Superior Agronomic Performance Research Articles

Improved Tolerance to Root Rot and Bacterial Blights in Kidney Bean: Registration of ‘Talon’ Dark Red Kidney and ‘Rosie’ Light Red Kidney

‘Talon’ dark red kidney (Reg. No. CV‐314, PI 674157; PVP #201500067) and ‘Rosie’ light red kidney (Reg. No. CV‐313, PI 674156; PVP #201500066) are two new kidney bean (Phaseolus vulgaris L.) cultivars developed by the dry bean breeding program at North Dakota State University and released by the North Dakota Agricultural Experimental Station. Talon has medium‐early maturity, while Rosie is late maturing. Both Talon and Rosie are high‐yielding cultivars with commercially acceptable seed size, shape, and appearance. Both Talon and Rosie were tested between 2006 and 2015 across 24 environments in Minnesota and North Dakota and have shown a superior seed yield compared with cultivars commonly grown in the region. Averaged across all environments, Talon produced 153 and 359 kg ha−1 more than ‘Montcalm’ and ‘Redhawk’, respectively. Rosie produced 991, 355, and 222 kg ha−1 more than ‘CELRK’, ‘Foxfire’, and ‘Pink Panther’, respectively. In comparison with the commercial checks, both Talon and Rosie displayed intermediate resistance to the root rot complex under field conditions in Minnesota. In addition, Talon displayed intermediate resistance and Rosie was rated as resistant to both common bacterial blight [caused by Xanthomonas axonopodis pv. phaseoli (Smith) Vauterin et al.] and halo blight [caused by Pseudomonas syringae pv. phaseolicola (Burkholder) Young et al.] in the field. The improved levels of resistance to both root rots and bacterial diseases combined with the superior agronomic performance over kidney bean cultivars commonly grown in the United States suggest that Rosie and Talon have the potential to be among the most important kidney cultivars in the United States.

Identifying Rare FHB-Resistant Segregants in Intransigent Backcross and F2 Winter Wheat Populations.

Fusarium head blight (FHB), caused mainly by Fusarium graminearum Schwabe [telomorph: Gibberella zeae Schwein.(Petch)] in the US, is one of the most destructive diseases of wheat (Triticum aestivum L. and T. durum L.). Infected grain is usually contaminated with deoxynivalenol (DON), a serious mycotoxin. The challenge in FHB resistance breeding is combining resistance with superior agronomic and quality characteristics. Exotic QTL are widely used to improve FHB resistance. Success depends on the genetic background into which the QTL are introgressed, whether through backcrossing or forward crossing; QTL expression is impossible to predict. In this study four high-yielding soft red winter wheat breeding lines with little or no scab resistance were each crossed to a donor parent (VA01W-476) with resistance alleles at two QTL: Fhb1 (chromosome 3BS) and QFhs.nau-2DL (chromosome 2DL) to generate backcross and F2 progeny. F2 individuals were genotyped and assigned to 4 groups according to presence/ absence of resistance alleles at one or both QTL. The effectiveness of these QTL in reducing FHB rating, incidence, index, severity, Fusarium-damaged kernels (FDK) and DON, in F2-derived lines was assessed over 2 years. Fhb1 showed an average reduction in DON of 17.5%, and conferred significant resistance in 3 of 4 populations. QFhs.nau-2DL reduced DON 6.7% on average and conferred significant resistance in 2 of 4 populations. The combination of Fhb1 and QFhs.nau-2DL resistance reduced DON 25.5% across all populations. Double resistant lines had significantly reduced DON compared to double susceptible lines in 3 populations. Backcross derived progeny were planted in replicated yield trials (2011 and 2012) and in a scab nursery in 2012. Several top yielding lines performed well in the scab nursery, with acceptable DON concentrations, even though the average effect of either QTL in this population was not significant. Population selection is often viewed as an “all or nothing” process: if the average resistance level is insufficient, the population is discarded. These results indicate that it may be possible to find rare segregants which combine scab resistance, superior agronomic performance and acceptable quality even in populations in which the average effect of the QTL is muted or negligible.

