G.S. Sethi, S.C. Sharma, K.S. Thakur, D.L. Sharma, A. Kumar, A. Sirohi, and S.C. Negi.

Among the cereals grown in Himachal Pradesh, wheat is the most important food grain crop occupying the largest area of about 378,000 ha with a total grain production of 596,000 t. The average productivity of wheat in the state is very low (15 g/ha) compared to the national average (24 g/ha), which is attributable to rainfed cultivation in 83 % of the area; prevalence of diseases, mainly stripe and leaf rusts, loose smut, powdery mildew, and bunts (hill bunt in the higher and karnal bunt in the lower hills); less area under improved cultivars; heavy infestation of weeds; broadcast sowing; and low and imbalanced use of fertilizers. Research efforts have been intensified to develop high-yielding, disease resistant, and widely adaptable wheat cultivars for diverse agroclimatic conditions under different production situations in the state.

Identification of elite wheat strains. Based on multilocational testing of newly developed wheat cultivars for grain yield, adaptability, resistance to stripe and leaf rusts, powdery mildew, and agronomic superiority, 17 new wheat strains were selected and inducted into coordinated trials during 1994-95 under different production conditions. Four wheat strains, HPW 93, HPW 107, HPW 109, and HPW 114, have been retained/promoted because they are in the top nonsignificant group in zonal mean grain yield and resistant to rusts. HPW 93 is in the final year of testing under late-sown, rainfed production conditions.

A newly developed wheat cultivar, HPW 89, has been found most promising, based on multilocational for several years performance with grain yields of 40 g/ha and 26.6 g/ha under timely-sown, irrigated and rainfed conditions, respectively (Table 1). HPW 89 also exhibited a high degree of resistance to stripe and leaf rusts under artificial epiphytotic conditions. In addition, HPW 89 recorded the highest 1,000-grain weight (47.5 g). It is a semidwarf cultivar with a plant height of 103 cm and takes 181 days to mature.

Table 1. Performance of wheat cultivar HPW 89 in the Northern Hill Zone.

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Overall

Cultivar/ Zonal mean grain yield (g/ha) mean Rust reaction*

production _____________________________ yield _________________

condition 1991-92 1992-93 1993-94 (g/ha) Stripe Leaf

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A. Timely-sown, rainfed.

HPW 89 29.8 24.8 25.1 26.6 0 20 MS

HS 240 (check) 29.2 25.9 24.5 26.5 0 40 MS (7.3)

Sonalika (check) - 18.8 l8.5 18.6 60S 80S

(56.7)

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C.D. (0.05) 3.7 1.5 1.6

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B. Timely-sown, irrigated.

HPW 89 39.6 38.8 41.5 40.0

Hs 240 (check) 38.3 41.9 41.9 40.7

Sonalika(check) - 33.7 33.8 33.7

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C.D. (0.05) 4.3 3.1 3.4

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* Under artificial epiphytotic conditions. Figures in parentheses denote average coefficients of

infection.

In the agronomic trials, HPW 89 produced the highest mean grain yield of 48.3 q/ha and was superior to both the checks, under early and late sowing, with the least reduction in yield in late sowing (Table 2).

Table 2: Mean grain yield (g/ha) of HPW 89 for dates of 'sowing x varieties'

(irrigated).

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Time of sowing

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Cultivar Early Normal Late Mean

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HPW 89 51.6 (+11.0) 46.5 46.7 (+ 0.4) 48.3

HS 240 (check) 45.9 (- 0.6) 46.2 40.1 (-13.2) 44.1

HD 2380(check) 51.4 (+ 8.0) 47.6 44.2 (- 7.1) 47.7

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Zonal mean 49.6 46.8 43.7

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HPW 89 is also responsive to fertilizer application and was found superior to the check cultivar, HS 240, at all levels of fertilizer application (Table 3) and, hence, merits consideration in view of its agronomic response.

Table 3. Levels of 'fertilizer x variety' (irrigated).

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F₀ F₁ F₂ F₃

Cultivar (0:0:0) (40:20:20) (80:40:27) (120:60:40) Mean

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EPW 89 16.0 23.8 (+48.8) 32.8 (+37.8) 38.9 (+18.6) 27.9

HS 40 (check) 15.8 21.3 (+34.8) 27.5 (+29.1) 36.4 (+32.4) 25.3

HD 2380 (check) 14.6 25.6 (+75.3) 30.4 (+18.8) 36.7 (+20.7) 26.8

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Zonal mean 15.5 23.6 30.2 37.3

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Figures in parentheses denote the percent increase in yield over the previous dose of fertilizer

(NPK - q/ha).

