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CHAPTER 6. GENETICS OF RESISTANCE TO INSECTS IN CROP PLANTS

CHAPTER 6. GENETICS OF RESISTANCE TO INSECTS IN CROP PLANTS

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224

VIII.



IX.



X.



XI.

XII.

XIII.



GURDEV S. KHUSH AND D. S. BRAR

Fruits

A. Rosy Leaf Curling Aphid of Apple (Dysaphis deuecta )

B. Rosy Apple Aphid (Dysaphis plantaginea )

C. Wooly Apple Aphid (Eriosoma lanigerum)

D. Rubus Aphid (Amphorophora rubi)

E. Black Currant Curling Midge (Dasyneura tetensi)

F. Black Currant Gall Mite (Cecidophyopsis ribis)

G. Red Scale Pest of Citrus (Aonidieila aurantii)

Vegetables

A. Melon Aphid (Aphis gossypii)

B. Red Pumpkin Beetle (Aulacophorafoveicollis)

C. Striped Cucumber Beetle (Acalymma uitfatum)

D. Two-Spotted Cucumber Spider Mite ( Tetranychus urticae)

E. Squash Bug (Anasa tristis)

F. Pumpkin Fruitfly (Dacus cucurbitae )

G. Lettuce Root Aphid (Pemphigus bursarius)

H. Lettuce Leaf Aphid (Nasonouia ribisnigri)

I. Arthropod Pests of Tomato

Forages and Legumes

A. Mexican Bean Beetle (Epiiachna uarivestis)

B. Bean Weevil (Callosobruchus chinensis )

C. Cowpea Seed Beetle ( Callosobruchus maculatus )

D. Cowpea Aphid (Aphis cracciuora )

E . Spotted Alfalfa Aphid ( Therioaphis maculara )

F. Pea Aphid of Alfalfa ( Acyrthosiphon pisum )

G . Sweet Clover Aphid (Therioaphis riehrni)

Tagging Insect Tolerance Genes with Molecular Markers

Genetic Engineering and Insect Tolerance

Conclusions

References



I. INTRODUCTION

Humans and insects have always competed for food and fiber, so they

have been constantly at war with each other. Insects cause millions of

dollars’ worth of losses annually to food crops and other plants all over the

world. Scientists have devised various control measures to minimize these

losses. The most practical and economical control measure is varietal

resistance to insects. Painter (1951)and others demonstrated that clear-cut

cases of host resistance existed in crop species of importance to agriculture.

During the last 50 years, screening techniques for evaluating germplasm

for insect resistance have been developed and sources of resistance to

major insects in several important crop species have been identified. Resistant entries from germplasm collections have served as resistance



GENETICS OF RESISTANCE TO INSECTS



225



sources in crop improvement programs. Resistant varieties of major crops

are now grown on millions of hectares annually. The most dramatic examples of the success of host resistance programs are the control of the

hessian fly through breeding of hessian fly-resistant wheats in the United

States and the control of brown planthopper (BPH) of rice in Asia through

resistant varieties.

Information on the inheritance of resistance is useful to the breeder in

deciding on the breeding methodology and the breeding strategies to be

adopted. Diverse genes for resistance are needed to cope with the development of new biotypes, to develop multiline varieties, and to attain regional

deployment of genes. Entomologists and breeders have investigated the

inheritance of resistance to insects of major crops to identify diverse genes

for resistance. The usefulness of genetic analysis for insect resistance is

illustrated by the success of the host resistance program for the BPH in

rice.

Sources of resistance to the BPH were identified in 1967 (Pathak et al.,

1969). The program on breeding and genetics was started in 1968. Two

genes for resistance, Bph-Z and bph-2, were identified in 1970 (Athwal et

al., 1971). The first resistant variety with Bph-I, IR26, was released in 1973

(Khush, 1977a).The variety was widely accepted in the Philippines, Indonesia, and Vietnam but became susceptible in 1976-1977 because of the

development of biotype 2 of the BPH. By that time, varieties IR36 and

IR38 with the bph-2 gene had been developed and released (Khush,

1977b). IR36 soon replaced IR26 and became the dominant rice variety. Its

resistance to BPH has held up for 14 years in most areas and it is still

widely grown.

