Development of long-coleoptile, semidwarf durums.
V.S. Rao and S.S. Gandhi.
The effect of the Rht1 gene on plant height
and coleoptile length in durum wheat is more drastic than in bread
wheat because of the dosage effect and poses a problem for emergence
of semidwarf durums. In view of this, a program was initiated
to develop long-coleoptile, semidwarf durums using the Italian
line `Castelporziano' (Rht14) and crossing
it with a tall variety Bijaga Yellow and an Rht1 semidwarf
variety HD 4502. From the F2 generation on, selections were made
for plant height and coleoptile length. Data for selected F7 lines
are given in Table 1.
In the crosses with the tall variety, semidwarf lines with a coleoptile length equal to that of the tall variety were recovered. In the presence of Rht1, although many progenies had a long coleoptile and a height comparable to that of HD 4502, none of the lines was GA insensitive. All the GA-insensitive lines had a short coleoptile. Lines 258, 267, and 270 were intermediate in GA-sensitivity and semidwarf. Rht1 is possibly epistatic to Rht14. These lines are being intercrossed further with superior semidwarf durums.
Table 1. Plant height and coleoptile length of selected progenies of the crosses with Castelporziano
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Cross
`Bijaga Yellow x Castelporziano' `HD 4502 x Castelporziano'
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Coleoptile
Plant length (mm) Plant
Coleoptile height ____________________ height
Line length (mm) (cm) Line no GA with GA (cm)
___________________________________________________________________________________
R 156 97.8 94.0 R 245 58.5 82.0 82.0
R 157 94.4 92.0 R 246 59.9 83.6 86.0
R 164 98.6 94.0 R 247 60.0 80.8 81.0
R 168 91.4 93.0 R 250 61.8 82 7 94.0
R 178 91.5 94.0 R 252 62.0 81.2 94.0
R 185 92.8 88.0 R 258 80.8 95.7 92.0
R 186 81.0 83.0 R 259 71.2 87.6 91.0
R 187 89.3 88.0 R 260 71.2 87.6 91.0
R 188 93.8 85.0 R 267 61.9 76.3 93.0
R 189 96.5 93.0 R 269 73.4 92.4 79.0
R 193 91.8 78.0 R 270 62.3 75.1 76.0
R 194 97.1 91.0 R 276 59.4 101.0 92.0
R 207 98.5 86.0 HD 4502 46.7 48.3 81.0
R 217 99.4 93.0
R 220 82.4 88.0
B.Y. 94.3 120.0
HD 4502 49.6 81.0
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NATIONAL CHEMICAL LABORATORY
Pune - 411 007 and Agharkar Research Institute, Pune -
411 004, India.
P.K. Ranjekar, V.S. Gupta, V.S. Prakasa Rao, S.A. Tamhankar, S.V. Naik, and S. Pujar.
A collaborative project on application of molecular biology techniques for durum wheat was initiated in 1994, between the National Chemical Laboratory and Agharkar Research Institute in Pune, with the objectives to
a) develop a genomic library in durum wheat,
b) study variability among the durum wheats and other tetraploid Triticum species by RFLP and RAPD techniques,
c) develop DNA fingerprints of Indian durum wheats, and
d) identify molecular markers for important economic
traits.
Construction of a durum wheat genomic library.
Two partial genomic libraries in plasmid vector pUC18
were constructed using PstI and Sau3AI digests of
the durum wheat cultivar MACS 9. More than 500 recombinant clones
were obtained from both the libraries. The insert sizes of the
clones from PstI ranged from 400 bp to 5 kb, whereas those
from Sau3AI ranged from 300 bp to 1 kb. Colony filters
from these libraries were screened for low-copy and repetitive
clones, and some of these were tried as RFLP probes on survey
filters prepared from digests of three representative DNAs from
wild tetraploid wheats. However, very few clones gave a polymorphic
pattern.
Characterization of a putative repeat clone.
One clone, designated 1A1, which showed a polymorphic
pattern on survey filters of wild tetraploids also showed good
hybridization with (GAA)6 and (CAC)5. Further characterization
of this clone showed that it has a small insert of 251 bp. Clone
1A1 showed organized bands in T. dicoccoides, but not in
T. timopheevii or T. carthlicum. Sequencing of this
clone revealed that it contained a few isolated GAA, CAC, and
AAAT repeats. Short stretches of TAAGT, AAAG, and GGA repeats
also were present. Further work is in progress.
Identification of a HaeIII repeat family.
During digests of durum wheat DNA, HaeIII
digests showed a number of bands ranging from 0.55 kbp to ~ 3.5
kbp. Among these, two bands of 0.55 kbp and ~ 1.8 kbp were the
most prominent. These bands were eluted and hybridized to a blot
of HaeIII-digested DNA from a few durum wheat cultivars.
The results suggested that these elements belong to two different
members of a HaeIII repeat family. Cloning of these elements
to facilitate further characterization is in progress.
Identification of PCR markers for leaf rust resistance gene Lr28.
