochemically, potato calli under Fe deficit exhibited decreases in chlorophyll and carotenoid contents, reduction in activities of antioxidant enzymes (peroxidase, catalase and ascorbate peroxidase), as well as an increase in ferric chelate reductase (FCR) activity, lipid peroxidation, phenolic production and hydrogen peroxide (H2O2) level. Perls staining revealed sparse Fe distribution in Fe-deficient callus cells whereas Fe was widely distributed and intensely stained among numerous actively dividing cells in Fe-sufficient calli. These responses of calli to Fe deficiency were more pronounced with prolonged exposure to such stress leading to severe chlorosis and/or death of cells in chlorosis-susceptible calli but potential chlorosis-tolerant callus cells maintained their greenness and viability. Over a prolonged period in culture, significantly positive correlations were found among callus fresh weight, chlorophyll and carotenoid contents, antioxidant enzyme activities and lipid peroxidation as Fe supplies to the medium was increased. FCR activity was strongly correlated in a negative manner with Fe deficiency, chlorophyll content and peroxidase activity. The responses of calli to Fe supply can serve as reliable indicators for detecting chlorosis tolerance and/or nutrient deficiency stress.

Physiological basis of iron chlorosis tolerance in rice (Oryza sativa) in relation to the root exudation capacity

ABSTRACTMicronutrient deficiency in cultivable soil, particularly that of iron (Fe) and zinc (Zn), is a major productivity constraint in the world. Low Fe availability due to the low solubility of the oxidized ferric forms is a challenge. An experiment was, thus, executed to assess the performance of eight genetically diverse rice genotypes on Fe-sufficient (100 µM) and Fe-deficient (1 µM) nutrient solution, and their ability to recover from Fe deficiency was measured. Fe efficiency under Fe deficiency in terms of biomass production showed a significant positive correlation with the root release of phytosiderophore (PS) (R2 = 0.62*). This study shows that the Fe deficiency tolerance of Pusa 33 was related to both a high release of PS by the root and an efficient translocation of Fe from the root to the shoot as the Fe–PS complex, which could be useful for improving the Fe nutrition of rice particularly under aerobic conditions.

Genetic relationships of some Citrus genotypes based on the candidate iron chlorosis genes

Iron is one of the most important elements in plant mineral nutrition. Fe deficiency is a critical abiotic stress factor for Mediterranean citriculture; the development of marker-assisted selection for this trait would greatly enhance rootstock breeding. In this study, DNA sequencing and single-stranded conformation polymorphism (SSCP) analyses were performed to determine the allelic diversity of genes associated with tolerance to iron chlorosis in citrus. Two candidate iron chlorosis tolerance genes were selected from existing Citrus EST databases and Arabidopsis thaliana genome databases. Ferritin-3 chloroplast precursor and putative membrane transporter candidate gene sequences were used to define primers in conserved regions. Six citrus genotypes from the basic taxon of Citrus were used to identify polymorphic regions in the genes. Direct sequencing of the amplified DNA fragments from the candidate genes was performed, and single nucleotide polymorphisms (SNPs) and insertions/deletions (indels) were identified after sequence alignment. Based on the DNA sequencing analysis, a total of 6840 nucleotides of DNA were sequenced to identify SNPs and indels. In total, 263 SNPs and 15 indels were identified for both genes. We detected 38.45 SNPs and 2.19 indels for each 1000 b on average from the DNA sequencing results. New primers were designed in conserved areas flanking polymorphic ones for SSCP analysis. SSCP-PCR analysis was performed with 25 citrus genotypes. The neighbor-joining method was used for cluster analysis. Trifoliate genotypes and their hybrids (known to be sensitive to iron chlorosis) clustered together, whereas genotypes tolerant to iron chlorosis were more spread out on the dendrogram. Mandarins also showed high diversity for both genes according to SSCP results. Differences were found among sour orange genotypes known to have differential tolerance behavior to iron chlorosis.