Meanwhile, 29 additional resistant varieties were analyzed genetically

and two new genes, Bph-3 and bph-4, were identified (Lakshminarayana

and Khush, 1977). These genes were incorporated into the improved

germplasm. In 1982, when a biotype capable of damaging IR36 appeared in

small pockets in the Philippines and in Indonesia, IR56 and IR60 with the

Bph-3 gene for resistance were released [International Rice Research

Institute (IRRI), 19831.1R66with bph-4 for resistance was released in 1987

and IR68, IR70, IR72, and IR74, all with Bph-3, were released in 1988.

These varieties are now widely grown in tropical and subtropical ricegrowing countries. If we had neglected gene identification work, the

planned incorporation of diverse genes for resistance to BPH would have

been impossible and we would not have been able to keep ahead of this

shifting enemy of the rice crop. The value of the genetic analysis of

resistance cannot therefore be overemphasized. In this article we review

the status of knowledge about genetics of resistance to insects in crop

plants.



226



GURDEV S. KHUSH AND D. S. BRAR



II. RICE

Rice is the host of more than 100 insect species, the most important of

which are the BPH, whitebacked planthopper (WBPH), green leafhopper

(GLH), gall midge, and stem borers. Inheritance of resistance to these five

insects has been investigated.



LUGENS)

A. BROWNPLANTHOPPER ( NILAPARVATA



The BPH is the most serious of the rice pests. It causes considerable

damage by direct feeding. It also transmits grassy stunt and ragged stunt

virus diseases. High levels of resistance to this insect have been found in

rice cultivars. More than a hundred resistant cultivars have been genetically analyzed. Athwal et al. (1971) showed that the resistance in.Mudgo,

C022, and MTU15 was governed by the same dominant gene, which they

designated Bph-J . A single recessive gene, designated bph-2, conveyed

resistance in ASD7. Bph-1 and bph-2 are closely linked and no recombination between them has been observed. Chen and Chang (1971) also reported that a single dominant gene controls resistance in Mudgo. Athwal

and Pathak (1972) reported that MGL2 possesses Bph-1, and Ptb 18 possesses bph-2. Martinez and Khush (1974) investigated the inheritance of

resistance in two breeding lines of rice that originated from the crosses of

susceptible parents. One of the lines, IR747B2-6, possessed Bph-J for

resistance; the other, IRll54-243, possessed bph-2. TKM6, the resistant

parent of IR747B2-6, is susceptible, but a small number of the F2 progenies

from its crosses with other susceptible varieties such as TN1, IR8, or IR24

are resistant. It was hypothesized that TKM6 is homozygous for Bph-I as

well as for a dominant inhibitory gene i-Bph-I, which inhibits Bph-I.

In a genetic study of 28 varieties, Lakshminarayana and Khush (1977)

found 9 varieties with Bph-I, 16 with bph-2, and one variety with both

genes. Two varieties were found to have new genes. A single dominant

gene, which conveys resistance in Rathu Heenati was designated Bph-3.

This gene segregates independently of Bph-J. A single recessive gene,

which controls resistance in Babawee, was designated bph-4. This gene

segregates independently of bph-2. Genetic analysis of 20 resistant varieties by Sidhu and Khush (1978) revealed that 7 varieties had Bph-3, 10 had

bph-4. and resistance in the remaining 3 was governed by 2 genes. Sidhu

and Khush (1979) also reported that Bph-3 and bph-4 were closely linked.

Genes bph-4 and Glh-3 are also linked with a map distance of 34 units. The

bph-4 gene appeared to be linked with sd-J (recessive gene for semidwarf



GENETICS OF RESISTANCE TO INSECTS



227



stature). However, bph-4 and Xa-4 (gene for bacterial blight resistance)

are inherited independently. Ikeda and Kaneda (1981) also found that

bph-2 as well as Bph-1 segregate independently of both Bph-3 and bph-4;

whereas Bph-3 and bph-4 as well as Bph-l and bph-2 are closely linked.

Ikeda and Kaneda (1982) reported that Bph-l segregated independently of

the gene for dwarf virus resistance in Kanto PL-3 and also of the gene

governing stripe disease resistance in Kanto PL-2.

