Relationship of Fe-tolerance to morphological changes in roots in upland NERICA lines under Fe-treated hydroponic conditions

Twenty-six upland lines of New Rice for Africa (NERICA) were tested with four Oryza sativa varieties in relation to Fe toxicity tolerance under hydroponic culture containing 1.44 mM Fe (+Fe) and 0 mM Fe (-Fe as a control). Three NERICAs, WAB450-IBP-24-HB (P24), WAB450-IBP-82-1-1 (P82), and WAB450-IBP-163-3-1 (P163) among the 30 lines/varieties tested possessed relatively strong tolerance judging from reduction of root length and dry weight and shoot dry weight in +Fe compared to -Fe and from iron toxicity score (ITS) in +Fe. Only P24, P82, and P163 showed emerged lateral roots from pericycle at the root elongation zone, whereas in the other 23 NERICAs and four O. sativa varieties lateral root was not observed in the root elongation or differentiation zones. Less disruption of cortex on root tissues was observed in P24, P82, and P163 than in WAB450-16-2-BL2-DV2 (BL2-DV2), the most susceptible NERICA identified. P24, P82, and P163 showed significantly lower Fe content in the shoots than BL2-DV2, suggesting that the tolerant NERICAs could have some mechanism to inhibit the absorption of Fe. The emergence of lateral roots from the root elongation zone in the three tolerant NERICAs would be closely associated with reducing Fe absorption into the plants.     

QTLs for phosphorus deficiency tolerance detected in upland NERICA varieties

Phosphorous (P) deficiency is a major yield limiting factor in rice (Oryza sativa L.) production. The interspecific New Rice for Africa (NERICA) varieties combine general stress tolerance from African cultivated rice (Oryza glaberrima Steud) with characteristics associated with high yield from O. sativa. However, little is known about their ability to tolerate P deficiency. Here, we examined the variation for tolerance to P deficiency among the 18 upland NERICAs and their parents in multi‐year field experiments. The good performance under P deficiency of the O. glaberrima parent CG 14 and some NERICAs suggested that these tolerant NERICAs contain loci associated with P deficiency tolerance inherited from CG 14. Additionally, four QTL clusters for P deficiency tolerance were detected on chromosomes 4, 6 and 11 using F₃ lines derived from the cross between the P deficiency tolerant variety NERICA10 and a Japonica‐type sensitive variety ‘Hitomebore’. These QTLs represent the first step in identifying stress tolerance genes from O. glaberrima that could subsequently be used to enhance P deficiency tolerance in O. sativa.     

Analysis of population structure and genetic diversity reveals gene flow and geographic patterns in cultivated rice (<Emphasis Type="Italic">O. sativa</Emphasis> and <Emphasis Type="Italic">O. glaberrima</Emphasis>) in West Africa

To fully exploit the diversity in African rice germplasm and to broaden the gene pool reliable information on the population genetic diversity and phenotypic characteristics is a prerequisite. In this paper, the population structure and genetic diversity of 42 cultivated African rice (Oryza spp.) accessions originating from West Africa (Benin, Mali and Nigeria, Liberia etc.) were investigated using 20 simple sequence repeats (SSR) and 77 amplified fragment length polymorphisms (AFLP). Additionally, field trials were set up to gain insight into phenotypic characteristics that differentiate the genetic populations among rice accessions. The analysis revealed considerably high polymorphisms for SSR markers (PIC mean?=?0.78) in the germplasm studied. A significant association was found between AFLP markers and geographic origin of rice accessions (R?=?0.72). Germplasm structure showed that Oryza sativa accessions were not totally isolated from Oryza glaberrima accessions. The results allowed identification of five O. glaberrima accessions which grouped together with O. sativa accessions, sharing common alleles of 18 loci out of the 20 SSR markers analyzed. Population structure analysis revealed existence of a gene flow between O. sativa and O. glaberrima rice accessions which can be used to combine several interesting traits in breeding programs. Further studies are needed to clarify the contributions of this gene flow to valuable traits such as abiotic and biotic stresses including disease resistance.     

