Characterization of wheat monogenic lines with known Sr genes and wheat cultivars for resistance to three new races of Puccinia graminis f. sp. tritici in China

Wheat stem rust, caused by Puccinia graminis f. sp. tritici(Pgt), is a potentially devastating fungal disease of wheat worldwide. The present study was to evaluate the resistance of 42 wheat monogenic lines with known stem rust resistance(Sr) genes and 69 wheat cultivars to three new Pgt races(34C0MRGQM, 34C3MKGQM, and 34C6MTGSM)identified from aeciospores at the seedling and adult-plant stages. The phenotyping results revealed that monogenic lines harboring resistance genes Sr9e, Sr17, Sr21, Sr22, Sr26, Sr30, Sr31, Sr33, Sr35, Sr36, Sr37, Sr38, Sr47, SrTmp,and SrTt3 were effectively resistant to all three Pgt races at the seedling and adult-plant stages. In contrast, monogenic lines containing Sr5, Sr6, Sr7b, Sr9a, Sr9d, Sr9f, Sr9g, Sr9b, Sr16, Sr24, Sr28, and Sr39 were highly susceptible to these races at both seedling and adult-plant stages. The other lines with Sr8a, Sr10, Sr11, Sr13, Sr14, Sr15, Sr18, Sr20,Sr19, Sr23, Sr25, Sr27, Sr29, Sr32, and Sr34, displayed variable levels of resistance to one or two of the tested races.Seedling infection types(ITs) and adult-plant infection responses(IRs) indicated that 41(59.4%) of the wheat cultivars showed high resistance to all the three races. Molecular marker analysis showed that four wheat culitvars likely carried Sr2, 20 wheat culitvars likely carried Sr31, 9 wheat culitvars likely carried Sr38, and none of the cultivars carried Sr24,Sr25, and Sr26. Our results provide a scientific basis for rational utilization of the tested Sr genes and wheat cultivars against these novel Pgt races.

Changes of Gas Exchanges in Leaves of Different Cultivars of Winter Wheat Released in Different Years

Three winter wheat cultivars ( Triticum aestivum L.), representatives of those widely cultivated in Beijing over the past six decades, were grown in the same environmental condition, and their physiological features were investigated. Daily changes of net photosynthetic rate (P-n), transpiration (T-r) in different growth stages were measured in order to find the relationship between leaf photosynthesis and yield. Instantaneous water use efficiency (WUE) of leaf was calculated from P-n/T-r. It is suggested that relationship between photosynthetic rate and yield changed with the developing stages of wheat. High yield wheat cultivar Jingdong 8 (released in the 1990s) had a higher photosynthetic rate ( the maximal P-n increased by 77%) and transpiration rate (the maximal T-r increased by 69%), but a lower WUE than the low yield cultivar Yanda 1817 (released in the 1940s) during the day time at stem elongation stage. However; difference of P-n among the three cultivars changed with wheat growth process. Before 10 o'clock P-n in leaves of Jingdong 8 usually was the highest of the three cultivars, but P-n of Yanda 1817 was the highest after 10 o'clock. At dough ripe stage, P-n in leaves of Yanda. 1817 was the highest among the three cultivars during the whole day. The difference of changing trend of transpiration in three wheat cultivars was similar to P,, but WUE of Yanda 1817 was the highest in those three cultivars, indicating that the higher yield of Jingdong 8 was achieved via a greater consumption of water. Contrary to the cultivars released in the later period, midday depression of photosynthesis was small in Yanda 1817, which might suggest that Yanda 1817 was resistant to photoinhibition. It is possible that photosynthetic potential in leaves of wheat increased as wheat cultivars was improved over the past six decades. However, it became less resistant to photoinhibition.