On the basis of trisomic analysis, Ikeda and Kaneda (1981) identified the

loci of Bph-3 and bph-4 on chromosome 10. In another study, Ikeda and

Kaneda (1983) located Bph-l on chromosome 4. No linkage was detected

between Bph-l on one hand and Ig and d-1 I markers of chromosome 4 on

the other. However, bph-2 was found linked with d-2, with a 39.4% recombination value. Khush et al. (1985) carried out a genetic analysis of

ARC10550. This cultivar is resistant to BPH populations in Bangladesh

and India (biotype 4) but is susceptible to biotypes 1 , 2 , and 3. It was found

to have a single recessive gene, bph-5, for resistance, which segregates

independently of Bph-1, bph-2, Bph-3, and bph-4.

Seventeen additional rice cultivars, resistant to biotype 4 but susceptible

to biotypes 1, 2, and 3, were genetically analyzed by Kabir and Khush

(1988). Seven were found to have a single dominant gene for resistance.

The dominant gene(s) of these cultivars segregated independently of

bph-5. The dominant gene of cultivar Swarnalata was designated Bphd. In

the remaining 10 cultivars, resistance is conferred by single recessive

genes. The recessive genes for resistance of eight cultivars were found to

be allelic to bph-5. However, the recessive genes of two cultivars are

nonallelic to bph-5. The recessive gene of T12 was designated bph-7.

Two Thai varieties, Col. 5 Thailand and Col. 1 I Thailand, and Chin Saba

from Burma were reported to have single recessive genes for resistance,

which are allelic to each other but are nonallelic to bph-2 and bph-4.

Similarly, cultivars Kaharmana, Balamawee, and Pokkali were found to

have single dominant genes that are allelic to each other but are different

from Bph-1 and Bph-3 (Ikeda, 1985). Since these cultivars are resistant to

biotypes 1, 2, and 3, as compared to cultivars with bph-5, Bph-6, and

bph-7, which are susceptible, Nemoto et a / . (1989) concluded that the

recessive gene of Col. 5 Thailand, Col. I 1 Thailand, and Chin Saba must

also be different from bph-5 and bph-7. They designated this gene as bph-8.

Similarly, they designated the dominant gene of Kaharmana, Balamawee,

and Pokkali as Bph-9.

Four BPH biotypes are known. Biotypes 1 and 2 are widely distributed

in Southeast Asia, biotype 3 is a laboratory biotype produced in the

Philippines, and biotype 4 occurs in the Indian subcontinent. Bph-I confers resistance to biotypes 1 and 3; bph-2 conveys resistance to biotypes 1



228



GURDEV S. KHUSH AND D. S. BRAR



and 2; Bph-3 and bph-4 confer resistance to all known biotypes; bph-5,

B p h d , and bph-7 convey resistance to biotype 4 only; and bph-8 and Bph-9

provide resistance to biotypes 1,2, and 3. Their reaction to biotype 4 is not

known (Table I).



B. WHITEBACKED PLANTHOPPER ( SOGATELLA FURCIFERA )

More than 300 cultivars resistant to the WBPH have been identified and

about 80 of them have been analyzed genetically. Five genes for resistance, one recessive and the others dominant, have been identified.

A single dominant gene, designated Wbph-1, was found to convey resistance to the WBPH in the variety N22 (Sidhu et al., 1979). Resistance in

ARC10239 is governed by a single dominant gene designated Wbph-2

(Angeles er al., 1981). This gene segregates independently of Wbph-1. Nair

et al. (1982) investigated 21 additional varieties: 19 had Wbph-1 and two

had Wbph-1 and an additional recessive gene. The resistance of 2 of the 14

varieties analyzed by Hernandez and Khush (1981) was governed by

Wbph-2. Eleven varieties each had a single dominant gene that segregated

independently of Wbph-1 and Wbph-2. The dominant gene of one such

variety, ADR52, was designated Wbph-3. Only one variety, Podiwi A8,

had a recessive gene, which was designated wbph-4. Saini et al. (1982)



Table I

Interrelationshipsbetween Biotypes of Brown Planthopper and Genes for

Resistance in Rice

Reaction to biotypes"

Variety



Gene



I



2



3



Mudgo

ASD 7

Rathu Heenati

Babawee

ARC 10550

Swarnalata

T 12

Chin Saba

Balamawee

TN 1



Bph-1

bph-2

Bph-3

bph-4

bph-5

Bphd



R

R

R

R

S

S

S

R

R

S



S

R

R

R

S

S

S

R

R

S



R

S

R

R

S

S

S

R

R

S



' R, resistant;



bph-7



bph-8

Bph-9

None



S, susceptible; -, not known.