Root and shoot responses of upland New Rice for Africa varieties to fluctuating soil moisture conditions as affected by different levels of nitrogen fertilization

Drought cycling and soil re-watering trends due to intermittent rainfall patterns are key stress factors that influence rice growth and yield under upland cultivation conditions. However, upland rice adaptation responses to fluctuating soil moisture conditions remain poorly understood. This study investigated root and shoot responses of upland New Rice for Africa (NERICA) varieties to episodic drought and re-watering during growth. We examined root and shoot growth of NERICA 1 and NERICA 4 compared with those of IR72, an improved lowland variety, and Dular, a traditional drought-tolerant variety, in terms of soil moisture fluctuations with different levels of nitrogen fertilization under field conditions that impeded deep root development. During soil moisture fluctuation, all varieties reduced shoot dry weight compared with well-watered plants, regardless of nitrogen fertilization levels. However, total root length for the three upland varieties was enhanced by soil moisture fluctuations at moderate and high nitrogen fertilization, while that of the lowland variety was reduced. Comparing root development during water fluctuations revealed that NERICA 1 had a greater root system than NERICA 4, which was attributed to lateral root development. Furthermore, we found that NERICA varieties increase lateral root mass during soil desiccation under adequate nitrogen fertilization, while Dular and IR72 reduced their root growth rate during drought and increased it after re-watering. Both root growth patterns developed, from around maximum tillering to heading. The analysis of regression between root elongation and shoot growth with fluctuating soil moisture indicated that an enhanced root system during drought, on adequate nitrogen fertilization, can contribute to shoot growth when sufficient water becomes available, specifically around the maximum tillering to the heading growth stage of rice.     

Genetic characterization of rainfed upland New Rice for Africa (NERICA) varieties

A total of 18 rainfed upland New Rice for Africa (NERICA) varieties were categorized as the heavy panicle and low tillering types and early heading, in compared with 32 different varieties. These chromosome components were clarified using 243 SSR markers which showed polymorphism among NERICA varieties and their parents, CG 14 (O. glaberrima Steud.) and one of the recurrent parents, WAB-56-104 (O. sativa L.). NERICA varieties were classified into three groups, which corresponded with these parents’ continuation including two exceptions, NERICAs 14 and 17, by a cluster analysis using polymorphism data of SSR markers and 14 differential markers among them were selected to classify NERICA varieties. However, three groups: NERICAs, 3 and 4, NERICAs, 8, 9 and 11 and NERICAs, 15 and 16 were not distinguishable. Association analysis was carried out for characterization of NERICA varieties by using SSR markers genotype and phenotype of agronomic traits. A total of 131 quantitative trait loci between SSR markers and 11 agronomic traits were detected. The characteristics of early maturity and heavy panicle of upland NERICA varieties were succeeded from Asian rice varieties and the characteristics of high dry matter production and late heading were introduced from CG 14 and the other varieties.     

玉米根系活力与耐铝性的关系

铝胁迫可提高耐铝自交系根系还原力，而铝敏感自交系TTC还原强度则显著下降,表明自交系根系TTC相对还原强度与耐铝性具有很好的一致性。耐铝自交系根系活跃吸收面积，尤其是根系活跃吸收面积占总吸收面积的比例相对较高。铝胁迫可维持或略提高铝自交系根系氧化力，而敏感自交系根系氧化力则有所下降，说明耐铝自交系在铝胁迫下仍可维持较高的呼吸代谢活性。铝胁迫可造成玉米自交系伤流量减少，且敏感自交系降幅较大。     

Linkage map construction and QTL identification of P-deficiency tolerance in <Emphasis Type="Italic">Oryza rufipogon</Emphasis> Griff. at early seedling stage

