Estimates of additive and dominance effects for Fusarium head blight resistance of winter triticale

The most effective strategy to control Fusarium head blight (FHB), a devastating disease of small‐grain cereals, is breeding resistant cultivars. This resistance study of F₁ crosses, F₂ and backcross generations of triticale estimates heterosis, general and specific combining ability (GCA, SCA), additive and dominance effects and compares parents with segregating generations. The genetic material consisted of 10 parents with their 45 F₁ crosses and of six parents with their 15 F₂ progeny and backcrosses to each parent. Genotypes were grown in various environments and artificially inoculated with an aggressive isolate of F. culmorum. FHB was assessed, by visual rating, as the mean of four to five individual ratings of disease development. Heterosis for FHB was of little importance. The correlation between the FHB rating of F₁ crosses and their mid‐parent performance was close. GCA was the predominant source of variation, although the significance of the SCA variance also implied non‐additive allelic interaction. The preponderance of additive gene effects is encouraging for increasing resistance by a recurrent selection programme. The relationship between the GCA effect of a parent and its per se performance was close, which gives the possibility of predicting FHB resistance in F₁ crosses. Additive effects were predominant in the F₂ progeny and also in the backcrosses. Transgressive segregants could not be detected. Searching for them should be postponed to the F₃ or later generations.     

Diallel analysis of barley for resistance to leaf stripe and impact of the disease on genetic variability for yield components

Barley breeders in Syria attempting to develop barley (Hordeum vulgare L.) cultivars resistant to barley leaf stripe (BLS) disease caused by Pyrenophora graminea Ito & Kuribayashi [anamorph Drechslera graminea (Rabenh. Ex. Schlech. Shoem.)]. Information on the combining ability for BLS resistance in Syria is not available. This study was conducted to evaluate, in 10 genetically diverse barley parents, general combining ability (GCA) and specific combining ability (SCA) effects towards the determination of the genetic basis of disease resistance and to estimate genetic variability for yield components and its modification by BLS. Ten parental genotypes varying in their reactions to BLS were crossed in a half-diallel mating design to generate 45 full-sib families. The families and the parents were inoculated with P. graminea and evaluated for resistance in replicated field tests (three inoculated and three non-inoculated plots). The parents chosen showed wide variations for resistance to BLS. Genetic component analysis showed significant effects for both GCA and SCA for resistance to BLS, suggesting that additive as well as non-additive genetic mechanisms were involved in the expression of resistance in these parents. GCA effects were more important than SCA effects. Resistant parents exhibited high negative GCA indicating that additive gene effects were more predominant, and suggesting their prime suitability for use in barley breeding programs to improve resistance to BLS. Narrow-sense heritability was 58% and broad-sense heritability was 99% indicating that selection for BLS resistance should be effective in these crosses. A high genetic variability for the agronomic traits studied was observed. Yield components decreased significantly in inoculated plants and more pronounced in diseased plants. Significant GCA was observed for all traits. Values for GCA were, in some cases, significantly modified by BLS. This indicates that attention must be paid to the danger of drawing conclusion in quantitative genetics studies dealing with both diseased and healthy plants. Two genotypes, Banteng and Igri, had high negative GCA effects and are promising parents for enhancement of BLS resistance.     

Combining ability analysis of resistance to head blight caused by <Emphasis Type="Italic">Fusarium graminearum</Emphasis> in spring wheat

Fusarium head blight (FHB) caused by Fusarium spp. is one of the most important fungal diseases of wheat (Triticum aestivum L.) in regions with wet climatic conditions. Improvement of the FHB resistance by developing new varieties requires sound knowledge on the inheritance of resistance. An 8 × 8 diallel analysis was performed to estimate general (GCA) and specific (SCA) combining ability of resistance to FHB. The F₁s and parental lines were evaluated under artificial inoculation at the experimental field of IFA-Tulln, Austria during 2001 and 2002. Disease severity was evaluated by repeated scoring of the percentage of infected spikelets and calculating an area under the disease progress curve (AUDPC). The analysis of combining ability across two years showed highly significant GCA and non-significant SCA effects indicating the importance of additive genetic components in controlling FHB resistance. The significant GCA-by-year interaction presented the role of environmental factors in influencing the FHB reaction of wheat lines. The comparison of the crosses with low FHB infection and GCA effects of their parents showed that such crosses involved at least one parent with high or average negative GCA effect. The results revealed that it is feasible to use highly or moderately resistant genotypes and conventional breeding methods to achieve genetic improvement of FHB resistance in spring wheat.     