Contrasting rice backcross inbred lines (BILs) for grain yield and heading under lowland reproductive stage moisture stress

Identification and understanding the role of physio-morphological drought responsive mechanisms leading to grain yield enhancement under water stress is a critical insight for designing appropriate strategies to breed drought-tolerant cultivars for any drought prone ecology. In this study, three pairs of contrasting BILs with varied maturity were characterized for several agronomical, physiological and morphological traits across a wide range of moisture stress environments at reproductive stage during 2012–2014. Within each group, BILs differ significantly for grain yield, heading, biomass and harvest index under drought stress, but showed similar yield potential, phenology and other traits under control condition. The most tolerant BIL, S-15 out yielded all BILs and standard checks under both conditions. Apart from superior agronomic performance, drought tolerant BILs maintained significantly higher assimilation rate, transpiration rate and transpiration efficiency compared to susceptible BILs under stress in all three groups. In addition, most tolerant BIL (S-15) showed significantly higher stomatal conductance than susceptible BIL (S-55) in early group. Among root traits, significant differences under stress was observed for root dry weight between contrasting BILs in each group, even though tolerant BILs had higher root length and root volume compared to susceptible BILs, which is non-significant. Hence, consideration of root traits an important strategy for drought avoidance in case of rice may not always contributes to significant yield improvement under moisture stress condition. Further, tolerant BILs also recorded significantly higher shoot dry weight and drought recovery score at seedling stage under stress. Our findings suggest that genotypes with higher photosynthetic efficiency and better plant water status are able to produce higher grain yield under drought stress environments.

Towards a new strategy to breed an autogamous plant: A case of study in Capsicum baccatum var. pendulum

New varieties of autogamous plant have been developed over the decades using different classical breeding methods, including pedigree. Our goal was to associated pedigree with mixed model analysis to select plants with superior agronomic performance in Capsicum baccatum var. pendulum, an autogamous species that has been underexploited by plant breeders. An F2 population was developed from biparental crosses (UENF 1616×UENF 1732) and 45 F2 individuals were selected using Mulamba and Mock Index considering dry fruit mass, fruit length, fruit wall thickness and soluble solid content. Lines F2:3 along with parents and a standard genotype were tested in field conditions and eight agronomic traits were evaluated. Considering genetic parameters estimation by mixed models, the heritability estimate of the progeny mean was high magnitude ranging from 0.68 to 0.88 while the narrow sense heritability ranged from 0.23 to 0.46 and the additive heritability within the plot reached magnitude between 0.15 and 0.43 for most characteristics, with an accuracy of selection close to unity indicating high accuracy in selection for all traits. Twenty lines with superior performance for each trait were selected considering the values for predict genetic additive effect ranking along with the new mean of improved population. Comparing the 20 selected lines with parents and standard genotype it was possible to observe that lines were superior for eleven out of the thirteen agronomic traits evaluated. The association of the classical pedigree method with more accurate statistical procedure can be useful to assist breeders in autogamous breeding program.

The gene PmYB confers broad-spectrum powdery mildew resistance in the multi-allelic Pm2 chromosome region of the Chinese wheat cultivar YingBo 700

It is important to detect wheat broad-spectrum powdery mildew resistance (Pm) genes in commercial cultivars with superior agronomic performance. YingBo 700, a Chinese commercial cultivar registered and released in 2012, showed a broad spectrum of resistance to 48 of 49 tested Blumeria graminis f. sp tritici (Bgt) isolates from different regions of China. Genetic analysis of F2 populations from the crosses YingBo 700 × Mingxian 169 and YingBo 700 × Shimai 15 and F2:3 lines from YingBo 700 × Mingxian 169 demonstrated that the resistance was controlled by a single dominant resistance gene, which was temporarily designated PmYB. Using molecular markers and bulked segregant analysis of the F 2:3 lines from YingBo 700 × Mingxian 169, PmYB was mapped to the multi-allelic Pm2 region of chromosome arm 5DS co-segregated with the sequence-characterized amplified region (SCAR) marker SCAR112 and flanked by the simple sequence repeat (SSR) marker Cfd81 and SCAR marker SCAR203 with genetic distance of 0.9 and 1.9 cM, respectively. YingBo 700 showed a unique response pattern to different Bgt isolates compared with the lines with documented Pm2a, Pm2b, Pm48, PmLX66, PmW14, PmZ155 and PmX3986-2 on chromosome arm 5DS. Therefore, PmYB appears to be a novel allele in this multi-allelic region. In order to validate applicability of the closely linked markers for marker-assisted selection, the closely linked markers Cfd81, SCAR112, SCAR203 and Mag6176 were evaluated for applicability in diagnosing the resistance gene in 62 cultivars from different regions of China. The results will contribute to rapidly transfer of PmYB into more cultivars.

