Genetic gains in Nordic spring barley breeding over sixty years

Accurate assessments of genetic gains ensuing from plant breeding for the most important agronomic characteristics in Nordic spring barley (Hordeum vulgareL.) are not available. Hence this research was aimed to determine the rate of genetic improvement in the Nordic barley breeding pool. This study included 90, 2-row spring barley cultivars released (1942–1988) and29, 6-row spring barley cultivars released(1930–1991) adopted by Nordic farmers that were tested in four Nordic locations for three consecutive years. Relative genetic gain owing to plant breeding was 13% in2-row barley and 34% in 6-row barley for grain yield. The absolute gain for this characteristic was 13 ± 3 kg ha^-1 year ^-1 in 2-row barley, and22 ± 3 kg ha^-1 year^-1 in6-row barley. Improved yield was achieved in Nordic barley by reducing plant height(0.20 ± 0.04 cm year^-1 for 2-rowbarley and 0.16 ± 0.06 cm year^-1for 6-row cultivars), thereby reducing significantly lodging (0.5 ± 0.1%year^-1 and 0.4 ± 0.1year^-1), and increasing significantly the harvest index (0.0008 ± 0.0002year^-1 and 0.0018 ± 0.0002year^-1). Additionally, in 2-row spring barley cultivars resistance to powdery mildew (0.19 ± 0.08% year^-1)and thousand-kernel weight (0.07 ±0.03 g year^-1) were also significantly enhanced, whereas hectoliter weight was improved (0.06 ± 0.02 kg year^-1)in 6-row barley cultivars in the period investigated. This revised version was published online in August 2006 with corrections to the Cover Date.     

Changes over time in the adaptation of barley releases in north-eastern Spain

The objective of this study was to characterize grain yield and adaptation of barley cultivars released in recent decades in north-eastern Spain. Ten six-rowed and 10 two-rowed barley genotypes were grown in eight environments. Mean yields varied among environments between 1.7 and 5.8 tha^?1. New releases showed higher mean yields and were specifically adapted to nonlimiting growing conditions. The average genetic advances were estimated as 40.7 and 32.9 kg ha^?1 years^?1 for two- and six-rowed genotypes, respectively, in the four most productive environments. Old genotypes, with lower overall grain yields, were specifically adapted to the poorer sites. A negative genetic gain, estimated as -14.8kg ha^?1 years^?1. was reorded for six-rowed culiivars in the four poorest sites. No significant association was observed between heading date and year of release. Variations in carbon isotope discrimination (Δ) were examined to assess whether changes in adaptation could be partially explained by shifts in the genoiypic transpiration efficiency (TE) over time, in the most favourable environments, new releases showed the highest grain yields and carbon isotope discrimination values (Δ). By contrast, older cultivars had constitutively? lower Δs and therefore higher TEs. These results suggest a genetic association between low TE and yield potential and specific adaptation to stress-free conditions so that selection for yield under favourable conditions could have resulted in an indirect downward genetic shift in the TE of modern cultivars.     

Breeding Progress in Grain Yield and Selected Agronomic Characters of Winter Barley (Hordeum vulgare L.) over the Last Quarter of a Century

This study gives estimates of breeding progress achieved in winter barley (Hordeum vulgare L.) since the 1960′s in grain yield and the change in several morphological traits for seventeen historically important cultivars: 12 six-rowed and 5 two-rowed, grouped into four epochs according to the period of major commercialization in Italy. All genotypes were evaluated across a range of soil fertility and climatic environments. The modern six-rowed cultivars have shown a consistent increase in tillers/m² and seeds/spike (16 and 28 %, respectively) over the local populations. In the modern two-rowed cultivar ‘Igri’ the increase in tillers/m² and seed weight were, respectively, 20 and 14 % snd seeds/spike decreased by 20 % over the local populations. The modern six-rowed and two-rowed cultivars have less lodging, are earlier and shorter than the old varieties and local populations. In the last quarter of a century, the breeding progress for gram yield has been increased by 52 and 74 kg/ ha/year or 0.75 and 1.1 % per year respectively, for six-rowed and two-rowed genotypes: while the gain in biomass yield in the same period was not uniform for six-rowed cuitivars and increased by 64 kg/ha/ year or 0.46 % in two-rowed cultivars. The grain yield improvement in the modern six-rowed and two-rowed cultivars is the result of a better partitioning of the photosynthetic products into the grain.     

