Relationship between grain weight and spike fertility index in wheat.

GONZALEZ FERNANDA G; GAZABA LUCIANA; TERRILE IGNACIO

Congreso; 6th International Crop Science Congress; 2012

The spike fertility index (SFIh), i.e. the number of grains per gram of non-grain spike dry matter at harvest, has been recently proposed as a promising trait to improve wheat yield potential. Nevertheless, a negative relationship has been observed between the SFIh and the average grain weight (GW), questioning the usefulness of the trait to improve wheat yield potential. The objective of the present study was to analyze the relationship between the grain weight and the SFI focusing on the first physiological determinant of potential grain weight, i.e. ovary weight at anthesis (ODWA). The experiment was carried out in the north of Buenos Aires Province (33º51´sl, 60º56´wl), at the Pergamino Research Station of INTA (National Institute for Agricultural Technology and Husbandry). Three adapted cultivars, two of high SFIh (Baguette Premium11 ?BP11- and Baguette 19 ?B19-) and one of low SFIh (BioINTA 2002 ?Bio2002-) were sown at optimum dates under potential growth conditions. All measurements were performed in the main stem spike. As expected, the SFIh was higher (p<0.05, LSD Fisher = 28) for B19 and BP11 (124 and 118 grains g-1, respectively) in relation to Bio 2002 (84 grains g-1). GW tended to be lower in B19 and BP11 (32 and 30 mg, respectively) in relation to Bio 2002 (34 mg), but the difference was smaller than that expected. This may be consequence of the reduced difference observed in the number of grains per main stem spike (40 ? 37- 36 for B19, BP11 and Bio 2002). When the SFI at anthesis (SFIa) was observed (number of fertile florets/ g of non-floret spike), the difference among cultivars was kept (187 ? 181 ? and 96 for B19, BP11 and Bio2002, respectively, p<0.05, LSD Fisher = 57). Nevertheless, the relation between the average ODWA (average of all ovaries of the spike) and the SFIa tended to be positive (0.42 ? 0.55 ? 0.31 mg for B19, BP11 and Bio2002, p<0.05 LSD Fisher = 0.12, for ODWA). The number of fertile florets per spike showed greater difference between cultivars of different SFIa (53, 60 and 48 for B19, BP11 and Bio2002, p= 0.06, LSD Fisher = 10) than that observed at harvest. Thus, the cultivars with higher SFI partitioned more biomass to ovary growth at anthesis than those of lower SFI. When the ODWA of florets of different positions within the central spikelet of the spike were measured, no great difference was observed for the same floret position among cultivars, but the floret 4 (with reduced ODWA) was only observed in the high SFI cultivars. These results would suggest that the cultivars with high SFI would not present reduced potential grain weight, thus, their reduce GW may be consequence of higher number of grains in distal positions from the rachis.