Mapping genetic loci for tolerance to lime-induced iron deficiency chlorosis in grapevine rootstocks (Vitis sp.)

Iron is essential to plants for chlorophyll formation as well as for the functioning of various iron-containing enzymes. Iron deficiency chlorosis is a wide-spread disorder of plants, in particular, of those growing on calcareous soils. Among the different ways to control iron deficiency problems for crops, plant material and especially rootstock breeding is a suitable and reliable method, especially for fruit trees and grapes. The aim of the experiment was to characterize the genetic basis of grapevine chlorosis tolerance under lime stress conditions. A segregating population of 138 F1 genotypes issued from an inter-specific cross between Vitis vinifera Cabernet Sauvignon (tolerant) × V. riparia Gloire de Montpellier (sensitive) was developed and phenotyped both as cuttings and as rootstock grafted with Cabernet Sauvignon scions in pots containing non-chlorosing and chlorosing soils. Tolerance was evaluated by chlorosis score, leaf chlorophyll content and growth parameters of the shoots and roots. The experiments were performed in 2001, 2003 and 2006. The plants analysed in 2006 were reassessed in 2007. The most significant findings of the trial were: (a) the soil properties strongly affect plant development, (b) there are differences in tolerance among segregating genotypes when grown as cuttings or as rootstocks on calcareous soil, (c) calcareous conditions induced chlorosis and revealed quantitative trait loci (QTLs) implicated in polygenic control of tolerance, (d) rootstock strongly contributes to lime-induced chlorosis response, and (e) a QTL with strong effect (from 10 to 25 % of the chlorotic symptom variance) was identified on chromosome 13. This QTL colocalized with a QTL for chlorophyll content (R (2) = 22 %) and a major QTL for plant development that explains about 50 % of both aerial and root system biomass variation. These findings were supported by stable results among the different years of experiment. These results open new insights into the genetic control of chlorosis tolerance and could aid the development of iron chlorosis-tolerant rootstocks.

Genetic analysis of iron chlorosis tolerance in Prunus rootstocks

The high economic losses caused by the occurrence of iron chlorosis in Prunus orchards in the Mediterranean area justifies the implementation of breeding programs to generate high-performance rootstocks for different edaphoclimatic area conditions. For that reason, the genetic control of iron chlorosis tolerance was studied in an F1 population derived from a three-way interspecific cross between a Myrobalan plum (P 2175) and an almond × peach hybrid (Felinem). Several phenotypic measurements were assessed to guarantee an accurate data set for genetic analysis. SPAD (Soil and Plant Analyzer Development) values, chlorophyll concentration, and visual diagnostic symptoms were highly correlated with leaf chlorosis in trees. SPAD value was the most reliable measure, since it was an objective, unbiased, and non-destructive method. Two significant quantitative trait loci (QTLs) involved in SPAD and chlorophyll concentration were identified for Felinem in linkage groups 4 and 6. Both QTLs were detected in four of the six consecutive years of the experiment. For P 2175, two of the three putative QTLs identified, pspad4.1 and chl4.1, were placed in linkage group 4. These QTLs were related to the SPAD values and chlorophyll concentration, respectively, and co-localized with QTLs detected in the Felinem map affecting the same traits. Candidate gene PFIT, related to iron metabolism, was localized within the confidence interval of the QTL in linkage group 4. This research suggests an association of this chromosome region with tolerance to iron chlorosis in Prunus, and it provides a first approach to localize candidate genes involved in tolerance to this abiotic stress.