IDENTIFICATION OF IDEOTYPES BY CANONICAL ANALYSIS IN Panicum maximum

Grouping of genotypes by canonical variable analysis is an important tool in breeding. It allows the grouping of individuals with similar characteristics that are associated with superior agronomic performance and may indicate the ideal profile of a plant for the region. The objective of the present study was to define, by canonical analysis, the agronomic profile of Panicum maximum plants adapted to the Agreste region. The experiment was conducted in a completely randomized design with 28 treatments, 22 genotypes of Panicum maximum, and cultivars Mombasa, Tanzania, Massai, Milenio, BRS Zuri, and BRS Tamani in triplicate in 4-m² plots. Plots were harvested five times and the following traits were evaluated: plant height; total, leaf, and stem; dead dry matter yields; leaf:stem ratio; leaf percentage; and volumetric density of forage. The analysis of canonical variables was performed based on the phenotypic means of the evaluated traits and on the residual variance and covariance matrix. Genotype PM34 showed higher mean leaf dry matter yield under the conditions of the Agreste of Alagoas (on average 53% higher than cultivars Mombasa, Tanzania, Milenio and Massai). It was possible to summarize the variation observed in eight agronomic characteristics in only two canonical variables accounting for 81.44 % of the data variation. The ideotype plant adapted to the conditions of the Agreste should be tall and present high leaf yield, leaf percentage, and leaf:stem ratio, and intermediate values of volumetric density of forage.

The genome of the stress-tolerant wild tomato species Solanum pennellii.

Solanum pennellii is a wild tomato species endemic to Andean regions in South America, where it has evolved to thrive in arid habitats. Because of its extreme stress tolerance and unusual morphology, it is an important donor of germplasm for the cultivated tomato Solanum lycopersicum. Introgression lines (ILs) in which large genomic regions of S. lycopersicum are replaced with the corresponding segments from S. pennellii can show remarkably superior agronomic performance. Here we describe a high-quality genome assembly of the parents of the IL population. By anchoring the S. pennellii genome to the genetic map, we define candidate genes for stress tolerance and provide evidence that transposable elements had a role in the evolution of these traits. Our work paves a path toward further tomato improvement and for deciphering the mechanisms underlying the myriad other agronomic traits that can be improved with S. pennellii germplasm.

Heterosis in early maize ear inflorescence development: a genome-wide transcription analysis for two maize inbred lines and their hybrid.

Heterosis, or hybrid vigor, contributes to superior agronomic performance of hybrids compared to their inbred parents. Despite its importance, little is known about the genetic and molecular basis of heterosis. Early maize ear inflorescences formation affects grain yield, and are thus an excellent model for molecular mechanisms involved in heterosis. To determine the parental contributions and their regulation during maize ear-development-genesis, we analyzed genome-wide digital gene expression profiles in two maize elite inbred lines (B73 and Mo17) and their F1 hybrid using deep sequencing technology. Our analysis revealed 17,128 genes expressed in these three genotypes and 22,789 genes expressed collectively in the present study. Approximately 38% of the genes were differentially expressed in early maize ear inflorescences from heterotic cross, including many transcription factor genes and some presence/absence variations (PAVs) genes, and exhibited multiple modes of gene action. These different genes showing differential expression patterns were mainly enriched in five cellular component categories (organelle, cell, cell part, organelle part and macromolecular complex), five molecular function categories (structural molecule activity, binding, transporter activity, nucleic acid binding transcription factor activity and catalytic activity), and eight biological process categories (cellular process, metabolic process, biological regulation, regulation of biological process, establishment of localization, cellular component organization or biogenesis, response to stimulus and localization). Additionally, a significant number of genes were expressed in only one inbred line or absent in both inbred lines. Comparison of the differences of modes of gene action between previous studies and the present study revealed only a small number of different genes had the same modes of gene action in both maize seedlings and ear inflorescences. This might be an indication that in different tissues or developmental stages, different global expression patterns prevail, which might nevertheless be related to heterosis. Our results support the hypotheses that multiple molecular mechanisms (dominance and overdominance modes) contribute to heterosis.