Screening of wheat genetic stocks for resistance to disease. A total of 2,148 genetic stocks of wheat from the National and International nurseries/sources was evaluated for different plant traits and resistance to stripe and leaf rusts under artificial epiphytotic conditions using pathotypes 11, 12, 12-2, 77, 77A, 77A-1, 77-2, 104, 104B, and 108 of leaf rust and pathotypes 20, 31, K, L, and N of stripe rust. In addition, about 1,500 stocks were evaluated against powdery mildew, and 700 against loose smut.

The numbers of genetic stocks selected as sources with multiple resistance against individual diseases are given below:

A. Free from leaf rust, stripe rust, and powdery mildew.

a. T. aestivum : 116

b. T. durum : 2 (CPAN 6174, CPAN 6205)

c. Triticale : 18

B. Resistant to leaf rust and free from stripe rust and powdery mildew.

a. T. aestivum : 49

b. T. durum : 2 (24-IDSN3, WH 905)

c. Triticale : 3

C. Free from leaf rust and powdery mildew.

T. aestivum : 27

D. Free from loose smut.

a. T. aestivum : 156

b. T. durum : 17

Forty land races of wheat also were evaluated for different plant traits. The selected genetic stocks will be utilized and channeled into our wheat breeding programme.

Hybridization, shuttling, and selection of wheat breeding material. One hundred forty single crosses were made involving proven sources of resistance to stripe and leaf rusts (CPAN 2051, CPAN 2055, CPAN 2063, CPAN 2099, CPAN 3031, CPAN 3067, CPAN 3071, CPAN 3078, CPAN 4OO2, CPAN 4006, Bobwhite, K 8504, HP 1531, MG 2878, HPW 42, and 2HEWSN 87) and desirable agronomic bases for creating genetic variability. The wheat breeding material generated in previous years was shuttled and, evaluated, and selections made on the basis of resistance and plant type at different locations during the winter of 1993-94 at Dhaulakuan (456 m), Bajaura (1,098 m), Kukumseri (2,300 m), and Palampur and Malan (1,300 m), which are the hot spots of leaf rust, stripe rust, powdery mildew, and both stripe and leaf rusts, respectively (Table 4).

Table 4. Shuttling, evaluation, and selection of wheat breeding material.

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Cultures

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Generation/Location Evaluated Selected

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F₂/F₃ Bajaura/Kukumseri 161 populations 163 progenies

F₂/F₅ Dhaulakuan/Kukumseri/Malan 297 progenies 204 single plants

F₆/F₈ Malan/Palampur 792 progenies 634 F₆ progenies

64 F₈ bulks 159 F₇ progenies

30 bulks

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Heavy natural incidence of stripe and leaf rusts (80S) and powdery mildew (9) were recorded at Kukumseri.

Wheat frontline demonstrations. Seven frontline demonstrations on newly released cultivars were conducted in the Kangra and Kullu Districts of the state on an approximately 28 ha area involving six released wheat cultivars, VL 616, HS 277, HS 240, HD2380, HPW 42, (Aradhna), and HS 295. These demonstrations showed a 37.2 % to 47.6 % increase in grain yield over local at the farmers fields. The latest released cultivars are gaining popularity among the farmers of the state.

Physiological specialization of Erysiphe graminis tritici. Virulence patterns were studied for 62 conidial isolates collected from different areas in Himachal Pradesh. Based on their reaction on near-isogenic lines/cultivars having known powdery mildew resistance gene(s), the isolates were grouped into 29 distinct pathotypes. Isolates from Kukumseri (Lahaul and Spiti) were more variable. Pathotypes I and XXII, with susceptible reactions on nine genes, were highly virulent. Some of the isolates differed on different sources having the same gene (Pm2 and Pm4a). Virulence with genes Pm1, Pm2 (Ulka/CC8), Pm4a, Pm2+6 was rare, whereas it was very high with genes Pm3a, Pm3c, Pm5, Pm6, Pm7, and Pm(Ma). The virulence frequency on gene Pm8 was more than 70 %. Out of 24, 26, and 31 isolates tested on Marris Dove (Mld), Kronjuwel (Pm4b+8), and Sappo (Pm2+Pm4b), respectively, only 3, 0, and 5 isolates were virulent. Hence, cultivars with a combination of two or more genes are likely to impart durable resistance against this disease.