Spatial variability of salt-affected soils in the middle Ebro Valley (Spain) and implications in plant breeding for increased productivity

Barley breeding programs have empirically selected for improving grain yield and quality. The objective of this study was to quantify genetic gains in yield in 2-rowed malting barley cultivars released from 1944to 1998 in Argentina, identifying the major physiological traits responsible for them. For this purpose, a field experiment was conducted in absence of biotic and abiotic stressful factors and with lodging being prevented mechanically. Until the 1970's,potential yield was maintained nearly constant at 5.25 mg ha^-1 and since then it increased at a rate of 41 kg ha^-1 year^-1. That bi-linear trend was closely related to the trend of averaged yields obtained by farmers. The contribution made by breeding yield potential to the total yield gains achieved by farmers was estimated in c. One third. Neither time to heading nor time to maturity were systematically modified by breeding. However, the partitioning of the developmental time was modified: time to achieve both maximum number of floret primordia and length of the jointing –heading period were increased with the year of release of the cultivars. The main component associated with yield was the number of grains per m², due to variations in number of spikes per m².Total and vegetative biomass at maturity increased with the year of release of the cultivars, at a rate of 45 and 19 kg ha^-1 year^-1, while both harvest index and stem height remained virtually unmodified. Differences in biomass at heading among cultivars were related to the improvement on the abilities to capture more radiation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Water use efficiency among dry bean landraces and cultivars in drought-stressed and non-stressed environments

The agricultural use of water is higher than 85% in the western USA, resulting in an increasing water deficit in the region; this situation is commonly encountered throughout the world where irrigated and irrigation-assisted production systems are operational. The objective of this study was to examine differences among dry bean (Phaseolus vulgaris L.) landraces and cultivars in terms of water use efficiency (WUE), subsequently identifying those with a high water use efficiency. Six medium-seeded (25–40 g 100 seed wt⁻¹) landraces and cultivars of pinto and red market classes were evaluated in intermittent drought-stressed (DS) and non-stressed (NS) environments at Kimberly, Idaho, USA in 2003 and 2004. Each market class comprised one each of a landrace and old and new cultivars. Mean evapotranspiration (ET) in the NS environment was 384 mm in 2003 and 432 mm in 2004; the respective ET values in the DS environment were 309 and 268 mm. Mean seed yield was higher in the DS (2678 kg ha⁻¹) and NS (3779 kg ha⁻¹) environments in 2004 than in 2003 (688 and 1800 kg ha⁻¹, respectively). Under severe drought stress in 2003, WUE in the pinto bean ranged from 1.5 for the Common Pinto landrace to 4.4 kg ha⁻¹ mm⁻¹ water for cv. Othello. The Common Red Mexican landrace had the highest WUE (3.7), followed by cvs. NW 63 (2.8) and UI 259 (1.4) in the red market class. Under favorable milder climatic conditions in 2004, the mean WUE value was 10 kg ha⁻¹ mm⁻¹ water in the DS environment and 8.7 kg ha⁻¹ mm⁻¹ water in the NS environment. We conclude that dry bean landraces and cultivars with high WUE should be used to reduce dependence on irrigation water and to develop drought-resistant cultivars to maximize yield and WUE.     

Quantitative trait loci for grain yield and yield components in a cross between a six-rowed and a two-rowed barley

Summary The positions of quantitative trait loci (QTL) for yield and yield components were estimated using a 85-point linkage map and phenotype data from a F₁-derived doubled haploid (DH) population of barley. Yield and its components were recorded in two growing seasons. Highly significant QTL effects were found for all traits at several sites in the genome. A major portion of the QTL was found on chromosome 2. The effect of the alleles in locus v on thousand grain weight and kernels per ear explained 70–80% of the genetic variation in the traits. QTL × year interaction was found for grain yield. Several different QTL were found within the two-rowed DH lines compared to those found in the six-rowed DH lines. Epistasis between locus v and several loci for yield and yield components indicates that genes are expressed differently in the two ear types. This may explain the difficulties of selecting high yielding lines from crosses between two-rowed and six-rowed barley.Abbreviations DH doubled haploid - QTL quantitative trait locus/loci - RAPD random amplified polymorphic DNA - RFLP restriction fragment length polymorphism - T. Prentice Tystofte Prentice - V. Gold Vogelsanger Gold     