Low phosphorus availability is a major factor limiting rice productivity. In this study, a population of backcross recombinant inbred lines (BILs) derived from an inter-specific cross (Oryza sativa L. × O. rufipogon Griff.) was used for genetic linkage map construction and quantitative trait locus (QTL) mapping. The results showed that a linkage map consisting of 153 markers was constructed. Twenty-one out of 231 BILs were tolerant of low-phosphorus according to the index to P-deficiency tolerance. Twenty-three QTLs on chromosomes 1, 2, 3, 7, 8, 9 and 11 were detected, of which eight QTLs showed high (22.93–37.32%) contribution to phenotypic variation. In addition, most of QTLs in this study (18 out of 23 QTLs) were located and overlapped on the chromosome 1, 3 and 11, which individually explained 6.07–34.70% phenotypic variation, indicating that there might be multiple main effect QTLs related to P-deficiency tolerance in O. rufipogon, and these QTLs might cluster in the same region. These results would provide helpful information for cloning and utilizing the P-deficiency tolerance-responsive genes from O. rufipogon.     

Micropropagation of <Emphasis Type="Italic">Kaempferia angustifolia</Emphasis> Roscoe - An Aromatic,Essential Oil Yielding,Underutilized Medicinal Plant of Zingiberaceae Family

Kaempferia angustifolia is an aromatic, essential oil-yielding plant of the Zingiberaceae family with an ethno-medicinal repute. We standardized an effective system for micropropagation of K. angustifolia, and this is probably the very first report of in vitro culture of this species. Axillary buds were cultured on a Murashige and Skoog (MS) medium supplemented with various concentrations and combinations of plant growth regulators (PGRs) and spermidine. Highest multiplication occurred when the MS medium was supplemented with a combination of 2.0 mg L^?1 6-benzylaminopurine (BAP), 2.0 mg L^?1 kinetin (KIN) and 1.0 mg L^?1 α-naphthalene acetic acid (NAA). Addition of spermidine (2.0 mM) along with optimum PGRs had further improved the multiplication rate with a maximum of 6.6 ± 0.36 shoots per explant within 60 days of implantation. The number of multiplied shoots per explant increased with each subsequent regeneration cycle; and the shoots per explant increased from 6.6 ± 0.36 on the 1^st regeneration cycle to 10.3 ± 0.42 on the 2^nd regeneration cycle and further increased to 13.7 ± 0.37 on the 3^rd regeneration cycle on the same medium composition. The best result for in vitro root induction of multiplied shoot was achieved on a half-strength MS medium fortified with 2.0 mg L^?1 IBA, with a maximum of 18.5 ± 0.28 roots per shoot. Regenerated plantlets were acclimatized with 88.9 % survival rate. After 9 months of field-transfer, all these plants were harvested and rhizomes were collected. However, the present protocol can definitely be applied for large-scale propagation and commercial cultivation of K. angustifolia.     

Evaluation of morpho-physiological traits of MRQ74 pyramided lines with drought yield QTLs

Drought regularly affects rainfed lowland and upland rice ecosystems in Malaysia. Three drought yield QTLs, viz qDTY _2.2 , qDTY _3.1 and qDTY _12.1 successfully pyramided into MRQ74 to increase its yield under reproductive stage drought stress (RS). Forty-eight genotypes comprising 39 pyramided lines (PLs) with different qDTYs combinations, four parents including MRQ74 (recipient) and five checks were evaluated for morpho-physiological traits under RS and non-stress (NS). This study aims to determine which traits influenced by individual qDTY and qDTY combinations and to gain better understanding of QTL interactions in enhancing grain yield (GY) under RS. Results showed plant height, number of panicles, root length, root weight, relative water content and 100-grain weight increased while chlorophyll content and GY decreased under RS compared to NS. No significant difference was observed in days to flowering, leaf rolling and grain length between selected PLs and MRQ74 under RS. Six PLs with yield advantage (YA) of 208.17–1751.63 kg ha^?1 compared to MRQ74 in RS but yielded similar to MRQ74 under NS were further selected. Under RS, qDTY class analysis showed qDTY _12.1 individually and combination qDTY _12.1  + ?qDTY _2.2 produced the highest yield of 1521.77 and 1092.30 kg ha^?1 respectively. qDTY _12.1 as single or combination with other qDTY is the best qDTY in stabilizing GY under RS. PL-77 with qDTY _12.1 is the best PL with YA of more than 1100 kg ha^?1 compared to MRQ74 in both RS and NS conditions can be recommended for cultivation in normal and drought-prone areas.     