Genetic analysis of resistance to root-lesion nematode (Pratylenchus thornei) in wheat

The inheritance of resistance to root‐lesion nematode was investigated in five synthetic hexaploid wheat lines and two bread wheat lines using a half‐diallel design of F₁ and F₂ crosses. The combining ability of resistance genes in the synthetic hexaploid wheat lines was compared with the performance of the bread wheat line ‘GS50a’, the source of resistance to Pratylenchus thornei used in Australian wheat breeding programmes. Replicated glasshouse trials identified P. thornei resistance as polygenic and additive in gene action. General combining ability (GCA) of the parents was more important than specific combining ability (SCA) effects in the inheritance of P. thornei resistance in both F₁ and F₂ populations. The synthetic hexaploid wheat line ‘CPI133872’ was identified as the best general combiner, however, all five synthetic hexaploid wheat lines possessed better GCA than ‘GS50a’ The synthetic hexaploid wheat lines contain novel sources of P. thornei resistance that will provide alternative and more effective sources of resistance to be utilized in wheat breeding programmes.     

Genetic analysis of mechanisms associated with inheritance of resistance to sheath rot of rice

Understanding genetic mechanisms controlling inheritance of disease resistance traits is essential in breeding investigations targeting development of resistant genotypes. Using North Carolina design II, 32 F₁ hybrids were generated by crossing eight susceptible to four resistant parents and submitted for field evaluation. The analysis of general and specific combining ability (GCA and SCA) indicated involvement of additive and non‐additive gene action controlling inheritance of horizontal resistance to sheath rot of rice. High GCA/SCA ratio and high heritability estimates revealed additive effects and were more predominant than none additive ones. The level of dominance indicated dominant genes was more important than recessive genes. Estimates of GCA and SCA analysis suggested that crop improvement programmes should be directed towards selection of superior parents or good combiners, emphasizing on GCA. As far as source of resistance is concerned, most promising genotypes were Cyicaro, Yunertian and Yunkeng. The predominance of additive genetic effects together with the relevance of dominant genes suggested possibilities of improving the resistance by introgression of resistance genes through recurrent selection coupled with phenotypic selection.     

Diallel analysis of sweetpotatoes for resistance to sweetpotato virus disease

Sweetpotato virus disease (SPVD) is due to the dual infection and synergistic interaction of Sweetpotato feathery mottle potyvirus (SPFMV) and Sweetpotato chlorotic stunt crinivirus(SPCSV), and causes up to 98% yield loss in sweetpotato in East Africa. This study was conducted to determine the inheritance of resistance to SPVD in sweetpotato and to estimate the nature of genetic variance. Ten parental clones varying in reaction to SPVD were crossed in a half diallel mating design to generate 45 full-sib families. The families were graft-inoculated with SPCSV and SPFMV to induce SPVD and evaluated for resistance in a randomized complete block design at two sites in Namulonge, Uganda during 1998–2000. In serological assays for SPFMV and SPCSV,resistance to symptom development and recovery from initial systemic SPVD symptoms, characterised resistant genotypes. Genetic component analysis showed significant effects for both general combining ability (GCA) and specific combining ability (SCA) for resistance to SPVD. GCA to SCA variance component ratios were large (0.51–0.87), hence GCA effects were more important than SCA effects. Resistant parents exhibited high GCA indicating that additive gene effects were predominant in the inheritance of resistance to SPVD and recovery. Narrow-sense heritability (31–41%) and broad-sense heritability (73–98%) were moderate to high, indicating that rapid genetic gains for SPVD resistance could be accomplished by mass selection breeding techniques. Two genotypes, New Kawogo and Sowola, had high negative GCA effects and had several families in specific crosses,which exhibited rapid recovery from SPVD,and are promising parents for enhancement of SPVD resistance and recovery. This revised version was published online in August 2006 with corrections to the Cover Date.     

Diallel analysis of Fusarium head blight resistance in genetically diverse winter wheat germplasm

New sources of partial resistance to Fusarium head blight (FHB) in wheat have been identified over the past decade; however, little is known of their breeding value. A 20 parent partial diallel that included resistant genotypes from the U.S., Europe, China and South America was used to evaluate the potential of these sources of resistance as parents in wheat breeding programs. Eight plants replication⁻¹ of each of 190 crosses and 20 parents were point-inoculated with Fusarium graminearum under greenhouse conditions in two replicated experiments. Both general (GCA) and specific combining ability (SCA) were significant. Most of the variance for FHB severity was associated with additive genes; however, estimates for SCA ranged from highly negative to highly positive in both resistant × resistant and resistant × susceptible crosses which suggest that improving FHB resistance through gene pyramiding strategies based on additive genetic variation may be complicated by interaction effects that condition FHB resistance.     