Agronomic and qualitative traits of T. turgidum ssp. dicoccum genotypes cultivated in Italy

Summary The increasing popularity of organic agriculture and health food products has led to a renewed interest in hulled wheat species such as emmer (Triticum turgidum ssp. dicoccumSchubler). Knowledge on agronomic and quality traits is required for effective and efficient use of germplasm collections in breeding programs. The objective of this study was to estimate agronomic and grain quality traits of emmer wheat cultivated in Italy. A total of 20 emmer accessions consisting of landraces, breeding lines or cultivars selected from landraces and modern cultivars were examined under low input conditions. The study was conducted for three successive years (2002–2004) at one location of Southern Italy (Foggia). The entries were characterized for agronomic and qualitative traits [grain yield (t ha⁻¹), thousand grain weight (g), test weight (kg hl⁻¹), grain protein content (%), HMWG composition, dry gluten content (%), gluten index and yellow index, alveograph indices and Total Organic Matter (TOM) on cooked pasta]. The results showed a large genetic variability for most of the traits measured and, even if most of the accessions showed inferior bread- and pasta-making performance, modern cultivars exhibited improved quality traits with some potential to perform healthy and tasty food.     

The effect of pedicel length on lateral kernel weight in two-six rowed near isogenic lines of barley (Hordeum vulgare L.)

Summary Fifteen backcross derived, six-rowed isogenic barley (Hordeum vulgare L.) lines with the genotype vvii, nine in a six-rowed background, and six in a two-rowed background, were evaluated over 3 years for pedicel length and lateral and central kernel weight.Within the six-rowed and two-rowed backgrounds there were significant differences between isolines for all three characteristics studied. The lateral kernel weights of the six-rowed isolines were approximately half of their central kernel weights. Isolines with club heads had signicantly longer pedicels and significantly lower lateral and central kernel weight than lax headed types. A significant negative correlation was found between pedicel length and lateral kernel weight for the 15 isolines and within the six-rowed background, indicating that as pedicel length increases, lateral kernel weight tends to decrease.We recommend that breeders making selections of six-rowed segregates from two x six-rowed crosses should select against pedicellate (vvii) laterals.Cooperative investigations of the Mont. Agric. Exp. Stn. and ARS, USDA. Published with the approval of the Director of the Mont. Agric. Exp. Stn. as Journal Series No. 1463.     

Genetic improvement of yield responsiveness to nitrogen fertilization and its physiological determinants in barley

Traditionally, barley in Argentina has been cultivated in low-yielding environments. A study was conducted to test whether breeding for improved performance under these conditions would have also improved the responsiveness to nitrogen availability. Four cultivars of two-rowed malting barley (released in 1944, 1960,1982 and 1998) were grown under 4 rates of nitrogen fertilizer at sowing (20, 50, 110and 160 kgN ha^-1). All cultivars increased their yield with the increase in soil nitrogen. But yield of modern cultivars responded more strongly than yield of old ones. For modern cultivars, increase in grain yield was of 12 ± 0.6 kgha^-1 for each 10 kg ha^-1 of increase in the mean yield (environmental index). Absolute values of genetic gain were related to nitrogen availability: 1.59, 2.58, 4.52 and 4.29 g m^-2 year^-1 for the N₂₀, N₅₀, N₁₁₀ and N₁₆₀ treatments, respectively. Grain yield was associated with grain number m^-2, which was dependent on spikes m^-2 and grains spike^-1. Total biomass at maturity also explained the changes in yield. It is concluded that selection under stress conditions was, in this case, beneficial to identify cultivars with high yields under a wide range of nitrogen availabilities. This revised version was published online in July 2006 with corrections to the Cover Date.     

