Assessment of seed yield and field screening against fusarium wilt in safflower (Carthamus tinctorius L.)

Introduction

Safflower (Carthamus tinctorius L.) is a valuable oilseed crop belonging to the family Asteraceae and is extensively grown under arid and semi-arid climatic conditions worldwide. Owing to its remarkable tolerance to drought and salinity, safflower is recognized as a versatile crop that provides high quality vegetable oil and natural carthamin dye obtained from its florets (Anon., 2001) [1] . In India, safflower is cultivated in an area of 0.64 lakh hectares, with a total production of 0.43 lakh tonnes and an average productivity of 672 kg ha -1 (Indiastat, 2024-25) [4] . Maharashtra and Karnataka are the major safflower growing states followed by Telangana. In Telangana, it is cultivated in an area of 0.02 lakh hectares, with a production and productivity of 0.03 lakh tonnes and 1316 kg ha -1 respectively. Despite its potential uses, safflower cultivation area in India has been declining alarmingly due to low seed yield, low oil content and susceptibility to biotic and abiotic stresses such as aphids, wilt and moisture stress (Nimbkar, 2009) [9] . Despite its immense agronomic adaptability to marginal environments, the global and national productivity of safflower is severely constrained by a wide array of biotic stresses, particularly fungal pathogens that damage the crop across various growth stages (Prabhavathi et al., 2025 and Reddy et al., 2025) [10,12] . Among the fungal diseases affecting safflower, wilt caused by Fusarium oxysporum f. sp. carthami is one of the most destructive soil-borne diseases (Klisiewicz and Houston, 1962) and is considered a major economic constraint to safflower production. It causes extensive vascular discoloration, severe chlorosis, acropetal wilting and eventual plant death (Reddy et al., 2025) [12] . It is reported to exhibit seed transmission rates of 10-40% (Chakrabarti and Basuchaudhary, 1980) [2] , facilitating rapid dissemination across geographical borders and resulting in yield losses ranging from 80 to 93% under susceptible cultivars and poorly drained conditions (Sastry and Ramachandram, 1994; Prabhavathi et al., 2025) [10,13] .

The management of Fusarium wilt using conventional chemical or cultural practices is generally ineffective and economically unviable due to its soil-borne nature. Therefore, the identification of resistant host plants represents the most effective strategy for the long-term management of this disease (Murumkar et al., 2008 and Reddy et al., 2025) [8,12] . Screening under field conditions in uniformly infected environments using specialized wilt-sick plots are considered the most dependable method for confirming resistance under natural disease pressure (Prabhavathi et al., 2025) [10] . The objective of the study is to identify high-yielding safflower genotypes with resistance to Fusarium wilt among diverse genotypes. Accordingly, this investigation was designed to evaluate the diverse panel of safflower genotypes for seed and oil yield, along with screening for resistance to Fusarium wilt.

Material and Methods

In the present study, 75 diverse safflower genotypes were evaluated for seed yield along with screening for resistance to Fusarium wilt. The experiment was conducted at the Experimental Farm of the Agricultural Research Station, Tandur, Telangana, during Rabi 2025-26. Two sets of experiments were carried out separately for evaluation of yield and its components and screening against Fusarium wilt under wilt-sick conditions. In the first experiment, 75 safflower genotypes were evaluated for seed yield and its components with four checks. The trial was laid out in Augmented Randomized Block Design in five blocks, each block consists of 15 genotypes and checks were repeated in each block. The genotypes were sown in a row of 5 m length with a spacing of 45 cm between rows and 20 cm between plants within a row. Recommended package of practices were followed to raise the crop. The observations were recorded on five randomly selected plants for the traits viz., plant height (cm), number of capitula plant⁻¹, diameter of primary capitulum, number of seeds primary capitulum⁻¹, 100 seed weight (g) and seed yield plant⁻¹ (g), while days to 50% flowering and days to maturity were recorded on a plot basis. The mean data was subjected to statistical analysis as per the Augmented Randomized Block Design suggested by Federer (1956). In the second set of experiment, the same 75 safflower genotypes, along with one resistant and one susceptible check, were screened against Fusarium wilt under wilt-sick plot by ensuring consistent disease pressure with a pathogen Foc population of 3.5 × 103 cfu/g. To monitor disease pressure and ensure uniformity of wilt incidence across the experimental area, a susceptible check (NIRA) and a resistant check (TSF-1) were included after every five test entries. All the recommended agronomic practices were followed except for the application of plant protection measures against Fusarium wilt. The genotypes were sown in a row of 5 m length with a spacing of 45 cm between rows and 15 cm plant-to-plant distance. Wilt observations were recorded starting from 30 days after sowing (DAS) and subsequently at 15 days intervals, with observations taken at 30, 45, 60, 75, 90, 105 and a final observation at 120 DAS. The Fusarium wilt incidence (%) for each genotype was calculated using the following formula:

Percentage wilt incidence (%) = (Number of wilted plants / Total plant population) × 100

The final disease response of each genotype was assessed based on the cumulative wilt incidence recorded up to 120 days after sowing. The genotypes were categorized according to the Fusarium wilt disease rating scale of the All India Coordinated Research Project (AICRP) on Safflower. Disease severity was also evaluated using a 0-9 disease rating scale (Mayee and Datar, 1986) [7] as presented below.