High frequency shoot proliferation from cotyledonary node of <Emphasis Type="Italic">Lawsonia inermis</Emphasis> L. and validation of their molecular finger printing

An efficient and reproducible protocol for in vitro plant regeneration was developed for Lawsonia inermis L. using cotyledonary node explant derived from axenic seedlings. Highest shoot proliferation frequency (ca 96.6%) was achieved on Murashige and Skoog’s, 1962 (MS) basal medium supplemented with 8.88 μM 6-Benzyladenine (BA) + 2.68 μM Napthalene acetic acid (NAA). Up-scaling of shoots was carried out using in vitro nodes on MS medium supplemented with 4.44 μM BA. So overall, an average of 238 shoots was produced at 75 days. Of the four different forms of cotyledonary node explants evaluated, highest shoot multiplication was observed in cotyledonary node explant with two whole cotyledons. In vitro regenerated shoots were best rooted (ca 34.3 roots / shoot) on ½ MS medium devoid of any growth regulator. The plantlets were successfully acclimated in sand:soil:: 1:1and established in the garden soil. Random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) analysis revealed a homogeneous amplification profile for all micropropagated plants validating the genetic fidelity of the in vitro-regenerated plants and supporting the regeneration protocol for economic commercial exploitation.     

Phenotypic variation in root architecture traits and their relationship with eco-geographical and agronomic features in a core collection of tetraploid wheat landraces (<Emphasis Type="Italic">Triticum turgidum</Emphasis> L.)

To obtain varieties with root systems adapted to marginal environments it is necessary to search for new genotypes in genetically diverse materials, such as landraces that are more likely to carry novel alleles for different root features. A core collection of ‘durum’ wheat, including three subspecies (dicoccon, turgidum and durum) from contrasting eco-geographical zones, was evaluated for root traits and shoot weight at the seminal root stage. Distinctive rooting phenotypes were characterized within each subspecies, mainly in subsp. durum. Contrasting rooting types, including large roots with shallow distributions, and others with high root numbers were identified. Correlations with climatic traits showed that root shape is more relevant in adaptation to eco-geographical zones in subsp. dicoccon, whereas in subsp. turgidum and durum, which come from warmer and drier areas, both size and shape of roots could have adaptive roles. Root traits with the largest positive effects on certain yield components under limited water conditions included root diameter in subsp. dicoccon, root size in turgidum, and root number in durum. Additionally, shoot weight at the seedling stage had important effects in subsp. turgidum and durum. Twenty-eight marker–trait associations (MTAs) previously identified in this collection for agronomic or quality traits were associated with seminal root traits. Some markers were associated with only one root trait, but others were associated with up to six traits. These MTAs and the genetic variability characterized for root traits in this collection can be exploited in further work to improve drought tolerance and resource capture in wheat.     

Genotypic differences in wheat Al tolerance

Summary Aluminium tolerance of 83 genotypes from Croatian and Yugoslav Triticum aestivum germplasm was evaluated in nutrient solutions having Al³⁺ activities of 0, 12.5 and 25 M. Relative root length (25 M Al³⁺/0 Al) of various genotypes ranged from 2 to 97% (from very sensitive to tolerant to Al). No genotype with Al tolerance close to that of very tolerant cultivar Atlas-66 was found. Soil, climatic, fertilization, and liming effects that wheat plants giving seeds for the nutrient solution Al-tolerance screening had been subjected to during their growth cycle did not influence the Al-tolerance ranking. Significant correlation was found between screening wheat for Al tolerance in nutrient solutions and in acid Pseudogley soil amended with five rates of limestone in a greenhouse experiment. Seed protein concentration was significantly related to the Al-tolerance ranking (r² = 0.962). Such a significant correlation was not obtained in a case of rheological and other quality characteristics of seeds. Al-tolerant wheat genotypes identified in this study will be used in breeding for improved Al tolerance.Abbreviations HSD Tukey's Honestly Significant Difference - RRL-2 relative root length, in % (12.5 M Al³⁺/0 Al) - RRL-4 relative root length, in % (25 M Al³/0 Al)     