Combining ability analysis of resistance to Helminthosporium leaf blight in spring wheat

Wheat breeders in South Asia are attempting to develop wheat (Triticum aestivum L.) cultivars resistant to Helminthosporium leaf blight (HLB), which occurs mainly as a complex of spot blotch caused by Cochliobolus sativus (Ito & Kuribayashi) Drechs. ex Dastur, and tan spot caused by Pyrenophora tritici-repentis (Died.) Drechs. Information on the combining ability for HLB resistance in wheat cultivars of South Asia is not available. This study was undertaken to examine the resistance to HLB in nine genetically diverse wheat parents, and to evaluate their general combining ability (GCA) and specific combining ability (SCA) effects toward determining the genetic basis of disease resistance. Nine parents were crossed in a half-diallel mating design to produce 36 populations. The F₁ and F₂ progenies, and the parents were evaluated in replicated field tests at Rampur, Nepal. Multiple disease scores were recorded, and area under the disease progress curve (AUDPC) was calculated to measure disease severity over time. The combining ability analysis was performed using Griffing's Method 2, Model 1. The parents chosen showed wide variation for resistance to HLB. They and the F₁ and F₂ progenies differed significantly for AUDPC. GCA and SCA effects were significant in both generations suggesting that additive as well as non-additive genetic mechanisms were involved in the expression of resistance in these parents. Wheat genotypes 'SW89-5422', 'G 162', 'NL 781'and 'Chirya 7' had significantly negative GCA effects for AUDPC in both F₁ and F₂ generations, suggesting their prime suitability for use in wheat breeding programs to improve resistance to HLB. The estimate of narrow-sense heritability was 0.77 in both generations suggesting that selection for HLB resistance should be effective in these crosses. The results indicate a predominance of additive gene action in the inheritance of HLB resistance in spring wheat.     

Combining ability for nodulation in common bean (Phaseolus vulgaris L.) genotypes from Andean and Middle American gene pools

Ten F₁'s obtained from crosses among five common bean genotypes of Andean (WAF 15, Mineiro Precoce and Batatinha) and Middle American (BAT 304 and Ouro) gene pools were assessed for their combining abilities for root nodulation with Rhizobium tropici strain CIAT 899. The plants were grown under controlled conditions and evaluated for number of nodules per plant (NN), nodule dry weight (NDW), mean nodule weight (MNW) and plant fresh weight (PFW). The subdivision of the treatment effects on the general (GCA) and specific combining effects (SCA) were performed according to Griffing's diallel analysis method 2, model 1. The analyses of variance and estimates of quadratic components showed that non-additive gene effects were more important in the expression of NN and PFW, whereas additive gene effect was predominant for NDW and MNW. A close association was observed between high number of nodules and GCA. Generally, crosses involving parents of different gene pools yielded hybrids with high positive estimates of SCA for all assessed traits. The genotypes of Andean origin WAF 15 and Mineiro Precoce are the most promising parents for breeding programs to increase NN and NDW in common beans. This revised version was published online in July 2006 with corrections to the Cover Date.     

Resistance to Coffee Berry Disease in Arabica Coffee Variety 'Ruiru 11'

General and specific combining ability effects for resistance to coffee berry disease (Colletotrichum coffeanum Noack sensu Hindorf) in Coffea arabica variety ‘Ruiru 11’ and its parents were estimated according to the North Carolina Design II. A set of nine male parents and eleven females were crossed in all possible combinations to generate ninety-nine single cross hybrids constituting the ‘Ruiru 11’ variety. The parents and their hybrid progenies were screened and the mean score data analyzed for possible genetic variation. The contributions of the parents to the total genetic variance were low hence the low narrow sense heritability (h²= 0.04). The male and female parents accounted for 9.36 % and 0.96 %, respectively, while their interaction effect accounted for 89.68 %. In the analysis of combining ability for resistance, ExB3.96 and Cat.90 exhibited significant negative general combining ability (GCA). Specific combining abilities (SCA) were negative and significant for Cat.86 × ExB3.99, Cat.127 × ExB3.116 and Cat.119 × ExB3.879 crosses. The implications of these results in selection for highly resistant ‘Ruiru 11’ progenies are discussed.     

