Genetic resistance to cereal cyst nematode Heterodera avenae Woll. in wild oat Avena sterilis I. 376

Summary Three dominant genes A, B and C are involved in the resistance of Avena sterilis I. 376 to Heterodera avenae. When associated, genes A and B are responsible for the high level of resistance in I. 376. In the absence of the first two genes, gene C confers intermediate resistance characterized by the presence of a limited number of cysts on the roots. Only the completely recessive genotype allows the nematode to develop normally.     

Inheritance of resistance to Puccinia coronata Corda and Rhynchosporium orthosporum Caldwell in Italian ryegrass

Summary Progeny analysis within Italian ryegrass (Lolium multiflorum) cv. RvP infected with a single clone of crown rust (Puccinia coronata f. sp. lolii) revealed major factors, one probably a single dominant gene, conferring resistance in two of twelve randomly selected parents. The remaining variation in resistance to this pathogen, and all of the variation in resistance to Rhynchosporium orthosporum, was controlled by a relatively large number of minor genes exhibiting neither dominance nor epistasis. There was no significant maternal inheritance. Absence of any correlation between progeny scores for reaction to the two pathogens indicated that resistance to each was inherited independently.     

Differential Response to Al-Toxicity of Two Populations of Avena sterilis L.

Negative correlation between Al concentrations and root and shoot growth was detected in two populations of Avena sterilis L. investigated [one from a bauxite area (1) and the other (2) from a pasture area]. Al solubility and Al content of plant tissue depend on pH levels of nutrient solution. Population-1 although in all treatments contained greater amounts of Al in its roots, was grown better than population-2, suggesting that population-1 is more tolerant than population-2. Al content of shoot and root of both populations was greater at pH 10.0 than at pH 4.5, a fact that may indicate that Al ions in alkaline medium are preferentially absorbed than Al ions in acid medium. The better growth of both populations observed in all Al concentrations at pH 10.0, where Al content of plant tissues was greater, may indicate that Al forms predominant in acid nutrient medium are more harmful than Al forms in alkaline nutrient medium.     

Genetic studies of resistance to the cereal cyst nematode (Heterodera avenae) in oats (Avena spp.)

Summary Genetic analysis of cereal cyst nematode resistance in three genotypes of oats indicates that resistance in Avena sterilis I.376 is controlled by two dominant genes and in A. sativa cv. Mortgage Lifter by two recessive genes. Resistance in A. byzantina P.I. 175021 is dominant and monogenic, and is probably at a locus distinct from the resistance loci in the other two genotypes.     

Inheritance of resistance to wildfire and angular leaf spot derived from Nicotiana rustica var. Brasilea

Summary The introgression of wildfire (races 0 and 1) and angular leaf spot (ALS) resistance from N. rustica var. Brasilea into N. tabacum has proved economically useful in Zimbabwe although the mode of inheritance of, and genetic relationships between the resistance are unknown. This study was undertaken to (1) examine the mode of inheritance of the resistance to races 0 and 1 of wildfire, and ALS, (2) determine the genetic relationship between the resistances and (3) establish whether the N. rustica-derived wildfire race 0 resistance is allelic to that obtained from N. longiflora. Inheritance was examined under greenhouse and field conditions by studying disease reactions in the parental, F1, F2 and backcross generations derived from crosses of three susceptible lines to a resistant line Nr-7. Three-point backcrosses to the susceptible parent were examined for linkage and segregating generations from a cross of Nr-7 to Burley 21 which carries the N. longiflora race 0 resistance were used to test for allelism. In general, we observed that all resistances are determined by a single dominant gene although some incosistent ratios were obtained likely due to misclassification of disease reactions and erratic transmission. All resistances showed linkage although pleiotropism cannot be ruled out. Allelism tests demonstrated that the N. rustica race 0 resistance is not allelic to that obtained from N. longiflora. Our findings are examined in relation to the efficacy of indirect selection for resistance.     

Inheritance of stalk rot resistance in cauliflower (Brassica oleracea var. Botrytis L.)

Summary The inheritance of resistance in cauliflower to stalk rot (Sclerotinia sclerotiorum (Lib.) de Bary) was investigated in population from six generations of six crosses. Disease incidence was recorded on 4 parents, 6 F^s ₁, 6 F^s ₂ and 12 back-crosses in a screenhouse under artificially created epiphytotic conditions. Resistance to stalk rot in this set of parents was found to be polygenic and under the control of recessive genes and due primarily to additive gene action. A breeding strategy emphasizing recurrent selection should lead to improvement in resistance.     

