Evaluation of heat stress and leaf rust tolerance between very late planted durum and bread wheat cultivars in central India

Soybean [ Glycine max (L.) Merr.] -wheat (Triticum aestivum L.) is the common cropping system in the Vertisols of central India. High temperatures prevailing during the reproductive phase and leaf rust infection of the lateplanted wheat crop affect the grain yield adversely. In the soybean -potato -wheat cropping system, which has recently become more popular, wheat is sown very late, so high temperature stress is a major concern. Understanding of the response of very late-sown durum and bread wheat to high temperature stress during grain filling will assist breeders in genotype improvement and development of best agronomic management practices for promotion of very late-sown wheat cultivation in the region. Information is lacking on the response of durum and bread wheat to leaf rust and heat stress under very late-sown situations. Field experiments were conducted for three consecutive spring (January to April) seasons, from 1996 to 1998, with 20 cultivars of durum (Triticum turgidum L. var. durum Desf.) and bread (Triticum aestivum L. emend. Fiori. and Paol.) wheat of timely and late-sown groups. The study objective was to: (i) identify durum and bread wheat cultivars suitable for very late planting in the newly established soybean -potato -wheat multiple cropping system; (ii) evaluate differential performance of durum and bread wheat under very late-sown conditions; and (iii) characterise plant traits associated with tolerance to heat stress during the grain filling period. Each year, all the cultivars were planted very late in January in lieu of normal sowing in mid-November. Compared with both the timely and late-sown groups of bread wheat cultivars, durum wheat produced an average 6% higher grain yield when sown very late. The 1000-grain weight was the most affected yield attribute under high temperature. Thus, under very late sown conditions, stable and high 1000-grain weight (45 -55 g), and high harvest index (41 -52%) contributed to the higher yield of durum wheat. Durum cultivar HI 8498 and bread wheat cultivars GW 173, HI 1418 and DL 788-2 of early to medium maturity and with high yields (> 4.0 t/ ha) and water use efficiency (12.7 -14.8 kg/ ha. mm) proved promising. Durum cultivars remained free from leaf rust infection, while significant yield reduction was recorded in susceptible bread wheat cultivars, particularly DL 803-3 and GW 190. This was due to severe rust infection during 1997 -98, when widespread incidence of leaf rust occurred in the region. Therefore, contrary to the popular belief, late planted durum wheat may be successfully grown in the soybean -potato -wheat cropping system in central India.