4



S



GENETICS OF RESISTANCE TO INSECTS



229



analyzed 13 additional varieties. Resistance was governed by Wbph-1 in

four varieties, Wbph-2 in six, Wbph-1 and Wbph-2 in two, and a single

dominant gene in Hornamawee segregated independently of Wbph-1 and

Wbph-2. Wu and Khush (1985) investigated the inheritance of resistance in

15 varieties. They found that resistance in nine was controlled by Wbph-1,

and resistance in four was conferred by two genes. The remaining two

varieties had single dominant genes for resistance, which segregated independently of Wbph-I, Wbph-2, and Wbph-3. The dominant gene of

N'Diang Marie was designated Wbph-5. Jayaraj and Murty (1983) studied

the inheritance of resistance in nine varieties. They found that it was

controlled by a single dominant gene in three varieties and by a recessive

gene in six other varieties.

Inheritance of resistance in 10 cultivars was investigated by Singh ef al.

(1990). Eight cultivars, i.e., ARC5838, ARC6579, ARC6624, ARC10464,

ARCl 1321, ARCl 1320, Balamawee, and IR2425-90-4-3, were found to

have single recessive genes for resistance. The recessive genes of IR241590-4-3, ARC5838, and ARCl 1324 were found to be allelic to each other.

Resistance in Ptbl9 and IET6288 was found to be under dominant gene

control.

( NEPHOTETTIX

VIRESCENS)

C. GREENLEAFHOPPER



The inheritance of resistance to the GLH was first investigated by

Athwal et al. (1971) in varieties Pankhari 203, ASD7, and IRE. They found

that resistance in each variety was controlled by one dominant gene. The

dominant gene in Pankhari 203'was designated Glh-1; that in ASD7, Glh-2;

and that in IR8, Glh-3. The three genes segregated independently of each

other. Two more genes were identified by Siwi and Khush (1977): one

recessive, designated glh-4; the other dominant, designated Gth-5. Two

dominant genes Glh-6 and Glh-7, were identified by Rezaul Karim and

Pathak (1982).

Avesi and Khush (1984) studied the inheritance of resistance in 18

varieties. Two had Glh-1, three had Glh-2, two had Glh-3, one glh-4, and

three had two genes. The allelic relationships of the resistance genes of

seven varieties are still not known. Ruangsook and Khush (1987) analyzed

15 rice cultivars genetically. The resistance was governed by two dominant genes in Katia Baudger 13-20, Laki 659, Lasane, Asmaita, and Choron Bawla, but by single dominant genes in the remaining ten cultivars.

Allele tests with the known genes revealed one of the two dominant genes

of Choron Bawla is allelic to Glh-2. The single dominant gene in Chiknal

and one of the two dominant genes of Laki 659 are allelic to Glh-3. The



230



GURDEV S. KHUSH AND D. S . BRAR



second of the two dominant genes of Katia Badger 13-20, Laki 659, and

Lasane are allelic to Glh-5. The two dominant genes of Asmaita and the

single dominant gene of Hashikalmi, Ghaiya, ARC10313, and Garia are

nonallelic to and independent of Glh-1, Glh-2, Glh-3, glh-4, and Glh-5.

Tomar and Tomar (1987) studied the inheritance of resistance in 11

cultivars. Resistance in eight cultivars was found to be governed by single

dominant genes, but single recessive genes conferred resistance in the

three other cultivars. Inheritance of resistance in 12 cultivars was investigated by Ghani and Khush (1988): single dominant genes confer resistance

in six cultivars, two independent dominant genes govern resistance in four

cultivars, and single recessive genes provide resistance in two other cultivars. The single recessive gene in ARC7012 is allelic to glh-4 but that in

DV85 is nonallelic to and independent of glh-4. The new recessive gene

was designated glh-8.