Diallel analysis of resistance to head blight caused by Fusarium culmorum in winter wheat

Summary Ten homozygous winter wheat genotypes representing different levels of resistance to Fusarium head blight were crossed in all possible combinations excluding reciprocals. Parents, F₁ and F₂ were inoculated with one pathogenic strain of Fusarium culmorum. Data for head blight, observed 21 days after first inoculation (OBS-2), and for the area under the disease progress curve, based on observations 14, 21 and 28 days after first inoculation (AUDPC), were analyzed. The contrast between parents and F₁ crosses indicated dommance effects of the resistance genes. Diallel analysis according to Griffing's Method 4, Model 1 showed significant general combining ability (GCA) effects for both F₁ and F₂; specific combining ability effects were not significant. With the exception of one genotype for which general performance for Fusarium resistance was not in agreement with its GCA, the resistance to F. culmorum was uniformly transmitted to all offspring, and the parents can be described in terms of GCA. It is suggested that in the progenies with one of the awned lines as parent, one resistance gene was linked with the gene coding for presence of awns, located on chromosome 4B. A single observation date, taken at the right time, was as effective in assessing resistance as the AUDPC.     

Heterotic effects for yield and tuber solids and type of gene action for five traits in 4x potato families derived from interploid (4x-2x) crosses

The degree of heterosis for total tuber yield (TTY) and total solids (TS) in 4x‐2x crosses was estimated by comparing the performance of 12 families with their respective parents in two locations in Wisconsin (USA). The parental 2x clones were Phureja‐haploid Tuberosum hybrids with 2n‐pollen production by first‐division restitution. The general combining ability (GCA) and specific combining ability (SCA) were estimated for TTY, TS, vine maturity (VM), length of tuber sprout dormancy (LD), and tuber eye depth (ED). Family performance for TTY ranged from 74 to 146% at Hancock (E#1) and from 77 to 287 at Rhinelander (E#2) when compared with that of the 4x parent group. For VM, the families were late maturing, but a few precocious ones were identified. For TS, the families had heterosis of 5.1% over the 4x parent group. The families had slightly higher ED values than the 4x parents, but families with values within the commercial range were identified. The family average for LD (54 days) was closer to the 2x group (51 days) than to the 4x group (88 days). The direction and magnitude of the parent‐family relationships were variable. The 4x parent TTY was correlated with progeny in E#1 but not E#2. The 2x parent VM had correlation with the offspring at E#2 but not at E#1. The type of gene action had a trait‐specific expression. Significant SCA and GCA variances were observed, suggesting that additive as well as non‐additive genetic effects were operating. The 4x‐2x crosses were able to generate heterotic families for TTY and TS in combination with other useful traits. However, no promising results were found for LD because of the apparent dominance of the short‐dormancy phenotype. This result indicates the need of additional selection and breeding efforts for some specific traits when using S. phureja‐derived germplasm.     

Diallel analysis of net blotch resistance in doubled haploid lines of Nordic spring barleys

A half-diallel was made between five six-rowed Nordic spring barleys to study the genetics of resistance to net blotch. Twenty-five doubled-haploid (DH) lines from each cross and the parents were sown in hill plots in Finland in 1997 and 1998. The plots were artificially inoculated with Pyrenophora teres Drechs. f. teres Smedeg. and assessed for resistance to net blotch. There were statistically significant differences in resistance of the five parents to net blotch. General combining ability (GCA) of the parents and specific combining ability (SCA) effects in the progeny were statistically significant in both years, but GCA effects predominated. Evidence for additive epistasis was minimal. Progeny of a particular cross were less resistant to net blotch than the better parent. The most resistant progeny were derived from the cross between the two most resistant parents, Pohto and WW7977, and resistance was governed by at least eleven effective factors. Narrow sense heritability estimates for resistance to net blotch were high during both years (0.84–0.99). It appears that net blotch resistance of progeny from crosses can be largely predicted from reactions of the parents. Quantitative resistance to net blotch can be further advanced by identification and incorporation of superior parents, from a screening such as reported here, into a recurrent selection breeding programme. This revised version was published online in August 2006 with corrections to the Cover Date.     