Marker-assisted selection and evaluation of high oil in vivo haploid inducers in maize

Doubled haploid technology, which is used to rapidly purify genetic resources, is one of the key technologies in modern maize breeding. In a previous study, the major quantitative trait locus qhir1, which influences in vivo haploid induction, was narrowed down to a 243-kb region, which made it feasible to use marker-assisted selection (MAS) for inducer development. Recently, a new method was developed for haploid identification using oil content (OC). The objective of this study was to develop high oil inducer lines using MAS of the qhir1 locus. We constructed an F2 population, two backcross populations that were backcrossed to the inducer CAU5 (BC1F1-CAU5) and the high oil inbred line GY923 (BC1F1-GY923), respectively, which was derived from the cross GY923 × CAU5, and subjected continuous selfing to develop high oil inducer lines. In each cycle, three different parameters including kernel OC, marker genotype at qhir1 and haploid induction rate (HIR) were used for pedigree selection. Three candidate high oil inducer lines were developed, with an OC of approximately 8.5 %, an HIR of approximately 8 % and superior agronomic performance, which are suitable values for the application of these lines to haploid identification by OC. Our results confirm the notion that HIR selection combined with MAS for qhir1 is an effective approach to haploid inducer breeding. In addition, we determined that the accuracy of haploid identification by OC is influenced by the female germplasm resource and the high oil inducer and that appropriate critical points for OC can balance the false discovery rate and false negative rate.

Characterization and use of genetic variability of bank active germplasm Coffea canephora Pierre ex Froehner

Efficient strategies to manipulate the genetic variability are crucial to the success of breeding programs Coffea canephora. Combinations between divergent parents express greater heterosis effect, and the selection of matrices consider both genetic divergence and superior agronomic performance. The objective of this study was to quantify the genetic diversity of C. canephora accesses Active Germplasm Bank of Embrapa Rondonia, in order to identify plants of greater genetic diversity and higher yield potential for hybridization. For this, between 1100 accessions were pre-selected 89 plants for evaluation of major components in the production of processed coffee. For quantification of genetic diversity technique for principal components associated landmarks to gather the information of genetic divergence and agricultural performance in a single analysis was used. The selected accessions showed significant genetic variability for the major components of production, highlighting the values of average blend above 17, which indicates a favorable condition for performing controlled crosses for selection of plants for increased productivity and grain size.

Variability in physiological traits among different male sterile systems and hybrids of pearl millet [Pennisetum glaucum (L). R. Br.

Quantitative differences in chlorophyll content and the relationship of chlorophyll, total carotenoid content, root length density and thousand grain weight to yield per plant were studied in 26 pearl millet lines comprising female parents from diverse sources of male sterility (A1, A4 and A5 systems), male elite restorers of A1 cytoplasm and 16 F1 hybrids. Chlorophyll a (Chl a), Chl b, total Chl and total carotenoid content were estimated at 55, 65 and 75 days after germination, which coincided with 10 days after flowering, grain filling and maturity stages, respectively. The results indicated significant amount of variability for all the studied parameters at different crop growth stages. Of the three types of male sterile lines studied, the A5 male sterile lines has higher chlorophyll content and showed overall superior agronomic performance compared to A1 and A4 male sterile lines.

The Interactive Effects of Transgenically Overexpressed 1Ax1 with Various HMW-GS Combinations on Dough Quality by Introgression of Exogenous Subunits into an Elite Chinese Wheat Variety