Disease scale

Results and Discussions Study of mean performances for seed yield and its components

The analysis of variance (ANOVA) revealed significant differences among the safflower genotypes for all the eight yield and yield contributing traits, indicating the existence of substantial genetic variability in the material under study (Table -1). Highly significant variation was observed for days to 50% flowering, days to maturity, plant height, number of capitula per plant, number of seeds per capitulum, 100-seed weight, seed yield per plant, volume weight, hull content and oil content, while the diameter of the primary capitulum showed significant variation. Mean performance of 79 safflower genotypes including four checks for seed yield and yield components revealed that six genotypes (GMU7915, GMU7919, GMU7886, GMU7908, GMU7892 and GMU7914) exhibited significant early flowering, whereas seven genotypes (GMU7914, GMU7915, GMU7908, GMU7892, GMU7886, GMU7918 and GMU7919) showed significantly early maturity over the earliest check ISF-764, indicating their potential as valuable sources for developing early duration cultivars (Table -2).

The per se performance of plant height ranged from 61.22 to 110.92 cm and the genotypes TSF-3442, TSF-860, GMU993-1 and TSF-3430 were found to be significantly taller than the best check PBNS-12. Among the genotypes studied, only two genotypes, TSF-3452 (24.40) and GMU7904 (24.00) exhibited significant superiority over the best check RVSAF-18- [11] and Reddy et al. (2025) [12] also identified immune donors in their wilt screening studies under high disease pressure. Five genotypes viz., TSF-3426, TSF-3437, TSF-3430, TSF-3450 and TSF-3431 exhibited a resistant (R) reaction, with a wilt incidence of 1-10%. These entries represent valuable genetic sources for developing high yielding Fusarium wilt resistant cultivars. Eight genotypes viz., GMU916, TSF-3429, TSF 861, TSF-3449, TSF-3455, TSF-3454, TSF-3452 and TSF-3457 were categorized as moderately resistant (MR) with wilt incidence ranging from 11-20%. Identification of these lines holds considerable value for safflower improvement programmes as resistant sources typically carry polygenic, partial resistance that provides more durable protection across fluctuating agro-climatic conditions. However, the vast majority of the evaluated lines were highly vulnerable to the pathogen, which falls into the susceptible (21-50% PWI) and highly susceptible (>51% PWI) categories. 41 genotypes showed susceptible reactions, with wilt incidences reaching up to 47.62% (GMU893). Furthermore, seventeen genotypes were placed in a highly susceptible category with severe plant mortality, among which the entries such as GMU7556 (87.50%), GMU7553 (86.36%) and GMU7892 (78.26%) demonstrated severe susceptibility. The high disease incidence observed in the susceptible check, NIRA (77.95%), confirmed the severe and uniform distribution of the pathogen across the experimental plots. Continuous field screening is imperative due to the variable nature of F. oxysporum f. sp. carthami. As recommended by Kalpana Sastry and Chattopadhyay (2003) [5] , the immune, resistant and moderately resistant identified donor parents could be directly utilized in introgression programs aiming to enhance the yield stability of safflower cultivars in wilt prone areas. GMU7915, GMU7908, GMU7870, GMU7914, GMU7871, GMU7918, GMU7907, GMU7518, GMU7905, GMU7913, GMU7920, GMU7886, GMU7861, GMU7921,

Conclusion

The present study revealed the existence of significant genetic variability for both seed yield and yield contributing traits and resistance to Fusarium wilt. Several genotypes were found significantly superior in performance over the superior checks for seed yield and its components. Even though, majority of the accessions were found highly vulnerable to wilt under wilt screening, four genotypes viz., TSF-3440, TSF-3439, TSF 845 and TSF-3442 were identified as immune and five genotypes viz., TSF-3426, TSF-3437, TSF-3430, TSF-3450, TSF-3431 were resistant. Notably, two genotypes TSF-845 and TSF-3439 were found promising with high seed yield and immune reaction to wilt. These genotypes can be utilized in future breeding programmes to develop stable, high yielding and Fusarium wilt resistant safflower cultivars specifically tailored for wilt-endemic regions. These genotypes can be further evaluated in multilocation trials or AICRP trials to further validate their yield stability and disease reaction.

References

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