Postulation of Seedlings Resistance Genes to Yellow Rust in Commercial Wheat Cultivars from Yunnan Province in China

The objective of this study was to characterize yellow （stripe） rust resistance gene（s） in 52 commercial wheat cultivars from Yunnan Province in China, and to provide information for their rational deployment in field. Seedlings of wheat cultivars were inoculated with 25 differential isolates ofPuccinia striiformis from foreign and home to postulate resistance genes to yellow rust, and then validated by pedigree. There were 10 probable resistance genes characterized in these cultivars, in which, Yr9 was most commonly postulated to be present in thirteen cultivars. Yr21, the second, was present in four cultivars. Yr8, the third, were present in three cultivars. Yr6, Yrl 7 and Yr26, the fourth, was present in two cultivars respectively. The other gene（s） such as, Yr2＋YrA, Yr7 and Yr27, were only present in single cultivar（s）; unknown gene（s） or gene（s） combination（s） were present in 22 cultivars. One cultivar （Yunmai 42） had no resistance gene tested in this study. Cultivars such as Yunmai 52, Mian 1971-98, Kunmai 4, and Yunmai 56 carried effective genes and can be popularized mainly; Yr9 should be planted with other Yr genes. In the meantime other effective genes should be introduced to realize gene diversity for controlling wheat yellow rust. Yunmai 42 should be reduced to avoid rust breakout. Unknown gene cultivars should be utilized and be researched deeply.

Effects of Molybdenum on the Intermediates of Chlorophyll Biosynthesis in Winter Wheat Cultivars Under Low Temperature

The objective was to probe the site where the biosynthesis of chlorophyll was blocked under Mo deficiency at low temperature, which led to the decrease of chlorophyll in winter wheat cultivars. The intermediates of chlorophyll biosynthesis were analyzed in winter wheat cultivars in soil culture, miniblock culture, and solution culture to study the effects of Mo on chlorophyll biosynthesis without Mo addition （CK, soil available Mo 0.112 mg kg^-1） and Mo addition （＋ Mo, 0.13 mg kg^-1 Mo was added）. Laevulinic acid （LA）, the competitive analog of δ-aminolaevulinic acid （ALA） was also introduced in the experiment. The ratio of Chl a/Chl b was constant between CK and ＋ Mo treatment, whereas it increased at low temperature, which indicated that Mo deficiency did not inhibit the transformation of Chl a to Chl b at low temperature. Under Mo deficiency, the contents of protochlorophyll （Pchl）, Mg-protoporphyrin Ⅸ （Mg-Proto Ⅸ）, protoporphyrin Ⅸ （proto IX）, and uroporphyrinogen Ⅲ （Uro Ⅲ） decreased [Uro Ⅲ decreased significantly （P 〈0.01）], whereas ALA and glutamate increased significantly （P 〈 0.01） compared with that of Mo addition, which suggested that the transformation from ALA to Uro Ⅲ might be inhibited. The content of ALA reversed after addition of LA, it was significantly higher （P 〈 0.01） in Mo addition than in CK. The results indicated that the transformation from ALA to Uro Ⅲ was blocked under Mo deficiency, which resulted in the inhibition of the biosynthesis of chlorophyll and led to the decrease of chlorophyll in winter wheat cultivars.

Contribution of ear photosynthesis to grain yield under rainfed and irrigation conditions for winter wheat cultivars released in the past 30 years in North China Plain

To understand the contribution of ear photosynthesis to grain yield and its response to water supply in the improvement of winter wheat, 15 cultivars released from 1980 to 2012 in North China Plain（NCP） were planted under rainfed and irrigated conditions from 2011 to 2013, and the ear photosynthesis was tested by ear shading. During the past 30 years, grain yield significantly increased, the flag leaf area slightly increased under irrigated condition but decreased significantly under rainfed condition, the ratio of grain weight：leaf area significantly increased, and the contribution of ear photosynthesis to grain yield changed from 33.6 to 64.5% and from 32.2 to 57.2% under rainfed and irrigated conditions, respectively. Grain yield, yield components, and ratio of grain weight：leaf area were positively related with contribution of ear photosynthesis. The increase in grain yield in winter wheat was related with improvement in ear photosynthesis contribution in NCP, especially under rainfed condition.