小麦条锈菌吸器的遗传分析

吸器（Haustorium）是条锈菌产生于小麦细胞内的唯一器官,为了研究小麦持久抗性品种中条锈菌吸器的遗传规律,选用小麦持久抗条锈品种Aquileja (AQ)、Libellula (LB)、咸农4号（XN）和感病品种铭贤169（MX）配制杂交组合MX×AQ、LB×XN和AQ×XN,组成亲本及杂交一代（F1）杂交二代（F2）和回交一代（BCp1、BCp2）6个世代,接种条锈菌后取样,测定单位菌丝面积内的吸器数目。结果表明：AQ和LB中条锈菌的吸器数目分别为44.2/mm2和23.74/mm2,两个品种对吸器均表现较强的抗性;XN中条锈菌吸器数目(89.83/mm2)与MX(102.02/mm2)无差异,未表现出明显的抗性。小麦持久抗性品种中条锈菌吸器的遗传为部分隐性,显性度为-0.47~-1.83;控制条锈菌吸器数目的基因大约有1~2个。尺度模型检验结果表明MX×AQ组合中条锈菌吸器的遗传符合加性模型,遗传力较高为68%,而LB×XN和AQ×XN经尺度检验分析不符合加性—显性模型,遗传力较低。     

Growth rate inheritance and associations with other traits in backcross populations of Avena sativa x A. sterilis

Summary Improved grain yields in lines of oats from matings of Avena sativa x A. sterilis were found to be due to increased plant growth rate. Growth rates of oats were quantitatively inherited, with the minimum number of effective factor pairs segregating in the interspecific matings ranging from 3 to 9. Heritability values for this trait averaged 0.4. Growth rate was highly and positively correlated with bundle weight, straw yield, grain yield, and unit straw weight, but it was uncorrelated with heading date and harvest index. Correlations with plant height were low. Thus, it should be possible for oat breeders to combine the high growth rates from A. sterilis with any combination of agronomic traits.Journal Paper No. J-8608 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa 50011. Project 1752. Supported in part by a grant from the Graduate College.Hirosaki University, Hirosaki, Japan (formerly Visiting Scientist at Iowa State University).     

Inheritance of resistance to black rot (Xanthomonas campestris pv. Campestris) in cauliflower (Brassica oleracea var. Botrytis)

Summary Black rot disease caused by Xanthomonas campestris pv. campestris is a limiting factor in the commercial production of the cauliflower crop. Crosses were attempted between SN 445, a mid season cultivar resistant to black rot and two highly susceptible commercial cultivars (Pusa Snowball-1 and K-1). Studies of the F₁'s, F₂'s and back crosses indicated that SN 445, carries a dominant gene imparting resistance to black rot.     

Genetics of resistance to Puccinia graminis tritici and Puccinia recondita tritici in Kenya Plume wheat

Summary Seven genes, viz. Sr5, Sr6, Sr7a, Sr8a, Sr9b, Sr12 and Sr17 were associated with seedling resistance to Puccinia graminis tritici in Kenya Plume wheat. The predominant field cultures were avirulent on seedlings with Sr7a, but possessed virulence for the other six genes. However, Sr7a did not confer adult-plant resistance when present on its own. Adult-plant resistance was attributed to Sr2 and possibly also to the interaction of Sr7a and Sr12.Two genes, Lr13 and Lr14a, were identified in seedling tests with various cultures of Puccinia recondita tritici. Lr13 conferred adult-plant resistance to the predominant field strains. Genetic recombination between Lr13 and Sr9b was estimated at 17.6±3.1%.     

Backcross variability for grain yield in oat species crosses (Avena sativa L. x A. sterilis L.)

Summary Avena sterilis introductions from the Middle East were useful sources of genes for improving the grain yield of adapted A. sativa cultivars for midwestern US. Introgression of genes from A. sterilis materials into A. sativa oat breeding populations was readily accomplished through a backcrossing procedure. Backcrossing successfully accomplished the recombination required to introgress complexly inherited traits. The BC₁F₂, BC₂F₂, BC₃F₂, and BC₄F₂ generations appeared to be best for selecting high-yielding transgressive segregates from the A. sativa x A. sterilis crosses.Journal Paper No. J-7919 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa 50010. Project No. 1752.     

Breeding wheat for resistance to Heterodera avenae in Southeastern Australia

Breeding wheat for resistance to Heterodera avenae in southern Australia has been in progress for nearly 30 years and recently a number of resistant varieties have been released. Early breeding work was hampered by three factors: • a lack of appreciation of the role and extent of the problem, • inaccurate, slow screening methods, ultimately being replaced by the 'tube' test and soon by linked molecular markers, • inappropriate breeding strategies, so that varietal releases have taken place only when the breeding has been fully integrated into the main programs. The experiences in southern Australia will be relevant to many other areas in the world where H. avenae is the major pest. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genetics of resistance to Puccinia recondita in two wheat crosses

Leaf rust resistance genes were identified in the common wheat variety ‘HUW 206’ and line HUWL 39 by inoculating their seedlings with 20 pathotypes of diverse avirulence–virulence combinations. The inheritance patterns and allelic relationships were studied by crossing these wheats with ‘Agra Local1 and a set of Thacher’ near-isogenic lines with genes for resistance. Seedling resistance studies revealed the presence of genes Lr1, Lr10 and Lr26 in ‘HUW 206’ and genes Lr10 and Lr26 in HUWL 39. The presence of genes Lr1 and Lr10 was confirmed indirectly by testing for the linked genes Sr31 and Yr9. An F₁ test for progressive necrosis in crosses of the lines with ‘Spica’ revealed the absence of Lr13.     