D. ZIGZAG LEAFHOPPER

( RECILIADORSALIS)

The genetics of resistance to the zigzag leafhopper (ZLH), WBPH,

BPH, and GLH in cultivars Rathu Heenati, Ptb21, and Ptb33 was investigated by Angeles et al. (1986). Single dominant genes that segregate independently of each other and conveyed resistance to ZLH were designated

Zlh-1 (Rathu Heenati), Zlh-2 (Ptb21), and Zlh-3 (Ptb33). Tests for independence of the various genes for resistance to leaf and planthoppers revealed

that Zlh-1, Zlh-2, and Zlh-3 are independent of Wbph-3. Zlh-2 and Zlh-3

also segregated independently of bph-2 and Bph-3.



E. GALLMIDGE( ORSEOLIA

ORYZAE)

Resistance to gall midge has been postulated to be due to two genes in

W1263 and four in Ptbl8 (Shastry et al., 1972). Sastry and Prakasa Rao

(1973) inferred the presence of three recessive genes for resistance in

W1263 and W12708. Satyanarayanaiah and Reddi (1972), however,

showed convincingly that resistance in W1263 was governed by a single

dominant gene. Resistance in CR57-MR-1523 was governed by two to

three dominant complementary genes (Sastry et al., 1984). Chaudhary et

al. (1986) studied inheritance of resistance in five cultivars. All of them

were found to have a single dominant gene for resistance. Allele tests

revealed that Usha, Samridhi, and BD6-1 have the same gene for resistance, which was designated Gm-I. Surekha and IET6285 have the same

gene for resistance, which is nonallelic to and independent of Gm-1; this



GENETICS OF RESISTANCE TO INSECTS



23 1



gene was designated Gm-2. Kalode et al. (1976) found differential reactions of W1263 and JBS446 at two locations, indicating biotypic variation

in gall midge.



F. STRIPED

STEMBORER( CHILOSLJPPRESSALIS)

Reports on the inheritance of resistance to stem borer are fragmentary.

From an analysis of the F2 population and F3 lines from the cross of Giza 14

and Sydney A , Koshiary et al. (1957) showed that the field resistance of

Giza 14 to stem borer was under polygenic control. On the other hand, the

field resistance of TKM6 to stem borer, as measured by the incidence of

whiteheads, was reported to be governed by a single recessive gene (Dutt

et al., 1980). Athwal and Pathak (1972) studied the inheritance of resistance in the greenhouse. Each of the 113 F2plants from the cross between

Rexoro (susceptible) and TKM6 (resistant) was infested with 10 larvae of

the striped borer. Plants on which the survival rate and body weight of the

larvae were normal were considered susceptible. Resistance was dominant in the FI. Larval weight was used as an index of resistance to stem

borers. From the frequency distribution of mean body weights of surviving

larvae on the F2plants, it was concluded that the particular component of

resistance to stem borer may be simply inherited.



Ill. WHEAT

A number of insects attack wheat; however, the genetics of resistance

has been studied mainly for the hessian fly, greenbug, cereal leaf beetle,

and wheat stem sawfly.



A. HESSIANFLY( M A Y E T ~ O LDAE S T R U C T O R )

Among the insect pests, the hessian fly provides the classical example of

the gene-for-gene relationship between resistance in the host (wheat) and

virulence in the insect. The interaction between wheat and hessian fly

genotypes is highly specific. Eleven biotypes (GP, A, B , C, D, E, J , L, M,

N , and 0)of the hessian fly have been reported (Cartwright el al., 1959;

Gallun and Reitz, 1971; Gallun, 1977; Sosa, 1981; Obanni et al., 1989b).