Performance of various grapefruit (<Emphasis Type="Italic">Citrus paradisi</Emphasis> Macf.) and pummelo (<Emphasis Type="Italic">C. maxima</Emphasis> Merr.) cultivars under the dry tropic conditions of Mexico

Grapefruit growers in the tropics require information about existing and new citrus cultivars with high productivity potential. The objective of this study was to determine the growth, yield, and fruit quality performance of seven pigmented and four white grapefruit cultivars under the dry tropic conditions of Colima, Mexico. The trees were budded on sour orange (Citrus aurantium L.) rootstock and planted at a distance of 8 × 4 m. ‘Oroblanco’ and ‘Marsh Gardner’ white-fleshed grapefruit cultivars and ‘Chandler’, a pink-fleshed pummelo, were the largest trees with the greatest height (5.0–5.6 m), canopy diameter (6.2–6.3 m), trunk diameter (21.9–23.3 cm), and canopy volume (109–123 m³). Lower height (4.3–4.8 m) and canopy volume (73–96 m³), but with similar canopy diameter to the previously mentioned cultivars, were recorded for the remaining pigmented cultivars. ‘Chandler’ pummelo and four pigmented grapefruit cultivars (‘Shambar’, ‘Río Red’, ‘Ray Ruby’, and ‘Redblush #3’) had yearly productions of 34.8, 34.9, 34.1, 32.7, and 30.6 ton ha⁻¹, respectively. The most productive white grapefruit cultivar was ‘Marsh Gardner’ (30.5 ton ha⁻¹). Grapefruit cultivars having the largest fruit size showed a higher inverse relationship between fruit weight and yield than those with small fruit. Most genotypes had higher values of fruit weight, juice content, and maturity index than those required by the local market. The most promising grapefruit cultivars based on their acceptable growth, yield superior to 30 ton ha⁻¹, and acceptable fruit color were ‘Río Red’, ‘Shambar’, ‘Ray Ruby’, and ‘Redblush #3’.     

Quantitative trait loci for dry matter digestibility and particle size traits in two-rowed × six-rowed barley population

More than half of the barley grown in the USA is used for livestock feed, with the remaining stocks diverted for human food and malting purposes. The use of barley grain as a major source of cattle feed has been criticized because of its rapid digestion in the rumen, which can result in digestive disorders in cattle. In sacco dry matter digestibility (ISDMD) and particle size (PS) after dry rolling have been found to play a role in the feedlot performance of barley as a feed grain. Reducing the rate of ISDMD is predicted to result in significantly improved animal health and average daily gain. A recombinant inbred line population derived from a cross between a high ISDMD, two-rowed barley cultivar (Valier) and a six-rowed Swiss landrace line (PI370970) exhibiting far slower ISDMD has been developed for studying the underlying genetic locations and mechanisms of these traits. To detect associated quantitative trait loci (QTLs), we collected and analyzed data from irrigated and rain-fed environments. A significant negative correlation was observed between ISDMD and PS. High heritability estimates for ISDMD and PS suggest that early selection for these traits during breeding would be achievable. Four QTLs were identified on chromosomes 2H, 6H, and 7H, explaining 73–85% of ISDMD phenotypic variation, while three QTLs on 2H and 7H were associated with variation in PS and explained 58–77% of its variation. A major QTL on chromosome 2H tightly linked to the morphology-modifying gene vrs1 was found to dramatically control 35–62% of the phenotypic variation of ISDMD and 26–53% of that of PS. The impact of the vrs1 locus on ISDMD was validated in two populations representing different genetic backgrounds. Our results suggest that it may also be advantageous to simultaneously overlap these QTLs around the vrs1 locus.     