Genetic transformation of pigeonpea (<Emphasis Type="Italic">Cajanus cajan</Emphasis> L.) and screening transgenic progenies based on lateral root inhibition

Production of transgenic pigeonpea is becoming increasingly important, but the methods currently employed in production and subsequent screening still requires improvement. Here, we describe Agrobacterium-mediated genetic transformation of pigeonpea with reporter uidA (gus) gene and selectable marker, neomycin phospho-transferase (nptII) gene. Histochemical assay demonstrate localization of gus activity in cells and transformed plants. Overall, a transformation frequency of 0.33% was achieved using the protocol. Grafting of in vitro-regenerated healthy shoots indicates higher survival percent (72.6%), when stock and scion are of the same variety. Seeds harvested from primary transgenic plants can be screened based on lateral root inhibition strategy. Approximately 87% of the screened T₁ plants were found to be PCR positive. In conclusion, in vitro grafting of transgenic pigeonpea shoots leads to better plant establishment and screening based on lateral root inhibition leads to quick identification of positive segregants.     

Induced expression of selected plant defence related genes in pot azalea, <Emphasis Type="Italic">Rhododendron simsii</Emphasis> hybrid

A set of putative marker genes to study plant defense responses against Polyphagotarsonemus latus, a key pest in the production of Rhododendron simsii hybrids, was selected and validated. Genes belonged to the biosynthetic pathway of phytohormones jasmonic acid (JA) (RsLOX, RsAOS, RsAOC, RsOPR3 and RsJMT) and salicylic acid (SA) (RsPAL and RsICS). Furthermore, RsPPO, a putative marker gene for oxidative stress response was successfully cloned from R. simsii. A CTAB-based extraction protocol was optimized to assure excellent RNA quality for subsequent RT-qPCR analysis. The RT-qPCR protocol was extensively tested and RsRG7 and RsRG14 were selected as reference genes from a geNorm pilot study. Validation of the marker genes was done after application with elicitors [methyl jasmonate (MeJA), coronatine, β-aminobutyric acid and acibenzolar-Smethyl] or wounding. Both 100 μM MeJA and 0.1 μM coronatine had a significant effect on the expression of all marker genes. Foliar application of MeJA on the shoots resulted in a significantly earlier response when compared to root application and subsequent sampling of the shoots. Expression patterns after MeJA treatment were generally the same in six R. simsii genotypes: ‘Nordlicht’, ‘Elien’, ‘Aiko Pink’, ‘Michelle Marie’, ‘Mevrouw Gerard Kint’ and ‘Sachsenstern’. Wounding resulted in the same expression patterns as MeJA treatment except for RsJMT. None of the genotypes showed a significant induction of the latter gene 6 h upon wounding. Findings of these experiments indicated that the tolerant genotype ‘Elien’ has low basal expression levels of RsPPO. This might be the first step towards the breeding of mite-tolerant genotypes.     

Evaluation of Cold Tolerance in NERICAs Compared with Japanese Standard Rice Varieties at the Reproductive Stage

