For the thickly populated Indo-Gangetic region, wheat is the lifeline for half of the population. Terminal heat stress and diminishing water resources are significant challenges to wheat production 1. It is believed that extending the crop duration by a certain amount should overcome the yield losses incurred by the rise in seasonal temperature, as shown by wheat lines that were 4-9 days earlier in heading in India 2. It is possible to extend the time windows for spring wheat when crops are planted in advance of the planting time. Shifting the planting time by one to two weeks earlier was found to be better by providing much longer time for the crop growth and saving one irrigation due to the presence of moisture after the monsoon season. As the monsoon period is the major rainfall period, farmers would like to plant wheat earlier in many parts of northwestern and central India to take advantage of the residual moisture. To meet the vast demand of farmers, breeding for early adaptation and genotype screening is necessary for this region.
On the other hand, Yellow Rust (YR) disease is currently regarded as the most critical disease in major wheat-growing countries worldwide, owing to the disease’s rapid evolution, dissemination, and violent presence of new pathotypes. Under extreme epidemic conditions, YR of wheat can cause up to 70% yield losses, affecting grain fill and quality. YR has traditionally been endemic to humid and cold summers or warm high-altitude areas with cool nights 3,4. However, in recent years, the disease has demonstrated more remarkable adaptation in warmer regions, previously less significant or functionally absent 5. The YR is more severe in northwestern India and Pakistan compared to the other two rusts 6. YR threatens 10 million hectares in Northern India. It threatens around 7 million hectares in Central and Peninsular India in comparison to stem rust 7. Normal planted wheat may also be vulnerable to YR, although it escapes when planting earlier than the recommended time. To know the actual resistance pattern of early adapted wheat, we conducted a wheat screening experiment under normal and early sown conditions using 600 genotypes in two replications at Borlaug Institute of South Asia (BISA) Ludhiana, Punjab, India. These trials were repeated for three seasons (Season 2017-18, 2018-19, and 2019-2020) with a separate set of genotypes each season developed at CIMMYT, Mexico. Early planting was found more suitable for yield potential along with a better performance in phenology, stature and physiological traits. Unfortunately, the well adapted genotypes for early establishment tend to have higher percentages of YR spots. The infection type scored for the genotype selected for early planting also shows more S (Susceptible) type reaction than timely adapted genotypes. Interestingly more R (resistant) and MR (Moderate Resistant) type of reactions were also found in early than timely adapted genotypes. Therefore, the potentiality of breeding for early establishment for Indo-Gangetic region need to have more focused research on YR screening.
