Journal of Heredity Advance Access originally published online on December 11, 2006
Journal of Heredity 2007 98(1):79-83; doi:10.1093/jhered/esl049
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Brief Communications |
Genetics of Resistance to Cotton Leaf Curl Disease in Gossypium hirsutum L. under Field Conditions
From the Central Institute for Cotton Research, Regional Station, Sirsa, Haryana 125 055, India
Address correspondence to S. L. Ahuja at the address above, or e-mail: slahuja2002{at}yahoo.com.
One hundred and forty two cotton germplasm lines were screened for cotton leaf curl virus symptoms in field evaluations during 2003, 2004, and 2005. Fifty cross combinations involving 30 of these lines classified resistant or susceptible were used for inheritance study of the disease. All the F1 plants of crosses involving resistant x resistant, resistant x susceptible, and susceptible x resistant parents were resistant, indicating dominant expression of the disease resistance and there were no maternal or cytoplasmic effects detected from reciprocal hybridization. In 22 crosses, 4 types of segregation patterns were obtained in the F2 generations. A good fit for 15 (resistant):1 (susceptible), 13 (resistant):3 (susceptible), 9 (resistant):7 (susceptible) ratios indicated digenic control of the trait with duplicate dominant, dominant inhibitory, and duplicate recessive epistasis, respectively. Three-gene control with triplicate dominant epistasis was obtained in one of the crosses. This segregation pattern, however, needs further confirmation due to smaller population size. The absence of complementary gene action was obtained in 1 susceptible x susceptible and 27 resistant x resistant crosses as their F1s were susceptible and resistant, respectively, and F2 generation lacked segregation.
The most important constraint in cotton productivity in India is susceptibility of the crop to insect pest and viruses. Cotton leaf curl disease (CLCuD) has emerged as a major disease of cotton in Northern India. In India, it was reported for the first time in 1989 on Gossypium hirsutum cotton at the Indian Agricultural Research Institute, New Delhi, and subsequently in the Sriganga Nagar district of Rajasthan in 1993. Thereafter, it has spread throughout Northern India in a short span of 4–5 years (Monga et al. 2004) and has now become a potential threat in the irrigated cotton production belt of the country.
The disease is caused by a begomovirus (family: Geminiviridae) in association with a newly identified class of single-stranded DNA satellites referred to as DNA ß (Mansoor et al. 2003) and characterized by the symptoms with leaf curling, darkened veins, vein swelling, and enations on the undersides of leaves that frequently develop into cup-shaped, leaf-like structures (Briddon and Markham 2001). The disease is transmitted exclusively by the whitefly Bemisia tabaci. The study on cloning and sequencing of the coat protein of the virus by Indian Institute of Science, Bangalore, revealed that at least 4 begomoviruses occur in India namely, Cotton leaf curl Rajasthan virus (CLCuRV), Cotton leaf curl Multan (CLCuMV), Cotton leaf curl Kokhran (CLCuKV), and Tomato leaf curl Bangalore virus-cotton (ToLCBV). Further distribution of the virus species among isolates characterized at Indian Agricultural Research Institute, New Delhi, indicated that at Sirsa location, where this study was conducted, predominance of CLCuRV and CLCuMV were observed (Malthi et al. 2004).
Agroinoculation is used efficiently to screen germplasm in greenhouses. Field evaluation is the most commonly used method for screening large number of germplasm lines for CLCuD resistance and susceptibility. Literature indicates that only a few reports are available on the inheritance of the disease. For developing high-yielding CLCuD resistant varieties of cotton, it is essential to identify sources of resistance and study of its inheritance. Therefore, the present investigation was carried out to identify the additional sources of resistance and to investigate the genetics of CLCuD occurring in Northern India.
