Yield potential and genetic gain in Indian and Mexican spring bread wheat
S. C. Tripathi1*K. D. Sayre2 and J. N. Kaul3
1DWR, PB No. 158, Karnal, PIN -132001, Haryana, India.
2Wheat Program, CIMMYT, Lisboa 27, Apartado Postal 6-641, 06600,
Mexico D.F., Mexico.
3Department of Agronomy, PAU, Ludhiana, PIN- 141004, Punjab, India.
Summary
Yield potential progress of 15 spring wheat (Triticum aestivum L.) genotypes (five of Indian and ten of Mexican origin) was studied under disease free, artificial lodging control by using mesh (20 x 20) and high N (300 kg/ha) application at CIMMYT (Centro Internacional de Mejoramiento de Maiz y Trigo), near Ciudad Obregon, Sonora, Mexico during 1997-98 and 1998-99. From pooled analysis, Super Seri, the latest variety named in 1999 produced significantly higher grain yield (9968 kg/ha) than other varieties and 23.7 % more grain yield than the lowest yielding variety Pavon 76 (8056 kg/ha) released in 1976. Even second highest yielding cultivar WH 542 produced 774 kg/ha less yield than Super Seri. Genetic progress, including both Indian and Mexican genotypes, showed that gain in grain yield was 48 kg/ha/year in absolute term and 0.54 % per year in relative term. Under real farm situation these genetic gains will be higher due to inability of farmers to control lodging and diseases. To quantify separately the effect of Indian and Mexican genotypes it was observed that Indian varieties, released during 1982 and 1995, gained grain yield @ 22.7 kg/ha/year or 0.25 % per year. On the other hand, Mexican cultivars released during 1976 and 1999 increased grain yield @ 57 kg/ha/year in absolute term or 0.63 % per year in relative term.
Key words: spring bread wheat, yield potential, genetic
gain
Introduction
The advent of Norin 10 dwarfing genes opened up era of semi-dwarf wheat, which dramatically increased the yield potential during mid 1960s. Maximum possible yield can be achieved where there are no biotic and abiotic constraints and crop is free from lodging. This yield will be close to the physiological yield potential, which is generally calculated from solar radiation and temperature and genetic ability of the plant to convert light energy into dry matter and subsequently partition this dry matter into economic grain yield (Hobbs et al. 1998). Genetic progress in the yield of spring bread wheat was 0.7 to 1.3 % per year (Byerlee and Moya 1993) and 0.88 % per year or 67 kg/ha/year (Sayre et al. 1997). Former study included the tall wheat whereas the latter involved from Pitic 62 released in 1962 to Bacanora 88 released in 1988. In both the studies, yield progress was associated with use of Norin 10 dwarfing genes Rht-1 or Rht-2, and with an increase in the harvest index. Whereas, Waddington et al. (1986) pointed out that the increase in grain yield (after 1975) was due to increased biomass rather than harvest index. In another study of 50 experiments, Bell et al. (1995) reported that genetic gain in yield was 0.7 % per year during 1968-1993, but it became slow down after 1980s. Yield potential progress of spring bread wheat during the last quarter of century (1975 to 2000) is not very well established. Therefore, present study was carried out under irrigated, high N application (300 kg/ha), disease free and artificial lodging control condition with use of 10 Mexican and 5 Indian high yielding spring wheat genotypes released during 1976 to 1999. This provided an opportunity to update the genetic progress made by Indian and Mexican spring bread wheat genotypes, all semi-dwarf wheat, developed during the last quarter of 20th century.