DETERMINATION BY SSCP MARKERS OF THE ALLELIC DIVERSITY OF CANDIDATE GENES FOR TOLERANCE TO IRON CHLOROSIS IN CITRUS GERMPLASM

Iron chlorosis is one of the main abiotic constraints for Mediterranean citriculture and the development of marker assisted selection (MAS) for this trait would be a great aid for rootstock breeding. We performed SSCP (Single Stranded Conformation Polymorphism) analysis in order to discover allelic diversity of candidate genes for iron chlorosis tolerance in citrus. Two iron chlorosis tolerance candidate genes were selected from existing Citrus ESTs databases and Arabidopsis thaliana genome databases. Iron-Sulfur assembly protein (Fe_S=AT2G16710) and root iron transporter (IRT1=AT4G19690) candidate gene sequences were used to define primers in conserved regions. Six Citrus genotypes from the basic taxon of Citrus where used to identify polymorphic areas in the genes. Direct sequencing of amplified DNA fragments of candidate genes was performed and SNPs (single-nucleotide polymorphisms) and Indels where searched after sequence alignment. A total of 2215 bp DNA fragments were sequenced and 56 SNPs and 2 Indels were determined. New primers were defined, in conserved areas flanking polymorphic ones, for Single Strand Conformation Polymorphism (SSCP) analysis for further diversity and routine genotyping. Two pairs of primers were defined for each gene. SSCP-PCR analysis was performed with twenty-five Citrus genotypes. The neighbor joining method was used for cluster analysis. Poncirus trifoliate genotypes and their hybrids known to be sensitive to iron chlorosis clustered together and mandarins showed high diversity for both genes. Differences were found among sour orange genotypes known to have differential tolerance behavior to iron chlorosis. (Resume d'auteur)

Physiological responses and differential gene expression in Prunus rootstocks under iron deficiency conditions

Two Prunus rootstocks, the Myrobalan plum P 2175 and the interspecific peach–almond hybrid, Felinem, were studied to characterize their biochemical and molecular responses induced under iron-Deficient conditions. Plants of both genotypes were submitted to different treatments using a hydroponic system that permitted removal of Fe from the nutrient solution. Control plants were grown in 90 μM Fe (III)-EDTA, Deficient plants were grown in an iron free solution, and plants submitted to an Inductor treatment were resupplied with 180 μM Fe (III)-EDTA over 1 and 2 days after a period of 4 or 15 days of growth on an iron-free solution. Felinem increased the activity of the iron chelate reductase (FC-R) in the Inductor treatment after 4 days of iron deprivation. In contrast, P 2175 did not show any response after at least 15 days without iron. The induction of the FC-R activity in this genotype was coincident in time with the medium acidification. These results suggest two different mechanisms of iron chlorosis tolerance in both Strategy I genotypes. Felinem would use the iron reduction as the main mechanism to capture the iron from the soil, and in P 2175, the mechanism of response would be slower and start with the acidification of the medium synchronized with the gradual loss of chlorophyll in leaves. To better understand the control of these responses at the molecular level, the differential expression of PFRO2, PIRT1 and PAHA2 genes involved in the reductase activity, the iron transport in roots, and the proton release, respectively, were analyzed. The expression of these genes, estimated by quantitative real-time PCR, was different between genotypes and among treatments. The results were in agreement with the physiological responses observed.

GENETIC ANALYSIS OF IRON CHLOROSIS TOLERANCE IN MYROBALAN PLUM X ALMOND-PEACH HYBRIDS

Iron deficiency is responsible for enormous economical losses in a wide range of crops in the Mediterranean area. Different species vary in their susceptibility from poorly to severely affected leaf chlorosis, one of the main common symptoms for the iron deficiency. The prevention of this nutritional disorder involves the use of tolerant rootstocks as the best alternative to palliate the problem in fruit tree plantations. The genetic control of the tolerance to this abiotic stress in trees is still unknown but studies in other crops suggested that it could be a quantitative trait. For that, this work is directed to understand the genetic control of iron chlorosis in tree fruits. Two approaches are being used: the quantitative genetics with detection of QTLs related with iron chlorosis and the molecular genetic approach with the search of candidates genes differentially expressed under iron deficiency. A F1 population derived from a three ways interspecific cross between the myrobalan (P. cerasifera): ‘P.2175’ and the almond x peach hybrid (P. dulcis x P. persica): Felinem (formerly GxN 22) was analyzed. SPAD measurements were performed in the leaves of the F1 individuals detecting segregation to iron chlorosis tolerance. Preliminary results showed correlation between the chlorophyll content and genomic regions located in chromosomes 2 and 6, close to other reported QTLs involved in fruit quality and fungus resistance. The candidate genes approach is being implemented based on in silico screening of genes shown to be expressed in response to iron deficiency in roots, such as those encoding FRO2, IRT1 and other candidate genes differentially expressed in grape rootstocks under iron induced chlorosis.