Nineteen genes (I8 dominant and 1 recessive) for resistance to this insect

have been identified (Gallun. 1984; Roberts and Gallun, 1984; Hatchett et



232



GURDEV S. KHUSH AND D. S. BRAR



al., 1981; Stebbins et al., 1983; Maas et al., 1987, 1989; Patterson et al.,

1988; Obanni et al., 1988,1989a,b). These genes have been designated H-I

and H-2 (Cartwright and Weibe, 1936; Noble and Suneson, 1943), H-3

(Caldwell et al., 1946; Abdel-Malek et al., 1966), h-4 (Suneson and Noble,

1950),H-5 (Shands and Cartwright, 1953),H-6 (Allan et al., 1959),H-7and

H-8 (Patterson and Gallun, 1973), H-9 (Stebbins et al., 1980), H-I0 (Stebbins et al., 1982), H-11 (Stebbins et al., 1983), H-12 (Oellermann et al.,

1983), H-13 (Hatchett et al., 1981; Gill et al., 1987),H-14 and H-15 (Maas

et al., 1989),H-16 (Patterson et al., 1988),H-17 (Obanni er al., 1988),H-18

(Maas et al., 1987; Obanni et al., 1988), and H-19 (Obanni er al., 1989b).

Among these, eight genes ( H - I , H-2, H-3, h-4, H-5, H-7, H-8, H - 1 2 ) have

been identified in common wheat. The other 11 genes ( H - 6 , H-9, H-10,

H-11, H-14, H-15, ff-16,H-17, ff-18,H - 1 9 ) have been derived from durum

wheat and H-13 from Aegilops squarrosa ( Triricum tauschii).

New genes for resistance to the hessian fly are continuously sought and

incorporated into commercial wheat cultivars. The reaction of some of the

wheat strains to five biotypes (A, B , C, D, L) of the hessian fly is shown in

Table 11. Certain genotypes such as Arthur 71 and Abe, which have H-3

and H-5 genes, are resistant to the four biotypes. PI94587 ( T. turgidum ) is

also resistant to biotypes A, B , C, and D. Common wheats with resistance

derived from PI94587, such as Knox 62 and Lathrop, inherited only one

dominant gene for resistance to biotypes A and B. Ribeiro, a source of H-5

gene, is resistant to biotypes A, B, C, and D. Breeding lines 916,920, and

941 derived from PI94587 have H-11, which is closely linked with H-5.

H-11 confers a higher level of resistance than H-5 at higher temperature

(27°C).

Carlson et al. (1978) reported resistance to biotype D in Elva and

C117714 ( T . Turgidum L.). One of the derived common wheat lines had a

single dominant gene and the two other lines contained two linked dominant genes for resistance to biotype D. Hatchett er al. (1981)identified new

sources of resistance to biotype D in five accessions of T . tauschii.

Stebbins et al. (1983) studied the inheritance of resistance of PI94587 T .

turgidum wheat (durum group) to biotypes B and D. Results indicated that

its resistance to biotype D was due to two independent dominant genes.

The test cross progenies susceptible to biotype D were tested for resistance to biotype B. Besides H-6, two or three genes segregated in the test

cross progenies. Thus, it appears that PI94587 may have four or five

independent dominant genes for resistance. Three selections from the

crosses of PI94587-916,920, and 941 were found to have a common dominant gene. This gene is linked with H-5 with 4.40 -+ 1.78 map units and was

designated H-11 .

Oellermann et al. (1983) studied the inheritance of resistance in Luso to



233



GENETICS OF RESISTANCE TO INSECTS

Table I1



Interrelationships between Biotypes of the Hessian Fly and Genes for Resistance in Wheat

Reaction to biotypes"



Cultivar or

breeding line



Gene(s) for

resistance



GP



A



B



C



D



L



Big club 60

Arthur

Arkan

Arthur 7 I

Abe

Knox 62

Lathrop

Caldwell

Seneca

PI94587

822-34

916,920, 941

Kay

Elva

Stella

817-1

Ella

Luso

KS81-H 1640-HF

ELS6404-160-5

PI94587

PI428435

Brule

PI422297

Jori

Blueboy



H - I , H-2

H-3

H-3

H-3, H-5

H-3, H-5

H-6

H-6

H-6

H-7, H-8

H-6, H-11

H-9

H-11

H-1 I

H-9, H-I0

H-9, H - I 0

H-9, H-I0

H-9

H-12

H-13

H-14, H-IS

H-16

H-17

H-18

H-19

H-20

None



R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

S



-



S



-



S

S

S

R

R

S

S

S

S

R

R

R

R

R

R

R

R

R

R

R



S

S

S

S

S

S

S

S

S

R

S

S

R

R

R/S

R

R

R

R

RIS

R

R

S



~~



R



R



R

R

R

R

S

R



-



R

R

R

R

R

S



R



R

R



-



-



R

R

R

R



R

R

R

R

R

R

R



-



R



-



-



-



R



-



R



R

R

R



S

S

S

S

R

R

R

R

R

R

MR

R

R

R

-



-



-



-



S



S



S



R

R

R

R

S



~



R, resistant; MR. moderately resistant; S, susceptible; RIS, mixture of resistant/susceptible plants;