Hybrid performance and heterosis in strawberry (Fragaria × ananassa Duchesne), regarding acidity,soluble solids and dry matter content in fruits

A top‐cross‐mating design among 29 S₄ inbred lines and tester (cultivar ‘Dukat’) was carried out to study their breeding value in terms of general combining ability (GCA). The objectives of this study were to evaluate the acidity, soluble solids and dry matter contents in fruits of progeny F₁ in comparison with S₄ inbred lines as well as the cultivars (S₀); identify strawberry genotypes with high value of GCA for use in cultivar development; and determine mid‐parent heterosis regarding S₄ inbred lines and cultivated strawberry. The 2‐year observations showed statistically significant differences between tested genotypes in terms of the studied traits. The highest breeding value based on GCA was estimated for Chandler 123‐5 for soluble solids and dry matter content, and Kent 7‐6 for acidity. Estimated mid‐parent heterosis had positive and negative values. The highest heterosis in terms of extract and dry matter content (26.71% and 17.50%, respectively) occurred in the offspring Chandler 123‐5 × ‘Dukat’, but as regards acidity in hybrid Chandler 123‐22 with cv. ‘Dukat’. The study of genetic divergence by dendrograms may help to identify parents suitable for obtaining hybrids with higher heterosis effects.     

Performance of upland coloured cotton germplasm lines in line × tester crosses

Anthracnose is a serious disease affecting dry bean production especially in the cool highland areas worldwide. The objective of this research was to study the inheritance of anthracnose resistance in market-class dry beans. A complete diallel set of crosses was generated from nine diverse parents comprising six resistant and three susceptible to anthracnose. The F₁ and F₂ crosses and parents were artificially inoculated with Colletotriclum lindenumthianum Race-767 in a growth room. There was significant variation for anthracnose resistance among genotypes. General combining ability (GCA) and specific combining ability effects were significant for resistance, indicating importance of both additive and non-additive effects, respectively. Preponderance of GCA effects (66%) suggested that additive effects were more important than non-additive effects (24%), which were also reflected by high heritability estimates (70%), and suggested that simple selection or backcrossing would be useful for improving the resistance in market class varieties. The study was not conclusive on whether epistatic gene action played a major role, but if available it might have biased the dominance gene effects. Reciprocal effects (10%) were not significant (P > 0.05), suggesting that cytoplasmic genes did not play a major role in modifying anthracnose resistance. Parental lines G2333, AB136, NAT002, and NAT003 showed highly negative GCA effects qualifying them as suitable parents for transferring resistance genes to their progenies. A few major genes, 1–3, displaying partial dominance conditioned anthracnose resistance, suggesting a possibility of using marker-assisted selection to improve anthracnose resistance in market-class dry beans.     

Genetic analysis of resistance to nematodes in inbred maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) and maize hybrids

Nematodes cause substantial grain yield loss in susceptible maize (Zea mays L.) cultivars. This study was conducted to estimate general combining ability (GCA), specific combining ability (SCA) and genetic effects associated with nematode resistance in maize. The 30 F ₁ hybrids generated from a 6 × 6 diallel and two local checks were evaluated in 2009 at three sites in Uganda. A split plot design was used with nematode treatments serving as whole plots and the hybrids as subplots but arranged in an 8 × 4 spatially adjusted alpha-lattice design. The experiment was replicated three times. Results showed GCA to be important for the reduction of P. zeae and Meloidogyne spp. densities and increase of root mass, with a contribution of 72 to 93% of the phenotypic variance. Inbreds MP709 and CML206 had the highest GCA for Pratylenchus zeae resistance, whereas for grain yield, it was CML444, CML312 and CML395 that were outstanding. The SCA influenced plant height and grain yield under nematode infestation, contributing 43 and 58% of the phenotypic variance, respectively. Observed reciprocal differences due to maternal effects also played a role in influencing the grain yield under nematode infestation. Overdominance genetic effects explained the non-additive variance recorded for the plant height, grain yield, number of root lesions, and P. zeae and Meloidogyne spp. densities under nematode infestation. The parents MP709, CML206, 5057, and CML444 contributed most of the dominant genes for the P. zeae resistance in all their crosses. The parent CML444 contributed most of the dominant genes for improved grain yield in all of its crosses. The high GCA effects among some parents support their utility in breeding of widely adapted nematode-resistant cultivars. The dominant genes and SCA effects would favour pedigree and various sib tests to improve grain yield under nematode pressure.     

