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Plant Genomics & Mol Breeding (PGMB) Labs, National Institute for Biotechnology and Genetic Engineering (NIBGE), P.O. Box 577, Jhang Road, Faisalabad, Pakistan
* Corresponding author (mehboob{at}nibge.org).
‘NIBGE-2’ cotton (Gossypium hirsutum L.) (Reg. No. CV-124, PI 647088, Pak 022845) was developed by the Plant Genomics & Molecular Breeding (PGMB) Labs, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan. It was released in December 2006 for its resistance to the Multan strain of cotton leaf curl disease (CLCuD, the most prevalent strain in Pakistan) and its high tolerance to the resistance-breaking Burewala strain of CLCuD. There are two major strains of CLCuD. The Multan strain consists of one, or more, of seven distinct begomovirus species (Cotton leaf curl Multan virus, Cotton leaf curl Khokhran virus, Papaya leaf curl virus, Tomato leaf curl Karnataka virus, Cotton leaf curl Alabad virus, Cotton leaf curl Rajastan virus, and Cotton leaf curl Bangalore virus) associated with a specific DNA satellite (Briddon, 2003; Mansoor et al., 2006). The Burewala strain has been studied only partially but consists of one begomovirus (Cotton leaf curl Burewala virus) and a recombinant satellite derived from the Multan strain. During the 1990s the Multan strain predominated, although in recent years the Burewala strain has increased in importance. In 1992 the disease affected 120,000 ha, reducing production by 30% (Mansoor et al., 1993). In 1993–1994 about 400,000 ha of cotton was affected by the disease, resulting in further decline in cotton yield (Rahman et al., 2005). The NIBGE-2 cultivar is best suited for irrigated as well as drought prone areas of Pakistan.
NIBGE-2 is from a cross of ‘LRA-5166’ with ‘S-12’, made in 1996. LRA-5166 is resistant to CLCuD and known to contain two resistance genes (R1CLCuDhir and R2CLCuDhir) and a suppressor of resistance (SCLCuDhir) (Rahman et al., 2005). S-12 is highly susceptible to CLCuD (Rahman et al., 2002) and originated from a cross of the released variety MNH-93 and unreleased genotype 7203-14-4 (Iqbal et al., 1997). The F2 plants from the cross, along with spreader rows of S-12 (every third row), were sown in the last week of June 1998 at the NIBGE cotton field to ensure maximum infection (Rahman et al., 2002). Control measures were not implemented throughout the season to allow the spread of vector population. Two-month-old F2 plants and succeeding generations were also graft inoculated with a highly infected bud by T-shaped grafting method to ensure the provision of virus inoculum. After insertion, the bud was wrapped with a polyethylene strip to avoid any chance of evaporation. The process was conducted in the evening (Rahman et al., 2002). Virus infection of plants was determined by visual symptom assessment as well as dot-blot hybridization and multiplex PCR diagnostic techniques (Rahman et al., 2005). Greenhouse-grown F3 progeny of the resistant F2 plants were challenged with CLCuD inoculum as described above. The plants were screened by visual assessment and the multiplex PCR test. Resistant F3 plants were advanced to F4 and again subjected to screening tests. The procedure was repeated to F5. In the following season, the most productive F5:6 progeny, with good quality parameters, was selected in comparison to commercial checks (FH-900, FH-901, and CIM-473) in the NIBGE cotton field in 2001 and 2002.
The cultivar was tested on 10 different sites of the Punjab province in the National Coordinated Varietal Trials (NCVT) for 2 yr (2003 and 2004). The mean seed cotton yield (SCY) of NIBGE-2 was 2792 Kg ha–1, compared with 2318 Kg ha–1 for standards (CIM-473 and CIM-499). NIBGE-2 was also tested in replicated trials under irrigated and limited water conditions in Faisalabad at NIBGE cotton field in 2006. In drought conditions, the SCY of NIBGE-2 was 1910 Kg ha–1, compared with 1362 Kg ha–1 for CIM-473 and 1164 Kg ha–1 for CIM-499 (Sarwar et al., 2007).
NIBGE-2 was tested extensively in areas of the Punjab with high disease incidence, for resistance to CLCuD, agronomic characteristics, earliness and fiber quality. Resistance to the disease was high compared with the other candidate lines tested in the NCVT for both seasons. NIBGE-2 is similar in maturity to CIM-473 on the basis of percentage first pick yield and has 10% more bolls than CIM-473 and CIM-499. Fiber bundle strength, measured by high volume instrument analysis, was 10.6 and 4.9% more than CIM-499 and CIM-473, respectively. Micronaire readings of NIBGE-2 averaged 0.1 units higher than that of CIM-473 but were similar to CIM-499. The upper half mean fiber length of NIBGE-2 was 0.9 and 1.1 mm shorter than CIM-499 and CIM-473, respectively.
In 2003–2004 a field screening trial on 33 cotton cultivars and genotypes, including NIBGE-2, was conducted in 10 different locations of Pakistan. The screening continued for two successive normal cotton-growing seasons (2004–2006). Out of the 33 cotton cultivars and genotypes, NIBGE-2 showed absolute resistance to the Multan strain of CLCuD, while it exhibited 5.2% disease incidence to the Burewala strain, compared with the trial mean of 43.7%.
The growth habit of this cultivar is of the spreading type with light green foliage. The variety is glanded, possesses normal-shaped leaves and bracts, has a pubescent stem and leaves, and is nectaried. The pollen color is creamy, and the boll shape is of the oval type. Occasional plants are 5 to 10 cm taller than the norm but similar in appearance.
NIBGE-2 will be useful for breeding cultivars against CLCuD and drought stress. Breeder seed of NIBGE-2 will be maintained by the PGMB Labs (NIBGE, Faisalabad, Pakistan). Limited quantities of seed for research purposes can be obtained from the corresponding author. It is requested that appropriate recognition be made if this cultivar contributes to the development of hybrids, new cultivars, or breeding lines.
Acknowledgments
This study is a part of Ph.D. thesis research work of Dr. Mehboob-ur-Rahman. The funds for the study were provided by Agriculture Department, Government of the Punjab, ADP scheme No. 27, and the Pakistan Science Foundation. The work was also supported by funding from the Ministry of Science & Technology (MoST), Islamabad Pakistan, through a project titled "Functional Genomics for Quality Traits in Crop Plants." We are also grateful to Dr. Rob W. Briddon, Foreign Faculty Professor, Higher Education Commission (HEC) Islamabad, Pakistan, for reviewing the manuscript and making helpful suggestions.
Footnotes
All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.
Received for publication February 7, 2007.
References
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