Phosphorus Uptake from Rhizosphere Soil by Two Wheat Cultivars

Inorganic soil phosphorus extractable with sodium bicarbonate (NaHCO3-Pi), soil pH and root hairs length and density in the rhizosphere of two winter wheat cultivars (Triticum aestivum L. cv. Shichun,Sleipner) grown on a high pH Chinese silt loam (52.7 mg NaHCO3-Pi kg-1) and a Danish sandy loam (43.4mg NaHCO3-Pi kg-1) were studied to assess how these wheat cultivars differed in phoephorus uptake.The rhizosphere soil pH of two wheat cultivars grown on the two soils were fairly unchanged with increasing distance from the root surface. However the root hairs of Shichun were 2.1 times longer than those of Sleipner. Root surface area (RSA) of Shichun increased by 192% due to root hairs whereas root hairs of Sleipner increased RSA by 68% only. Hence the root system of Shichun was in contact with more soil than that of Sleipner, even though Sleipner had a longer root. Grown at the lower pH and level of NaHCO3-Pi in the Danish soil Shichun absorbed more inorganic phosphorus than Sleipner whereas at the higher pH and level of NaHCO3-Pi in the Chinese soil there was no phosphorus uptake difference between the two wheat cultivars.

The allelic distribution and variation analysis of the NAM-B1 gene in Chinese wheat cultivars

The NAM-B1 gene is a member of the NAC（NAM,ATAF,and CUC）transcription factor family and plays an important role in regulating wheat grain protein content（GPC）.The ancestral NAM-B1 allele has been discovered in many tetraploid wild emmer（Triticum turgidum ssp.dicoccoides）accessions and few domesticated emmer accessions（T.turgidum ssp.dicoccum）,however,it is rarely found in hexaploid bread wheat（Triticum aestivum L.）.There are no systematic reports on the distribution of NAM-B1 alleles in Chinese wheat cultivars.In this study,the NAM-B1 alleles in 218 Chinese cultivars were investigated.The cultivars were collected from five major wheat regions（12 provinces）,covering most of the winter wheat growing regions in China.The results showed that the NAM-B1 gene is present in 53（24.3%）cultivars and absent in the remaining 165（75.7%）cultivars.Further analysis revealed that in contrast to the wild-type allele,the NAM-B1 gene in Chinese wheat cultivars contained a 1-bp insertion in the coding region.This caused a frame-shift mutation and introduced a stop codon in the middle of the gene,rendering it non-functional.Polymorphisms were detected in DNA sequences of 21cultivars among these 53 cultivars.However,cD NA sequence analysis suggested that these variations in the exon region were not able to restore NAM-B1 gene（1-bp insertion）function.Thus,exploring the distribution of NAM-B1 gene variations（1-bp insertion and deletion）can provide some information for improving the quality of winter wheat in China and other countries.

In vitro gastrointestinal digestion study of two wheat cultivars and evaluation of xylanase supplementation

Background： The filamentous fungus Talaromyces versatifis is known to improve the metabolizable energy of wheat- based poultry diets thanks to its ability to produce a pool of CAZymes and particularly endo-β（1,4）-xylanases. In order to appreciate their in vivo mode of action, the supplementation effect of two of its xylanases, XynD and XynB from families GH10 and GHll respectively, have been evaluated on two different wheat cultivars Caphorn and Isengrain, which were chosen amongst 6 varieties for their difference in non starch polysaccharides content and arabinoxylan composition. Results： Polysaccharides digestion was followed during 6 h along the digestive tract using the TNO gastrointestinal model-1, to mimic monogastric metabolism. Polysaccharide degradation appeared to occur mainly at the jejunal level and was higher with Isengrain than with Caphorn. For both cultivars, XynD and XynB supplementation increased notably the amount of reducing end sugars into the jejuno-ileal dialysates, which has been confirmed by a valuable increase of the soluble glucose into the jejunal dialysates. Conclusions： The amounts of arabinose and xylose into the dialysates and ileal deliveries increased consequently mainly for Caphorn, suggesting that XynD and XynB supplementation in wheat-based diet could alleviate the anti-nutritional effects of arabinoxylans by limiting the physical entrapment of starch and could increase the available metabolizable energy.