Seed storage proteins in wheat endosperm, particularly high-molecular-weight glutenin subunits (HMW-GS), are primary determinants of dough properties, and affect both end-use quality and grain utilization of wheat (Triticum aestivum L). In order to investigate the interactive effects between the transgenically overexpressed 1Ax1 subunit with different HMW-GS on dough quality traits, we developed a set of 8 introgression lines (ILs) overexpressing the transgenic HMW-glutenin subunit 1Ax1 by introgression of this transgene from transgenic line B102-1-2/1 into an elite Chinese wheat variety Chuanmai107 (C107), using conventional crossing and backcrossing breeding technique. The donor C107 strain lacks 1Ax1 but contains the HMW-GS pairs 1Dx2+1Dy12 and 1Bx7+1By9. The resultant ILs showed robust and stable expression of 1Ax1 even after five generations of self-pollination, and crossing/backcrossing three times. In addition, overexpression of 1Ax1 was compensated by the endogenous gluten proteins. All ILs exhibited superior agronomic performance when compared to the transgenic parent line, B102-1-2/1. Mixograph results demonstrated that overexpressed 1Ax1 significantly improved dough strength, resistance to extension and over-mixing tolerance, in the targeted wheat cultivar C107. Further, comparisons among the ILs showed the interactive effects of endogenous subunits on dough properties when 1Ax1 was overexpressed: subunit pair 17+18 contributed to increased over-mixing tolerance of the dough; expression of the Glu-D1 allele maintained an appropriate balance between x-type and y-type subunits and thereby improved dough quality. It is consistent with ILs C4 (HMW-GS are 1, 17+18, 2+12) had the highest gluten index and Zeleny sedimentation value. This study demonstrates that wheat quality could be improved by using transgenic wheat overexpressing HMW-GS and the feasibility of using such transgenic lines in wheat quality breeding programs.

Improved winter wheat genotypes for Central and West Asia

High grain yield and resistance to stripe (yellow) rust are the most important traits for successful adoption of winter wheat varieties in Central and West Asia. This study was conducted to determine the stripe rust response and agronomic performance of a set of breeding lines recently developed by the International Winter Wheat Improvement Program (IWWIP). Replicated field studies were conducted in 2010 and 2011 using 38 experimental lines, one regional check (Konya) and one local check. Stripe rust scores were recorded at Karshi, Uzbekistan, and Karaj and Mashhad, Iran, in 2010. Grain yield was recorded at two sites each in Uzbekistan (Karshi and Kibray) and Iran (Karaj and Mashhad) and one site in Turkey (Eskisehir). The test lines showed variation for stripe rust severity, grain yield, 1,000-kernel weight, days to heading and plant height. Several stripe rust resistant genotypes were either higher yielding or equal to the local checks at different sites. Based on stripe rust resistance and yield performance in 2010, a set of 16 genotypes was selected and evaluated in 2011. All 16 were resistant at Almaty, Kazakhstan, and Dushanbe, Tajikistan, in 2011, whereas 9 of the 16 were resistant at Terter, Azerbaijan. The genotypes ‘TCI-02-138, ‘Solh’, ‘CMSS97M00541S’, ‘TCI -2-88(A)’ and ‘TCI-02-88(C)’ were consistently resistant to stripe across all sites in both years. Several lines showed high grain yields and superior agronomic performance across four sites in Uzbekistan and one site in Tajikistan. One genotype has been released in Uzbekistan and another in Tajikistan.

Registration of ‘NE01481’ Hard Red Winter Wheat

‘NE01481’ (Reg. No. CV‐1061, PI 659689) hard red winter wheat (Triticum aestivum L.) was developed cooperatively by the Nebraska Agricultural Experiment Station and the USDA‐ARS and released in April 2010. NE01481 will be marketed as Husker Genetics brand McGill. In addition to superior agronomic performance, Nebraska wheat growers would like to have increased resistance to Wheat soilborne mosaic virus. NE01481 was selected from the cross NE92458/‘Ike’ that was made in 1995. The pedigree of NE92458 is OK83201/‘Redland’ and the pedigree of OK83201, an experimental line developed by Oklahoma State University is ‘Vona’//‘Chisholm’/‘Plainsman V’. NE01481 was selected with the bulk‐breeding method as an F3:4 line in 1999, and in 2001 it was assigned experimental line number NE01481. NE01481 was released because of its superior grain yield in rainfed wheat production systems in southeastern, south central, and southwestern Nebraska and that it is the first modern release from our program with resistance to Wheat soilborne mosaic virus.