New Rice for Africa (NERICA) is a general name for interspecific rice varieties derived from a cross between the high‐yielding Asian rice (Oryza sativa L.) between locally adapted African rice (Oryza glaberrima Steud.). Eight NERICAs were evaluated for cold tolerance (CT) at the reproductive stage and compared with their O. sativa parents and three Japanese standard rice varieties over 3 years. Cold tolerance was evaluated based on the filled grain ratio (FGR) after cold water irrigation. The FGR was greatly reduced by cold water irrigation. NERICA 1, 2 and 7 had higher FGR (51.9–57.9 %), while NERICA 6, 15 and 16 had lower FGR (6.2–14.5 %). NERICA 1, 2 and 7 were less affected by cold stress, with a 31 % mean reduction in FGR, while NERICA 6, 15 and 16 were greatly affected, with their FGRs being reduced by more than 80 %. NERICA 3 and 4 were moderately affected by cold stress, with about 45 % reduction rate in FGR. FGR significantly influenced the grain weights of the varieties with strong positive correlations (r = 0.83–0.91; P < 0.001), and thus, similar trends in grain weights were observed. Grain weights were reduced by 61.7–96.4 % under cold stress. NERICA 1, 2 and 7 showed significantly better performance than NERICA 3 and 4, while NERICA 6, 15 and 16 performed poorly under cold water irrigation. The Japanese varieties Koshihikari (very tolerant) and Ozora (moderately tolerant) were more affected by cold water irrigation than NERICA 1, 2 and 7. On the basis of the mean reduction rate (%) in FGR under cold stress, the varieties were classified as follows: NERICA 1, 2 and 7 as tolerant; NERICA 3 and 4 as moderately tolerant; and NERICA 6, 15 and 16 as susceptible to cold stress. However, NERICA 7 grain yields were lower under cold stress due to both greatly reduced number of panicles per plant and number of spikelets per panicle. Therefore, NERICA 1 and 2 are suitable candidates for production in the highland regions of East Africa and should be promoted for production.     

玉米自交系耐铝性评价及根系形态解剖特征

采用营养液培养方法,对9个玉米自交系的耐铝性进行了评价,并对其中两个耐铝性不同的典型自交系的根系形态和解剖特征进行了比较。结果表明,玉米自交系在含铝营养液中的耐铝性评价结果与酸性土壤上的耐酸性筛选结果基本一致。耐铝基因型具有苏木精着色程度较低、种子根相对伸长率和植株相对生物量较高的共同特点。种子根相     

Direct shoot organogenesis from rhizomes of medicinal zingiber <Emphasis Type="Italic">Alpinia calcarata</Emphasis> Rosc. and evaluation of genetic stability by RAPD and ISSR markers

A simple and efficient protocol for direct in vitro shoot multiplication and plant regeneration was established for an important aromatic medicinal plant, Alpinia calcarata. Preinduction of rhizome segments in medium containing 8.8 μM 6-benzylamino purine (BAP) rescued the buds from dormancy in 60% of the cultures. An average of 6.2 shoots were produced from rhizomatous bud explants on Murashige and Skoog (MS) medium supplemented with 5 μM BAP, 10 μM kinetin, and 2.5 μM α-Naphthalene acetic acid (NAA). The mother cultures retained their morphogenetic potential upto four subcultures and a maximum of 1.77-fold increase in shoot multiplication was recorded after the 3^rd subculture. Rooting was simultaneously induced during subculture on shoot multiplication medium eliminating an additional step for rooting induction. Rooted plantlets were successfully acclimatized in pots in the greenhouse and subsequently established in the experimental garden without any visible symptoms of wilting and necrosis. The genetic fidelity of regenerated plants was evaluated by adapting to two PCR-based DNA marker techniques, Random Amplified Polymorphic DNA (RAPD) and Inter Simple Sequence Repeats (ISSR) which detected no variability in the in vitro multiplied plantlets of A. calcarata. This efficient method of clonal multiplication may be useful for commercial scale multiplication, and in situ and ex situ conservation of elite germplasm of A. calcarata.     