Combining ability of seed vigor and seed yield in soybean

Studies have shown no consensus in relationships between seed yield and vigor in soybean [Glycine max (L.) Merrill]. The lack of information regarding the inheritance of seed vigor prompted this study to determine the types of gene action and combining ability estimates for seed vigor and its related traits. Five high and six low seed vigor soybean genotypes were crossed in a diallel, and selfed to produce 55 F₂ progenies, which were examined, along with the parents, for seed vigor, yield, and seed weight. Significant genotype and environment effects were found for seed vigor and yield. General combining ability (GCA) effects for seed vigor and seed yield were significant (p≤ 0.01) and larger than specific combining ability (SCA) effects. Significant GCA and SCA effects were found for seed weight, indicating that both additive and non additive genetic effects were involved in conditioning seed weight. The ratios of mean square, 2GCA / (2GCA+SCA), were 0.96 for seed vigor and 0.93 for seed yield. These ratios indicated that additive gene effects were more important than non additive gene effects for seed vigor and seed yield in these crosses. Mean seed vigor(83.8%), as determined by accelerated aging germination, and mean seed yield (2,155 kg ha^-1)in high vigor × high vigor crosses were higher than the high vigor × low vigor and low vigor × low vigor crosses. Mean percent accelerated aging germination rates in F₂ populations from diallel crosses were significantly related to mid-parent seed vigor(r² = 0.52^**) and midparent seed size (r² = 0.31^**). These results indicated that levels of seed vigor can be improved through breeding, while maintaining high yields because of the predominance of GCA effects in both seed vigor and seed yield. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inheritance of threshing percentage in pearl millet

Summary The threshing percentage (TH%) has been suggested as a selection criterion to identify the pearl millet (Pennisetum glaucum (L.) R.Br.) lines with improved ability to fill and set grains under water limiting conditions. In this study, eight genetically diverse pearl millet inbreds and their 28 crosses produced by half diallel crossing design were used to examine range in TH%, to evaluate general combining ability (GCA) of parents and specific combining ability (SCA) effects of crosses. The results showed significant variation among parental lines for TH%. The inbreds differed for their GCA effects and crosses for their SCA effects. Parents with high TH% and positive GCA effects were identified. The results of the study revealed that both additive and dominance components, with the preponderance of later, were important in the inheritance of TH%. Heritability in narrow sense was moderate (55%) indicating that selection for high TH% might be effective.     

Mapping QTL involved in adult plant resistance to powdery mildew in the winter wheat line RE714 in two susceptible genetic backgrounds

The objective was to study the genetic basis of adult plant resistance to powdery mildew of the winter wheat line RE714 by quantitative trait loci (QTL) analysis and to investigate the stability of the QTL detected in two different genetic backgrounds. Two DH populations from the crosses between RE714 and the susceptible parents ‘Festin’ and ‘Hardi’ were used. Reaction of the DH lines to powdery mildew was assessed in different environments in Belgium under natural disease infection. Considering both populations and according to the environment tested, one to seven QTL were detected. Among them, residual effects of the race‐specific resistance genes Pm4b and MIRE were found. Two major QTL were very stable (on chromosome 5D and at the MIRE locus), since they were detected in both populations and over all environments tested. The QTL detected varied according to the susceptible parent used, and a residual effect at the Pm4b gene was not observed with the genetic background of ‘Hardi’.     

Inheritance of resistance to the 'Kanpur' race of Phytophthora drechsleri in pigeonpea

Phytophthora drechsleri causes stem blight, which is one of the most serious diseases of pigeonpea. Eight races of this fungus have been identified, but the inheritance of resistance to all these races is not clear except for race P2. This study examined the inheritance of resistance to race ‘Kanpur’ (KPR) of P. drechsleri in eight crosses involving four resistant parents, viz.‘KPBR 80‐2‐1′, ‘KPBR 80‐2‐2′, ‘Hy 3C and ‘BDN 1′, and two susceptible parents, viz.‘Bahar’ and ‘PDA 10′. The reactions of the parental lines, and their F₁, F₂ and backcross generations were studied in an infected plot. In the F₁ generation of all crosses, a susceptible reaction was observed that indicated dominance of susceptibility over resistance. The segregation pattern in F₂ indicated that two homozygous recessive genes (pdr₁pdr₁pdr₂pdr₂) were responsible for imparting resistance in the parents, ‘KPBR 80‐2‐1’ and ‘KPBR 80‐2‐2′, and that a single homozygous recessive gene (pdrpdr) was responsible for resistance in the parents ‘Hy 3C and ‘BDN 1′. Therefore, ‘KPBR 80‐2‐1’ and ‘KPBR 80‐2‐2’ with two genes for resistance are better donors because the resistance transferred from them will be more durable compared with ‘Hy3C and ‘BDN1’ with only one gene for resistance.