Comparative proteomic study reveals dynamic proteome changes between superhybrid rice LYP9 and its parents at different developmental stages

Heterosis is a common phenomenon in which the hybrids exhibit superior agronomic performance than either inbred parental lines. Although hybrid rice is one of the most successful apotheoses in crops utilizing heterosis, the molecular mechanisms underlying rice heterosis remain elusive. To gain a better understanding of the molecular mechanisms of rice heterosis, comparative leaf proteomic analysis between a superhybrid rice LYP9 and its parental cultivars 9311 and PA64s at tillering, flowering and grain-filling stages were carried out. A total of 384 differentially expressed proteins (DP) were detected and 297 DP were identified, corresponding to 222 unique proteins. As DP were divided into those between the parents (DPPP) and between the hybrid and its parents (DPHP), the comparative results demonstrate that proteins in the categories of photosynthesis, glycolysis, and disease/defense were mainly enriched in DP. Moreover, the number of identified DPHP involved in photosynthesis, glycolysis, and disease/defense increased at flowering and grain-filling stages as compared to that at the tillering stage. Most of the up-regulated DPHP involved in the three categories showed greater expression in LYP9 at flowering and grain-filling stages than at the tillering stage. In addition, CO2 assimilation rate and apparent quantum yield of photosynthesis also showed a greater increase in LYP9 at flowering and grain-filling stages than at the tillering stage. These results suggest that the proteins involved in photosynthesis, glycolysis, and disease/defense as well as their dynamic regulation at different developmental stages may be responsible for heterosis in rice.

Expression Analysis of miRNAs and Highly‐expressed Small RNAs in Two Rice Subspecies and their Reciprocal Hybrids

Heterosis, or hybrid vigor, is the phenomenon whereby progeny of two inbred lines exhibit superior agronomic performance compared with either parent. We analyzed the expression of miRNAs and highly expressed small RNAs (defined according to Solexa sequencing results) in two rice (Oryza sativa) subspecies (japonica cv. Nipponbare and indica cv. 93-11) and their reciprocal hybrids using microarrays. We found that of all the 1141 small RNAs tested, 140 (12%, 140 of 1141) and 157 (13%, 157 of 1141) were identified being significantly differentially expressed in two reciprocal hybrids, respectively. All possible modes of action, including additive, high- and low- parent, above high- and below low-parent modes were exhibited. Both F1 hybrids showed non-additive expression patterns, with downregulation predominating. Interestingly, 15 miRNAs displayed stark opposite expression trends relative to mid-parent in reciprocal hybrids. Computational prediction of targets of differentially expressed miRNAs showed that they participated in multifaceted developmental pathways, and were not distinguishable from the targets of non-differentially expressed miRNAs. Together, our findings reveal that small RNAs play roles in heterosis and add a new layer in the understanding and exploitation of molecular mechanisms of heterosis.

Agronomic performance of introduced banana varieties in lowlands of Rwanda

Most of Rwandan banana cultivars are low-yielding and susceptible to pests and diseases. High yielding and pest/disease resistant varieties have been obtained in advanced breeding centers recently. Introduction, evaluation and adoption of such varieties by local producers may be one of the options to boost yields. The objective of this study was to evaluate the agronomic performance of FHIA hybrids in lowlands of Rwanda. Completely randomised design was used with 9 treatments (varieties) and 20 replicates. Data were recorded on plant growth and yield components, banana bunchy top virus and yellow Sigatoka incidence. All hybrids matured later than local cultivars except FHIA 18 which was the earliest maturing variety. FHIA 17 and FHIA 25 matured 1 and 3 month late compared to the average cycle of the 2 local checks. However, it was compensated by high bunch weight of 53.4 and 52.3 kg for FHIA 17 and FHIA 25, versus 26.9 and 19.5 kg for Poyo and Barabeshya, respectively. FHIA 17, FHIA 25 and FHIA 18 had the highest yield of 55.7, 52.6 and 46.5 t ha-1 per year, respectively. Considering their resistance to fusarium wilt and yellow Sigatoka and superior agronomic performance, they may be released for Rwandan lowlands after conducting palatability tests.

In vitro regeneration of cocona (Solanum sessiliflorum, Solanaceae) cultivars for commercial production