Development of salt tolerant IR64 near isogenic lines through marker-assisted breeding

Salt stress causes considerable damage to rice with a consequent reduction in grain yield, however, conventional breeding for this stress is time-consuming and costly. Recently, marker-assisted breeding has shown enormous potential to accelerate breeding of stress tolerant varieties because of its precision, time saving, and cost effectiveness. The present study was carried out to transfer Saltol, a major QTL on chromosome 1 associated with salinity tolerance, from FL478, a tolerant genotype, into IR64, a popular lowland variety through marker-assisted backcrossing (MABC). This technique considerably enhanced the recovery rate of the recurrent parent genome within three backcross generations, which could have saved several backcrosses compared with conventional schemes to achieve the same results. By using this technique, up to 99.7% of the recurrent parent genome was recovered at BC₃F₂ generation, saving at least three backcrosses compared with conventional breeding schemes. Salinity tolerance of IR64-Saltol lines was evaluated using saline culture solution adjusted to electrical conductivity of 12 dS m^-1 using NaCl. Based on selected physiological and growth parameters, the new Saltol introgression lines showed a significantly higher tolerance of salinity than their recurrent parent IR64. The results of this study confirm the benefits of using molecular markers in plant breeding to enhance tolerance of abiotic stresses.     

Identification of drought responsive QTLs during vegetative growth stage of rice using a saturated GBS-based SNP linkage map

Drought is a major abiotic constraint for rice production worldwide. The quantitative trait loci (QTLs) for drought tolerance traits identified in earlier studies have large confidence intervals due to low density linkage maps. Further, these studies largely focused on the above ground traits. Therefore, this study aims to identify QTLs for root and shoot traits at the vegetative growth stage using a genotyping by sequencing (GBS) based saturated SNP linkage map. A recombinant inbred line (RIL) population from a cross between Cocodrie and N-22 was evaluated for eight morphological traits under drought stress. Drought was imposed to plants grown in 75 cm long plastic pots at the vegetative growth stage. Using a saturated SNP linkage map, 14 additive QTLs were identified for root length, shoot length, fresh root mass, fresh shoot mass, number of tillers, dry root mass, dry shoot mass, and root-shoot ratio. Majority of the drought responsive QTLs were located on chromosome 1. The expression of QTLs varied under stress and irrigated condition. Shoot length QTLs qSL1.38 and qSL1.11 were congruent to dry shoot mass QTL qDSM1.38 and dry root mass QTL qDRM1.11, respectively. Analysis of genes present within QTL confidence intervals revealed many potential candidate genes such as laccase, Calvin cycle protein, serine threonine protein kinase, heat shock protein, and WRKY protein. Another important gene, Brevis radix, present in the root length QTL region, was known to modulate root growth through cell proliferation and elongation. The candidate genes and the QTL information will be helpful for marker-assisted pyramiding to improve drought tolerance in rice.     

Relationship between hybrid performance and genetic variation in self-fertile and self-sterile sugar beet pollinators as estimated by SSR markers

Sugar beet hybrid varieties are produced through the crosses between male sterile lines and the multigerm pollinators. The uniformity of pollinators used for hybrid crosses depends on the presence of self-sterility (S ^s ) and self-fertility (S ^f ) genes. The aim of the study was to analyze correlation between hybrid performance and genetic distance or heterozygosity of the sugar beet pollinators. Twelve diploid pollinators classified as self-sterile (S ^s ) or self-fertile (S ^f ) and two cytoplasmic male sterile (CMS) lines were crossed in line × tester scheme, producing 24 F₁ hybrids. The parents and the hybrids were evaluated for root yield and quality traits, from which F₁ performance, combining abilities, mid-parent and high-parent heterosis were calculated. Parental genetic distance and diversity of the pollinators were estimated by SSR markers and, together with GCA and F₁ performance, correlated with the heterosis effects. The S ^f hybrids had better GCA and higher values of root yield, root weight, and root circumference than the S ^s hybrids. Heterosis was recorded in more combinations with the S ^f than with the S ^s pollinators. Parameters of genetic diversity were higher in the S ^s (Na = 3.125; Ne = 2.341; He = 0.555) than in the S ^f pollinators (Na = 3.000; Ne = 2.188; He = 0.510). Genetic distance between the tested pollinators and the CMS lines was low (0.072–0.224) indicating that the genetic base of the investigated germplasm was narrow. Correlation of the heterosis effects with GD and heterozygosity was detected only for the root yield traits.