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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 or mehboob_pbd{at}yahoo.com).
NIBGE-115 cotton (Gossypium hirsutum L.) (Reg. No. GP-880, PI 643972) was developed in 2002 by the Plant Genomics and Molecular Breeding (PGMB) Labs, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan, and was released in 2006. It was bred as part of an ongoing effort to develop cultivars with improved resistance to a resistance breaking strain of cotton leaf curl disease (CLCuD; transmitted by the whitefly Bemisia tabaci Genn.) called the Burewala strain (Briddon, 2003). The original strain of CLCuD is caused by one (or more) of seven begomoviruses and a distinct DNA satellite (Briddon et al., 2001; Briddon, 2003). The resistance breaking strain of CLCuD (Burewala strain) has yet to be fully characterized but is associated with a recombinant satellite (Amin et al., 2006).
NIBGE-115 was developed by pedigree selection from a cross (made in 1997–1998) of the unreleased genotype LRA-5166 (primary source of resistance to the old strain of CLCuD) and ‘S-12’ (highly susceptible to the old strain of CLCuD). The F2 plant from the cross along with spreader rows of the highly susceptible S-12 (every third row) were sown in the last week of June 1998 at NIBGE cotton field to ensure maximum infection (Rahman et al., 2002). No whitefly control measures were implemented, thus allowing the spread of vector populations throughout the season. F2 plants and succeeding generations were screened using three procedures: field evaluation, whitefly transmission assay, and graft inoculation (Rahman et al., 2002). Viral infection of the plant was determined by visual symptom assessment as well as dot-blot and multiplex polymerase chain reaction (PCR) diagnostic techniques (Rahman et al., 2005). Greenhouse grown F3 progeny of the resistant F2 plants were raised and screened by the visual assessment and multiplex PCR diagnostic tests. Resistant F3 plants were advanced to F4 and again subjected to screening tests in 1999. The procedure was repeated to F7. These lines were given the acronym NIBGE after the institute's name, National Institute of Biotechnology and Genetic Engineering, in 2002.
In the normal cotton growing season of 2002–2003, the recombinant inbred lines resistant to the old strain of CLCuD were grown in the Burewala region (Cotton Research Station, Vehari, Pakistan) to provide maximum inoculum of the Burewala strain of CLCuD. Out of these, NIBGE-115 was found virus free (Rahman et al., 2004; Rezian, 2005). In 2003–2004, NIBGE-115 along with cultivars and genotypes highly susceptible and resistant to the old virus strain of CLCuD were raised in the Burewala region and screened for resistance to Burewala strain, both visually and with a PCR-based diagnostic test (Amin et al., 2006). A standard randomized complete block design with four replications was followed. The screening was continued for two successive normal cotton-growing seasons (2004–2006). Out of the 20 cotton cultivars and genotypes, NIBGE-115 showed field resistance against the Burewala strain of CLCuD.
NIBGE-115 is nectaried, possesses normal-shaped leaves and bracts with pubescent stems and leaves, and is glanded, exhibiting a spreading type plant habit with 0 to 4 monopodial branches. Flowering initiates 40 to 47 d after planting with the pollen being cream colored. Average lint yields of the NIBGE-115 were 7.48% more than CIM-496 (standard) at all locations conducted from 2004 to 2006. Fiber properties of the line (measured with high volume instrument) were fairly acceptable (3% shorter, 5% stronger, and 5% higher micronaire value than that of CIM-496).
The germplasm will be useful for breeding cultivars against the Burewala virus strain of the cotton leaf curl disease. Limited quantity of seed will be distributed on written request to the corresponding author. The receiving agency or entrepreneur will be asked to make appropriate recognition of the source of germplasm if it contributes in developing hybrids, new cultivars, or breeding lines.
Acknowledgments
The funds for the present studies were provided through an umbrella project to combat Burewala virus strain funded by the Ministry of Food Agriculture & Livestock (MINFAL) Islamabad Pakistan. We are also grateful to Dr A. Mujeeb Kazi, 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 December 10, 2006.
References
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