Effect of row type,flowering type and several other spike characters on resistance to Fusarium head blight in barley

Fusarium head blight (FHB) is a destructive disease of barley. The genetics and expression of resistance to FHB in barley is complex, and various spike characters are thought to possibly influence resistance. Tests using spray-inoculation of Fusarium graminearum at anthesis in greenhouse environments showed that two-rowed and cleistogamous varieties from Japan belong to the highest resistance group, while six-rowed and chasmogamous varieties are mostly susceptible. In order to evaluate the effect of such spike characters, including row type and flowering type, on FHB resistance, near-isogenic lines (NILs) differing in these characters were tested for their resistance. Two testing methods were used: the pot-plant and cut-spike methods, in which spikes at anthesis were spray-inoculated in greenhouse environments. The chasmogamous NILs and some six-rowed NILs were significantly more diseased than cleistogamous and two-rowed parent lines, respectively, and the difference in FHB severity was greater and more stable between cleistogamous/chasmogamous NIL pairs than between two-/six-rowed pairs. Slight or no differences were observed in glaucous/non-glaucous, normal/dense spike, normal/uzu type and normal/deficiens NIL pairs. The results indicate that the contribution of cleistogamy and/or the genetic background toward FHB resistance is more than that of row type and the other tested spike characters. Further, it should be possible to develop six-rowed varieties with FHB resistance nearly as good as that of the two-rowed varieties.     

The origin of six-rowed ‘wild’ barley from the western Himalaya

Summary Plants were grown from seed of two-rowed wild barley, Hordeum spontaneum, and six-rowed brittlerachised barley. H. agriocrithon, collected in Ladakh, north-western India. Whereas the H. spontaneum remained true to type, segregation for morphological characters was observed in progeny rows grown from heads of H. agriocrithon plants. The H. agriocrithon heads also showed segregation for a biochemical character, the polypeptide pattern of the endosperm storage protein fraction (hordein). The H. agriocrithon seed therefore originated from natural hybridization between cultivated H. vulgare and weedy H. spontaneum. Crosses of H. vulgare and H. spontaneum gave progeny which resembled H. agriocrithon and showed similar hordein polypeptide segregation patterns. The results indicate that six-rowed brittle-rach ised barleys from the Himalayas have a similar origin to forms found in the Middle East, and that H. agriocrithon does not play a direct role in the evolution of barley.     

Genetic diversity among elite Bulgarian barley varieties evaluated by RFLP and RAPD markers

Genetic variation among five elite winter barley cultivars (H. vulgare L.) currently grown in Bulgaria was assessed at the molecular level using restriction fragment length polymorphism (RFLP) and randomly amplified polymorphic DNA (RAPD) markers. The present study sampled RFLPs in four well characterized multigene families in barley: the seed storage protein loci; the 18S, 5.8S and 26S ribosomal DNA loci; the loci coding for 5S ribosomal RNA and the loci coding subunit α of ATP-A complex in the mitochondrial genome. RFLPs were detected in three out of five investigated chromosomal loci in the barley cultivars studied. RAPD assay using arbitrary 10-base primers was applied to generate amplified length polymorphic markers in barley. Overall a total of 15 polymorphic phenotypes were found among the studied barley cultivars by using 11 out of 25 tested primers. All RAPDs were considered as dominant genetic markers except for two, where PCR and Southern blot analysis indicated the presence of codominant amplification products. Five RAPD polymorphisms in F₁ and F₂ progenies of the cross between Alpha and Obzor were inherited in Mendelian fashion. The determined values for the genetic variation proved a high genetic similarity among the tested cultivars. Genetic similarity (GS) calculated from RFLP and RAPD data ranged from 0.888 to 0.997 with a mean GS – 0.933. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inheritance of (1–3)(1–4)-beta-D-glucan content in barley (<Emphasis Type="Italic">Hordeum vulgare</Emphasis> L.)

β-glucan is the soluble dietary fiber component and occurs at its highest in barley. This study aims to evaluate the inheritance of β-glucan content in barley grains and to map quantitative trait loci (QTL) associated with this trait. F₅-derived 107 lines from the cross of the six-rowed waxy hulless barley, ‘Yonezawa Mochi’ and the six rowed non-waxy hulless barley,’ Neulssalbori’ were measured for their agronomic traits and β-glucan level at four different environments. These recombinant lines showed significant genotypic variation (P < 0.01) and normal distribution for β-glucan content with a range of 43.6–62.1 g kg⁻¹ across environments. A significant genotype-by-environment interaction was also found. The broad-sense heritability estimates for β-glucan content ranged from 0.42 to 0.82 across environments. Using one-factor analysis and composite interval mapping, a main effect of QTL associated with β-glucan content was identified in the genomic region near waxy gene (wx) and HVM4 on chromosome 7H. The major QTL at this region explained on average 44.4% of the variation for the mean of β-glucan content across environments with LOD values that ranged from 5.7 in Suwon in 2001 to 13.9 in Suwon in 2003. Two minor QTLs were identified but their significance of association with β-glucan content was inconsistent across environments.     