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Materials and Methods |
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 Top Materials and Methods Results and DiscussionReferences |
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Field Evaluation of CLCuD Susceptibility and Origin of Cotton Germplasm
As one of the component programs of Technology Mission on Cotton project, screening of 142 germplasm lines of G. hirsutum for identification of cotton leaf curl resistant genotypes was carried out. These lines were collected from cotton research centers throughout India and were planted for 3 years: 2003, 2004, and 2005 in 2 different dates of sowings, that is, normal sowing and late sowing. Each year, selfed seeds from symptomless (resistant) plants were collected for next year sowing and visual observations for susceptibility and resistance were taken. All the cotton germplasm lines were planted in second week of May (normal sowing) and first week of June (late sowing) in field with repeated planting of susceptible cotton variety HS-6 after every 10 rows. Each germplasm line was grown in randomized block design with 2 replications keeping spacing of row to row and plant to plant 100 x 30 cm to accommodate 42 plants per genotype per replication. Near by the experiment, there was also a CLCuD field nursery maintained by Pathology Division of the Station. No whitefly control measures were implemented, thus allowing the spread of vector populations throughout the season. Each and every plant was observed visually for susceptibility beginning 50 days after sowing till maturity during 2003, 2004, and 2005 crop seasons. For the purpose of disease reaction classification, a genotype found susceptible in all the 3 years at any stage in both the sowings was considered susceptible and vice versa. Observations were recorded only when symptoms of CLCuD appeared in susceptible check variety HS-6 and the germplasm lines were considered susceptible/resistant accordingly. The disease appeared on susceptible check variety HS-6 in all the 3 years of the study.
Development of F1 and F2 Population
Eight hundred crosses were attempted during 2003 using 142 germplasm lines. The F1s were planted in the field in 2004 with 2 replication and repeated planting of susceptible cotton variety HS-6 after every 10 rows. Spread of the vector population was allowed by avoiding spraying for whitefly control. Near by the experiment, there was also a CLCuD field nursery maintained by Pathology Division of the station. Susceptibility for leaf curl virus was visually observed beginning 50 days after sowing till maturity and symptomless (resistant) and susceptible crosses were identified. Selfed seed of the 139 high-yielding, high fiber strength, and good fiber length crosses were used for raising F2 population. During rainy season 2004, F1 crosses (139 high yielding) of 2003 were repeated. The seed of F1, F2 and parents of all crosses were sown under field condition in rainy season 2005 in 2, 8, and 4 rows, respectively, of 5.4 m length with a spacing of 100 x 30 cm to accommodate 19 plants per row. Similar to germplasm evaluation after every 10 lines, susceptible cotton variety HS-6 was repeated and disease reaction classification was done similar to germplasm screening. Numbers of resistant and susceptible plants were counted. Observations recorded in segregating generations were subjected to chi-square test for goodness-of-fit. For dealing with 2 classes as there is binomial distribution Yates' correction for continuity was used. Chi-square values were calculated by the formula:
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A test of homogeneity (Mather 1957) was performed to decide whether the separate populations were sufficiently uniform to be added together. For homogeneity test as chi square of each individual sample is calculated based on expected ratio and these are to be added, the Yates' correction factor was not used. Fifty cross combinations involving 30 germplasm lines (resistant: CISV-24, RS-2013, RST-2315, M-45, CSH-17, TCH-4557, TCH-1569, F-2009, H-1242, CSH-3017, CSH-33, BRR-22, SGNR-1, SGNR-16, CNH-36 Z-2-3, RACH-11-3, CCH-526612, RS-810, CPD-447, and CNH-36 and susceptible: LH-1960, CA-531, CSH-14, CISV-56, RS-2283, CITH-77, LH-1995, SGNR-2, and AKH-9618) based on their consistency for being noted as resistant or susceptible in all the 3 years were evaluated and tested against possible genetic models.
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Results and Discussion |
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TopMaterials and MethodsResults and DiscussionReferences |
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The cotton cultivation season in North zone of India typically begins with sowing during mid-April. Farmers are advised not to sow before April to avoid early CLCuD infection. Susceptible cotton usually shows the first symptom of infection within 50 days of sowing. Temperatures during the early part of the growing season usually approach a maximum close to 45 °C, a temperature at which CLCuD symptom expression is most severe. Screening cotton for resistance to CLCuD is complicated by the fact that the disease is not mechanically transmissible and by the requirement of a high temperature (40 °C) for optimum symptom expression (Briddon and Makham 2001). During 2003 and 2004, crop seasons CLCuD were observed in June and become severe in the month of July and August. The progress of disease slowed down later. In 2005, the disease was severe during the entire crop season. During the crop seasons of 2003, 2004, and 2005, temperature varied between 44.2–24.7 °C, 43.4–25.6 °C, and 44.2–23.6 °C, respectively, and relative humidity (%) between 86.0–41.0, 85.0–35.0, and 84.0–35 that favored the disease incidence. For the purpose of disease reaction classification, a genotype found susceptible in all the 3 years at any stage in both the sowings was considered susceptible and vice versa. Observations were recorded only when symptoms of CLCuV appeared in susceptible check variety HS-6 and the germplasm lines were considered susceptible/resistant accordingly. The disease appeared on susceptible check variety HS-6 in all the 3 years of the study.