Molecular Screening and Resistance Evaluation of American Wheat Cultivars to Chinese Stripe Rust Races

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the major diseases of wheat in China. In order to asses the resistance levels and existing Yr genes among 59 wheat cultivars （lines） from the Pacific Northwest （PNW） of the United States, to provide resistance resources for genetic improvement of wheat stripe rust resistance in China, 59 wheat cultivars （lines） from PNW of the United States were infected by 3 mixed races of predominant Chinese stripe rust races CRY31, CRY32, and CRY33 to evaluate their resistance at seedling and adult plant stages, and screened with molecular markers tightly linked to currently effective all-stage resistance genes YrlO, Yrl5 and adult plant resistance genes Yrl8, Yr39. Of 59 American cultivars （lines）, five cultivars （lines）, Expresso, 02W50076, ACS52610, WA008012, and WA00801833, had all-stage resistance, showing resistance to mixed races of CRY31, CRY32, and CRY33 at both seedling and adult plant stages. 33 cultivars （lines） had adult plant resistance, only showing resistance to stripe rust at adult stage. Based on the molecular screening, none of the 59 PNW cultivars （lines） had the polymorphic bands of linked markers to YrlO. There were 12, 33 and 29 cultivars （lines） which bad polymorphic bands of linked markers to Yr15, Yr18 and Yr39, accounting for 20, 55 and 49% of the 59 PNW cultivars （lines）, respectively. All these results suggested that Yr15, Yr18 and Yr39 were widespread among PNW cultivars （cultivars） and could be utilized in Chinese wheat stripe rust resistance breeding.

Growth Responses of Wheat Cultivars to Rock Phosphate in Hydroponics

Screening cultivars to grow under conditions of low phosphorus (P) availability and utilize P efficiently from compounds of low solubility in soils may be beneficial to overcome poor plant growth in P-deficient soils. The growth behavior and P utilization efficiency of seven wheat cultivars grown in hydroponics were studied, using rock phosphate as P source. The wheat cultivars grown for 30 days were significantly different in biomass accumulation, P uptake and P utilization efficiency. The dry matter production of all the cultivars was significantly correlated with P uptake, which in turn correlated to the drop in the root medium pH. The ranking of wheat cultivars on the basis of dry matter yield, P uptake and P utilization efficiency was Zamindar 80 > Yecora > C 271 > WL 711 > Barani 83 > PARI 73 > Rohtas. The cultivar Zamindar 80 appeared to possess the best growth potential in P-deficient soils.

Seed Yield Potential of Five Wheat Species/Cultivars without and with Phosphorus Fertilizer Application on a P-Deficient Soil in Northeastern Saskatchewan

In the Canadian Prairies, many soils on organic farms are low in available phosphorus (P). Previous research has shown that wheat species/cultivars vary in their sensitivity to P deficiency, yield response to applied P fertilizer, P uptake and P use efficiency on P-deficient soils. A 3-year field experiment was conducted from 2012 to 2014 on a P-deficient soil at Kelvington, Saskatchewan, Canada, to determine the potential of five wheat species/cultivars (Spelt and Kamut representing “ancient”, Red Fife representing “old”, and Unity and Goodeve representing “modern” wheat species/cultivars) for seed yield, protein concentration (PC) in seed, partial factor of productivity (PFP, kg seed kg-1 of N applied), total N and P uptake, P use efficiency (PUE, kg seed kg-1 of P applied) and % recovery of applied P in seed under zero-P and with P fertilizer (triple superphosphate) applied at 20 kg P ha-1. Seed yield, PFP and PUE were determined in all 3 years, but PC, total N and P uptake, and % recovery of applied P in seed were determined only in 2012. There was a marked and significant response of seed yield and PFP of all wheat species/cultivars to P fertilizer in all 3 years, but the actual seed yield and PFP, without and with applied P fertilizer, as well as PUE, varied with species/cultivar in different years. On the average of 3 years, seed yield and PFP were greatest for Unity in both without and with applied P fertilizer treatments. Seed yield increases from applied P were 1111, 773, 890, 1810 and 2028 kg·ha-1, respectively, for Spelt, Kamut, Red Fife, Unity and Goodeve. Total N and P uptake were lowest for Kamut and greatest for Unity or Goodeve, in both without and with applied P fertilizer treatments. Percent recovery of applied P in seed was greatest for Goodeve or Unity and lowest for Spelt or Kamut. Protein concentration in seed usually decreased with P fertilizer, and wheat species/cultivars with higher PC in seed usually showed greater reduction in PC with P application. In conclusion, the findings suggest that the “modern” wheat species/cultivars Unity or Goodeve might be more suitable for high sustainable seed yield and total P or N uptake than the “ancient” wheat species Spelt and Kamut or the “old” wheat cultivar Red Fife, especially when adequate amount of P fertilizer is applied to optimize crop production on a P-deficient soil.