Simplified AFLP procedure as a tool for identification of strawberry cultivars and advanced breeding lines

DNA polymorphisms among 6 cultivars of Fragaria × ananassa (Duch.) and 13salinity tolerant clones were evaluated using simplified – PstI based Amplified Fragment Length Polymorphism procedure(^PstIAFLP). Out of 129 amplification products obtained with 10 selective primers, 116 markers were polymorphic and could be used to distinguish all analyzed materials. Coordinate and cluster analyses revealed 2 main groups of clones and divided strawberry cultivars (CUL) and tested F₁ hybrids of ‘Sweet Heart’(HYB). Mean genetic similarities in groups of cultivars and selected breeding lines (SEL) were significantly higher (0.722 and0.706, respectively, p < 0.05) than in group of SH hybrids (0.485). Results suggest that ^PstIAFLP method is sufficient for effective identification and useful for assessing the level of genetic diversity in strawberry cultivars and breeding lines. The presented method can bean alternative multilocus marker system to widespread RAPD method. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic improvement of spring barley cultivars grown in eastern Canada from 1910 to 1988

Summary Spring barley is an important feed crop in eastern Canada, and the development of high-yielding, high grain protein cultivars is desirable. This study was conducted to assess the impact of breeding on the yield and protein aspects of cultivar development, and to identify related changes in plant characteristics which may have been altered over time. A 3-year field experiment was conducted to evaluate twenty six-rowed spring barley genotypes representing the majority of cultivars developed from 1910 to 1988 for eastern Canada. The yields of barley cultivars released from 1935 to 1988 increased at a rate of about 0.03 t ha^-1 yr^-1, and showed no evidence of having reached a plateau. Increases in yield were associated with higher total dry matter production and harvest index, reduced plant height and increased lodging resistance. No consistent change in main stem or tiller yield components was observed. Grain protein concentration decreased progressively with time, especially with the newer cultivars. Reduction in grain protein concentration was not associated with lower protein content on a per grain basis, but rather with an increase in the amount of non-structural carbohydrate per grain. Total plant and grain N accumulation showed positive trends with time. No trends were observed for N harvest index, apparent post-heading N uptake, N retranslocation, and retranslocation efficiency. Thus, while the newer cultivars accumulated more total and grain N, proportional N partitioning to the grain was not altered.     

QTL-based analysis of genotype-by-environment interaction for grain yield of rice in stress and non-stress environments

Use of DNA-based markers can accelerate cultivar development in variable cultivation environments since, in contrast to phenotype, DNA markers are environment-independent. In an effort to elucidate the genetic basis of genotype-by-environment interaction (G × E) for yield of rice (Oryza sativa L.), the associations between 139 AFLP markers and grain yield were determined for rice grown in fresh water (EC of 0.65 dS m⁻¹) and saline conditions (EC of 4–8 dS m⁻¹) with 0 kg ha⁻¹ or 100 kg ha⁻¹ nitrogen fertilizer in the years 2000 and 2001. A population of recombinant inbred lines of rice, developed from an IR29 × Pokkali cross, was used in the study. Both genotype × salinity and genotype × nitrogen level interactions were significant, with the genotype × salinity interaction being stronger. Through multiple regression analysis using a stepwise procedure for selecting markers, 36 markers were detected for grain yield in the four test conditions and of these 28 were detected in only one test condition implying strong environmental specificity for yield QTL expression. However, the fact that eight QTLs were detected in more than one test condition points to the existence of wide-adaptability genes in this cross. Markers with significant associations with yield explained between 37% and 48% of the yield variation in each test condition. Superior genotypes of rice were identified in all four test conditions based on their marker signatures. Furthermore, across N fertilizer regimes, yield predicted from summed additive effects of QTLs were significantly correlated with observed yield in the same year and across years. Thus marker-assisted selection can help breeders overcome the problem of low selection efficiency encountered during phenotypic selection for yield in stress environments.     