Evaluation of 50 cross combinations involving 30 parents based on their consistency for being noted as resistant or susceptible in all the 3 years indicated that the segregation pattern of the 10 crosses with parental combination R x S (resistant x susceptible) and S x R (susceptible x resistant) fitted in to 15 (resistant):1 (susceptible) ratio (Table 1). The homogeneity chi-square value was well within the accepted limit; hence the populations were homogeneous. The data could therefore be pooled and summed data chi square thus represented a test for 15:1 ratio. Dominant allele at either of the loci could mask the expression of recessive allele at 2 loci resulting in 15:1 phenotypic ratio in F2. The F1s involving R x S and S x R genotypes were resistant to leaf curl virus disease, suggesting that the disease was governed by dominant genes (duplicate dominant epistasis). The crosses involved resistant genotypes: CISV-24, RST-2315, M-45, CNH-36, Z-2-3, SGNR-16, RACH-11-3, and susceptible: RS-2283, CA-531, LH-1960, CITH-77, LH-1995, and SGNR-2 (Table 1). Kumar (2002) investigated the inheritance of CLCuD in crosses between susceptible x susceptible, susceptible x resistant, resistant x resistant parents and reported that resistance to CLCuD was dominant over susceptibility. Furthermore, in the F2 generation of susceptible x resistant crosses, segregation for resistance under field conditions and in the screen house gave a good fit to the phenotypic ratio 15 (resistant):1 (susceptible) that was indicative of duplicate dominant gene interaction.
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In another 3 crosses derived from cross combinations of susceptible x resistant and resistant x susceptible parents, F2 segregation gave a good fit for 3 (resistant):1 (susceptible) ratio and F1s were resistant to leaf curl virus disease, suggesting presence of single dominant gene control of the disease (Table 2). The homogeneity chi-square value was well with in the accepted limit for these 3 crosses; hence the populations were homogeneous. The data could therefore be pooled and summed data chi square thus represented a test of 3:1 ratio. CCH-526612, SGNR-16, and M-45 were the resistant and RS-2283, CISV-56, and SGNR-10 susceptible genotypes involved in these crosses. An experiment conducted to study the inheritance of CLCuD at Central Cotton Research Institute, Multan, revealed that a single dominant gene controlled resistance (Ali 1997). Sajjad et al. (2003) also reported single dominant gene control with modifiers. They also reported that there was no maternal effect.
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Segregation of another 6 crosses with cross combination involving R x S and S x R parents gave good fit for 13 (resistant):3 (susceptible) ratio that was confirmed by acceptable chi-square values for the homogeneity test (Table 3). The segregation ratio of the F2 population (13:3) suggested the presence of 2 genes for resistance to CLCuD with dominant inhibitory epistasis. Resistant genotypes involved in these crosses were CISV-24, F-2009, and CCH-526612 and susceptible parents CA-531, CSH-14, CISV-56, and LH-1995 (Table 3).
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The above 9 crosses, that is, 6 crosses exhibiting 13 (resistant):3 (susceptible) ratio and 3 (resistant):1(susceptible) ratio were subjected to homogeneity test for 13 (resistant):3 (susceptible) ratio. The homogeneity chi-square value was well within the accepted limit; hence the populations were homogeneous. The data could therefore be pooled and summed data chi square thus represented a test of 13:3 ratio. All the 9 crosses also gave a good fit for 13 (resistant):3 (susceptible) ratio indicating thereby that populations of these 9 crosses are from a homogeneous set and suggested the presence of 2 genes for resistance to CLCuD with dominant inhibitory epistasis (Table 4). Rahman et al. (2005) in the crosses between the most susceptible variety (S-12) and highly resistant varieties (CP-15/2, LRA-5166, and CIM-443) found that all F1 plants of these crosses were resistant, showing dominant expression of the resistance as well as the absence of extra chromosomal inheritance. Their F2 plants arising from the crosses CP-15/2 x S12, LRA-5166 x S-12, and CIM-443 x S12 exhibited a ratio of 13 resistant (symptomless) to 3 susceptible (with symptoms). The F3 progeny of susceptible F2 plants segregated for resistance, indicating the probable presence of a suppressor gene (S). These findings are consistent with 3 genes being involved in G. hirsutum resistance to CLCuD, 2 for resistance and a suppressor of resistance.