Categories and Inheritance of Resistance to Russian Wheat Aphid (Homoptera: Aphididae) Biotype 2 in a Selection from Wheat Cereal Introduction 2401

The Russian wheat aphid, Diuraphis noxia (Kurdjumov) (Homoptera: Aphididae), is one of the most devastating insect pests of wheat (Triticum spp.) and barley (Hordeum spp.) in the world. Yield losses and control costs are valued at several hundred million dollars each year. The use of D. noxia-resistant cultivars is an ecologically, economically, and biologically sound method of managing this pest. Several D. noxia resistance (Dn) genes from wheat have been used to develop cultivars resistant to D. noxia. However, a new U.S. D. noxia biotype (biotype 2) in Colorado is virulent to all known Dn genes except the Dn7 gene from rye (Secale spp.). Hence, there is an immediate need to identify and characterize unique sources of D. noxia resistance to biotypes. In this article, we report resistance to D. noxia biotype 2, identified in a selection from wheat cereal introduction (CItr) 2401, that is controlled by two dominant genes. CItr2401 has a strong antibiosis effect that is exhibited as a reduced intrinsic rate of increase of D. noxia biotype 2. CItr2401 plants also exhibit tolerance to leaf rolling and chlorosis. No antixenosis was detected in CItr2401.

Inheritance of tolerance to leaf iron deficiency chlorosis in tomato

By using two tomato genotypes, “227/1” (Fe chlorosis susceptible) and “Roza” (Fe chlorosis tolerant), and their reciprocal F1, F2 and BC1 generations, the inheritance of tolerance to leaf Fe deficiency chlorosis of Roza was studied. Plants were grown in a nutrient solution and subjected to 2.0 × 10−6 M Fe EDDHA and 10 mM NaHCO3 to induce Fe deficiency stress by stabilization of pH to 7.8–8.2. A rating scale of 1–3 for chlorophyll was used and both monogenic and polygenic inheritance hypotheses were tested. Better responses to Fe deficiency, as measured by SPAD meter values, were obtained from the cross “Roza × 227/1” than from the reciprocal cross. Data from F2 and BC1 suggest Fe chlorosis tolerance of Roza is to be controlled by polygenic loci with a relatively high additive effect.

THE ITALIAN NATIONAL PEACH BREEDING PROJECT

In 1994 the Ministry for Agricultural and Forestry Policy (Mi.P.A.F.) has financed a national research program named “Fruit Growing”, coordinated by the Istituto Sperimentale per la Frutticoltura (ISF) and composed of several projects relevant to stone fruit breeding, pome fruit breeding, rootstock breeding, strawberry breeding, tree training, post harvest, and marketing. Working groups on peach are active within the stone fruit and rootstock breeding projects. The main objectives of the breeding programs were: improved fruit quality, resistance or tolerance to diseases and pests (both for scions and rootstocks), suitability for difficult soils (for rootstocks). Nine units, belonging to Mi.P.A.F. (Fruit Tree and Plant Pathology Research Institutes) and University (Bologna, Florence and Pisa), were involved. Up to now, 7 peach cultivars, 1 nectarine and 2 rootstocks have been commercially released and several scion advanced selections are under evaluation for brown rot, leaf curl, green aphid resistance or tolerance, and rootstock selections for chlorosis, asphixya, nematodes, Armillaria and Phytophthora resistance or tolerance.