Evaluation of wild Arachis species for abiotic stress tolerance: I. Thermal stress and leaf water relations

The Indian groundnut cultivars have a narrow genetic base. Hence, it was of interest to investigate the genetic variability among wild Arachis species and their accessions for tolerance to thermal stress. A wide variation was observed in leaf morphological characters such as colour, shape, hairiness, length and width and thickness (SLA). The temperature and time required for 50% leaf injury was worked out with limited number of genotypes and was found to be 54°C for 50 min. Among 36 genotypes (having SLA in the range of 66 and 161 cm² g⁻¹) screened, the inherent potential for cold as well as heat tolerance in terms of relative leaf injury (RI) was observed. Thus, based on RI-values, A. glabrata 11824 and A. paraguariensis 12042 were identified as heat-tolerant and cold-tolerant genotypes, respectively while A. appresipila 11786 was found to be susceptible to both heat and cold. Correlation between SLA and RI values for heat (r = 0.38, P < 0.05) and cold (r = 0.52, P < 0.05) tolerance was positive, indicating that thicker the leaf the lower the injury or higher the tolerance. Among six species and 13 accessions, comprising both heat-tolerant and heat- susceptible genotypes, the concentrations of various leaf chemical constituents such as total protein, phenols, sugars, reducing sugar, amino acids, proline, epicuticular wax load and chlorophyll varied significantly. The epicuticular wax load ranged between 1.1 and 2.5 mg dm² among 13 A.glabrata accessions. These accessions were categorized into two groups, i.e. high-wax (range: 2.0–2.5 mg dm²) and low-wax types (range: 1.1–1.6 mg dm²). The high-wax type showed a higher diffusion resistance (dr) as compared to low-wax type; though the transpiration rate (tr) in high-wax type was moderate (between 9.5 and 11.6 μg cm⁻² s⁻¹). Genetic variability in parameters such as canopy temperature, dr and tr was also distinct. The fully turgid leaves with relative water content ≥91%, showed leaf water potential (ψ_leaf) between −0.7 and −1.2 MPa. Results indicated that the plants with thicker leaves are better protected from heat injuries. Further, epicuticular wax load seems to help in maintaining stomatal regulation and leaf water relations, thus affording adaptation to wild Arachis species to thrive under water-limited environments. The sources of tolerance, as identified in this study, could be utilized to improve thermal tolerance of the groundnut cultivars by intra-specific hybridization, following either conventional breeding using embryo rescue techniques, if required or utilizing biotechnological tools.     

A cytoplasmic-nuclear male-sterility system derived from a cross between <Emphasis Type="Italic">Cajanus cajanifolius</Emphasis> and <Emphasis Type="Italic">Cajanus cajan</Emphasis>

Cytoplasmic-nuclear male-sterility is an important biological tool, which has been used by plant breeders to increase yields in cross-pollinated cereals and vegetables by commercial exploitation of the phenomenon of hybrid vigor. In legumes, no such example exists due to the absence of an economic way of mass pollen transfer from male to female parent. Pigeonpea [Cajanus cajan (L.) Millsp.], however, is a different legume where a moderate level of insect-aided natural out-crossing (25–70%) exists and it can be used to produce commercial hybrid cultivars, if an efficient and stable cytoplasmic-nuclear male-sterility (CMS) system is available. This paper reports the development of a stable CMS system (ICP 2039A), derived from an inter-specific hybrid of Cajanus cajanifolius, a wild relative of pigeonpea, with a cultivar ICP 11501. Using this genetic material, designated as the A₄ cytoplasm, a number of fertility restorers and maintainers have been developed. The best short-duration experimental pigeonpea hybrid ICPH 2470 produced 3205 kg ha⁻¹ grain yield in 125 days, exhibiting 77.5% advantage over the control cultivar UPAS 120. At present, all the important biological systems necessary for a successful commercial hybrid breeding program are available in pigeonpea and the package of this technology has been adopted by private seed sector in India for the production and marketing of hybrid varieties.