Construction of Gliadin Fingerprints Database for the Main Wheat Cultivars Grown in North China

The standard gliadin fingerprints and their database of 68 major cultivars and a part of backbone parents, which have ever been extensively grown in North China since the 1950' s, were constructed by using CAWGES software and an improved method of pH 3.2 A-PAGE. In the meantime, investigations were made on the utilization of the database in the area of gliadin fingerprints analysis, variety identification and genetic relationship study. The results showed that it provided an effective method for building core collections and variety identification.

Responses of Some American, European and Japanese Wheat Cultivars to Soil-Borne Wheat Viruses in China

Wheat seeds of 109 cultivars from USA, Europe and Japan were sown in experiments at seven sites in different provinces of China for one or two seasons. Five of the sites were infested with the bymovirus wheat yellow mosaic virus (WYMV) and two jointly with WYMV and the furovirus Chinese wheat mosaic virus (CWMV). Disease symptoms were assessed visually and leaf samples were tested for virus (es) by ELISA. At least 29 cultivars were resistant to WYMV at the sites where only this virus was present but all the cultivars were severely infected at Rongcheng (Shandong Province) where CWMV was mixed with WYMV. There was evidence that the presence of CWMV assisted infection by WYMV and also resulted in more severe symptoms. At the mixed site in Yantai, Shandong Province, symptoms were mild and many cultivars had symptomless infection . Of the two strains of WYMV identified in Japan, the Chinese sites seem to be most similar to the type isolated, WYMV-T. Eleven cultivars seemed to be susceptible to WYMV only at Loutian (Hubei Province),suggesting that the virus at this site would be worth studying further.

Grain zinc and iron concentrations of Chinese wheat landraces and cultivars and their responses to foliar micronutrient applications

Grain zinc(Zn) and iron(Fe) concentrations and their responses to foliar application of micronutrients in 28 Chinese wheat landraces and 63 cultivars were investigated in a two-year field experiment. The average grain Zn and Fe concentrations were 41.8 mg kg^(-1)(29.0-63.3 mg kg^(-1)) and 39.7 mg kg^(-1)(27.9-67.0 mg kg^(-1)), respectively. Compared with cultivars, landraces had greater grain Zn(11.0%) and Fe(4.8%) concentrations but lower harvest index(HI), grain weight per spike(GWS), grain number per spike(GNS) and thousand grain weight(TGW). Both Zn and Fe concentrations were negatively and significantly correlated with HI, GWS, and GNS, while showed a poor association with TGW, suggesting that lower HI, GWS, and GNS, but not TGW, accounted for higher Zn and Fe concentrations for landraces than for cultivars. Grain Zn concentrations of both cultivars and landraces significantly increased after foliar Zn spray and the increase was two-fold greater for landraces(12.6 mg kg^(-1)) than for cultivars(6.4 mg kg^(-1)). Foliar Fe spray increased grain Fe concentrations of landraces(3.4 mg kg^(-1)) and cultivars(1.2 mg kg^(-1)), but these increases were not statistically significant. This study showed that Chinese wheat landraces had higher grain Zn and Fe concentrations than cultivars, and greater increases occurred in grain Zn concentration than in grain Fe concentration in response to fertilization, suggesting that Chinese wheat landraces could serve as a potential genetic source for enhancing grain mineral levels in modern wheat cultivars.