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Segregation pattern for CLCuD in F2 generation of 2 (S x R) crosses showed a good fit for 9 (resistant):7 (susceptible) and their acceptable homogeneity chi square confirmed existence of 2 genes with duplicate recessive epistasis (Table 5). CISV-24 and Z-2-3 were the resistant and RS-2213 and TCH-4457 susceptible parents involved in these crosses. This segregation pattern could not receive support by earlier workers to date.
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In one of the cross involving susceptible (RS-2283) x resistant (CCH-526612) parents, a good fit for 63:1 ratio indicated 3 gene control with triplicate dominant epistasis for the inheritance of the disease. As the population size was not large enough to confirm the results, the segregation pattern needs further confirmation (Table 6).
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The F1 hybrids either involving R x S or S x R cross combinations in all the above segregating populations had resistant population. This indicated the dominance of CLCuD resistance over susceptibility. Gene interaction differed with difference in the genotype involved in the cross combinations.
Rest of the 20 crosses involving resistant x resistant (27) and susceptible x susceptible (1) genotypes gave resistant and susceptible F1 population, respectively, and there was no segregation. Resistant x resistant crosses were CISV-24 x RACH-11-3, RS-2013 x CNH-36, RS-2013 x CPD-447, RS-2013 x SGNR-1, H-1242 x CCH-526612, H-1242 x SGNR-16, H-1242 x Z-2-2, H-1242 x CISV-24, F-2009 x CPD-447, F-2009 x SGNR-16, F-2009 x CNH-36, F-2009 x RACH-11-3, F-2009 x LRK-516, F-2009 x RS-2013, RST-2315 x Z-2-3, RST-2315 x CNH-36, RST-2315 x SGNR-16, RST-2315 x LRK-516, M-45 x SGNR-16, Z-2-2 x RS-2013, CSH-3017 x CNH-36, CSH-33 x CISV-24, TCH-1569 x CISV-24, RS-2283 x SGNR-16, CNH-36 x RS-2013, SGNR-16 x RS-2013, and BRR-22 x CCH-526612 and susceptible x susceptible LH-1960 x LH-1995. Literature also shows that there was absence of complementary gene action as in susceptible x susceptible LH-1960 x LH-1995 and resistant x resistant crosses, all plants in segregating as well as nonsegregating populations were susceptible and resistant, respectively (Kumar 2002).
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Footnotes |
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Corresponding Editor: Prem Jauhar
Received March 1, 2006
Accepted October 5, 2006
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References |
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TopMaterials and MethodsResults and DiscussionReferences |
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Ali M. (1997) Breeding of cotton varieties for resistance to cotton leaf curl virus. Pak J Phytopathol 9:1–7.
Briddon RW and Markham PG. (2001) Cotton leaf curl virus disease. Virus Res 71:151–159.
Kumar B. (2002) Genetic studies on cotton leaf curl virus disease and characters of economic importance in cotton (Gossypium hirsutum L.) [PhD thesis](CCS Haryana Agricultural University, Hisar, India).
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Mansoor S, Briddon RW, Bull SE, Bedford ID, Bashir A, Hussain M, Saeed M, Zafar Y, Malik KA, Fauquet C, Markham PG. (2003) Leaf curl disease is associated with multiple monopartite Begomoviruses supported by single DNA ß. Arch Virol 148:1969–1986.[CrossRef][Web of Science][Medline]
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Rahman M, Hussain D, Malik TA, Zafar Y. (2005) Genetics of resistance to cotton leaf curl disease in Gossypium hirsutum. Plant Pathol 54:764–772.[CrossRef]
Sajjad H, Khan IA, Sahid M. (2003) Genetics of cotton leaf curl virus disease in upland cotton. Sarhad J Agri 19:207–210.
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