-, not known.



determine the number of genes for resistance to biotypes B or D. The

partial resistance of Luso to biotypes B and D was found to be due to a

single dominant gene. The results indicate that this gene was distinct from,

and probably independent of, all the known genes that confer resistance to

biotype D ( H - 5 , H-9, H-10, and H-11 ). The new gene designated H-12 is

most likely located in the A or B genome of wheat.

A comparison of resistance levels conferred by H-12 and other genes

indicates that H-12 does not confer as high a level of resistance as H-5,

H-6, H-9, and H-10. Lines with H-6 and H-11 do not have resistance to

biotype L but PI94587 has. A single partially dominant gene was trans-



234



GURDEV S. KHUSH AND D. S. BRAR



ferred from PI94587 to susceptible durum D6647. Reaction to biotypes B,

C, D, and L indicated it was not H-10, H-12, or the Marquillo gene. The

newly isolated gene was designated as H-16 (Patterson et al., 1988). Maas

etal. (1989)found that ELS6404-160-5 is resistant to biotypes B, C, D, and

L and resistance to biotype D is stable at three temperatures. The genes

from ELS6404-160-5 were designated H-14 and H-15. Obanni et al. (1989b)

analyzed a number of genes controlling the resistance of PI422297 to

biotype D. The two genes governing resistance were independent of H-5,

H-9, H-10, H-14, H-15, and H-17. One of the two genes in PI422297 is

different from all known genes for resistance and was designated H-19.

Recently, Amri et a f . (1990) tested 217 Tunisian wheats for resistance to

GP biotypes and to biotypes D and L, and 25 Moroccan wheats were

evaluated for resistance to biotypes D and L. Among the Tunisian wheats,

88% were considered potential sources of resistance to biotype GP, 86% to

biotype D, and 59% to biotype L, whereas 60% of the Moroccan wheats

were resistant to one or both biotypes. Four resistant Moroccan durum

wheats-Qued Zenati, BD1026 (land races), and Jori and Hajj Mouline

(cu1tivars)-were intercrossed as well as crossed with either one or two

susceptible checks, Zerameks and ACSAD65. The Fz and F3 populations

showed that three genes in the Morocco durum wheats appear to be

different from the previously designated H-1 through H-13, based on

reactions to biotypes D and L and to populations of hessian fly in Morocco.

The presence of three independent genes in a sample of four durum wheats

indicates that North African germplasm is a rich source of new genes for

resistance to hessian fly.

Hatchett et al. (1981) crossed hessian fly-resistant synthetic amphiploids

of diploid and tetraploid wheats with susceptible wheat cultivars Amigo

and Eagle, and found that resistance to biotype D derived from T. tauschii

was controlled by a single dominant gene. This T. tauschii gene is different

from H - I , H-2, H-7, or H-8 and it was designated as H-13 (Gill et al., 1987).

Obanni et al. (1989a) determined the reaction of 11 wheat lines to biotype

D at 19,23, and 26°C. The lines Portugal 2536, Portugal 2852, and Ribeiro

are stable at high temperatures and are highly resistant to biotypes B, D,

and L. Further, the genetic background influenced the expression of certain genes for resistance. The durum line IN8464 showed resistance to H-5

in 100% of the seedlings but was expressed in lower proportions of Abe.

Stebbins et al. (1980, 1982, 1983) and Oellermann et a f . (1983) have

summarized the interrelationships among wheat genes for resistance to the

hessian fly. The genes H-11 and H-5 are linked with a 4.4% recombination

value. H-9 and H-6 are linked with a 2.0% recombination value. The

resistance gene of Luso ( H - 1 2 ) segregates independently of H-5, H-9,

H-10, and H-11. The genes H-3 and H-6 showed a 9.0% linkage value,



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