Effect of Postponing Nitrogen Application on Growth and Yield of Different Wheat Cultivars

[Objective] The aim was to study whether there are differences in top- dressing period for wheat cultivars. [Method] With three representative wheat culti- vats selected, effects of different N topdressing period on wheat tiller dynamics and yield components were studied. [Result] Appropriately postponing N topdressing time improved the yield of wheat. Appropriate N topdressing time tended to be volatile upon wheat cultivar. Jointing stage was appropriate for topdresSing for most wheat cultivars such as Jimai 22 and Linmai No. 4 and flowering stage was appropriate for the cultivar featured by early-senescence such as LN66. [Conclusion]It is neces- sary to select the optimal topdressing time according to wheat characteristics.

Resistance Analysis of Wheat Cultivars against Powdery Mildew in Anhui Province of China

[ Objective ] The paper was to determine the resistance level of the tried and pre-examination wheat cultivars against powdery mildew in Anhui Province of China. [ Method ] By using artificial inoculation and identification method in fields, the resistance of wheat cultivars was identified in consecutive three years from 2010 to 2012. [ Result] The highly susceptible （HS） cultivar accounted for 30%, 42% and 11% of total tested cultivars in the years of 2010, 2011 and 2012, respectively; moderately susceptible （MS） cultivar accounted for 53% of total tested cuhivars in 2010, which accounted for 47% and 57% in 2011 and 2012, respectively; moderately resistant （MR） cuhivar accounted for 17% of total tested cultivars in 2010, which accounted for 11% and 32% in 2011 and 2012, respectively. [ Conclusion] The paper can guide breeding direction, and also provide scientific basis for variety approval.

A Standardized Method for Determining Tillering Capacity of Wheat Cultivars

Genotype and agronomic management greatly influence crop growth and grain yield in wheat (Triticum aestivum L.). To ensure sustainable production, seeding rate selection is important to maximize efficiency of every plant. Tillering can allow wheat plants to adjust growth relative to plant density and quality of growing conditions. This research sought to determine a method for assessing tillering of wheat cultivars and develop a standardized approach for characterizing cultivar tillering capacity. Nine cultivars with diverse genetic and phenotypic characteristics were seeded in 2017-2018 at Prosper, ND using various seeding techniques at differing plant spacing arrangements to evaluate tillering habit and spikes plant-1. Cultivars grown at population densities common in grower fields did not express full tillering potential. Spaced-plantings of cultivars promoted cultivar expression of tillering phenotype. The SOFATT (seed only a few, and then thin) method, where average spikes plant-1 was determined from multiple plants sampled from a cultivar grown at spaced-plantings (inter-row and intra-row spacing at 30 ± 12 cm), is recommended to properly assess tillering habits of wheat cultivars. Breeders and researchers can use results from SOFATT evaluations to determine tillering capacity rating for each cultivar based on raw or transformed z-score values for spikes plant-1.

Evaluation of Dryland Wheat Cultivars on the Market in South Africa for Resistance against Four Known Russian Wheat Aphid, <i>Diuraphis noxia</i>, Biotypes in South Africa

An increased wheat yield potential under changing environmental conditions is a challenge in agriculture. Resistant wheat lines can yield more than susceptible wheat lines in the presence of Russian wheat aphid infestation. There are currently four Russian wheat aphid (RWA) biotypes known in South Africa with different virulence against different wheat cultivars. To keep up with the ever-changing patterns it is necessary to screen the cultivars for resistance against these Russian wheat aphid (RWA) biotypes. All the dryland wheat cultivars on the market were evaluated for resistance against the four known Russian wheat aphid (RWA) biotypes in South Africa. Through this evaluation, the status of Russian wheat aphid (RWA) resistance in South African dryland wheat cultivars can be updated to adapt to environmental changes and the wheat industry can adapt to changes in virulence of Russian wheat aphid (RWA) biotypes that may cause damage to Russian wheat aphid (RWA) resistant cultivars, subsequently affecting yield. Evaluations were done in the glasshouse by screening wheat cultivars against four different South African Russian wheat aphid (RWA) biotypes, RWASA1-RWASA4, under controlled conditions. The glasshouse evaluations showed that out of the 19 dryland wheat cultivars currently on the market in South Africa 16 are resistant against RWASA1, 7 are resistant against RWASA2, 7 are resistant against RWASA3 and 5 are resistant against RWASA4. Dryland wheat cultivars were also evaluated under field conditions at four different field localities. In the field, 5 cultivars were resistant to RWASA3 at two localities, respectively, and 3 and 5 cultivars were resistant to RWASA4 at two localities, respectively. Since Russian wheat aphid (RWA) damage can influence the final yield of a wheat cultivar significantly, changing conditions can influence both resistant cultivars, and the virulence of Russian wheat aphid (RWA). It is advisable to evaluate wheat cultivars on the market under different conditions and with all known Russian wheat aphid (RWA) biotypes in an area.