Leaf rust is an important disease in all parts of
India. Of the several Lr genes reported, Lr28 is
one of the most effective genes in India. This gene, located on
chromosome 4AL, was transferred from T. speltoides (syn.
Ae. speltoides) and is not associated with any deleterious
characters. Pyramiding of this gene with other genes will help
in developing durable resistance in Indian wheat varieties. In
the present study, random primers (Operon Technologies, USA) were
used to screen NILs for Lr28. Out of the several primers
so far tested, those from series OPK and OPJ produced polymorphic
bands. Polymorphic fragments were excised after separation on
an agarose gel. The polymorphic RAPD product will be tested on
southern blot with NILs, resistant and susceptible F2 bulks, and
recurrent and nonrecurrent parents. We propose to clone these
into a PCR cloning vector and sequence. Based on the sequence
information, STS primers will be designed.
Characterization and use of quality traits in wheat aided by molecular markers.
The Agharkar Research Institute, together with the
National Cemical Laboratory, are participating in a network project
on the `characterization and use of quality traits in wheat
aided by molecular markers' funded by the Department of
Biotechnology, Government of India. The other cooperating centers
are: Directorate of Wheat Research, Karnal; Punjab Agricultural
University, Ludhiana; G.B. Pant Agricultural University, Pantnagar;
and CCS University, Meerut. The National Chemical Laboratory at
Pune will provide a training facility for staff of DWR, Karnal
and ARI, Pune, in addition to identifying molecular markers for
the selected quality traits. The DWR, Karnal; PAU, Ludhiana; and
ARI, Pune will develop mapping populations for the quality parameters
in both bread and durum wheats. G.B. Pant University, Pantnagar,
and Meerut University will concentrate on Triticin and microsatellites,
respectively.
BHARATHIAR UNIVERSITY
Cytogenetic Laboratory, Department of Botany, Coimbatore -
641 046, India.
Studies confirming of transfer of rust-resistance genes into Indian wheats.
P. Viswanathan, R. Asir, S. Dhamodaran, and V.R.K. Reddy.
Eight specific stripe rust-resistance genes (Yr9,
Yr11, Yr12, Yr13, Yr14, Yr15,
Yr16, and Yr17) from eight hexaploid wheat stocks
of spring and winter habit, two leaf rust-resistance genes (Lr19
and Lr26), and four stem rust-resistance genes
(Sr27, Sr31, Sr25, and Sr26) from
two rye and two Agropyron addition lines were transferred
successfully into four popular Unnath (improved for leaf and stem
rust) and original high-yielding Indian wheat varieties, HD 2285,
HW 741, Kalyansona, and Sonalika.
The successful transfer of the above rust-resistance
genes into Indian wheats was confirmed through morphological,
genetical, and biochemical studies. For the morphological markers,
spike characteristics of the donor parents, such as awned vs awnless
and club vs lax head, were utilized. The spikes of the F1 hybrids
from crosses between Indian wheat varieties and stocks carrying
stripe rust- resistance genes (Yr11, Yr12, Yr13,
Yr14, and Yr16) were predominantly either awnless
or awnletted, and the F1 hybrid plants exhihited complete resistance
to yellow rust, indicating that along with the lack of awns or
awnlets, the yellow rust-resistance genes also were transferred.
Similarly, the club spike of Cap-5BL-7BL with the Yr16
gene and the lax spike of `Moulin' (Yr14) were
transfered from the donor parent to the Indian wheats along with
respective resistance genes.
Inheritance studies of the rust-resistance genes
in the newly constituted lines showed that, except for the two
stripe rust- resistance genes Yr15 and Yr17, all
the other 12 leaf, stem, and, stripe rust resistance genes were
dominant. All the F1 hybrid plants between the constituted lines
and universal susceptible cultivar Agra local were found to be
resistant to the respective rusts. The F2 plants had a 3:1 ratio
of resistant to susceptible plants at the seedling and the adult
plant stages. A ratio of 1:1 in the BC1 generation indicates that
resistance in each of the constituted lines was from the successful
transfer of a single dominant gene.
Biochemical studies revealed significant increases
in nuclear DNA content, total free phenols, tannins, ribonuclease
I, combined ribonuclease II, nuclease I, and peroxidase activity
in the newly constituted rust-resistant lines over the Indian
wheat parents. These were manifestations of the rust resistance
genes, thereby confirming their successful transfer.
Publications.
Reddy VRK, Asir R, and Viswanathan P. 1995. Development
of rust resistance in wheat variety HW 741. Cereal Res Commum
23(1-2):147-152.
Reddy VRK, Asir R, Dhamodaran S, Viswanathan P, and
Arumugam S. 1995. Performance of newly constituted wheat lines
carrying stripe rust resistance genes. Ann Wheat Newslet 41:106-108.
Reddy VRK, Aloka S, Dhamodaran S, Asir R, Viswanathan
P, and Arumugam S. 1995. Variation in biochemistry and nuclear
DNA content in susceptible and constituted rust-resistant lines
of Indian wheat. Ann Wheat Newslet 41:109.