Cocona (Solanum sessiliflorum Dunal) is a solanaceous shrub native to the Amazon region that produces an edible fruit. This species has numerous advantages, particularly a high nutritional value and productivity. However, due to irregular germination and rapid loss of seed viability, there are few plantations for production on a large scale. Development of alternative propagation strategies is essential for the production of homogeneous seedlings of genotypes with superior agronomic performance. We developed techniques for in vitro regeneration of the cocona varieties Santa Luzia and Thaís for large-scale production of healthy plantlets. Twenty days after seeding, seedling segments germinated in vitro were used as explant sources. Three successive experiments were performed: one to test the effect of the explant source and combinations of two growth regulators, auxin (indole acetic acid, IAA) and kinetin (KIN), on the morphogenetic response; another to investigate the effect of the combination of growth regulators on the morphogenetic response of hypocotyl segments, and another to evaluate how sucrose concentration affects the development of adventitious shoots. The best shoot induction was obtained using hypocotyl segments and stem apices, while rhizogenesis was greatest in leaves with a petiole. The number of adventitious shoots per explant on hypocotyl segments increased with 10 and 20 mg/L KIN, combined with 0.02 mg/L IAA in the variety Santa Luzia. Sucrose combined with these growth regulator levels increased the average number of calli; these were optimally produced when 45 g/L sucrose and 0.01 mg/L IAA + 20 mg/L KIN were applied. Only sucrose concentration influenced shoot proliferation in the two S. sessiliflorum varieties, with a maximum at 17.5 g/L.

Combining superior agronomic performance and terminal heat tolerance with resistance to spot blotch ( Bipolaris sorokiniana) of wheat in the warm humid Gangetic Plains of South Asia

Seven hundred twenty-nine lines of diverse wheat germplasm lines were evaluated in eight locations of three countries (India, Nepal and Bangladesh) of South Asia for 5 years (1999–2000 to 2003–2004) through Eastern Gangetic Plains Screening Nursery (EGPSN) organized by CIMMYT South Asia, Nepal, for agronomic performance and tolerance to spot blotch of wheat. Each year, the number of lines represented a new set of 150 lines that included six common checks and a different local check at each of the eight locations. One hundred and five lines, 21 in each year, advanced from EGPSN were also tested for 5 years (2000–2001 to 2004–2005) in five locations of South Asia through Eastern Gangetic Plains Yield Trials (EGPYT) to verify spot blotch tolerance and superior yield performance of the selected germplasm. Many lines yielded significantly more than the best check and possessed high levels of spot blotch resistance under warm humid environments of South Asia. The most promising 25 lines have been listed as sources of strong resistance, with 9 lines better yielding than the best resistant check PBW 343 in fewer days to maturity. Most of these superior lines represented elite CIMMYT germplasm and around half were derived from Kauz and Veery. The line EGPYT 67, Kauz//Kauz/Star/3/Prinia/4/Milan/Kauz, was the best for spot blotch resistance, yield, days to maturity, and 1000 grain weight (TKW). The next two lines in the order of merit were EGPYT 84 (Mrng/Buc//Blo/Pvn/3/Pjb 81) and EGPYT 69 (Chirya3/Pastor). The results demonstrate that additional spot blotch resistant wheat genotypes with high grain yield and TKW, and early maturity, have become available as a result of the regional and international collaboration in South Asia.

A Comparison of Liquid Phosphoric Acid and Dry Phosphorus Fertilizer Sources for Irrigated Alfalfa Production on Calcareous Soils

Alfalfa production in the Western United States requires large quantities of phosphorus (P) fertilizer. In 1998, phosphoric acid (PA) became available as a fertilizer source. Phosphoric acid was more expensive per kg of P than other fertilizers, but was promoted on the basis of convenience of application when tank mixed with other chemicals, and superior agronomic performance (higher yield per kg P applied) in alkaline soils due to the neutralizing effect of the acid. The objective of this study was to compare the effects of PA, triple superphosphate (TSP, 0-45-0), and monoammonium phosphate (MAP, 11-52-0) on alfalfa yield and soil and plant tissue nutrient levels. Phosphorus was broadcast at rates based on soil test recommendations for two years at two sites having calcareous soils typical of alfalfa production systems in the Western U.S. At one site, potassium chloride (KCl, 0-0-60) and zinc sulfate were also mixed with the PA based on soil test recommendations. Responses to fertilizer ranged from less than 1 Mg/ha (7 to 10%) to above 6 Mg/ha (44 to 62%) relative to the control. Yield and soil test P were not significantly different among fertilizer sources in either year or location. At one location where more intensive soil and plant tissue testing was done, there were no differences among fertilizer sources in soil or tissue test K or micronutrient concentrations. These results indicate that PA does not have an agronomic (yield) benefit relative to traditional dry P fertilizers for alfalfa produced on calcareous soils. Therefore, the higher cost per kg of P with PA would have to be justified by considerations other than agronomic performance.