Distribution and Association of Arbuscular Mycorrhizal Fungi in Different Cultivars of Wheat from Lalganj Pratapgarh District of Utter Pradesh, India

Arbuscular mycorrhizal fungi are key components of soil micro-flora and obviously interact with other microorganisms in the rhizosphere which is the zone of influence of plant roots on microbial populations and other soil constituents. Keeping in view the importance of AM fungi, the present study was undertaken for assessing the AM fungal spore population dynamics in the rhizosphere soil and its colonization in rhizosphere soils in relation to soil physico-chemical factors. Present study represents an attempt to establish the qualitative and quantitative distribution of AM fungal species in rhizosphere soils of wheat. Thirteen different wheat cultivars collected from four different sites of Lalganj Pratapgarh (U.P.), India were examined for the AM infection. All the wheat cultivars were found to be infected with arbuscular mycorrhizae. However, their population in rhizosphere and root infection varied to a considerable extent from species to species. The maximum spore population and highest percentage of root colonization were found with the rhizosphere soil of cultivars Ankur Kedar.

Field Screening of Lesotho and South African Wheat Cultivars for Russian Wheat Aphid Resistance

Russian wheat aphid (Diuraphis noxia) is an international wheat pest and was first recorded in South Africa in 1978 in the Bethlehem area in the Eastern Free State. Le-sotho lies adjacent to one of the largest wheat producing areas in South Africa, the Eastern Free State, where winter wheat and facultative types are cultivated under dry land conditions. Wheat (Triticum aestivum L.) is an important crop adapted to all agro-ecological zones of Lesotho. Russian wheat aphid may have a significant impact on wheat yield. No monitoring or pest control is being done in Lesotho and at this stage there is very little information on the Russian wheat aphid resistance of wheat culti-vars cultivated in Lesotho. In view of this it is important to monitor the distribution of Russian wheat aphid biotypes in Lesotho and determine the level of Russian wheat aphid resistance in local Lesotho wheat cultivars. Two local Lesotho wheat cultivars, Bolane and Makalaote were screened together with South African cultivars Elands, Matlabas, Senqu, PAN3379, PAN3118 and SST387, in the glasshouse against all four known biotypes that occur in South Africa. All these cultivars were also planted in 5 m plots in the field at two localities Leribe and Roma in the lowlands of Lesotho. These cultivars were screened in the field for Russian wheat aphid resistance. The predomi-nant Russian wheat aphid biotypes in these areas were also determined. The Lesotho cultivar, Bolane had resistance against RWASA2 in the glasshouse, while Makalaote did not have any Russian wheat aphid resistance in either the glasshouse or field screenings. To contribute to food security an increasing wheat yield potential is a high priority. Russian wheat aphid has been included in the list of important international cereal pests. Russian wheat aphid adapts to changing environments and taking their ecology, distribution, virulence patterns, and variability into account is important in minimizing the gap between actual and attainable yields. Current management prac-tices for winter wheat in South Africa include the use of resistant cultivars, which is the most economical management strategy for Russian wheat aphid. Introducing Russian wheat aphid resistant cultivars in Lesotho will improve overall yield and as a result food security. This will also result in lower Russian wheat aphid pest pressure in the adjacent wheat production areas in the Eastern Free State, South Africa.