Inheritance of resistance to tipburn in cabbage

Summary Tipburn resistance was identified as being highly but not completely dominant in three nearly isogenic populations of cabbage. Narrow sense heritability estimates of 0.14, 0.34, and 0.49 and broad sense heritability estimates of 0.64, 0.74, and 0.77 were obtained with 2–4 genes controlling resistance. Analysis of resistance was made under conditions of high fertility, especially high N and plentiful moisture and generally high humidity which together resulted in very severe tipburn in susceptible plants.Journal Paper No. 3038 of the New York State Agricultural Experiment Station, Geneva, New York, USA.     

Investigations on resistance of oats to Heterodera avenae: Location of resistance genes

Summary By using 15 available mono/nullisomic lines of Sun II back ground, the Heterodera avenae resistance gene in Nelson (from Avena sativa CI 3444) and Panema (from A. sterilis I. 376) were located on monosome XV. Genes with smaller effects were located on monosomes VIII and X. The absence of these genes derived from Sun II would increase cyst production on plants lacking major resistance genes.     

Inheritance of resistance to Xanthomonas campestris pv. translucens in triticale

Summary Three triticale lines, Siskiyou, M2A-Beagle, and OK 77842 have been reported to possess resistance to bacterial leaf streak caused by Xanthomonas campestris, pv. translucens (Xct.). The three resistant lines were crossed to susceptible lines and crossed with each other. F₂, BC₁-F₁, BC₂-F₁ plants were inoculated with a mixture of two Xct strains. The segregation data indicate the presence of a single dominant gene in each of the three resistant lines to bacterial leaf streak. These three genes are either the same or closely linked herein designated as Xct₁.     

Variation for resistance to Puccinia hordei in Ethiopian barley landraces

Summary Up to 100 single plant derived lines of 18 Ethiopian barley landraces were evaluated for infection type in the seedling and adult plant stage, and for latent period in the adult plant stage only. A low infection type indicates the presence of race-specific resistance genes of the hypersensitive type, while the latent period is the major component of the polygenic, partial resistance.In the seedling stage 1721 of these single plant derived landrace lines were assessed for infection type against two barley leaf rust races. In the adult plant stage 1227 from these 1721 lines were evaluated for infection type against one race. In the seedling stage 2 (against race 1-2-1) and 29 against race A) out of the 1721 lines showed an infection type lower than 6–7 on the 0 to 9 scale. In the adult plant stage none of the 1227 lines had an infection type lower than 6–7 against race 1-2-1.The variation between and within the landraces for latent period in the adult plant stage was large. Some landraces such as landrace 212845 showed a highly significant and longer mean latent period than most other landraces. Virtually all plants in all landraces carry at least some partial resistance.The near-absence of race-specific, major, resistance genes and the high frequency of moderate levels of partial resistance indicates that the durability of leaf rust resistance in Ethiopian barley landraces is due to the latter type of resistance, and that the multiline principle does not operate.     

Temperature-sensitive genes for resistance to Puccinia striiformis in Triticum dicoccoides

Summary Twenty-six selections of wild emmer collected at different sites in Israel and three entries obtained from Turkey were studied for the possible presence of temperature-sensitive genes controlling reaction to Puccinia striiformis. In tests carried out in Israel with a local P. striiformis isolate at two temperature regimes, 16 selections showed a change in infection rating toward resistance at the higher temperature regime. In comparable tests performed in the United States with a Montana P. striiformis isolate of different virulence pattern-including 14 of the same selection—ten entries displayed a temperature-sensitive reaction. Although slightly different temperature regimes were used in Israel and the United States, the results obtained were in general agreement. The shift toward resistance observed in the seedling tests at the higher temperature-profile was also evident in the field in the mature plant stage with increasing spring temperatures.     

Inheritance of resistance to Botrytis cinerea Pers. in Cicer arietinum L.

Summary Chickpea (Cicer arietinum L.) line ICC 1069 was selected as resistant parent after screening for resistance to grey mould (Botrytis cinerea Pers.) under artificial inoculation conditions. It was crossed with four high yielding susceptible varieties of chickpea. Crosses ICC 1069 × BGM 413 and ICC 1069 × BG 256 showed monogenic dominant resistance in ratio of 3R (resistant): 1S (susceptible). However, in crosses, ICC 1069 × BGM 419 and ICC 1069 × BGM 408, a ratio of 13S (susceptible) : 3R (resistant) was obtained indicating the presence of epistatic interaction. The results pointed towards the presence of a type of major gene resistance to grey mould in chickpea.