Studying the cumulative vigor response index of morpho-physiological, quality, and yield-related traits of wheat cultivars using planting dates

Wheat (Triticum aestivum L) is one of the major staple food crops consumed globally. Nonetheless, the cultivation of wheat is influenced by various environmental factors, with the planting date being significantly impacted by the effects of climate change. Addressing these changes could involve evaluating wheat genotypes to identify appropriate planting dates. A phenotypic screening experiment was conducted in the field crop station of Agriculture College of Tikrit University to determine the suitable planting time for wheat cultivars under local environmental conditions during 2022-23. Several morpho-physiological, quality, and yield traits were measured. Factorial experiment using spilt plot through randomized completely block design (RCBD). was used with three replications. The five planting dates (5-10, 25-10, 15-11, 5-12, and 25-12) were considered as the main plot, and the eight wheat cultivars (Ipaa99, Al-Rasheed, Al-Baraka, Sham6, Tammuz2, Al-Hashimiya, Al-Noor, and Al-Adnanieh) as sub-main plot. Data were used to calculate the Individual, Cumulative, and Total Vigor Response Indices (IRI, CRI & TRI). Cultivars were classified into different categories using total cumulative early or late planting date vigor response index values (TRI-e) or (TRI-l) and standard deviation (SD). The (TRI-e) values ranged from 36.07 (sensitive) for the cultivar Al-Baraka to 39.13 (tolerant) for the cultivar Al-Hashimiya. However, the (TRI-l) values ranged from 36.59 (sensitive) for the cultivar Al-Noor to 39.52 (tolerant) for the cultivar Al-Hashimiya. The correlation coefficient (r2) between the (TRI-e) and cumulative very early/early planting date vigor response index was positively correlated (r2 = 0.70 for very early planting date (5-Oct) and r2 = 0.60 for early planting date (25-Oct). Furthermore, 76% of the total variation in the (TRI-l) was explained by the cumulative very late planting date vigor response index (CRI-vl) while just 49% of the total variation was explained by the cumulative late planting date vigor response index (CRI-l). Based on those results, wheat producers could select either tolerant cultivars for early planting or tolerant cultivars for late planting to maximize wheat production in their specific growing environments including planting dates.